1 00:00:00,080 --> 00:00:01,670 The following content is provided 2 00:00:01,670 --> 00:00:03,810 under a Creative Commons license. 3 00:00:03,810 --> 00:00:06,540 Your support will help MIT OpenCourseWare continue 4 00:00:06,540 --> 00:00:10,150 to offer high quality educational resources for free. 5 00:00:10,150 --> 00:00:12,690 To make a donation or to view additional materials 6 00:00:12,690 --> 00:00:16,600 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:16,600 --> 00:00:21,628 at ocw.mit.edu 8 00:00:21,628 --> 00:00:23,503 PROFESSOR: All right good afternoon everyone. 9 00:00:27,830 --> 00:00:31,200 What I have on the board here is what we're going to cover today 10 00:00:31,200 --> 00:00:33,400 and what we had covered the last time. 11 00:00:34,830 --> 00:00:38,220 Those in blue here are the ones we have covered the last time 12 00:00:38,220 --> 00:00:40,810 and the rest of them, five through nine, 13 00:00:40,810 --> 00:00:43,270 are the ones we are going to cover today. 14 00:00:43,270 --> 00:00:47,740 Actually the last time I didn't have this last step here, 15 00:00:47,740 --> 00:00:50,410 dreaming and rapid eye-movement sleep, 16 00:00:50,410 --> 00:00:53,800 if there is time I want to say a few words about that 17 00:00:53,800 --> 00:00:56,250 because that's a very interesting topic 18 00:00:56,250 --> 00:01:01,780 and brings us to make a few comments about Freudian theory. 19 00:01:06,980 --> 00:01:10,280 All right then so we are going to then start 20 00:01:10,280 --> 00:01:12,550 with a description of the cortical structures 21 00:01:12,550 --> 00:01:15,135 that are involved in eye-movement control. 22 00:01:20,010 --> 00:01:22,160 Now the first thing I want to do is 23 00:01:22,160 --> 00:01:24,275 to show you once again the monkey brain. 24 00:01:26,770 --> 00:01:30,400 You're already familiar with those items which are on here. 25 00:01:30,400 --> 00:01:34,580 Here's V1, here's V4, here's the superior temporal sulcus 26 00:01:34,580 --> 00:01:38,590 that contains areas MT and MST and of course 27 00:01:38,590 --> 00:01:41,620 here's the central sulcus, principalis, and the arcuate. 28 00:01:41,620 --> 00:01:44,810 Another structure involved in eye-movement control 29 00:01:44,810 --> 00:01:48,930 is the lateral intraparietal sulcus which is in here, 30 00:01:48,930 --> 00:01:52,600 and then another one is the medial intraparietal sulcus 31 00:01:52,600 --> 00:01:55,960 but those two perform service similar tasks 32 00:01:55,960 --> 00:01:59,090 and so I'm not going to talk about the MIP 33 00:01:59,090 --> 00:02:00,730 separately from LIP. 34 00:02:00,730 --> 00:02:02,690 And then here in the frontal lobe 35 00:02:02,690 --> 00:02:06,760 we have the frontal eye fields as the name implies of course, 36 00:02:06,760 --> 00:02:09,330 it has a lot to do with eye-movement control 37 00:02:09,330 --> 00:02:11,840 and then here very close to the midline 38 00:02:11,840 --> 00:02:14,760 we have the medial eye fields which 39 00:02:14,760 --> 00:02:17,210 also play a role in eye movement control. 40 00:02:17,210 --> 00:02:19,380 So now we have all these structures 41 00:02:19,380 --> 00:02:23,170 and this is not by any means totally complete, 42 00:02:23,170 --> 00:02:26,780 because these deal mostly with saccadic eye movements 43 00:02:26,780 --> 00:02:29,170 and to a lesser degree with pursuit eye movements 44 00:02:29,170 --> 00:02:32,650 but the fact is it that all these areas that 45 00:02:32,650 --> 00:02:35,500 play a significant role in eye-movement control 46 00:02:35,500 --> 00:02:38,370 and of course, those people who want to understand 47 00:02:38,370 --> 00:02:41,000 eye-movement control need to figure out 48 00:02:41,000 --> 00:02:45,790 what these various structures do for you to enable you to look 49 00:02:45,790 --> 00:02:49,380 around with the great ease that you can look around 50 00:02:49,380 --> 00:02:50,620 with actually. 51 00:02:50,620 --> 00:02:55,660 So anyway let's try a number of views 52 00:02:55,660 --> 00:02:59,680 of how to go about finding out the operational characteristics 53 00:02:59,680 --> 00:03:02,970 of these areas and furthermore also to find out 54 00:03:02,970 --> 00:03:03,886 how they interconnect. 55 00:03:05,400 --> 00:03:10,930 Now one approach that has been very useful in delineating 56 00:03:10,930 --> 00:03:16,090 the areas in the visual cortex and even in subcortical areas 57 00:03:16,090 --> 00:03:18,630 is to use electrical stimulation. 58 00:03:18,630 --> 00:03:21,400 Because it has been found as, as we had discussed 59 00:03:21,400 --> 00:03:25,200 like the last time that when you electrically stimulate 60 00:03:25,200 --> 00:03:27,250 some structures heavily involved in eye movement 61 00:03:27,250 --> 00:03:31,910 control of like the colliculus, at low current levels 62 00:03:31,910 --> 00:03:35,260 electrical stimulation can elicit a saccade 63 00:03:35,260 --> 00:03:38,200 and by looking at the characteristics of that 64 00:03:38,200 --> 00:03:42,100 as we had in the colliculus, you can gain further insight 65 00:03:42,100 --> 00:03:45,150 about what the roles are of these various areas. 66 00:03:45,150 --> 00:03:48,130 And of course people have done electrical stimulation 67 00:03:48,130 --> 00:03:51,580 all over creation in the visual cortex 68 00:03:51,580 --> 00:03:55,110 as well as in other cortical areas, 69 00:03:55,110 --> 00:03:58,360 thereby trying to determine whether or not 70 00:03:58,360 --> 00:04:01,500 the electrical stimulation elicits a motor response 71 00:04:01,500 --> 00:04:03,910 and of course if you do this in motor cortex 72 00:04:03,910 --> 00:04:06,830 then you get a motor response and if you do 73 00:04:06,830 --> 00:04:09,680 do it in areas which is specifically connected 74 00:04:09,680 --> 00:04:13,060 with eye-movement control you get eye movement. 75 00:04:13,060 --> 00:04:17,029 So here is an example of the kinds of things we can do. 76 00:04:17,029 --> 00:04:20,320 Here is a monkey brain and of course 77 00:04:20,320 --> 00:04:23,080 as we have discussed already, from the brain stem 78 00:04:23,080 --> 00:04:27,500 the signal is sent to the eye muscles which provides 79 00:04:27,500 --> 00:04:30,060 the so-called rate code and then above that 80 00:04:30,060 --> 00:04:33,840 via the superior colliculus and then in the back 81 00:04:33,840 --> 00:04:38,070 we have V1 that you're already familiar with V2, LIP, 82 00:04:38,070 --> 00:04:40,460 frontal eye fields, and the medial eye fields. 83 00:04:40,460 --> 00:04:42,410 So now let's ask the question, what 84 00:04:42,410 --> 00:04:45,940 happens when you electrically stimulate these cortical areas? 85 00:04:45,940 --> 00:04:47,580 And also to compare that with what 86 00:04:47,580 --> 00:04:51,700 happens when you stimulate in the superior colliculus. 87 00:04:51,700 --> 00:04:56,630 So we already know that when you stimulate the colliculus what 88 00:04:56,630 --> 00:05:00,040 you get is wherever you put the electrodes in the colliculus 89 00:05:00,040 --> 00:05:03,670 and you find out where the receptive field is of the cells 90 00:05:03,670 --> 00:05:06,910 that you will be stimulating, that when you then convert 91 00:05:06,910 --> 00:05:09,880 and stimulate you get a saccade that brings 92 00:05:09,880 --> 00:05:14,770 the fovea into the center of the receptive fields of the neurons 93 00:05:14,770 --> 00:05:17,600 that you are stimulating and that is laid out 94 00:05:17,600 --> 00:05:22,110 in a nice topographic fashion and that is shown here 95 00:05:22,110 --> 00:05:24,040 in a schematic fashion. 96 00:05:24,040 --> 00:05:28,060 So that no matter where the eye starts, at any given point, 97 00:05:28,060 --> 00:05:29,520 if you electrically stimulate you 98 00:05:29,520 --> 00:05:33,560 get the same vector saccade in the superior colliculus. 99 00:05:34,670 --> 00:05:37,360 So you have what is called the vector code which 100 00:05:37,360 --> 00:05:39,800 if you remember, is quite different from the code 101 00:05:39,800 --> 00:05:43,860 that you have in the brain stem where you have a rate code. 102 00:05:43,860 --> 00:05:46,330 So now the question is suppose we now 103 00:05:46,330 --> 00:05:48,860 start stimulating these other cortical areas 104 00:05:48,860 --> 00:05:51,860 that I had designated in the previous slide 105 00:05:51,860 --> 00:05:55,220 and ask the question what happens in those places? 106 00:05:55,220 --> 00:05:58,840 All right so if you stimulate the visual cortex in this case 107 00:05:58,840 --> 00:06:03,810 V1 for example, you get the same kind of coding operation, 108 00:06:03,810 --> 00:06:07,080 you get vector saccades OK, constant vector saccades. 109 00:06:08,270 --> 00:06:11,210 Then if you do the same thing in LIP 110 00:06:11,210 --> 00:06:13,940 you also get a constant vector saccade 111 00:06:13,940 --> 00:06:16,130 and if you do that in the frontal eye fields 112 00:06:16,130 --> 00:06:17,410 you still get the same thing. 113 00:06:18,420 --> 00:06:23,490 So all of these areas seem to be coding saccadic vectors 114 00:06:23,490 --> 00:06:26,970 but now when you stimulate in the medial eye fields 115 00:06:26,970 --> 00:06:29,590 you get a very different kind of effect. 116 00:06:29,590 --> 00:06:32,370 Very interesting what you get here 117 00:06:32,370 --> 00:06:37,990 is what is called a place code, meaning that when you stimulate 118 00:06:37,990 --> 00:06:41,610 in various regions of the medial eye fields, the eye 119 00:06:41,610 --> 00:06:45,860 wherever it starts, converges on a particular point which you, 120 00:06:45,860 --> 00:06:49,480 we'll call the motor field, OK? 121 00:06:49,480 --> 00:06:53,250 And different regions in the medial eye fields 122 00:06:53,250 --> 00:06:59,300 have motor fields that generate different locations to which 123 00:06:59,300 --> 00:07:02,860 the eye will saccade when you stimulate there. 124 00:07:02,860 --> 00:07:05,545 So that's a very different kind of code from all the others. 125 00:07:08,190 --> 00:07:11,800 So now the next question is that you're going to pose is, 126 00:07:11,800 --> 00:07:15,140 how do the signals from all these cortical areas 127 00:07:15,140 --> 00:07:16,730 get down to the brain stem? 128 00:07:17,970 --> 00:07:19,510 So what kind of experiment do you 129 00:07:19,510 --> 00:07:23,470 think you would want to do to get some easy answers to that? 130 00:07:24,990 --> 00:07:31,870 So to, to perhaps highlight that some people thought, 131 00:07:31,870 --> 00:07:35,510 that the signals from all of these areas 132 00:07:35,510 --> 00:07:39,330 go down to the colliculus and then the colliculus sends 133 00:07:39,330 --> 00:07:42,150 its signals down to the brain stem. 134 00:07:42,150 --> 00:07:43,970 So if that's the case, what would you, 135 00:07:43,970 --> 00:07:45,250 what experiment would you do? 136 00:07:47,790 --> 00:07:49,550 Well the experiment you would do is 137 00:07:49,550 --> 00:07:52,980 you would remove the superior colliculus OK? 138 00:07:52,980 --> 00:07:55,110 And then again stimulate all of these areas. 139 00:07:57,040 --> 00:08:01,600 If that hypothesis, that all these areas send their signals 140 00:08:01,600 --> 00:08:05,030 through the superior colliculus of the brain stem is correct, 141 00:08:05,030 --> 00:08:08,950 then you would no longer get any saccades when you electrically 142 00:08:08,950 --> 00:08:12,680 stimulate in the cortex at any of these sites. 143 00:08:12,680 --> 00:08:13,740 Got it? 144 00:08:13,740 --> 00:08:17,790 All right now, let's see if an experiment like that 145 00:08:17,790 --> 00:08:21,200 had been done and yes, yes it has been. 146 00:08:21,200 --> 00:08:24,450 So here it is, here we're going to remove 147 00:08:24,450 --> 00:08:26,080 the superior colliculus. 148 00:08:26,080 --> 00:08:27,930 All right think about it for a minute, 149 00:08:27,930 --> 00:08:32,500 think what you would hypothesize will happen? 150 00:08:32,500 --> 00:08:35,350 Well what happens is quite dramatic. 151 00:08:35,350 --> 00:08:41,784 When you stimulate in V1, V2, and LIP 152 00:08:41,784 --> 00:08:42,950 you no longer get a saccade. 153 00:08:44,120 --> 00:08:47,950 Somehow the signals to generate the saccade from these areas 154 00:08:47,950 --> 00:08:50,210 seem to be going through the colliculus 155 00:08:50,210 --> 00:08:52,246 because once the colliculus is not there 156 00:08:52,246 --> 00:08:53,495 those signals are ineffective. 157 00:08:54,510 --> 00:08:56,430 Now what happens in the frontal lobe? 158 00:08:56,430 --> 00:08:59,460 All right what happens there is quite interesting. 159 00:08:59,460 --> 00:09:02,000 You still get saccades and you still 160 00:09:02,000 --> 00:09:03,810 get the same coding operation. 161 00:09:03,810 --> 00:09:05,720 You get a constant vector code when 162 00:09:05,720 --> 00:09:07,710 you stimulate the frontal eye fields 163 00:09:07,710 --> 00:09:12,260 and you get your place code in the medial eye fields 164 00:09:12,260 --> 00:09:14,550 and you get that at the same old threshold. 165 00:09:14,550 --> 00:09:19,810 So that discovery then resulted in the hypothesis first of all 166 00:09:19,810 --> 00:09:22,870 that these posterior areas send the signals to the brain 167 00:09:22,870 --> 00:09:28,020 stem from the colliculus which are called the posterior system 168 00:09:28,020 --> 00:09:31,630 and the ones in the anterior portions of the brain 169 00:09:31,630 --> 00:09:33,080 from medial and frontal eye fields 170 00:09:33,080 --> 00:09:37,290 seem to be able to gain direct access bypassing 171 00:09:37,290 --> 00:09:41,620 the colliculus to the brain stem is 172 00:09:41,620 --> 00:09:44,550 because they're still effective when you stimulate there 173 00:09:44,550 --> 00:09:47,610 and so we can call that the anterior system. 174 00:09:47,610 --> 00:09:50,960 All right, now of course these two systems 175 00:09:50,960 --> 00:09:53,643 need to talk to each other, which they do, there are plenty 176 00:09:53,643 --> 00:09:56,770 of connections there because of course, if you will, 177 00:09:56,770 --> 00:09:59,860 the left hand, it's got to know what the right hand is doing. 178 00:09:59,860 --> 00:10:04,100 So anyway this is then a very summary arrangement 179 00:10:04,100 --> 00:10:07,170 and now we can proceed to ask some questions 180 00:10:07,170 --> 00:10:10,090 about just what do these various areas do? 181 00:10:11,350 --> 00:10:13,710 And to understand that data we need 182 00:10:13,710 --> 00:10:17,320 to look into more detail about the nature 183 00:10:17,320 --> 00:10:20,130 of electrical stimulation and compare that 184 00:10:20,130 --> 00:10:25,240 with the nature of eye movements made to visual target. 185 00:10:25,240 --> 00:10:27,140 So let's look at that next time. 186 00:10:27,140 --> 00:10:29,330 So we can look at the effects of paired 187 00:10:29,330 --> 00:10:32,670 electrical and visual stimulation. 188 00:10:32,670 --> 00:10:36,690 All right so, the first thing we're going to look at 189 00:10:36,690 --> 00:10:38,620 is what happens when you stimulate 190 00:10:38,620 --> 00:10:41,990 two sites say in the colliculus at the same time? 191 00:10:43,200 --> 00:10:46,380 And if you remember, medial is up and lateral is down. 192 00:10:46,380 --> 00:10:49,420 So if you stimulate each of those alone 193 00:10:49,420 --> 00:10:53,730 you get here in number one you get an upward saccade, 194 00:10:53,730 --> 00:10:55,950 you simulate number two you get a downward saccade. 195 00:10:57,150 --> 00:10:59,330 Now the question comes up, what happens 196 00:10:59,330 --> 00:11:02,430 when you stimulate both at the same time? 197 00:11:02,430 --> 00:11:05,070 Well the number of hypotheses that 198 00:11:05,070 --> 00:11:08,390 have been proposed and by now it's been well established 199 00:11:08,390 --> 00:11:12,890 that what happened is that you get a vector average saccade 200 00:11:12,890 --> 00:11:16,530 not vector summation, but vector averaging OK? 201 00:11:16,530 --> 00:11:18,770 Now, to prove that that is indeed 202 00:11:18,770 --> 00:11:22,350 vector averaging if you take the same experiment 203 00:11:22,350 --> 00:11:25,130 but you put one electrode in the anterior 204 00:11:25,130 --> 00:11:28,340 portion and the other electrode in the posterior 205 00:11:28,340 --> 00:11:30,890 one of the colliculus, this one of course 206 00:11:30,890 --> 00:11:34,120 generates a small saccade and this one a large saccade. 207 00:11:34,120 --> 00:11:35,920 So if its vector averages, you should 208 00:11:35,920 --> 00:11:37,690 get an in-between saccade. 209 00:11:37,690 --> 00:11:40,460 If your vector sums then it should get a bigger saccade 210 00:11:40,460 --> 00:11:42,960 than either of those and you indeed 211 00:11:42,960 --> 00:11:45,280 get a vector average saccade. 212 00:11:45,280 --> 00:11:47,260 So depending on this arrangement, 213 00:11:47,260 --> 00:11:51,060 or this arrangement, you get the same vector average saccade 214 00:11:51,060 --> 00:11:54,690 because the only thing that's happening here 215 00:11:54,690 --> 00:11:58,910 is you excite the neurons in the colliculus 216 00:11:58,910 --> 00:12:00,725 by virtue of this electrical stimulation. 217 00:12:02,440 --> 00:12:04,330 Now think about that for a minute. 218 00:12:04,330 --> 00:12:08,890 If this were the case with visual stimuli, 219 00:12:08,890 --> 00:12:11,440 suppose two visual stimuli come up, 220 00:12:11,440 --> 00:12:13,020 it would be a total disaster if you 221 00:12:13,020 --> 00:12:16,570 made an eye movement between the two of them wouldn't it? 222 00:12:16,570 --> 00:12:18,960 So somehow there's some mechanisms 223 00:12:18,960 --> 00:12:23,810 in the brain that force you, force you, 224 00:12:23,810 --> 00:12:28,580 I guess that may not be the right word, 225 00:12:28,580 --> 00:12:31,610 achieve the ability to select one 226 00:12:31,610 --> 00:12:33,420 or the other of the visual targets 227 00:12:33,420 --> 00:12:37,490 accurately and not be vector averaging it. 228 00:12:37,490 --> 00:12:41,950 Now to accomplish that logically speaking, what you need 229 00:12:41,950 --> 00:12:45,360 is some inhibitory circuits and the mechanism 230 00:12:45,360 --> 00:12:49,570 for selection and then a decision as to where to look. 231 00:12:49,570 --> 00:12:52,630 All right so to highlight that let 232 00:12:52,630 --> 00:12:55,060 me just say one more thing about electrical stimulation. 233 00:12:55,060 --> 00:12:57,960 This is true what I told you about vector averaging 234 00:12:57,960 --> 00:13:03,500 with electrical stimulation even when you stimulate the two, 235 00:13:03,500 --> 00:13:07,240 the two superior colliculi or two different locations 236 00:13:07,240 --> 00:13:11,200 in the brain each of those gives you an eye movement 237 00:13:11,200 --> 00:13:13,610 into the left or right hemifield and yet 238 00:13:13,610 --> 00:13:15,340 they also vector average. 239 00:13:15,340 --> 00:13:17,120 So now let's look at what happens 240 00:13:17,120 --> 00:13:21,840 when a similar situation is used in a real experiment where 241 00:13:21,840 --> 00:13:25,880 the monkey looks at visual targets and so what you do here 242 00:13:25,880 --> 00:13:30,050 is you present these two targets at the same time. 243 00:13:30,050 --> 00:13:32,770 And so the monkey in a sense has to make a decision 244 00:13:32,770 --> 00:13:36,290 or you have to make a decision as to where to look. 245 00:13:36,290 --> 00:13:38,980 And as long as there's a nice big separation here 246 00:13:38,980 --> 00:13:42,480 which is 90 degrees in this case, what you can see here 247 00:13:42,480 --> 00:13:45,640 are the real eye movements that half the time the monkey looks 248 00:13:45,640 --> 00:13:47,520 to the left, half the time to the right 249 00:13:47,520 --> 00:13:50,370 and it makes very very few in-between saccades. 250 00:13:50,370 --> 00:13:52,240 Whereas if you electrically stimulated 251 00:13:52,240 --> 00:13:54,390 at these sites in the colliculus you'd 252 00:13:54,390 --> 00:13:56,000 get a vector average saccade just 253 00:13:56,000 --> 00:13:59,665 like what I've shown you here OK? 254 00:14:02,370 --> 00:14:06,460 All right so now that being the case, 255 00:14:06,460 --> 00:14:09,350 we can move on and ask some additional questions 256 00:14:09,350 --> 00:14:12,710 about what happens when you bring the two 257 00:14:12,710 --> 00:14:15,980 stimuli closer together, all right? 258 00:14:15,980 --> 00:14:19,020 The closer together they get the more difficult 259 00:14:19,020 --> 00:14:21,650 it is to make an independent decision 260 00:14:21,650 --> 00:14:25,230 as to whether to look to the left or the right target that 261 00:14:25,230 --> 00:14:27,470 comes up above the fixation spot. 262 00:14:27,470 --> 00:14:30,750 So here's an example of that, actually what 263 00:14:30,750 --> 00:14:32,410 I'm going to do is this. 264 00:14:32,410 --> 00:14:36,100 Let me delay for a little bit what happens with that 265 00:14:36,100 --> 00:14:39,220 and first I want to tell you about what 266 00:14:39,220 --> 00:14:42,320 happens with various kinds of lesions 267 00:14:42,320 --> 00:14:44,420 that you make on eye movements and then we'll 268 00:14:44,420 --> 00:14:47,910 talk about this question of the angular 269 00:14:47,910 --> 00:14:50,085 separation between the two visual targets. 270 00:14:51,250 --> 00:14:56,600 So therefore let's do-- the reason I want to do this first 271 00:14:56,600 --> 00:14:59,400 is to give you sort of a real sense when you 272 00:14:59,400 --> 00:15:04,150 do very informal kind of testing and by informal testing what 273 00:15:04,150 --> 00:15:07,890 I mean is that you're going to see a monkey actually 274 00:15:07,890 --> 00:15:10,090 perform eye movements OK? 275 00:15:11,680 --> 00:15:17,530 So here we are, here's a monkey, here's his brain so to speak 276 00:15:17,530 --> 00:15:21,490 and this is what we call of course an intact animal and now 277 00:15:21,490 --> 00:15:24,250 what I'm going to do, I'm going to start the movie for you 278 00:15:24,250 --> 00:15:26,030 to see what kinds of eye movements 279 00:15:26,030 --> 00:15:30,010 he makes when we present some apple pieces for the monkey 280 00:15:30,010 --> 00:15:31,010 to eat. 281 00:15:31,010 --> 00:15:32,040 OK are you ready? 282 00:15:32,040 --> 00:15:32,660 Here it is. 283 00:15:40,740 --> 00:15:42,200 Can everybody see this OK? 284 00:15:49,610 --> 00:15:52,570 So you can see that when an apple piece appears 285 00:15:52,570 --> 00:15:56,780 the monkey makes a saccade to it and grabs it and stuffs 286 00:15:56,780 --> 00:15:58,950 in his mouth and eats it. 287 00:15:58,950 --> 00:16:02,180 OK so that's what a normal monkey does 288 00:16:02,180 --> 00:16:06,010 with his fully intact, functional brain. 289 00:16:06,010 --> 00:16:08,650 So now we're going to ask the question, what 290 00:16:08,650 --> 00:16:13,370 happens if you take out the colliculus on one side, 291 00:16:13,370 --> 00:16:16,620 meaning a unilaterally lesion, what happens to the eye 292 00:16:16,620 --> 00:16:21,010 movements the monkey makes subsequent to such a lesion? 293 00:16:21,010 --> 00:16:22,610 Are you ready for that? 294 00:16:22,610 --> 00:16:23,546 Here we are. 295 00:16:23,546 --> 00:16:24,420 It's the same monkey. 296 00:16:27,382 --> 00:16:28,965 You can see that his eye movements may 297 00:16:28,965 --> 00:16:32,750 be a little bit slower perhaps but he still looks to the left 298 00:16:32,750 --> 00:16:34,750 and to the right quite well. 299 00:16:37,200 --> 00:16:40,950 He tends to sort of look towards the side of the lesion when 300 00:16:40,950 --> 00:16:45,190 there's no stimulus OK, but other than that he seems 301 00:16:45,190 --> 00:16:49,340 to make really rather, rather good eye movement in spite 302 00:16:49,340 --> 00:16:52,410 of the fact that he has a colliculus missing on one side. 303 00:16:54,780 --> 00:17:01,130 So what that means is that just looking at what the monkey does 304 00:17:01,130 --> 00:17:04,390 in this qualitative manner is not 305 00:17:04,390 --> 00:17:10,640 going to tell you too much about what these various structures 306 00:17:10,640 --> 00:17:15,720 do and so consequently you have to carry out some more 307 00:17:15,720 --> 00:17:20,490 refined experiments to determine what kinds of deficits 308 00:17:20,490 --> 00:17:24,180 do arise when you take out the colliculus, you take out 309 00:17:24,180 --> 00:17:29,710 other cortical structures for the generation of eye movement. 310 00:17:29,710 --> 00:17:34,430 So let me first of all tell you about a really interesting 311 00:17:34,430 --> 00:17:38,550 finding that was made that had nothing 312 00:17:38,550 --> 00:17:40,890 to do with the colliculus at the time it was made, 313 00:17:40,890 --> 00:17:44,990 was a strictly behavioral study much of it done on humans. 314 00:17:44,990 --> 00:17:48,530 What was done is first of all a fixation spot came on 315 00:17:48,530 --> 00:17:50,990 and then a single target appeared 316 00:17:50,990 --> 00:17:54,050 and often what was done is that the fixation spot was turned 317 00:17:54,050 --> 00:17:59,560 off just a few milliseconds before the target came 318 00:17:59,560 --> 00:18:03,760 on and on each trial it appeared someplace else OK? 319 00:18:03,760 --> 00:18:07,010 So then you've collected a lot of data 320 00:18:07,010 --> 00:18:11,030 to see what is the nature of the monkey's eye movements 321 00:18:11,030 --> 00:18:17,210 and in particular that initial study examined by Fischer 322 00:18:17,210 --> 00:18:21,170 and Boch, examined what the latency distribution was 323 00:18:21,170 --> 00:18:23,710 of the eye movements made and they made 324 00:18:23,710 --> 00:18:26,990 an incredible discovery that they subsequently generated 325 00:18:26,990 --> 00:18:30,500 hundreds of studies published in numerous journals, 326 00:18:30,500 --> 00:18:32,850 and this is the discovery. 327 00:18:32,850 --> 00:18:36,320 Here we have the latency of saccades made 328 00:18:36,320 --> 00:18:38,840 and here's a number of saccades and what 329 00:18:38,840 --> 00:18:41,260 you get is a bimodal distribution 330 00:18:41,260 --> 00:18:44,380 of saccadic latencies, amazing. 331 00:18:44,380 --> 00:18:47,030 They call the first mode, which takes 332 00:18:47,030 --> 00:18:50,290 place in the latency of average latency for bright stimulus 333 00:18:50,290 --> 00:18:55,450 over about 100 milliseconds, called express saccades. 334 00:18:55,450 --> 00:18:58,380 The second mode they called regular saccades and that 335 00:18:58,380 --> 00:19:02,950 took about I don't know, 135, 140 milliseconds 336 00:19:02,950 --> 00:19:03,640 on the average. 337 00:19:04,800 --> 00:19:07,750 So that got this bimodal distribution 338 00:19:07,750 --> 00:19:12,670 and so people said, my goodness what could this be due to? 339 00:19:12,670 --> 00:19:14,540 How do we explain this effect? 340 00:19:14,540 --> 00:19:16,560 What other cortical or subcortical 341 00:19:16,560 --> 00:19:19,920 mechanisms that give rise to a bimodal distribution 342 00:19:19,920 --> 00:19:20,890 of saccadic latencies? 343 00:19:21,940 --> 00:19:24,360 As I've said a huge number of experiments 344 00:19:24,360 --> 00:19:27,440 had been carried out to find this out. 345 00:19:27,440 --> 00:19:30,800 So when one group of investigators 346 00:19:30,800 --> 00:19:33,986 saw this phenomenon and they did experiments 347 00:19:33,986 --> 00:19:35,360 with monkey's and they found this 348 00:19:35,360 --> 00:19:38,750 is a real effect everywhere, these findings were initially 349 00:19:38,750 --> 00:19:42,320 made in Germany and even, even in the United States 350 00:19:42,320 --> 00:19:44,430 you get a bimodal distribution of saccades 351 00:19:44,430 --> 00:19:46,830 in both humans and monkeys. 352 00:19:46,830 --> 00:19:52,500 So once it was established as a really solid effect 353 00:19:52,500 --> 00:19:56,080 people began to speculate as to what are the neural, 354 00:19:56,080 --> 00:19:57,040 underlying mechanisms? 355 00:19:58,580 --> 00:20:02,940 And as I've told you earlier it was 356 00:20:02,940 --> 00:20:11,580 noted that based on those lesion studies of the colliculus which 357 00:20:11,580 --> 00:20:15,540 eliminated saccades from the posterior portion of the cortex 358 00:20:15,540 --> 00:20:19,330 but not from the interior, that there 359 00:20:19,330 --> 00:20:24,940 is a reasonable hypothesis involved in proposing that you 360 00:20:24,940 --> 00:20:29,320 have a posterior system and an anterior system. 361 00:20:29,320 --> 00:20:32,220 And so when people saw this they said aha, 362 00:20:32,220 --> 00:20:34,990 now we know why we have these two systems. 363 00:20:34,990 --> 00:20:37,320 One is for making rapid saccades and the other 364 00:20:37,320 --> 00:20:39,380 is to making regular saccades. 365 00:20:39,380 --> 00:20:43,020 And so they proposed that the posterior system does 366 00:20:43,020 --> 00:20:47,060 one of these and the anterior system does the other. 367 00:20:47,060 --> 00:20:50,550 Well that was a nice hypothesis but so often 368 00:20:50,550 --> 00:20:55,020 when it comes to hypotheses as to how the brain works, 369 00:20:55,020 --> 00:20:59,270 often most of the time the hypotheses end up being wrong 370 00:20:59,270 --> 00:21:02,870 and so what you need to do rather than just hypothesize is 371 00:21:02,870 --> 00:21:05,290 to actually carry out experiments 372 00:21:05,290 --> 00:21:07,440 to test the hypothesis. 373 00:21:07,440 --> 00:21:10,540 So what is the test of this hypothesis? 374 00:21:10,540 --> 00:21:12,206 What would you do as an experimentalist? 375 00:21:15,400 --> 00:21:17,112 Well, yes. 376 00:21:19,036 --> 00:21:21,922 AUDIENCE: You could ablate either posterior 377 00:21:21,922 --> 00:21:23,860 or the anterior pathways. 378 00:21:23,860 --> 00:21:25,880 PROFESSOR: Very good you could ablate. 379 00:21:25,880 --> 00:21:27,660 All right so one thing you can do 380 00:21:27,660 --> 00:21:32,460 first of all you can ablate the superior colliculus even 381 00:21:32,460 --> 00:21:39,800 though when you saw that just with regular easy test just 382 00:21:39,800 --> 00:21:43,880 filming it, you didn't see much of a deficit. 383 00:21:43,880 --> 00:21:47,642 You sort of sense that maybe the monkey's a bit slower but other 384 00:21:47,642 --> 00:21:49,140 than that it wasn't that clear. 385 00:21:49,140 --> 00:21:51,110 But if you take out the colliculus 386 00:21:51,110 --> 00:21:55,170 then you eliminate the posterior system in essence all right, 387 00:21:55,170 --> 00:21:57,886 and so the question is what happens when you do that? 388 00:21:57,886 --> 00:21:59,260 And then you can ask the question 389 00:21:59,260 --> 00:22:02,760 what happens when you take out some other cortical areas? 390 00:22:02,760 --> 00:22:03,850 So let's look at this. 391 00:22:06,240 --> 00:22:11,880 Here we have a monkey 10 weeks after the colliculus has been 392 00:22:11,880 --> 00:22:14,510 ablated, we're talking about a major effect here 393 00:22:14,510 --> 00:22:17,640 that doesn't recover, and you took out 394 00:22:17,640 --> 00:22:21,090 the colliculus on one side on the left OK, 395 00:22:21,090 --> 00:22:23,910 so that controls rightward saccades 396 00:22:23,910 --> 00:22:26,920 and therefore when you look at the leftward saccades that's 397 00:22:26,920 --> 00:22:28,980 to the intact side of the brain you 398 00:22:28,980 --> 00:22:31,100 get the usual bimodal distribution 399 00:22:31,100 --> 00:22:32,810 of saccadic latencies. 400 00:22:32,810 --> 00:22:35,460 But then when you look at rightward saccades 401 00:22:35,460 --> 00:22:39,160 Lo and behold, you don't see a single express saccade 402 00:22:39,160 --> 00:22:40,660 and even the regular saccades have 403 00:22:40,660 --> 00:22:45,822 a longer latency than the ones to they intact side 404 00:22:45,822 --> 00:22:47,530 and these are collected at the same time. 405 00:22:47,530 --> 00:22:49,940 The monkey's sitting there with his head fixed 406 00:22:49,940 --> 00:22:51,740 and sometimes a target appears on the left 407 00:22:51,740 --> 00:22:54,960 sometimes on the right and you collect hundreds of thousands 408 00:22:54,960 --> 00:22:59,190 of trials that way and you test this over various time periods 409 00:22:59,190 --> 00:23:03,720 and this is at least 10 weeks, 2 and 1/2 months after the lesion 410 00:23:03,720 --> 00:23:05,950 and even if you test the monkey a year 411 00:23:05,950 --> 00:23:08,390 later you still get the same effect. 412 00:23:08,390 --> 00:23:11,100 So this clearly points out the fact 413 00:23:11,100 --> 00:23:15,400 that your ability to make these rapid reflex-like saccades 414 00:23:15,400 --> 00:23:19,980 is something that's got to go through the superior colliculus 415 00:23:19,980 --> 00:23:21,260 OK? 416 00:23:21,260 --> 00:23:25,090 So now we can ask the question, well, what about if one 417 00:23:25,090 --> 00:23:28,310 makes lesions in the frontal and medial eye fields? 418 00:23:28,310 --> 00:23:31,713 All right so think about that for a minute what would 419 00:23:31,713 --> 00:23:32,213 you predict? 420 00:23:35,710 --> 00:23:38,170 All right so here we go. 421 00:23:38,170 --> 00:23:41,110 We take out the frontal eye fields in this case, ready? 422 00:23:42,830 --> 00:23:44,400 Oops let me go back. 423 00:23:45,690 --> 00:23:47,390 We take out the frontal eye fields 424 00:23:47,390 --> 00:23:52,090 but to give you a sense of this overall effect first of all 425 00:23:52,090 --> 00:23:56,520 let's just do the same informal testing that I've shown you 426 00:23:56,520 --> 00:23:59,460 before with the colliculus and see 427 00:23:59,460 --> 00:24:01,600 what the movie looks like OK? 428 00:24:01,600 --> 00:24:04,660 Here's a monkey not as handsome as the other one, 429 00:24:04,660 --> 00:24:08,040 but what you do here is a person behind 430 00:24:08,040 --> 00:24:10,100 there sometimes just presents a target 431 00:24:10,100 --> 00:24:13,000 and sometimes just moves it around so the monkey tracks it, 432 00:24:13,000 --> 00:24:13,770 can you see that? 433 00:24:15,370 --> 00:24:17,566 And what I shouldn't have told you which one I feel 434 00:24:17,566 --> 00:24:18,315 have been ablated. 435 00:24:19,920 --> 00:24:26,490 Look at how nicely he tracks on both sides, 436 00:24:26,490 --> 00:24:29,040 grabs it, puts it in his, stuffs it in his mouth 437 00:24:29,040 --> 00:24:32,620 and so the monkey seems to be perfectly fine with making 438 00:24:32,620 --> 00:24:37,630 saccades to either side and perfectly fine making pursuit 439 00:24:37,630 --> 00:24:41,240 eye movements either direction, indicating 440 00:24:41,240 --> 00:24:45,740 that this informal testing doesn't reveal anything truly 441 00:24:45,740 --> 00:24:50,090 obvious about the deficit that you have in eye movement 442 00:24:50,090 --> 00:24:52,630 control when you take out the frontal eye fields. 443 00:24:52,630 --> 00:24:55,490 So therefore you again need to go on 444 00:24:55,490 --> 00:24:59,090 to carry out some more careful experiments 445 00:24:59,090 --> 00:25:03,320 to obtain some detailed quantitative data. 446 00:25:03,320 --> 00:25:05,380 So let's look at that. 447 00:25:05,380 --> 00:25:09,010 First of all let's go back and look at express saccades. 448 00:25:09,010 --> 00:25:11,670 You take out the frontal eye fields and Lo and behold, 449 00:25:11,670 --> 00:25:14,990 you still get express saccades indicating 450 00:25:14,990 --> 00:25:20,780 that that is definitely specific for the posterior system 451 00:25:20,780 --> 00:25:23,670 even further if you do this experiment what 452 00:25:23,670 --> 00:25:26,680 you find if you take out both the medial and frontal eye 453 00:25:26,680 --> 00:25:29,310 fields you still get it, you still 454 00:25:29,310 --> 00:25:31,130 get your express saccades. 455 00:25:31,130 --> 00:25:35,130 So clearly these two areas are not directly involved 456 00:25:35,130 --> 00:25:38,330 in generating quick rapid saccadic eye movements 457 00:25:38,330 --> 00:25:42,270 and it's still bimodal so that initial hypothesis 458 00:25:42,270 --> 00:25:44,290 that the first mode is the colliculus 459 00:25:44,290 --> 00:25:47,250 and the second posterior system the colliculus 460 00:25:47,250 --> 00:25:51,570 and the second mode is the anterior system 461 00:25:51,570 --> 00:25:52,990 is clearly totally wrong. 462 00:25:55,560 --> 00:25:57,430 All right so that's what then happens 463 00:25:57,430 --> 00:26:01,810 and once this has been done, you say, well, you've 464 00:26:01,810 --> 00:26:04,690 got to find something that the frontal eye and the medial eye 465 00:26:04,690 --> 00:26:05,450 fields are doing. 466 00:26:05,450 --> 00:26:08,330 So let's come up with some other experiments 467 00:26:08,330 --> 00:26:13,120 to see whether the monkey is selective for anything else 468 00:26:13,120 --> 00:26:16,610 when it comes to lesions of the frontal and the medial eye 469 00:26:16,610 --> 00:26:17,580 fields. 470 00:26:17,580 --> 00:26:22,460 All right so one thing that had been proposed 471 00:26:22,460 --> 00:26:27,070 is that maybe the important factor is some high level eye 472 00:26:27,070 --> 00:26:32,130 movement activity such as making saccades in quick succession 473 00:26:32,130 --> 00:26:35,870 to successive targets that are out there OK? 474 00:26:35,870 --> 00:26:38,760 So the way that can be done quantitatively 475 00:26:38,760 --> 00:26:41,790 is you have the monkey first fixate OK, 476 00:26:41,790 --> 00:26:45,220 and after they fixate you present the target 477 00:26:45,220 --> 00:26:47,310 and then you present the second target. 478 00:26:47,310 --> 00:26:50,330 So the monkey has to make two successive saccades 479 00:26:50,330 --> 00:26:52,670 and what you can do is you can vary 480 00:26:52,670 --> 00:26:56,900 the temporal delay between their succession. 481 00:26:56,900 --> 00:27:02,540 So the monkey then has to make a plan to makes two saccades 482 00:27:02,540 --> 00:27:05,820 because these two stimuli appear before the monkey starts 483 00:27:05,820 --> 00:27:09,130 his initial saccade when the temporal interval is short. 484 00:27:09,130 --> 00:27:11,420 So then the monkey somehow knows it's easier 485 00:27:11,420 --> 00:27:15,840 to do, he has to do this even though he starts a saccade only 486 00:27:15,840 --> 00:27:19,740 after the two targets have come on when they are presented 487 00:27:19,740 --> 00:27:22,810 indeed in the short, the short latency. 488 00:27:22,810 --> 00:27:25,900 So that's what happens and of course in different trials 489 00:27:25,900 --> 00:27:28,560 you have different kinds of pairings like that 490 00:27:28,560 --> 00:27:31,115 and if you do that what you find is very interesting 491 00:27:31,115 --> 00:27:33,250 here are the four conditions, this 492 00:27:33,250 --> 00:27:37,650 shows the monkey's performance 18 weeks post 493 00:27:37,650 --> 00:27:39,890 left frontal eye field lesion and this shows it 494 00:27:39,890 --> 00:27:44,420 60 weeks after and it shows this to the intact side 495 00:27:44,420 --> 00:27:47,160 and the side where the frontal eye fields are missing 496 00:27:47,160 --> 00:27:49,240 and what you can see very dramatically 497 00:27:49,240 --> 00:27:52,540 is that the monkey really has difficulties 498 00:27:52,540 --> 00:27:58,820 in making a plan to execute two saccades in a row. 499 00:27:58,820 --> 00:28:02,880 Quite dramatic effect significant [INAUDIBLE] one 500 00:28:02,880 --> 00:28:06,970 level, of course indicating that the frontal eye fields 501 00:28:06,970 --> 00:28:10,750 play a role in planning sequences of eye movements. 502 00:28:10,750 --> 00:28:15,860 Now then another, well this I want to show you, 503 00:28:15,860 --> 00:28:19,560 what happens with the, when you compare 504 00:28:19,560 --> 00:28:21,770 the effects of the frontal eye field 505 00:28:21,770 --> 00:28:24,510 lesions and the medial eye field lesion 506 00:28:24,510 --> 00:28:29,210 and this is done over various sequence durations 507 00:28:29,210 --> 00:28:35,030 and for several weeks and what you find is that in both cases 508 00:28:35,030 --> 00:28:38,170 there is a recovery but the effect 509 00:28:38,170 --> 00:28:41,600 is much, much more dramatic with the frontal eye field lesion 510 00:28:41,600 --> 00:28:43,540 than a medial eye field lesion. 511 00:28:44,840 --> 00:28:47,640 So indeed there's for the frontal eye 512 00:28:47,640 --> 00:28:50,080 fields we can say the frontal eye fields play 513 00:28:50,080 --> 00:28:53,680 an important role in planning sequences of eye movements 514 00:28:53,680 --> 00:28:58,440 which is sort of a high level activity in executing 515 00:28:58,440 --> 00:29:00,110 saccadic eye movements. 516 00:29:00,110 --> 00:29:06,070 Now then what we can do is to examine what 517 00:29:06,070 --> 00:29:10,840 about making a decision of where to look when 518 00:29:10,840 --> 00:29:14,020 more than one target comes up and the simplest form of that 519 00:29:14,020 --> 00:29:17,769 is that you present two targets like that OK? 520 00:29:17,769 --> 00:29:19,560 And so the monkey has to make a decision am 521 00:29:19,560 --> 00:29:21,970 I going to look to the left or to the right? 522 00:29:21,970 --> 00:29:24,240 And then what you do is you can vary 523 00:29:24,240 --> 00:29:32,510 the temporal delay between the two like that, or like that OK? 524 00:29:32,510 --> 00:29:35,350 And then you can do that again either to intact 525 00:29:35,350 --> 00:29:37,180 parts of the visual field or those 526 00:29:37,180 --> 00:29:40,470 where either frontal eye fields or some other structure 527 00:29:40,470 --> 00:29:41,450 is missing. 528 00:29:41,450 --> 00:29:43,710 All right so let's look at what happens. 529 00:29:43,710 --> 00:29:46,620 Here is what we have is the intact monkey 530 00:29:46,620 --> 00:29:49,020 this part I've shown you before. 531 00:29:49,020 --> 00:29:51,970 All right this is when the two targets come 532 00:29:51,970 --> 00:29:55,330 on simultaneously and in this case 533 00:29:55,330 --> 00:29:58,550 the left target comes on 34 milliseconds before the right 534 00:29:58,550 --> 00:30:00,360 and here's the reverse and what you 535 00:30:00,360 --> 00:30:04,010 can see that even a 34 millisecond delay causes 536 00:30:04,010 --> 00:30:08,840 the monkey to very much prefer to go to the, to the target, 537 00:30:08,840 --> 00:30:13,090 make a saccade to the target that had appeared first. 538 00:30:13,090 --> 00:30:16,620 So that's what happens in a normal intact monkey. 539 00:30:16,620 --> 00:30:20,680 Now we can ask the next related questions still 540 00:30:20,680 --> 00:30:22,350 in the normal intact monkey, what 541 00:30:22,350 --> 00:30:24,870 happens when you put the two stimuli closer together? 542 00:30:25,900 --> 00:30:29,010 OK so here's an example they're, now they're separated only 543 00:30:29,010 --> 00:30:32,630 by 40 degrees and here the data again it 544 00:30:32,630 --> 00:30:37,530 shows that when it's, in this case 67 milliseconds apart 545 00:30:37,530 --> 00:30:39,700 the monkey chooses almost exclusively 546 00:30:39,700 --> 00:30:41,640 the target that comes on first. 547 00:30:41,640 --> 00:30:45,270 When they're simultaneous what happens is interesting, 548 00:30:45,270 --> 00:30:47,980 you get some so-called vector average saccades 549 00:30:47,980 --> 00:30:50,870 that you always get with electrical stimulation. 550 00:30:50,870 --> 00:30:54,140 So those you get, it's still a minority of the saccades. 551 00:30:54,140 --> 00:30:56,530 And the closer you bring the two together, 552 00:30:56,530 --> 00:30:59,480 the more frequent will be the vector average saccades. 553 00:30:59,480 --> 00:31:02,440 When they're only separated by set 10 degrees 554 00:31:02,440 --> 00:31:04,960 they will be all vector average saccades So this 555 00:31:04,960 --> 00:31:08,900 is what happens in the normal monkey you 556 00:31:08,900 --> 00:31:12,168 get this nice bimodal distribution and vector 557 00:31:12,168 --> 00:31:14,126 average saccades when the two are simultaneous. 558 00:31:15,290 --> 00:31:19,370 Now let's ask the question what happens when you take out 559 00:31:19,370 --> 00:31:23,360 a cortical structure in this case the frontal eye fields 560 00:31:23,360 --> 00:31:26,930 and here we are you take out the left frontal eye fields. 561 00:31:26,930 --> 00:31:30,280 These above are the same the data I just shown you 562 00:31:30,280 --> 00:31:35,190 adding a bigger delay here, just to make it even clearer that 563 00:31:35,190 --> 00:31:37,590 by that time the monkey never chooses 564 00:31:37,590 --> 00:31:39,180 the target that comes on second. 565 00:31:40,530 --> 00:31:45,690 And here we have the monkey after left frontal eye field 566 00:31:45,690 --> 00:31:48,300 lesion and look at what, what happens. 567 00:31:48,300 --> 00:31:52,000 What happens is that the monkey at 0 568 00:31:52,000 --> 00:31:56,790 chooses 100% saccade to the intact side OK. 569 00:31:56,790 --> 00:31:59,860 There seem to be a little bit of a shift here 570 00:31:59,860 --> 00:32:02,870 and then when they're 100 milliseconds, 571 00:32:02,870 --> 00:32:04,370 then you have an equal distribution. 572 00:32:05,420 --> 00:32:09,980 So to equalize the choice that the brain makes 573 00:32:09,980 --> 00:32:13,170 you have to now because of the missing frontal eye fields, 574 00:32:13,170 --> 00:32:18,950 present one of the targets a 100 milliseconds earlier 575 00:32:18,950 --> 00:32:23,500 on the affected side to get the same kind of distribution 576 00:32:23,500 --> 00:32:25,560 that you get in the intact monkey. 577 00:32:25,560 --> 00:32:27,870 So this further highlights the fact 578 00:32:27,870 --> 00:32:32,660 that the frontal eye fields play a significant role 579 00:32:32,660 --> 00:32:40,595 in making decisions about the selection of visual targets. 580 00:32:42,350 --> 00:32:46,260 All right now we can look at this more quantitatively. 581 00:32:46,260 --> 00:32:54,270 This shows the distribution of choices OK, to the left target, 582 00:32:54,270 --> 00:32:56,702 this is the intact monkey preoperative 583 00:32:56,702 --> 00:32:58,660 and then when you take out the left frontal eye 584 00:32:58,660 --> 00:33:03,670 fields it's a huge movement over the equal choices 585 00:33:03,670 --> 00:33:08,420 has to be about 130 milliseconds separated 586 00:33:08,420 --> 00:33:11,590 with the affected side getting the target a 130 milliseconds 587 00:33:11,590 --> 00:33:12,330 earlier. 588 00:33:12,330 --> 00:33:15,690 Then if you keep doing this there's some recovery 589 00:33:15,690 --> 00:33:19,795 but even four years later you still have a huge effect. 590 00:33:21,320 --> 00:33:23,220 Now you can ask the question what 591 00:33:23,220 --> 00:33:26,750 if you do the same experiment in the medial eye fields? 592 00:33:26,750 --> 00:33:29,600 And so if you do that you first of all get a small effect 593 00:33:29,600 --> 00:33:34,600 to begin with and after just 16 weeks there's full recovery. 594 00:33:34,600 --> 00:33:36,780 So obviously the medial eye fields 595 00:33:36,780 --> 00:33:40,710 don't, do not seem to play a central role 596 00:33:40,710 --> 00:33:44,140 in making decisions as to which target 597 00:33:44,140 --> 00:33:45,980 to look at when more than one target appears 598 00:33:45,980 --> 00:33:47,490 in the visual field. 599 00:33:47,490 --> 00:33:52,620 All right so now having done that quantitative work 600 00:33:52,620 --> 00:33:54,990 indicating that the frontal eye fields play 601 00:33:54,990 --> 00:33:57,070 an important role in target selection 602 00:33:57,070 --> 00:33:59,450 and the sequencing of eye movements. 603 00:33:59,450 --> 00:34:01,150 We can move on and ask the question, 604 00:34:01,150 --> 00:34:04,690 well we talked about the posterior 605 00:34:04,690 --> 00:34:06,775 system and the anterior system. 606 00:34:09,070 --> 00:34:12,500 Is it true that there are these two systems? 607 00:34:12,500 --> 00:34:16,110 Or are there many more systems that we're not aware of? 608 00:34:17,400 --> 00:34:20,214 This should remind you of the fact 609 00:34:20,214 --> 00:34:21,880 that it had been proposed when we talked 610 00:34:21,880 --> 00:34:26,510 about extrastriate cortex that area of V4 611 00:34:26,510 --> 00:34:36,020 essential for processing high level activity including color, 612 00:34:36,020 --> 00:34:42,340 whereas the area MT and MST play an important role in emotion 613 00:34:42,340 --> 00:34:44,380 and so it was purported that these two 614 00:34:44,380 --> 00:34:48,139 major systems in the posterior cortex, the medial and lateral 615 00:34:48,139 --> 00:34:48,909 if you will. 616 00:34:51,290 --> 00:34:55,080 So the question was raised if you remove both of these areas, 617 00:34:55,080 --> 00:35:03,190 meaning the gateway to these areas, V4 and MT what happens? 618 00:35:03,190 --> 00:35:05,970 And when you do that they still the monkey's 619 00:35:05,970 --> 00:35:09,830 able to do a lot of things indicating that we have more 620 00:35:09,830 --> 00:35:15,690 pathways from V1 than just these two the anterior, the medial 621 00:35:15,690 --> 00:35:16,750 and the lateral. 622 00:35:16,750 --> 00:35:18,590 So now the question is what about when 623 00:35:18,590 --> 00:35:20,250 it comes to this eye movement control? 624 00:35:21,972 --> 00:35:23,680 We should do the same kind of experiment. 625 00:35:25,180 --> 00:35:28,850 We should remove the colliculus that supposedly eliminates 626 00:35:28,850 --> 00:35:32,380 the posterior system and then we should remove the frontal eye 627 00:35:32,380 --> 00:35:37,190 fields bilaterally, that eliminates the anterior system. 628 00:35:37,190 --> 00:35:41,580 So now the question is what happens when you do that? 629 00:35:41,580 --> 00:35:44,810 And again, we going to turn to the informal test, 630 00:35:44,810 --> 00:35:46,880 meaning we going to, we going to take 631 00:35:46,880 --> 00:35:51,674 a movie of the monkey who has these areas removed. 632 00:35:51,674 --> 00:35:54,340 Think about it for a minute what do you think's going to happen? 633 00:35:56,630 --> 00:35:58,280 OK so here's the monkey. 634 00:35:58,280 --> 00:35:58,780 Ready? 635 00:36:06,780 --> 00:36:15,700 The monkey sees well, he makes his movements with his hands 636 00:36:15,700 --> 00:36:19,940 quite accurately but what, what happens to the eyes, 637 00:36:19,940 --> 00:36:21,310 you watching the eyes right? 638 00:36:22,350 --> 00:36:23,055 No eye movement. 639 00:36:24,110 --> 00:36:25,152 Everybody see this? 640 00:36:25,152 --> 00:36:26,110 Should I show it again? 641 00:36:31,150 --> 00:36:33,090 The monkey makes no eye movements. 642 00:36:33,090 --> 00:36:36,260 He cannot make eye movements because his natural tendency 643 00:36:36,260 --> 00:36:38,930 would be just like I'd seen in the previous movies that he 644 00:36:38,930 --> 00:36:45,260 makes eye movements to the apple pieces so he can grab them. 645 00:36:45,260 --> 00:36:47,440 He still pays attention to them everything 646 00:36:47,440 --> 00:36:51,520 is fine except he doesn't move his eyes because he can't move 647 00:36:51,520 --> 00:36:54,630 his eyes as a result of having eliminated these two 648 00:36:54,630 --> 00:36:57,500 systems and because of that we can say 649 00:36:57,500 --> 00:37:02,400 with confidence that it's, as far as the visual as far 650 00:37:02,400 --> 00:37:06,300 as the ocular motor system is concerned we indeed have 651 00:37:06,300 --> 00:37:10,630 these two major pathways which when they're eliminated 652 00:37:10,630 --> 00:37:13,690 eliminates their ability to move, 653 00:37:13,690 --> 00:37:15,670 make saccadic eye movements. 654 00:37:15,670 --> 00:37:22,530 OK now let's go back to the effect 655 00:37:22,530 --> 00:37:29,130 of electrical stimulation to gain further insight about what 656 00:37:29,130 --> 00:37:31,310 these various areas do and what you 657 00:37:31,310 --> 00:37:34,160 can do in these experiments is not only 658 00:37:34,160 --> 00:37:37,990 to stimulate at a high level to elicit a saccade 659 00:37:37,990 --> 00:37:41,820 but you can simulate at a lower level 660 00:37:41,820 --> 00:37:46,540 and then pair that with the appearance of a visual target. 661 00:37:46,540 --> 00:37:51,610 This then enables you to see whether there's summation here 662 00:37:51,610 --> 00:37:54,720 or if there's interference, so let's look at that. 663 00:37:55,940 --> 00:37:58,240 All right here is again a monkey brain 664 00:37:58,240 --> 00:38:00,970 and what I'm going to tell you is what happens when you 665 00:38:00,970 --> 00:38:04,980 do this experiment in V1, in LIP, and in the frontal eye 666 00:38:04,980 --> 00:38:08,310 fields, even maybe I think I may have something 667 00:38:08,310 --> 00:38:09,900 also in the medial eye fields. 668 00:38:09,900 --> 00:38:13,640 All right so let me describe the experimental procedure for you 669 00:38:13,640 --> 00:38:16,060 so that you understand how these kinds of experiments 670 00:38:16,060 --> 00:38:17,280 are conducted. 671 00:38:17,280 --> 00:38:20,370 You put an electrode in to any of these structures 672 00:38:20,370 --> 00:38:23,050 and you find the receptive field first all right? 673 00:38:23,050 --> 00:38:26,200 Once you've found the receptive field you electrically 674 00:38:26,200 --> 00:38:28,610 stimulate then you confirm the fact 675 00:38:28,610 --> 00:38:33,020 that the electrical stimulation brings the fovea 676 00:38:33,020 --> 00:38:36,990 into the receptive field of the simulated neuron's when 677 00:38:36,990 --> 00:38:40,000 you do this in all the areas except in the medial eye 678 00:38:40,000 --> 00:38:40,770 fields. 679 00:38:40,770 --> 00:38:45,690 Then what you do is you actually present the visual target there 680 00:38:45,690 --> 00:38:46,560 OK? 681 00:38:46,560 --> 00:38:51,830 And lastly you present two visual targets 682 00:38:51,830 --> 00:38:54,180 and you electrically stimulate to see 683 00:38:54,180 --> 00:38:58,920 how it biases your choice as a result of this 684 00:38:58,920 --> 00:39:02,570 in most cases sub-threshold electrical stimulation. 685 00:39:02,570 --> 00:39:06,490 So if you do that what you find is, first of all, 686 00:39:06,490 --> 00:39:09,740 if you do this experiment with a intact monkey 687 00:39:09,740 --> 00:39:15,400 without stimulation you find say a receptive field here 688 00:39:15,400 --> 00:39:19,110 and then you simply see what the monkey's choices are left 689 00:39:19,110 --> 00:39:21,920 to the right and what you plot here 690 00:39:21,920 --> 00:39:25,979 is the saccades made to the target in the receptive field 691 00:39:25,979 --> 00:39:27,770 and what you can see is what I've shown you 692 00:39:27,770 --> 00:39:31,380 before namely when the targets are simultaneous then 693 00:39:31,380 --> 00:39:34,440 the monkey chooses left or right with equal probability. 694 00:39:35,640 --> 00:39:38,625 Now we're going to add the electrical stimulation 695 00:39:38,625 --> 00:39:42,960 and ask the question can we shift the curve to the left? 696 00:39:42,960 --> 00:39:44,940 If you shift it to the left, that 697 00:39:44,940 --> 00:39:47,780 means that the electrical stimulation facilitated 698 00:39:47,780 --> 00:39:52,020 the choice and if you shift to the right it means that it 699 00:39:52,020 --> 00:39:55,470 caused interference, it lessened the chances 700 00:39:55,470 --> 00:39:57,560 of the monkey making a saccade into that area, 701 00:39:57,560 --> 00:40:00,540 meaning the stimulation created inhibition. 702 00:40:00,540 --> 00:40:01,570 Got it? 703 00:40:01,570 --> 00:40:04,580 All right, so here's an example in the lower 704 00:40:04,580 --> 00:40:09,980 layers of V1 remember in layer six of area 705 00:40:09,980 --> 00:40:14,740 V1 is where you have your complex cells that project down 706 00:40:14,740 --> 00:40:16,070 to the superior colliculus. 707 00:40:16,070 --> 00:40:19,590 So here if you stimulate at sub-threshold levels and some 708 00:40:19,590 --> 00:40:23,220 of these are very low levels only 7 1/2 and 10 microamps. 709 00:40:23,220 --> 00:40:26,180 OK, really very, very fine currents 710 00:40:26,180 --> 00:40:28,710 using themselves going to elicit an eye movement. 711 00:40:28,710 --> 00:40:32,400 So if you do that the stimulation created 712 00:40:32,400 --> 00:40:35,450 a significant, highly significant facilitatory 713 00:40:35,450 --> 00:40:36,050 affect. 714 00:40:36,050 --> 00:40:38,070 This is in the lower layers. 715 00:40:38,070 --> 00:40:41,730 Now if you do the same experiment in the upper layers 716 00:40:41,730 --> 00:40:45,800 you get the opposite effect we get a gigantic even-- look 717 00:40:45,800 --> 00:40:50,670 at this five and 10 microamps, --even at that low, incredibly 718 00:40:50,670 --> 00:40:54,220 low level you get a gigantic interference effect. 719 00:40:54,220 --> 00:40:59,660 So that says that there's a complex interplay in V1 720 00:40:59,660 --> 00:41:02,700 in the decision process that arises 721 00:41:02,700 --> 00:41:04,785 as to whether you're going to look at a target, 722 00:41:04,785 --> 00:41:07,250 or whether you're not going to look at a target. 723 00:41:07,250 --> 00:41:10,230 Now we can do the same experiment in LIP 724 00:41:10,230 --> 00:41:13,550 and in some regions you get this huge facilitatory effect 725 00:41:13,550 --> 00:41:16,470 and in other regions you get an inhibitory effect, 726 00:41:16,470 --> 00:41:17,890 so that's LIP. 727 00:41:17,890 --> 00:41:21,850 So therefore this structure also plays a significant role 728 00:41:21,850 --> 00:41:24,720 in deciding whether to look at or not 729 00:41:24,720 --> 00:41:27,970 to look at a visual stimulus and here it 730 00:41:27,970 --> 00:41:31,930 shows that in LIP as you increase the current 731 00:41:31,930 --> 00:41:35,430 you get a gigantic increase in the latency 732 00:41:35,430 --> 00:41:38,330 in these inhibitory areas with which 733 00:41:38,330 --> 00:41:42,360 a saccade can be generated indicating that LIP plays 734 00:41:42,360 --> 00:41:45,552 an important role in whether you're 735 00:41:45,552 --> 00:41:47,510 going to look at a target or whether you're not 736 00:41:47,510 --> 00:41:48,860 going to look at target. 737 00:41:48,860 --> 00:41:51,560 OK and then if you do the frontal eye fields 738 00:41:51,560 --> 00:41:53,370 everywhere in the frontal eye fields 739 00:41:53,370 --> 00:41:56,830 you get a huge facilitatory effect 740 00:41:56,830 --> 00:42:03,560 and in the medial eye fields you also get a facilitatory effect 741 00:42:03,560 --> 00:42:08,170 as long as the motor field is where 742 00:42:08,170 --> 00:42:09,410 the visual target appears. 743 00:42:10,540 --> 00:42:13,510 But now you can remember what I told you about the medial eye 744 00:42:13,510 --> 00:42:17,390 fields the fact is that they have a place code. 745 00:42:17,390 --> 00:42:19,710 So one can do a different experiment 746 00:42:19,710 --> 00:42:26,170 in which instead of presenting the target in the motor field 747 00:42:26,170 --> 00:42:34,780 you can present the fixation spot there. 748 00:42:34,780 --> 00:42:39,030 So here again to remind you, we have this place code. 749 00:42:39,030 --> 00:42:41,550 So now we do this experiment, just 750 00:42:41,550 --> 00:42:44,040 like what I've shown you before just to repeat it, 751 00:42:44,040 --> 00:42:49,320 in this case the target appears and that causes a facilitation 752 00:42:49,320 --> 00:42:52,660 in this case we put the fixation spot in there 753 00:42:52,660 --> 00:42:56,720 and the location of the target's just displaced 754 00:42:56,720 --> 00:42:59,620 and when you do that you get a huge inhibitory 755 00:42:59,620 --> 00:43:04,700 effect because somehow the electrical stimulation forces 756 00:43:04,700 --> 00:43:10,300 the animal keep the eye at the location where the motor 757 00:43:10,300 --> 00:43:13,870 field is in the medial eye fields 758 00:43:13,870 --> 00:43:16,410 and this is a very important point 759 00:43:16,410 --> 00:43:20,710 and it means that the medial eye fields plays a significant role 760 00:43:20,710 --> 00:43:23,940 in deciding how long to look at a target 761 00:43:23,940 --> 00:43:25,550 before making the next saccade. 762 00:43:27,940 --> 00:43:32,410 OK so now we going to, there's a lot of facts, so 763 00:43:32,410 --> 00:43:34,580 and you're going to get some more lot of facts. 764 00:43:34,580 --> 00:43:36,530 So now I'm going to summarize what I told you 765 00:43:36,530 --> 00:43:39,220 about the effects of sub-threshold electrical 766 00:43:39,220 --> 00:43:41,080 stimulation OK? 767 00:43:41,080 --> 00:43:44,560 If you stimulate in the upper layers of V1 and V2, 768 00:43:44,560 --> 00:43:47,490 V2 I should add to this you get interference, 769 00:43:47,490 --> 00:43:51,760 in the lower layers you get facilitation in V4 there was 770 00:43:51,760 --> 00:43:55,910 no effect I didn't talk about that before in LIP you can get 771 00:43:55,910 --> 00:43:59,950 both facilitation interference and also fixation increase. 772 00:43:59,950 --> 00:44:02,720 In the frontal eye fields you get facilitation 773 00:44:02,720 --> 00:44:04,880 and the medial eye fields depending 774 00:44:04,880 --> 00:44:07,840 on how you set it up you can get facilitation 775 00:44:07,840 --> 00:44:12,010 if the target appears in the motor field 776 00:44:12,010 --> 00:44:16,910 and you get inhibition when it appear, 777 00:44:16,910 --> 00:44:19,550 when the fixation spot appears in it. 778 00:44:19,550 --> 00:44:23,850 So that's the basic summary of these effects. 779 00:44:23,850 --> 00:44:29,130 Now what these findings indicate that somehow 780 00:44:29,130 --> 00:44:34,670 inhibitory circuits are essential in our ability 781 00:44:34,670 --> 00:44:38,960 to make saccades to selected visual targets 782 00:44:38,960 --> 00:44:41,700 and therefore what we want to do is 783 00:44:41,700 --> 00:44:45,070 to examine what happens when you use 784 00:44:45,070 --> 00:44:48,490 various kinds of pharmacological agents 785 00:44:48,490 --> 00:44:56,720 that either facilitate or increase inhibition. 786 00:44:56,720 --> 00:45:01,760 So to explain that then let me first of all point out to you 787 00:45:01,760 --> 00:45:04,340 that if you take again the whole brain 788 00:45:04,340 --> 00:45:08,180 and you look at the colliculus and you look at V1, 789 00:45:08,180 --> 00:45:11,140 you look at LIP, you look at the frontal eye fields 790 00:45:11,140 --> 00:45:15,150 you can study these areas by injecting 791 00:45:15,150 --> 00:45:16,990 two kinds of pharmacological agents, 792 00:45:16,990 --> 00:45:20,190 bicuculline and muscimol some people believe 793 00:45:20,190 --> 00:45:23,870 you've heard of this as muscimol I call it muscimol. 794 00:45:23,870 --> 00:45:25,850 At any rate you all know I'm sure 795 00:45:25,850 --> 00:45:30,500 but this is bicuculline is a GABA antagonist meaning 796 00:45:30,500 --> 00:45:35,840 that if you inject it OK, it stops 797 00:45:35,840 --> 00:45:39,390 the effectiveness of inhibition by GABA. 798 00:45:39,390 --> 00:45:42,230 Muscimol on the other hand is a GABA agonist 799 00:45:42,230 --> 00:45:44,720 meaning that if you inject it you 800 00:45:44,720 --> 00:45:47,740 increase inhibition all right? 801 00:45:47,740 --> 00:45:50,440 Now I'm sure that all of you must 802 00:45:50,440 --> 00:45:55,250 have had enough of a background in biochemistry 803 00:45:55,250 --> 00:45:57,230 to know what these two agents are. 804 00:46:01,740 --> 00:46:07,840 So now what we can do is we can inject 805 00:46:07,840 --> 00:46:13,840 either one or the other of these agents and assess two things. 806 00:46:13,840 --> 00:46:15,580 First off we assess eye movements 807 00:46:15,580 --> 00:46:18,090 and secondly we also have to obviously assess 808 00:46:18,090 --> 00:46:19,910 how it affects your visual ability. 809 00:46:21,010 --> 00:46:23,450 So let's move on and do this. 810 00:46:25,270 --> 00:46:28,200 The first set of experiments done with this 811 00:46:28,200 --> 00:46:31,640 was by Hikosaka and Woods many years ago in the colliculus. 812 00:46:34,280 --> 00:46:38,100 So what they did, very clever beautiful experiment, 813 00:46:38,100 --> 00:46:42,180 is that they would put a microelectrode 814 00:46:42,180 --> 00:46:45,640 into the colliculus and then initially just stimulate 815 00:46:45,640 --> 00:46:48,590 to see what kind of eye movement you get and then they 816 00:46:48,590 --> 00:46:54,580 would inject either muscimol or what's the other agent? 817 00:46:56,302 --> 00:46:57,270 AUDIENCE: [INAUDIBLE] 818 00:46:57,270 --> 00:47:00,090 PROFESSOR: Very good and see what happens. 819 00:47:00,090 --> 00:47:02,355 Now which of those causes more inhibition? 820 00:47:03,590 --> 00:47:04,530 AUDIENCE: [INAUDIBLE] 821 00:47:09,230 --> 00:47:13,190 PROFESSOR: OK, so let's look at that then. 822 00:47:13,190 --> 00:47:15,550 If you electrically stimulate just like I've shown you 823 00:47:15,550 --> 00:47:19,100 before you get a constant vector saccade no matter 824 00:47:19,100 --> 00:47:21,585 where the eye starts you get the same vector. 825 00:47:22,620 --> 00:47:25,630 Now the question is what happens to the spontaneous eye 826 00:47:25,630 --> 00:47:32,300 movements of the monkey when you first inject muscimol OK? 827 00:47:32,300 --> 00:47:37,220 Which is an agent that mimics if you will your GABA, 828 00:47:37,220 --> 00:47:40,050 meaning it increases inhibition and what happens 829 00:47:40,050 --> 00:47:43,010 is that the monkey hardly ever makes a saccade 830 00:47:43,010 --> 00:47:46,170 with the vectors represented by the area that 831 00:47:46,170 --> 00:47:47,640 has been injected. 832 00:47:47,640 --> 00:47:52,280 By contrast if you inject bicuculline 833 00:47:52,280 --> 00:47:56,790 the monkey keeps making saccades with that vector even when 834 00:47:56,790 --> 00:47:59,330 there's nothing out there like the release of area 835 00:47:59,330 --> 00:48:00,530 for inhibition. 836 00:48:00,530 --> 00:48:03,070 And the signal is sent down to the brain step move your eye, 837 00:48:03,070 --> 00:48:05,230 move your eye, move your eye, move your eye, 838 00:48:05,230 --> 00:48:06,530 that's what happens. 839 00:48:06,530 --> 00:48:12,860 So to show this in more detail then 840 00:48:12,860 --> 00:48:18,140 we can ask what happens when you use two behavioral tasks OK, 841 00:48:18,140 --> 00:48:20,140 the so-called paired target task that we already 842 00:48:20,140 --> 00:48:22,740 talked about quite a bit and you talk 843 00:48:22,740 --> 00:48:25,540 about a visual discrimination task 844 00:48:25,540 --> 00:48:27,380 and that one is that you're already 845 00:48:27,380 --> 00:48:30,470 familiar with the so-called audited task you present 846 00:48:30,470 --> 00:48:34,340 several stimuli one of which is different from the others. 847 00:48:34,340 --> 00:48:38,580 All right so here is an example of the paired target task. 848 00:48:38,580 --> 00:48:41,740 What we do here again we vary the temporal asynchrony 849 00:48:41,740 --> 00:48:43,340 between the two targets just like what 850 00:48:43,340 --> 00:48:45,320 I've shown with the electrical stimulation 851 00:48:45,320 --> 00:48:47,940 and this is the monkey's normal behavior when the two 852 00:48:47,940 --> 00:48:53,190 targets are simultaneous the monkey chooses each randomly. 853 00:48:54,440 --> 00:48:59,050 Now let's ask the question what happens is again to remind you, 854 00:48:59,050 --> 00:49:02,290 if it goes this way the curve goes this way it's facilitation 855 00:49:02,290 --> 00:49:05,620 if the current curve goes that way we get interference. 856 00:49:05,620 --> 00:49:09,520 So let's ask what happens first of all, no let me also tell you 857 00:49:09,520 --> 00:49:12,760 about the oddity task just to make sure that you have it. 858 00:49:12,760 --> 00:49:16,020 All right that's the oddity task you know that already. 859 00:49:16,020 --> 00:49:19,520 All right so we can now go on and first examine 860 00:49:19,520 --> 00:49:22,790 what happens with muscimol or muscimol 861 00:49:22,790 --> 00:49:25,120 or whatever you prefer to use OK? 862 00:49:25,120 --> 00:49:27,651 Well again what, what does this agent do? 863 00:49:27,651 --> 00:49:29,150 Does it do excitation or inhibition? 864 00:49:30,314 --> 00:49:31,610 AUDIENCE: Inhibition. 865 00:49:31,610 --> 00:49:35,710 PROFESSOR: Very good, inhibition because it mimics GABA 866 00:49:35,710 --> 00:49:36,430 all right? 867 00:49:36,430 --> 00:49:38,120 So let's look at what happens. 868 00:49:38,120 --> 00:49:41,300 Here we have a normal monkey same experiment 869 00:49:41,300 --> 00:49:45,980 as before, here is the this is V1, 870 00:49:45,980 --> 00:49:48,880 here's a receptive field you present one visual target 871 00:49:48,880 --> 00:49:51,760 there, the other there, then you vary the temporary asynchrony 872 00:49:51,760 --> 00:49:56,330 between them, this is what happens in the normal case OK? 873 00:49:56,330 --> 00:50:00,120 Now you're going to inject the muscimol 874 00:50:00,120 --> 00:50:01,800 and ask yourself the question, we 875 00:50:01,800 --> 00:50:04,490 increased inhibition what do you think is going to happen? 876 00:50:04,490 --> 00:50:06,100 Well it should be pretty obvious, 877 00:50:06,100 --> 00:50:09,120 what happens is you get gigantic inhibition 878 00:50:09,120 --> 00:50:11,190 the monkey practically never looks 879 00:50:11,190 --> 00:50:14,880 at here because that area is not being activated 880 00:50:14,880 --> 00:50:18,690 by the visual stimulus because of the inhibition. 881 00:50:18,690 --> 00:50:22,520 Then if you do this over time, even four hours later there's 882 00:50:22,520 --> 00:50:24,790 a huge, huge effect but by the next day 883 00:50:24,790 --> 00:50:28,690 the monkey recovers luckily so one can do this experiment 884 00:50:28,690 --> 00:50:31,860 several times because this agent is something 885 00:50:31,860 --> 00:50:33,780 that washes out of the brain. 886 00:50:33,780 --> 00:50:36,870 All right so now let's look at what 887 00:50:36,870 --> 00:50:38,780 happens in the frontal eye fields. 888 00:50:38,780 --> 00:50:42,560 Same experiment, all right, just a different location 889 00:50:42,560 --> 00:50:43,597 with the electrode. 890 00:50:43,597 --> 00:50:45,430 And what you get, this is your preinjection. 891 00:50:46,510 --> 00:50:49,970 And once again, after the injection, 892 00:50:49,970 --> 00:50:52,390 you get a big interference effect 893 00:50:52,390 --> 00:50:54,120 which recovers by the next day. 894 00:50:55,410 --> 00:50:57,850 So that is what you get that with that. 895 00:50:57,850 --> 00:51:02,010 Then let's examine what happens in LIP. 896 00:51:03,280 --> 00:51:05,990 Curiously in LIP there was no effect. 897 00:51:07,220 --> 00:51:07,720 All right. 898 00:51:07,720 --> 00:51:13,640 So now let's next turn to the so-called oddity task meaning 899 00:51:13,640 --> 00:51:16,900 several stimuli, one of which is different from the others 900 00:51:16,900 --> 00:51:21,230 and what is the monkey's ability to choose 901 00:51:21,230 --> 00:51:22,970 the different stimulus. 902 00:51:22,970 --> 00:51:26,260 So if you do this with a muscimol injection 903 00:51:26,260 --> 00:51:29,260 there's a huge deficit for V1 that you 904 00:51:29,260 --> 00:51:32,720 would expect because it destroyed the monkey's ability 905 00:51:32,720 --> 00:51:35,250 to analyze the visual stimulus that 906 00:51:35,250 --> 00:51:37,840 appeared in the receptive field. 907 00:51:37,840 --> 00:51:40,870 Then if you do the same thing in the frontal eye fields 908 00:51:40,870 --> 00:51:45,110 you find a mild deficit and then if you do the same thing in LIP 909 00:51:45,110 --> 00:51:47,800 you get no deficit at all. 910 00:51:47,800 --> 00:51:51,960 So this is what then happens with the oddities task 911 00:51:51,960 --> 00:51:55,860 and now what you can do is ask what happens when instead 912 00:51:55,860 --> 00:51:59,410 of muscimol we're going to inject bicuculline? 913 00:52:01,920 --> 00:52:04,560 And we're going to go through the same procedure 914 00:52:04,560 --> 00:52:10,529 as what I just shown you and so we start here in V1 915 00:52:10,529 --> 00:52:12,570 and when you do that think about it for a minute, 916 00:52:12,570 --> 00:52:15,680 now you're facilitating supposedly 917 00:52:15,680 --> 00:52:17,370 because you're eliminating inhibition 918 00:52:17,370 --> 00:52:18,703 what do you think you would get? 919 00:52:19,560 --> 00:52:22,150 Well, you'll be in for a surprise, what 920 00:52:22,150 --> 00:52:25,230 you get is gigantic interference again 921 00:52:25,230 --> 00:52:30,400 because putting bicuculline in also screwed up you're 922 00:52:30,400 --> 00:52:35,370 ability in the visual cortex to analyze the visual percept. 923 00:52:36,510 --> 00:52:39,700 This again recovers over time by the next day 924 00:52:39,700 --> 00:52:41,020 it's back to normal. 925 00:52:41,020 --> 00:52:43,719 Then if you do the same experiment in the frontal eye 926 00:52:43,719 --> 00:52:45,510 fields what do you think's going to happen? 927 00:52:45,510 --> 00:52:47,670 Can you predict what's going to happen just 928 00:52:47,670 --> 00:52:48,660 looking at this slide? 929 00:52:49,900 --> 00:52:53,753 Why do you think this is such a big empty space here huh? 930 00:52:55,110 --> 00:53:01,550 OK well look at that, when you put in bicuculline we 931 00:53:01,550 --> 00:53:03,066 get this incredible facilitation. 932 00:53:04,180 --> 00:53:07,300 OK the monkey just like in the colliculus 933 00:53:07,300 --> 00:53:12,340 barely can help himself to make a saccade into the field 934 00:53:12,340 --> 00:53:20,170 that has been disinhibited OK?, and that again recovers, 935 00:53:20,170 --> 00:53:22,100 bicuculline is washed out more rapidly 936 00:53:22,100 --> 00:53:24,900 than muscimol and by the next day 937 00:53:24,900 --> 00:53:26,750 certainly is back to normal. 938 00:53:26,750 --> 00:53:29,200 Now we can do the same thing just looking 939 00:53:29,200 --> 00:53:33,490 at the eye movements themselves to further highlight 940 00:53:33,490 --> 00:53:35,140 what I've shown you before. 941 00:53:35,140 --> 00:53:38,670 If you'd put bicuculline in OK, in the frontal eye fields 942 00:53:38,670 --> 00:53:44,290 the monkey cannot help but make saccades with similar vectors 943 00:53:44,290 --> 00:53:49,410 that are represented by the neurons in the injected site 944 00:53:49,410 --> 00:53:52,320 and that's why you have all this is its full stack of saccades 945 00:53:52,320 --> 00:53:55,290 buh, buh, buh, buh, bang the monkey just can't help 946 00:53:55,290 --> 00:53:59,301 but makes saccades because the signal to make the saccade has 947 00:53:59,301 --> 00:54:00,050 been disinhibited. 948 00:54:01,660 --> 00:54:06,000 All right so then you can ask what happens in LIP 949 00:54:06,000 --> 00:54:09,420 and when you do that you get no effect at all, 950 00:54:09,420 --> 00:54:14,200 and if you do now the bicuculline injection 951 00:54:14,200 --> 00:54:16,880 with the oddities task we can once again 952 00:54:16,880 --> 00:54:19,150 ask well what happens with that? 953 00:54:19,150 --> 00:54:23,530 And then once again as I've already indicated, 954 00:54:23,530 --> 00:54:28,020 both bicuculline and muscimol cause a major interference 955 00:54:28,020 --> 00:54:34,340 in your ability to select the odd target, 956 00:54:34,340 --> 00:54:37,780 in other words to visually discriminate, 957 00:54:37,780 --> 00:54:40,220 but if you do the same thing in the frontal eye fields 958 00:54:40,220 --> 00:54:44,460 and in the medial and LIP you get no effect at all. 959 00:54:47,110 --> 00:54:52,820 So what this then says to summarize all right 960 00:54:52,820 --> 00:54:53,575 is the following. 961 00:54:54,960 --> 00:54:57,640 We talk about target selection, which was a two target 962 00:54:57,640 --> 00:55:00,930 task, individual discrimination which was the oddities task 963 00:55:00,930 --> 00:55:03,950 and here we have muscimol and here bicuculline. 964 00:55:03,950 --> 00:55:07,810 So if you do that in the frontal eye field, in V1 first, 965 00:55:07,810 --> 00:55:10,920 you get interference, you do it in the frontal eye 966 00:55:10,920 --> 00:55:12,900 fields you get interference of muscimol 967 00:55:12,900 --> 00:55:16,630 with great facilitation, with bicuculline 968 00:55:16,630 --> 00:55:18,430 and LIP has no effec. 969 00:55:18,430 --> 00:55:20,850 And then, just to remind you, it has already 970 00:55:20,850 --> 00:55:23,110 been shown by Hikosaka and Woods, 971 00:55:23,110 --> 00:55:25,690 that you get interference of facilitation 972 00:55:25,690 --> 00:55:28,770 in the superior colliculus with these two agents. 973 00:55:28,770 --> 00:55:31,220 You do the same thing with visual discrimination, 974 00:55:31,220 --> 00:55:34,350 you get a major deficit in V1 for both 975 00:55:34,350 --> 00:55:41,070 and you get a mild effect for both actually no effect 976 00:55:41,070 --> 00:55:42,820 really with bicuculline in the frontal eye 977 00:55:42,820 --> 00:55:46,140 fields and no effect at all in LIP. 978 00:55:46,140 --> 00:55:49,120 So these manipulations then gives you 979 00:55:49,120 --> 00:55:54,470 sort of a sense of what these various areas do 980 00:55:54,470 --> 00:55:56,780 in the generation of eye movements 981 00:55:56,780 --> 00:55:59,830 that involve not only just to make a saccade to a target 982 00:55:59,830 --> 00:56:03,780 but to select targets individual field, make a decision as 983 00:56:03,780 --> 00:56:08,820 to where to look, and also to decide when to look, 984 00:56:08,820 --> 00:56:10,700 because any time you make an eye movement 985 00:56:10,700 --> 00:56:14,270 and I should've mentioned that more thoroughly before, you 986 00:56:14,270 --> 00:56:16,840 look at something and how long you look at it 987 00:56:16,840 --> 00:56:19,890 depends on how long it takes you to analyze what you're looking 988 00:56:19,890 --> 00:56:20,465 at. 989 00:56:20,465 --> 00:56:24,480 Now in most cases it takes you maybe I 990 00:56:24,480 --> 00:56:27,220 don't know 200 milliseconds or less to say, 991 00:56:27,220 --> 00:56:30,310 oh yeah that's letter a or whatever 992 00:56:30,310 --> 00:56:35,677 and then you say it's your brain mechanisms tell you, OK, now 993 00:56:35,677 --> 00:56:36,510 you know what it is. 994 00:56:36,510 --> 00:56:38,830 It's OK for you to move your eye. 995 00:56:38,830 --> 00:56:42,000 OK so that's involved and then thirdly, 996 00:56:42,000 --> 00:56:44,710 you have an important task in making sequences 997 00:56:44,710 --> 00:56:46,490 of eye movements so that when you 998 00:56:46,490 --> 00:56:49,910 look at a picture like the movie I showed you in the beginning 999 00:56:49,910 --> 00:56:53,300 in the previous lecture, when you look at something 1000 00:56:53,300 --> 00:56:55,480 then you make a decision as to where to look next, 1001 00:56:55,480 --> 00:56:57,970 where to look next and if you keep doing this 1002 00:56:57,970 --> 00:57:01,310 for I don't know 20, 30 saccades then you get to a state 1003 00:57:01,310 --> 00:57:02,730 where you say oh now I understand 1004 00:57:02,730 --> 00:57:03,750 the picture as a whole. 1005 00:57:04,860 --> 00:57:08,350 All right so now we're going to summarize 1006 00:57:08,350 --> 00:57:11,560 what the tasks are in a very simple situation 1007 00:57:11,560 --> 00:57:13,870 and what brain structures are involved in it. 1008 00:57:13,870 --> 00:57:15,990 First of all let's imagine that you're 1009 00:57:15,990 --> 00:57:20,780 looking at fixation spot designated by a. 1010 00:57:20,780 --> 00:57:23,240 Let's assume the two stimuli come on 1011 00:57:23,240 --> 00:57:26,110 and that means that you have to make a decision as 1012 00:57:26,110 --> 00:57:28,310 to what those two targets are, you 1013 00:57:28,310 --> 00:57:31,770 have to identify them because you have to select one of those 1014 00:57:31,770 --> 00:57:32,400 OK? 1015 00:57:32,400 --> 00:57:35,100 Of course in most cases you're talking about many targets that 1016 00:57:35,100 --> 00:57:38,860 are out there this is a highly simplified version. 1017 00:57:38,860 --> 00:57:41,510 The next step is to decide which of these two 1018 00:57:41,510 --> 00:57:45,130 targets now that I know one says a and the other says b, which 1019 00:57:45,130 --> 00:57:49,030 of those two targets, actually b and c in the picture here 1020 00:57:49,030 --> 00:57:50,960 which of these targets should I look at, 1021 00:57:50,960 --> 00:57:54,470 and so you make a decision all right, that generates 1022 00:57:54,470 --> 00:57:58,530 excitation and inhibitin, inhibition through excitatory 1023 00:57:58,530 --> 00:58:00,880 and inhibitory circuits, and then you 1024 00:58:00,880 --> 00:58:03,400 decide OK we going to look here and that 1025 00:58:03,400 --> 00:58:06,920 means that you have to decide which one not to look 1026 00:58:06,920 --> 00:58:09,640 at in addition to deciding which one to look at, 1027 00:58:09,640 --> 00:58:13,930 because you've got to make an accurate saccade so you 1028 00:58:13,930 --> 00:58:15,810 don't want a vector average. 1029 00:58:15,810 --> 00:58:16,310 All right. 1030 00:58:16,310 --> 00:58:22,500 And then what you need of course is a map, 1031 00:58:22,500 --> 00:58:29,350 if you will, of the motor field so that you can generate 1032 00:58:29,350 --> 00:58:33,610 the appropriate direction of the saccade 1033 00:58:33,610 --> 00:58:36,720 so that you can decide where you're going to look at 1034 00:58:36,720 --> 00:58:40,190 and then lastly as I've mentioned already before, 1035 00:58:40,190 --> 00:58:42,260 you also have to make a decision as 1036 00:58:42,260 --> 00:58:44,880 to when to make that eye movement. 1037 00:58:44,880 --> 00:58:48,620 So now in a very summary fashion we 1038 00:58:48,620 --> 00:58:53,500 can talk about the various brain areas involved. 1039 00:58:53,500 --> 00:58:55,500 Quite a number of different areas 1040 00:58:55,500 --> 00:58:59,570 are involved in the decision as to what these two stimuli are, 1041 00:58:59,570 --> 00:59:02,940 they of course involve much of the visual system including 1042 00:59:02,940 --> 00:59:05,650 also LIP and several other areas. 1043 00:59:05,650 --> 00:59:07,920 Then, then you have to make a decision as 1044 00:59:07,920 --> 00:59:11,470 to which one to look at, again several areas involve notably 1045 00:59:11,470 --> 00:59:14,510 among them are the frontal eye fields, LIP, and also 1046 00:59:14,510 --> 00:59:16,440 the medial eye fields. 1047 00:59:16,440 --> 00:59:20,560 Then you also have to decide which ones not to look at, 1048 00:59:20,560 --> 00:59:23,460 that it was largely the same areas 1049 00:59:23,460 --> 00:59:27,770 and then you need of course a topographic arrangement 1050 00:59:27,770 --> 00:59:30,830 to know where things are and that you 1051 00:59:30,830 --> 00:59:33,890 can find in many areas, including V1, V2, 1052 00:59:33,890 --> 00:59:36,590 the frontal eye fields, and the colliculi which are laid out 1053 00:59:36,590 --> 00:59:39,550 in a nice topographic fashion, and then 1054 00:59:39,550 --> 00:59:42,550 lastly LIP is important for that, 1055 00:59:42,550 --> 00:59:45,190 and I think to some degree also the medial eye fields 1056 00:59:45,190 --> 00:59:49,160 but I'm not sure about that to decide when you should generate 1057 00:59:49,160 --> 00:59:51,090 saccadic eye movements. 1058 00:59:51,090 --> 00:59:52,800 Well that's very nice and makes you 1059 00:59:52,800 --> 00:59:55,160 realize that even though we never 1060 00:59:55,160 --> 00:59:58,940 think about making eye movement all this stuff is going 1061 00:59:58,940 --> 01:00:02,370 on three times a second it's amazing. 1062 01:00:02,370 --> 01:00:05,980 So now you're going to look at what the various visual areas 1063 01:00:05,980 --> 01:00:10,900 and ocular motor areas are that play a role in this OK, 1064 01:00:10,900 --> 01:00:14,300 and so we're going to create a summary diagram. 1065 01:00:14,300 --> 01:00:16,140 So here we have, that's the first one 1066 01:00:16,140 --> 01:00:19,720 I shown you, which has a rate code that from the brain stem 1067 01:00:19,720 --> 01:00:22,930 connects with the eye muscles and activates them. 1068 01:00:22,930 --> 01:00:25,340 Then we have the superior colliculus, 1069 01:00:25,340 --> 01:00:34,420 now the superior colliculus is under strong inhibitory control 1070 01:00:34,420 --> 01:00:37,310 all right, and they're several inhibitory circuits that 1071 01:00:37,310 --> 01:00:46,960 are involved in that and those include the substantia nigra 1072 01:00:46,960 --> 01:00:48,840 that sends inhibitory circuits down 1073 01:00:48,840 --> 01:00:54,830 to the colliculus that then prevents the colliculus 1074 01:00:54,830 --> 01:00:57,190 from generating an eye movement because it 1075 01:00:57,190 --> 01:00:59,350 is under inhibition, because every time you 1076 01:00:59,350 --> 01:01:02,120 look around thousands and thousands 1077 01:01:02,120 --> 01:01:05,670 of impressions impinge on the colliculus 1078 01:01:05,670 --> 01:01:07,800 and you only want one of those to actually get down 1079 01:01:07,800 --> 01:01:09,400 to the deep place, the colliculus, 1080 01:01:09,400 --> 01:01:12,390 to generate an eye movement. 1081 01:01:12,390 --> 01:01:18,410 Now then the substantia nigra is under the control 1082 01:01:18,410 --> 01:01:22,010 of several neural structures which, many of which 1083 01:01:22,010 --> 01:01:24,510 go through this so-called basal ganglia. 1084 01:01:25,880 --> 01:01:29,490 Now we can expand on this and look at the visual input 1085 01:01:29,490 --> 01:01:30,580 to do this. 1086 01:01:30,580 --> 01:01:32,400 We already talked about this a lot 1087 01:01:32,400 --> 01:01:35,350 you, pointed out to you that you have these three 1088 01:01:35,350 --> 01:01:39,290 major, many, many different types of ganglion cells. 1089 01:01:39,290 --> 01:01:40,860 The three major ones we talked about 1090 01:01:40,860 --> 01:01:46,350 are the midget parasol and the so-called W-cells 1091 01:01:46,350 --> 01:01:48,980 that go to the cortex. 1092 01:01:48,980 --> 01:01:52,670 And the W-cells also project directly to the colliculus. 1093 01:01:52,670 --> 01:01:57,310 Then from layer five in the visual cortex 1094 01:01:57,310 --> 01:02:01,410 you have the cells that project to the superior colliculus 1095 01:02:01,410 --> 01:02:09,370 and the intermediate layers and that down flow is controlled 1096 01:02:09,370 --> 01:02:15,370 predominantly by the parasol system as we had described. 1097 01:02:15,370 --> 01:02:17,970 Then we have all these other areas 1098 01:02:17,970 --> 01:02:24,000 that V1 projects to, V2, MT, V4, and so on some of them 1099 01:02:24,000 --> 01:02:27,420 dominated by input from the parasol system 1100 01:02:27,420 --> 01:02:30,060 and others get input from both, and those 1101 01:02:30,060 --> 01:02:33,120 in turn project to the parietal and temporal lobes 1102 01:02:33,120 --> 01:02:37,150 and those in turn have an important influence 1103 01:02:37,150 --> 01:02:41,700 on the inhibitory circuits through the basal ganglia 1104 01:02:41,700 --> 01:02:44,200 and the substantia nigra. 1105 01:02:44,200 --> 01:02:47,700 Now let me finally come to the frontal lobe, the frontal eye 1106 01:02:47,700 --> 01:02:50,640 fields, and the medial eye fields and they in turn 1107 01:02:50,640 --> 01:02:54,520 have direct access to the brain stem 1108 01:02:54,520 --> 01:02:56,920 and also connect to the superior colliculus. 1109 01:02:58,560 --> 01:03:00,600 Now this is still not the whole story 1110 01:03:00,600 --> 01:03:02,450 because what you have in addition is 1111 01:03:02,450 --> 01:03:09,150 a bunch of interconnections among numerous cortical areas 1112 01:03:09,150 --> 01:03:11,950 they talk back and forth to each other 1113 01:03:11,950 --> 01:03:14,590 that enables you to make these decisions as 1114 01:03:14,590 --> 01:03:16,340 to where to look next. 1115 01:03:16,340 --> 01:03:17,730 Now if you think this is complete 1116 01:03:17,730 --> 01:03:21,140 you're still wrong because now what you have to realize 1117 01:03:21,140 --> 01:03:25,530 is that all this circuitry is also 1118 01:03:25,530 --> 01:03:28,161 one that receives input from several other areas, 1119 01:03:28,161 --> 01:03:29,660 with the auditory system that you're 1120 01:03:29,660 --> 01:03:32,860 going to hear a lot about later on in the course, 1121 01:03:32,860 --> 01:03:36,020 the somatosensory system, the olfactory system, 1122 01:03:36,020 --> 01:03:38,370 the smooth pursuit system that we'll mention 1123 01:03:38,370 --> 01:03:40,500 a little bit next time, the vestibular 1124 01:03:40,500 --> 01:03:43,050 system, the accessory optic system we'll 1125 01:03:43,050 --> 01:03:46,290 talk about next time, and the vergence system. 1126 01:03:46,290 --> 01:03:49,950 So all these fit into this incredibly complex circuitry 1127 01:03:49,950 --> 01:03:55,050 already and essential elements in your ability 1128 01:03:55,050 --> 01:03:56,850 to move your eyes about. 1129 01:03:56,850 --> 01:04:04,680 So I think you need to realize therefore that something even 1130 01:04:04,680 --> 01:04:10,040 as simple as just moving your eyes about it's an incredibly 1131 01:04:10,040 --> 01:04:15,510 complicated system involving many structures 1132 01:04:15,510 --> 01:04:19,360 and involving excitatory and inhibitory circuits, 1133 01:04:19,360 --> 01:04:22,130 interconnections it's just, it's almost dumbfounding. 1134 01:04:23,170 --> 01:04:29,050 So that then is the essence of these connections, 1135 01:04:29,050 --> 01:04:31,349 and what I want turn to next I think 1136 01:04:31,349 --> 01:04:32,515 we still have a little time. 1137 01:04:33,600 --> 01:04:37,220 Before I summarize our results for today, 1138 01:04:37,220 --> 01:04:40,723 I want to say something about dreaming and rapid eye 1139 01:04:40,723 --> 01:04:41,222 movements. 1140 01:04:43,958 --> 01:04:49,340 I think all of you know that every night you sleep you dream 1141 01:04:49,340 --> 01:04:51,780 and what you also know that has been discovered more 1142 01:04:51,780 --> 01:04:56,110 recently is when you dream you make rapid eye movement so it's 1143 01:04:56,110 --> 01:05:03,960 called REM sleep, and so the question arose why do we dream? 1144 01:05:03,960 --> 01:05:06,000 Why do we have REM sleep? 1145 01:05:07,560 --> 01:05:16,320 Now, the major influence as to why we dream 1146 01:05:16,320 --> 01:05:19,710 comes from the work of Sigmund Freud who 1147 01:05:19,710 --> 01:05:23,750 published a famous book one of his really great works called, 1148 01:05:23,750 --> 01:05:26,330 The Interpretation Of Dreams, which 1149 01:05:26,330 --> 01:05:31,850 was the original version in German was published in 1900. 1150 01:05:31,850 --> 01:05:35,310 OK so 113 years ago. 1151 01:05:35,310 --> 01:05:38,860 Now this was an incredibly influential book and also 1152 01:05:38,860 --> 01:05:43,240 central for the emergence of psychoanalysis 1153 01:05:43,240 --> 01:05:51,350 and has been used extensively to interpret quotes why we dream. 1154 01:05:51,350 --> 01:05:55,670 Now the prime, in very summary fashion, 1155 01:05:55,670 --> 01:06:00,260 the prime idea that Freud expressed 1156 01:06:00,260 --> 01:06:09,830 is that dreaming is equivalent to wish-fulling your dreams, 1157 01:06:09,830 --> 01:06:15,110 your wishes, to fulfilling your wishes. 1158 01:06:15,110 --> 01:06:18,320 So that's why it's called wish fulfillment dreams. 1159 01:06:18,320 --> 01:06:24,100 Now, that's interesting because one of the stories he has 1160 01:06:24,100 --> 01:06:26,810 in that book of his, Interpretation Of Dreams, 1161 01:06:26,810 --> 01:06:33,280 is a woman he was psychoanalyzing who one day 1162 01:06:33,280 --> 01:06:38,080 when she came to be, to her session said you know you told 1163 01:06:38,080 --> 01:06:41,710 me the other day that dreams are wish fulfillment's. 1164 01:06:41,710 --> 01:06:46,280 She said, I don't believe that, I had a dream last night 1165 01:06:46,280 --> 01:06:51,610 and it didn't go along with wish fulfillment and Freud said, 1166 01:06:51,610 --> 01:06:54,216 I want you to tell me what the dream was about. 1167 01:06:54,216 --> 01:06:57,510 Well, my dream was that I went to a store 1168 01:06:57,510 --> 01:07:01,930 to buy some food because I was going to have a dinner party 1169 01:07:01,930 --> 01:07:06,890 and when I got to the store it was closed and I could, 1170 01:07:06,890 --> 01:07:08,870 as much as I wanted to I couldn't 1171 01:07:08,870 --> 01:07:10,320 buy the food for the dinner. 1172 01:07:11,740 --> 01:07:15,840 Freud scratched his eyes, you know I'm making that up, 1173 01:07:15,840 --> 01:07:21,730 and he said that's true, he said you know what? 1174 01:07:21,730 --> 01:07:23,370 You didn't want to give a dinner party 1175 01:07:23,370 --> 01:07:25,430 that's why you dreamt that. 1176 01:07:25,430 --> 01:07:29,620 So that's famous psychoanalytic stuff. 1177 01:07:29,620 --> 01:07:31,830 You can always twist things around so 1178 01:07:31,830 --> 01:07:34,760 that it fits with your hypotheses, 1179 01:07:34,760 --> 01:07:39,400 in this case Freud felt that indeed even though she had 1180 01:07:39,400 --> 01:07:42,680 this, what she thought was a contrary dream it was a wish 1181 01:07:42,680 --> 01:07:44,190 fulfillment dream. 1182 01:07:44,190 --> 01:07:46,650 Well that's one part of dreaming, 1183 01:07:46,650 --> 01:07:49,440 what the other part that Freud had emphasized 1184 01:07:49,440 --> 01:07:55,710 is that when we dream so many of our wishes 1185 01:07:55,710 --> 01:07:59,150 are actually unacceptable to ourselves 1186 01:07:59,150 --> 01:08:01,290 and therefore we dream it at night 1187 01:08:01,290 --> 01:08:06,590 and so he constructed in many other studies 1188 01:08:06,590 --> 01:08:11,920 the idea that in humans we have three subdivisions of the mind. 1189 01:08:11,920 --> 01:08:14,660 We have the Id, the ego and the super ego, 1190 01:08:14,660 --> 01:08:16,120 you all know that right? 1191 01:08:16,120 --> 01:08:21,109 So what it means that when you dream at night some 1192 01:08:21,109 --> 01:08:23,370 of the wishes that you, unacceptable 1193 01:08:23,370 --> 01:08:26,240 wishes that aren't in your Id, kind 1194 01:08:26,240 --> 01:08:29,580 of seep through because the super ego 1195 01:08:29,580 --> 01:08:32,965 is not under control since you're asleep. 1196 01:08:34,189 --> 01:08:40,059 So that was his basic idea and of course it 1197 01:08:40,059 --> 01:08:43,979 was then many years later discovered that whenever 1198 01:08:43,979 --> 01:08:48,759 you dream you make all kinds of eye movements. 1199 01:08:48,759 --> 01:08:50,800 You don't make eye movements when you don't dream 1200 01:08:50,800 --> 01:08:52,549 but when you dream you make eye movements. 1201 01:08:53,899 --> 01:08:58,200 Now one of the problems with the Freudian theory 1202 01:08:58,200 --> 01:09:06,380 is that animals also dream and in fact most dramatically, 1203 01:09:06,380 --> 01:09:11,620 animals that hibernate do a lot of dreaming and not 1204 01:09:11,620 --> 01:09:13,740 only dreaming but those animals also 1205 01:09:13,740 --> 01:09:16,029 move their eyes about a lot OK? 1206 01:09:19,200 --> 01:09:25,010 So that observation then kind of shifted 1207 01:09:25,010 --> 01:09:29,069 the notion as to why we have REM sleep 1208 01:09:29,069 --> 01:09:32,800 and so people thought about that and one observation that 1209 01:09:32,800 --> 01:09:37,920 had been made is that when you eliminate a persons 1210 01:09:37,920 --> 01:09:42,899 ability to move the eyes, such as you lose somehow the ability 1211 01:09:42,899 --> 01:09:47,100 to activate your eye muscles, this 1212 01:09:47,100 --> 01:09:48,390 can be done also in monkeys. 1213 01:09:50,109 --> 01:09:56,110 What happens in fairly short order 1214 01:09:56,110 --> 01:10:01,610 is it your eye becomes ill-affected 1215 01:10:01,610 --> 01:10:05,050 and what I mean by that is that the eye loses 1216 01:10:05,050 --> 01:10:07,700 it's perfect roundness to some degree 1217 01:10:07,700 --> 01:10:10,010 and more notably even what happens 1218 01:10:10,010 --> 01:10:13,540 is that your cornea becomes uneven, 1219 01:10:13,540 --> 01:10:17,070 becomes ridged, because you're not moving your eye. 1220 01:10:17,070 --> 01:10:21,920 So that discovery then has led to an alternate theory 1221 01:10:21,920 --> 01:10:25,320 about why we dream which is not nearly as 1222 01:10:25,320 --> 01:10:29,480 romantic or intriguing as Freudian theory, 1223 01:10:29,480 --> 01:10:35,460 namely that we have REM sleep at night in order-- 1224 01:10:35,460 --> 01:10:38,930 and especially have it in animals that hibernate-- 1225 01:10:38,930 --> 01:10:41,920 in order to keep the eyes in healthy condition 1226 01:10:41,920 --> 01:10:47,210 and to keep the cornea nice and smooth and even 1227 01:10:47,210 --> 01:10:50,300 because if you were not to dream at all 1228 01:10:50,300 --> 01:10:52,030 and you would sleep eight or 10 hours. 1229 01:10:52,030 --> 01:10:55,870 Then you would have an uneven, would 1230 01:10:55,870 --> 01:11:02,560 result in having an uneven cornea that 1231 01:11:02,560 --> 01:11:05,420 would make it more difficult for you to see 1232 01:11:05,420 --> 01:11:10,040 and the reason for this then is that animals 1233 01:11:10,040 --> 01:11:13,600 that, which presumably don't have Ids, egos, and super egos 1234 01:11:13,600 --> 01:11:16,900 also dream as do animals that hibernate 1235 01:11:16,900 --> 01:11:22,900 and so there's a necessity to move your eyes while you 1236 01:11:22,900 --> 01:11:25,290 are sleeping or hibernating. 1237 01:11:25,290 --> 01:11:28,200 So that's an alternate theory and we'll 1238 01:11:28,200 --> 01:11:31,420 see one of these years whether they're correct 1239 01:11:31,420 --> 01:11:33,110 but I can tell you, which may not 1240 01:11:33,110 --> 01:11:39,770 be very nice, that basically Freudian theory has taken quite 1241 01:11:39,770 --> 01:11:45,670 a nose dive and in fact today psychoanalysis has become 1242 01:11:45,670 --> 01:11:50,070 largely dead for a number of reasons, 1243 01:11:50,070 --> 01:11:54,140 and so you don't have too many psychiatrists or psychoanalysts 1244 01:11:54,140 --> 01:12:01,620 out there performing those psychoanalytic tasks that they 1245 01:12:01,620 --> 01:12:03,960 had, in which a patient lies down 1246 01:12:03,960 --> 01:12:06,740 on a couch and sort of free associates 1247 01:12:06,740 --> 01:12:13,050 and sometimes even gets hypnotized to talk about some 1248 01:12:13,050 --> 01:12:15,460 of his unconscious wishes and so on. 1249 01:12:15,460 --> 01:12:18,300 So anyway that's the story for today 1250 01:12:18,300 --> 01:12:22,760 and that brings me to an end to eye movement control. 1251 01:12:22,760 --> 01:12:24,430 I hope you'll appreciate the fact 1252 01:12:24,430 --> 01:12:27,660 that even a simple system like eye movements 1253 01:12:27,660 --> 01:12:30,340 is unbelievably complex when it comes 1254 01:12:30,340 --> 01:12:33,270 to the brain controlling it. 1255 01:12:34,460 --> 01:12:37,370 Next time we're going to talk about eye movements 1256 01:12:37,370 --> 01:12:40,390 and towards the end of that I'll come back a little bit 1257 01:12:40,390 --> 01:12:45,862 and talk more about yet another aspect of eye movement control. 1258 01:12:45,862 --> 01:12:47,195 Does anybody have any questions? 1259 01:12:49,550 --> 01:12:50,200 Yes please. 1260 01:12:50,200 --> 01:12:52,444 AUDIENCE: Can you just explain again 1261 01:12:52,444 --> 01:12:55,010 quickly why the bicuculline injection in V1 1262 01:12:55,010 --> 01:12:56,519 causes interference? 1263 01:12:56,519 --> 01:12:58,310 PROFESSOR: OK, that's a very good question. 1264 01:12:58,310 --> 01:13:04,140 Why does bicuculline in the, in V1 cause interference? 1265 01:13:04,140 --> 01:13:09,610 Because it screws up the neurons ability 1266 01:13:09,610 --> 01:13:12,620 to analyze the visual scene. 1267 01:13:12,620 --> 01:13:17,252 You mess up the centers around antagonism, 1268 01:13:17,252 --> 01:13:20,600 you mess up the orientation selectivity of these cells, 1269 01:13:20,600 --> 01:13:22,830 or direction selectivity of them, 1270 01:13:22,830 --> 01:13:26,780 so they're no longer able to analyze the visual scene 1271 01:13:26,780 --> 01:13:27,840 in the normal fashion. 1272 01:13:29,190 --> 01:13:32,670 Yeah that's, and, it certainly you see, 1273 01:13:32,670 --> 01:13:36,070 the V1 is quite far removed really 1274 01:13:36,070 --> 01:13:39,190 from the generation of a motor response. 1275 01:13:39,190 --> 01:13:45,230 If you inject GABA inhibitors into areas 1276 01:13:45,230 --> 01:13:49,500 which are closely linked to the execution of motor acts 1277 01:13:49,500 --> 01:14:00,070 then the, the effect is seen because you generate a motor 1278 01:14:00,070 --> 01:14:03,940 response or if it's muscimol then you inhibit the motor 1279 01:14:03,940 --> 01:14:07,815 response but the frontal, you see this in the frontal eye 1280 01:14:07,815 --> 01:14:10,420 fields but you don't see this in V1 1281 01:14:10,420 --> 01:14:14,240 because V1 is predominantly the system that 1282 01:14:14,240 --> 01:14:18,770 analyzes visual percepts, as are V2 and V4 and all 1283 01:14:18,770 --> 01:14:21,495 those other higher cortical visual areas. 1284 01:14:24,599 --> 01:14:25,515 Any further questions? 1285 01:14:27,170 --> 01:14:30,009 All right very good so I will see you then next Monday 1286 01:14:30,009 --> 01:14:31,425 and I think you'll find that we'll 1287 01:14:31,425 --> 01:14:32,800 have an interesting session. 1288 01:14:32,800 --> 01:14:35,250 We're going talk about movement and we're not going talk 1289 01:14:35,250 --> 01:14:38,010 about regular movement, we're also 1290 01:14:38,010 --> 01:14:44,820 going to talk about confusing kinds of movements, 1291 01:14:44,820 --> 01:14:47,460 like especially very important apparent motion. 1292 01:14:48,700 --> 01:14:51,810 You realize and just to say one more word here, 1293 01:14:51,810 --> 01:14:59,970 that nowadays when you go home and watch television almost all 1294 01:14:59,970 --> 01:15:02,580 the motion that you see on the TV 1295 01:15:02,580 --> 01:15:06,150 is apparent motion, not real motion 1296 01:15:06,150 --> 01:15:07,575 and I-- keep thinking about that-- 1297 01:15:07,575 --> 01:15:09,200 and I'll tell you about that next time. 1298 01:15:11,575 --> 01:15:13,967 AUDIENCE: Monday is actually a Holiday. 1299 01:15:13,967 --> 01:15:14,800 PROFESSOR: Oh, yeah. 1300 01:15:14,800 --> 01:15:15,800 Sorry it's not Monday. 1301 01:15:15,800 --> 01:15:19,840 It's our next session is next Wednesday. 1302 01:15:19,840 --> 01:15:21,390 Sorry about that.