1 00:00:00,250 --> 00:00:01,800 The following content is provided 2 00:00:01,800 --> 00:00:04,040 under a Creative Commons license. 3 00:00:04,040 --> 00:00:06,890 Your support will help MIT OpenCourseWare continue 4 00:00:06,890 --> 00:00:10,740 to offer high quality educational resources for free. 5 00:00:10,740 --> 00:00:13,360 To make a donation or view additional materials 6 00:00:13,360 --> 00:00:15,810 from hundreds of MIT courses, visit 7 00:00:15,810 --> 00:00:23,170 MIT OpenCourseWare at ocw.mit.edu 8 00:00:23,170 --> 00:00:26,160 PROFESSOR: This is where we ended last time. 9 00:00:26,160 --> 00:00:30,480 We had just talked about these major types 10 00:00:30,480 --> 00:00:33,666 of functions of neocortex. 11 00:00:36,660 --> 00:00:42,210 And I've named them according to how I think it involved, 12 00:00:42,210 --> 00:00:47,250 location sense, object sense, functions 13 00:00:47,250 --> 00:00:50,810 of the prefrontal elaborations of motor cortex for planning. 14 00:00:50,810 --> 00:00:53,270 And I'm going to go through that a little more. 15 00:00:53,270 --> 00:00:57,320 And that's basically what these questions are about. 16 00:00:57,320 --> 00:00:59,735 We had talked about the hippocampal system. 17 00:01:02,530 --> 00:01:05,870 I want you to think about how that facilitates the ability 18 00:01:05,870 --> 00:01:09,440 to anticipate the stimuli that you're about to encounter-- 19 00:01:09,440 --> 00:01:11,620 any animal is going to encounter. 20 00:01:11,620 --> 00:01:14,820 How does that location information 21 00:01:14,820 --> 00:01:17,060 that is handled by the hippocampus 22 00:01:17,060 --> 00:01:21,660 remember how it evolved to know where 23 00:01:21,660 --> 00:01:25,420 the animal is in the local environment, 24 00:01:25,420 --> 00:01:28,070 and eventually in many different local environments, 25 00:01:28,070 --> 00:01:29,762 and we remember them. 26 00:01:29,762 --> 00:01:33,320 Our parietal cortex remembers them, 27 00:01:33,320 --> 00:01:35,725 so the hippocampus doesn't have to totally relearn it 28 00:01:35,725 --> 00:01:39,042 every time when you go to a different area. 29 00:01:39,042 --> 00:01:42,260 But because, every time you turn your head, 30 00:01:42,260 --> 00:01:48,330 the way that system works, this information 31 00:01:48,330 --> 00:01:52,850 is sent from the hippocampus back to the mammillary bodies. 32 00:01:52,850 --> 00:01:55,910 That means the hippocampus is getting that information based 33 00:01:55,910 --> 00:01:58,680 on the direction we're looking. 34 00:01:58,680 --> 00:02:02,730 So it can call up all the relevant memories, 35 00:02:02,730 --> 00:02:05,790 the things in front of us. 36 00:02:05,790 --> 00:02:10,970 So it's a major factor in how the motivations make 37 00:02:10,970 --> 00:02:14,030 us decide to go in the one direction or another 38 00:02:14,030 --> 00:02:18,290 in an animal-- I shouldn't say humans, primarily. 39 00:02:18,290 --> 00:02:22,230 But it's for navigating the world. 40 00:02:22,230 --> 00:02:25,880 And that we know that motivation is a major factor. 41 00:02:25,880 --> 00:02:29,120 And people haven't considered enough the role 42 00:02:29,120 --> 00:02:31,952 of the hippocampus in motivation, 43 00:02:31,952 --> 00:02:36,380 and why this whole system for memory, long-term memory, 44 00:02:36,380 --> 00:02:40,720 evolved within the hippocampus within the limbic system, 45 00:02:40,720 --> 00:02:43,360 basically. 46 00:02:43,360 --> 00:02:48,580 But anyway you need to contrast that 47 00:02:48,580 --> 00:02:57,015 with the kind of anticipatory activity 48 00:02:57,015 --> 00:03:00,024 that is parietal in temporal association areas 49 00:03:00,024 --> 00:03:00,690 or concernments. 50 00:03:00,690 --> 00:03:03,970 So we'll be talking more about that. 51 00:03:03,970 --> 00:03:08,240 So it's all in the book, and it's just 52 00:03:08,240 --> 00:03:11,070 a different way of looking at it in these slides where 53 00:03:11,070 --> 00:03:14,150 I summarize these major points. 54 00:03:14,150 --> 00:03:21,940 The main, I think, anticipation, ability to anticipate stimuli, 55 00:03:21,940 --> 00:03:27,515 ability to plan movements, and other kind of anticipation, 56 00:03:27,515 --> 00:03:30,780 were major innovations of the cortex. 57 00:03:30,780 --> 00:03:34,270 It's not what the tectum does. 58 00:03:34,270 --> 00:03:37,890 It's not what subcortical systems do. 59 00:03:37,890 --> 00:03:42,246 This temporal aspect is so important for your cortex 60 00:03:42,246 --> 00:03:43,850 and, of course, planning. 61 00:03:43,850 --> 00:03:48,445 You know how important prefrontal areas are. 62 00:03:52,290 --> 00:03:58,810 You could say that in that original multimodal cortex, 63 00:03:58,810 --> 00:04:01,780 the motor cortex evolved very early. 64 00:04:01,780 --> 00:04:05,020 Initially, [INAUDIBLE] just another sensory area. 65 00:04:05,020 --> 00:04:11,300 But once it became specialized for control of movement, 66 00:04:11,300 --> 00:04:14,000 then the areas near it became involved 67 00:04:14,000 --> 00:04:20,079 in anticipating movement, mainly planning it. 68 00:04:20,079 --> 00:04:33,720 And this is mostly theory, but I mention here support for it. 69 00:04:33,720 --> 00:04:36,560 The laboratory studies of Sokolov in Moscow 70 00:04:36,560 --> 00:04:39,580 back in the '60s, he made extensive studies 71 00:04:39,580 --> 00:04:42,150 of reactions of humans to a novelty. 72 00:04:42,150 --> 00:04:46,020 And he studied animals as well. 73 00:04:46,020 --> 00:04:50,170 And how any kind of unexpected input, 74 00:04:50,170 --> 00:04:53,430 even if it was an unexpected lack of input, 75 00:04:53,430 --> 00:04:55,250 could cause an arousal response that 76 00:04:55,250 --> 00:04:58,310 alter the electrical activity of the neocortex. 77 00:05:02,300 --> 00:05:04,060 And when your inputs become familiar, 78 00:05:04,060 --> 00:05:06,578 then you don't get those arousal effects. 79 00:05:15,300 --> 00:05:23,060 So in theoretical terms, he said that there was a central model. 80 00:05:23,060 --> 00:05:27,260 This is how the brain is simulating what's going on. 81 00:05:27,260 --> 00:05:31,850 When you're dreaming, all you're doing is using that system. 82 00:05:31,850 --> 00:05:35,005 Your brain is totally capable of simulating the environment 83 00:05:35,005 --> 00:05:37,540 in incredible detail. 84 00:05:37,540 --> 00:05:41,100 Have you ever had hypnagogic imagery 85 00:05:41,100 --> 00:05:47,670 or vivid dreaming where you actually don't know for sure 86 00:05:47,670 --> 00:05:49,702 that you're dreaming? 87 00:05:49,702 --> 00:05:53,065 You know, you see cartoons of people pinching themselves 88 00:05:53,065 --> 00:05:54,740 to see if they're asleep. 89 00:05:54,740 --> 00:05:58,765 Have you ever had such vivid dreams that you couldn't tell? 90 00:05:58,765 --> 00:05:59,390 AUDIENCE: Yeah. 91 00:05:59,390 --> 00:06:00,806 PROFESSOR: Has everybody had them? 92 00:06:00,806 --> 00:06:03,365 Some people don't, or at least, they don't remember. 93 00:06:03,365 --> 00:06:07,680 But I've had them and really not very many and only 94 00:06:07,680 --> 00:06:09,970 when I was younger. 95 00:06:09,970 --> 00:06:12,320 Most of the time, I don't have difficulty 96 00:06:12,320 --> 00:06:14,340 knowing that I'm dreaming. 97 00:06:14,340 --> 00:06:17,770 AUDIENCE: What about, like, your motivations, right? 98 00:06:17,770 --> 00:06:22,670 Like if you're dreaming that you [INAUDIBLE] 99 00:06:22,670 --> 00:06:25,432 and then you wake up? 100 00:06:25,432 --> 00:06:27,140 PROFESSOR: Yeah, that's an anxiety dream. 101 00:06:27,140 --> 00:06:30,300 But in hypnagogic imagery, it's a good question. 102 00:06:30,300 --> 00:06:32,940 I don't know, we should look-- there is a literature on it, 103 00:06:32,940 --> 00:06:34,630 and you can read about it. 104 00:06:34,630 --> 00:06:41,780 And do all of the senses come to play? 105 00:06:41,780 --> 00:06:45,030 You know, I remember when I had them auditory, 106 00:06:45,030 --> 00:06:48,410 visual, somatosensory, they were all there. 107 00:06:48,410 --> 00:06:52,760 I cannot remember any olfactory imagery. 108 00:06:52,760 --> 00:06:56,466 I'm not saying it's not possible in some people, 109 00:06:56,466 --> 00:07:01,530 but often it's true that some of the modalities are missing. 110 00:07:01,530 --> 00:07:04,200 And what you asked about emotion, 111 00:07:04,200 --> 00:07:08,610 that's a major issue in that kind of imagery 112 00:07:08,610 --> 00:07:13,310 because if it involves these association areas, 113 00:07:13,310 --> 00:07:17,450 the posterior cortex will generate 114 00:07:17,450 --> 00:07:20,530 our images of the world, the posterior parietal primarily. 115 00:07:25,370 --> 00:07:27,840 The connections to emotion could be missing, 116 00:07:27,840 --> 00:07:30,580 and it could still generate these images. 117 00:07:30,580 --> 00:07:37,300 So if I have another one, I'll do the investigation. 118 00:07:37,300 --> 00:07:48,310 Anyway, so that same model can control endogenous generation 119 00:07:48,310 --> 00:07:49,210 of actions. 120 00:07:49,210 --> 00:07:52,645 This is the way the frontal areas 121 00:07:52,645 --> 00:07:56,240 and the posterior areas that do this kind of simulation 122 00:07:56,240 --> 00:07:58,540 of the world are connected. 123 00:07:58,540 --> 00:08:00,980 And you can use that model to plan your actions, 124 00:08:00,980 --> 00:08:04,210 and we do it all the time. 125 00:08:04,210 --> 00:08:08,780 It's a view that became unpopular for a while 126 00:08:08,780 --> 00:08:14,440 although, back in the '60s, Don MacKay developed it. 127 00:08:14,440 --> 00:08:18,470 But more recently, people have come back to it 128 00:08:18,470 --> 00:08:19,860 and they've updated it. 129 00:08:19,860 --> 00:08:24,180 There was a whole issue of, I think, the journal Cerebral 130 00:08:24,180 --> 00:08:26,110 Cortex, one of these major journals 131 00:08:26,110 --> 00:08:32,789 that talks about cortex had a whole issue on this. 132 00:08:32,789 --> 00:08:37,039 I think I mention it in the book if I'm remembering right. 133 00:08:37,039 --> 00:08:42,490 OK, so now we've not mentioned striatum in this. 134 00:08:42,490 --> 00:08:45,540 Actually, both the striatum and the cortex 135 00:08:45,540 --> 00:08:50,950 expanded in evolution including recent evolution. 136 00:08:50,950 --> 00:08:54,170 They can operate relatively independently, 137 00:08:54,170 --> 00:08:58,360 and that's because they don't operate independently 138 00:08:58,360 --> 00:09:00,650 in humans at all. 139 00:09:00,650 --> 00:09:03,460 But in animals, it's quite possible for them 140 00:09:03,460 --> 00:09:04,790 to operate independently. 141 00:09:04,790 --> 00:09:10,370 You can have an animal where much of the cortex 142 00:09:10,370 --> 00:09:13,020 is rendered nonfunctional, and he can still 143 00:09:13,020 --> 00:09:15,210 use his striatal system. 144 00:09:15,210 --> 00:09:16,701 Why is that? 145 00:09:16,701 --> 00:09:19,330 How is the striatum then getting its inputs? 146 00:09:22,059 --> 00:09:23,600 Where did they get its inputs if they 147 00:09:23,600 --> 00:09:24,840 don't come from the cortex? 148 00:09:28,680 --> 00:09:34,750 Remember they come from the polar parts of the thalamus. 149 00:09:34,750 --> 00:09:38,590 The nuclei we call the intralaminar and midline 150 00:09:38,590 --> 00:09:42,770 nuclei, they're mostly getting multimodal input. 151 00:09:42,770 --> 00:09:45,060 But some of those nuclei are more 152 00:09:45,060 --> 00:09:49,000 dominated by the visual areas of the tectum. 153 00:09:49,000 --> 00:09:52,130 They're getting a lot of input from the optic tectum. 154 00:09:52,130 --> 00:09:55,700 The somatosensory system pathways don't all 155 00:09:55,700 --> 00:09:57,250 come through the tectum, some of them 156 00:09:57,250 --> 00:09:59,890 come directly from the spinal [INAUDIBLE]. 157 00:10:06,480 --> 00:10:09,020 And auditory inputs also reach those. 158 00:10:09,020 --> 00:10:11,980 And in addition to the intralaminar and midline 159 00:10:11,980 --> 00:10:15,210 nuclei, there are what appear to be 160 00:10:15,210 --> 00:10:19,990 older parts of the thalamus in the posterior thalamus. 161 00:10:19,990 --> 00:10:24,320 There's a group of nuclei sort of in the interstices 162 00:10:24,320 --> 00:10:28,260 between the visual, somatosensory, and auditory-- 163 00:10:28,260 --> 00:10:31,450 the main nuclei we consider to be 164 00:10:31,450 --> 00:10:33,800 involved in those three senses. 165 00:10:33,800 --> 00:10:38,040 But outside those nuclei there's the posterior group of nuclei, 166 00:10:38,040 --> 00:10:42,211 and it's basically multimodal cells 167 00:10:42,211 --> 00:10:46,630 that project to multimodal cortical areas. 168 00:10:46,630 --> 00:10:51,068 OK, well we'll be talking more about that in a minute. 169 00:10:51,068 --> 00:10:57,420 But how did the cortex expand? 170 00:10:57,420 --> 00:11:01,080 We've talked about this before. 171 00:11:01,080 --> 00:11:05,060 It expanded by individual areas getting a lot bigger. 172 00:11:05,060 --> 00:11:08,120 Like the striate area, especially the foveal area, 173 00:11:08,120 --> 00:11:12,680 got quite large, like here in the owl monkey. 174 00:11:12,680 --> 00:11:15,470 But also there's been a multiplication 175 00:11:15,470 --> 00:11:19,160 of different representations of the same sensory surface. 176 00:11:19,160 --> 00:11:20,590 So in this case, the retina. 177 00:11:20,590 --> 00:11:25,010 And it's represented in different ways. 178 00:11:25,010 --> 00:11:26,740 And sometimes we don't understand 179 00:11:26,740 --> 00:11:31,030 the functional differences, and in some cases we do understand. 180 00:11:31,030 --> 00:11:33,310 And that's an area that the functional imaging 181 00:11:33,310 --> 00:11:37,160 work in recent years has contributed quite a bit to 182 00:11:37,160 --> 00:11:39,010 for understanding this in the human brain. 183 00:11:43,110 --> 00:11:46,470 So what was probably the earliest parcellation 184 00:11:46,470 --> 00:11:49,200 of the pallium? 185 00:11:49,200 --> 00:11:54,610 Parcellation meaning it gets divided into different parts. 186 00:11:54,610 --> 00:11:56,350 How did the pallium get started? 187 00:11:59,060 --> 00:12:02,800 The whole endbrain, initially, grew out 188 00:12:02,800 --> 00:12:05,100 of the olfactory system. 189 00:12:05,100 --> 00:12:08,730 It was totally dominated by olfaction. 190 00:12:08,730 --> 00:12:13,340 This view is actually a common one. 191 00:12:13,340 --> 00:12:20,322 It was argued by C. Judson Herrick, for example, 192 00:12:20,322 --> 00:12:22,440 in the early part of the 20th century. 193 00:12:24,990 --> 00:12:27,640 It was commonly believed that the evidence for it 194 00:12:27,640 --> 00:12:29,690 wasn't major. 195 00:12:29,690 --> 00:12:34,380 They didn't know about some of the most primitive vertebrates. 196 00:12:34,380 --> 00:12:41,120 So he used the tiger salamander more than any other animal 197 00:12:41,120 --> 00:12:43,220 and based a lot of his conclusions 198 00:12:43,220 --> 00:12:46,620 on what he found in the tiger salamander. 199 00:12:46,620 --> 00:12:48,900 At that time, they didn't have the really good 200 00:12:48,900 --> 00:12:54,720 experimental tracing methods for looking at connections. 201 00:12:54,720 --> 00:12:57,870 But I have the big advantage now in writing 202 00:12:57,870 --> 00:13:01,750 about this stuff in that the techniques are much more 203 00:13:01,750 --> 00:13:05,090 sensitive, and they have been applied in a number of studies 204 00:13:05,090 --> 00:13:07,990 to some of these really primitive vertebrates. 205 00:13:07,990 --> 00:13:12,210 And that's why, when we talk about olfactory system, 206 00:13:12,210 --> 00:13:16,850 we talked about the sea lampreys and the hagfish. 207 00:13:16,850 --> 00:13:19,712 You know, hagfish are more specialized. 208 00:13:19,712 --> 00:13:21,920 So some people don't think they're a very good model. 209 00:13:21,920 --> 00:13:27,670 But in both of those animals, olfactory projections 210 00:13:27,670 --> 00:13:30,650 go to everywhere in the endbrain, everywhere. 211 00:13:30,650 --> 00:13:33,630 In fact, they even go into the diencephalon 212 00:13:33,630 --> 00:13:37,260 directly from the olfactory bulbs. 213 00:13:37,260 --> 00:13:40,662 So the earliest parcellation is separation 214 00:13:40,662 --> 00:13:45,510 of the olfactory inputs from the non-olfactory. 215 00:13:45,510 --> 00:13:47,650 That's the earliest parcellation. 216 00:13:47,650 --> 00:13:51,700 So if you look at the gene expression data in the sea 217 00:13:51,700 --> 00:13:56,326 lamprey, it's been a little controversial 218 00:13:56,326 --> 00:13:58,470 with some varying results. 219 00:13:58,470 --> 00:14:01,372 But people that have reviewed it-- 220 00:14:01,372 --> 00:14:04,600 that have gone over all of it and reviewed it carefully-- 221 00:14:04,600 --> 00:14:10,360 will tell you that there's at least two main types according 222 00:14:10,360 --> 00:14:11,820 to gene expression. 223 00:14:11,820 --> 00:14:15,476 And it corresponds to the non-olfactory areas. 224 00:14:15,476 --> 00:14:17,110 AUDIENCE: Corresponds to what? 225 00:14:17,110 --> 00:14:20,350 PROFESSOR: Non-olfactory and olfactory. 226 00:14:20,350 --> 00:14:27,460 OK, so that was the earliest parcellation in the pallium, 227 00:14:27,460 --> 00:14:31,110 and we know that that olfactory cortex doesn't 228 00:14:31,110 --> 00:14:35,176 get direct olfactory input from the olfactory bulbs, right? 229 00:14:35,176 --> 00:14:39,030 Because olfactory bulbs project directly to it. 230 00:14:39,030 --> 00:14:42,520 But the part that the olfactory bulb doesn't project to, 231 00:14:42,520 --> 00:14:47,890 it's dominated by the thalamus 232 00:14:47,890 --> 00:14:50,280 So then I ask about factors that influence 233 00:14:50,280 --> 00:14:55,810 thalamic parcellation, so we'll look at that. 234 00:14:55,810 --> 00:14:58,570 And then I mention what you commonly hear-- and you'll 235 00:14:58,570 --> 00:15:00,120 probably hear it in medical schools, 236 00:15:00,120 --> 00:15:04,120 if you take [? neuromatter-- ?] but these multimodal 237 00:15:04,120 --> 00:15:07,530 association areas are the most recent to evolve. 238 00:15:10,640 --> 00:15:14,400 I would change that a little bit and say, no. 239 00:15:14,400 --> 00:15:16,560 They were probably the oldest type of cortex, 240 00:15:16,560 --> 00:15:19,070 but they're the most recent to really expand 241 00:15:19,070 --> 00:15:24,870 in the human brain because there's evidence 242 00:15:24,870 --> 00:15:30,300 that the unimodal areas are evolved out 243 00:15:30,300 --> 00:15:31,960 of the multimodal areas. 244 00:15:37,440 --> 00:15:41,360 If you look at the brains of some rodents that 245 00:15:41,360 --> 00:15:44,100 are a little more primitive in their structure, 246 00:15:44,100 --> 00:15:50,310 like the prairie voles, have been well-studied with this, 247 00:15:50,310 --> 00:15:52,990 and look at the cortical unit recording work. 248 00:15:52,990 --> 00:15:59,960 You'll find that there's a lot of multimodal input into areas 249 00:15:59,960 --> 00:16:03,550 that we used to think were unimodal. 250 00:16:03,550 --> 00:16:04,850 They are multimodal. 251 00:16:04,850 --> 00:16:07,900 And even in the primary sensory areas, 252 00:16:07,900 --> 00:16:09,625 there's often more than one modality. 253 00:16:09,625 --> 00:16:11,870 You find other modalities going right 254 00:16:11,870 --> 00:16:14,647 into auditory cortex and visual cortex, for example. 255 00:16:17,330 --> 00:16:20,580 All of it supporting this view. 256 00:16:20,580 --> 00:16:22,822 Yeah? 257 00:16:22,822 --> 00:16:26,842 AUDIENCE: In the centipede, do they 258 00:16:26,842 --> 00:16:29,460 find like incomplete parcellations? 259 00:16:29,460 --> 00:16:32,980 PROFESSOR: That is so loud in the back, I'm having trouble. 260 00:16:32,980 --> 00:16:38,764 AUDIENCE: Centipedes, do they find incomplete parcellations? 261 00:16:38,764 --> 00:16:40,930 PROFESSOR: There's a lot of incomplete parcellation. 262 00:16:40,930 --> 00:16:44,800 In fact, with some of those families, 263 00:16:44,800 --> 00:16:47,920 you never find complete parcellation 264 00:16:47,920 --> 00:16:50,270 into the sensory areas. 265 00:16:50,270 --> 00:16:52,250 And that is just never taught. 266 00:16:52,250 --> 00:16:53,710 I don't know why it's not taught. 267 00:16:53,710 --> 00:16:56,090 Even Hubel and Wiesel, here at Harvard, 268 00:16:56,090 --> 00:16:58,155 doing that beautiful work on the visual cortex. 269 00:16:58,155 --> 00:17:00,390 They started with cats. 270 00:17:00,390 --> 00:17:03,590 They found some auditory inputs into the visual cortex 271 00:17:03,590 --> 00:17:08,210 of the cat, and you have to look very hard for it 272 00:17:08,210 --> 00:17:09,420 in their early papers. 273 00:17:09,420 --> 00:17:11,040 And I asked them about it one time, 274 00:17:11,040 --> 00:17:16,490 and Torsten told me, yes, we did find that. 275 00:17:16,490 --> 00:17:20,839 And we didn't know what to do with it, 276 00:17:20,839 --> 00:17:23,270 so we sort of forgot about it. 277 00:17:23,270 --> 00:17:27,149 They were just working out how the cascade specification 278 00:17:27,149 --> 00:17:31,000 of unit properties in the visual system because that 279 00:17:31,000 --> 00:17:32,120 wasn't known yet. 280 00:17:32,120 --> 00:17:36,260 So they focused on that and so the auditory input just 281 00:17:36,260 --> 00:17:39,115 wasn't important enough to understand the main things 282 00:17:39,115 --> 00:17:41,060 that the visual cortex was doing. 283 00:17:41,060 --> 00:17:44,520 And I'm saying, well, if we're interested in evolution, 284 00:17:44,520 --> 00:17:47,434 though, we have to pay attention to these kinds of things. 285 00:17:47,434 --> 00:17:49,346 AUDIENCE: [INAUDIBLE] was asking what 286 00:17:49,346 --> 00:17:53,529 if-- like if there were people who have synesthesia. 287 00:17:53,529 --> 00:17:54,820 PROFESSOR: Oh, the synesthesia. 288 00:17:54,820 --> 00:17:55,320 OK. 289 00:17:55,320 --> 00:17:59,538 AUDIENCE: Is the lack of a conversion 290 00:17:59,538 --> 00:18:05,638 from a multiunit area into a unimodal area 291 00:18:05,638 --> 00:18:09,054 part of what causes the phenomena? 292 00:18:09,054 --> 00:18:11,740 PROFESSOR: Yeah, there is no evidence for that 293 00:18:11,740 --> 00:18:13,540 that I know of. 294 00:18:13,540 --> 00:18:17,320 But now with good functional imaging methods, 295 00:18:17,320 --> 00:18:20,283 it would be possible to study synesthesia in a way 296 00:18:20,283 --> 00:18:21,786 that we couldn't before. 297 00:18:21,786 --> 00:18:23,480 You know, it's a good question. 298 00:18:27,560 --> 00:18:29,315 I will look into that because it's 299 00:18:29,315 --> 00:18:33,762 such an interesting question, you know. 300 00:18:33,762 --> 00:18:37,650 But I really doubt its result in any major differences 301 00:18:37,650 --> 00:18:42,405 in the way the human brain is connected. 302 00:18:46,760 --> 00:18:48,813 So this is just what we're talking about. 303 00:18:57,410 --> 00:19:00,330 And the evidence I talk about, this 304 00:19:00,330 --> 00:19:03,985 is actually from data from hamsters that I studied. 305 00:19:03,985 --> 00:19:07,960 You're looking at projections from inferior colliculus, 306 00:19:07,960 --> 00:19:10,320 superficial and deep, superior colliculus, 307 00:19:10,320 --> 00:19:12,330 and from the pretectal area. 308 00:19:12,330 --> 00:19:14,640 And looking at where they go and the pattern they 309 00:19:14,640 --> 00:19:17,520 form in the thalamus. 310 00:19:17,520 --> 00:19:20,480 And if you look carefully at this 311 00:19:20,480 --> 00:19:22,200 you see that, in the thalamus, you 312 00:19:22,200 --> 00:19:23,635 have the same spatial arrangement 313 00:19:23,635 --> 00:19:25,920 that you have this here. 314 00:19:25,920 --> 00:19:32,010 The auditory input comes in in this more inferior 315 00:19:32,010 --> 00:19:37,380 lateral position, and that's where it forms its connections. 316 00:19:37,380 --> 00:19:39,590 But it's right next to multimodal parts 317 00:19:39,590 --> 00:19:41,730 of the lateral posterior nucleus. 318 00:19:41,730 --> 00:19:45,270 And then in the more superficial parts of the lateral posterior 319 00:19:45,270 --> 00:19:48,900 getting inputs directly from the superior colliculus, 320 00:19:48,900 --> 00:19:51,210 it's visual. 321 00:19:51,210 --> 00:19:54,240 And up in front you have the pretectal area, 322 00:19:54,240 --> 00:19:57,700 and those axons course rostrally near the midline. 323 00:19:57,700 --> 00:20:00,210 And they go right into the rostral parts 324 00:20:00,210 --> 00:20:01,810 of the lateral nucleus. 325 00:20:01,810 --> 00:20:06,910 Highly neglected that pathway, and it's only recently 326 00:20:06,910 --> 00:20:13,470 that you can find studies of what it might be doing. 327 00:20:13,470 --> 00:20:14,980 Because I've worked in this area, 328 00:20:14,980 --> 00:20:17,075 I've paid a lot of attention to that. 329 00:20:21,260 --> 00:20:23,890 I think when this picture was reproduced in the book, 330 00:20:23,890 --> 00:20:27,360 they put just L. But it's usually 331 00:20:27,360 --> 00:20:30,830 called the lateral dorsal nucleus. 332 00:20:30,830 --> 00:20:36,520 A few older [? papers ?] will call it lateralis inferior. 333 00:20:36,520 --> 00:20:40,020 OK, and then my interpretation of parcellation 334 00:20:40,020 --> 00:20:43,690 is that this shows input from the retina, 335 00:20:43,690 --> 00:20:47,705 here in the dark blue, input from pretectum 336 00:20:47,705 --> 00:20:51,300 and inferior colliculus and superior colliculus 337 00:20:51,300 --> 00:20:54,800 coming into the thalamus, and how, initially, it's 338 00:20:54,800 --> 00:20:59,940 almost certain this big tectum sending projections into what, 339 00:20:59,940 --> 00:21:02,650 initially, was a pretty small diencephalon. 340 00:21:02,650 --> 00:21:04,030 They overlap a lot. 341 00:21:04,030 --> 00:21:08,360 And if you look at the brain like at the tiger salamander, 342 00:21:08,360 --> 00:21:11,730 you find these kind of widely-branched axons 343 00:21:11,730 --> 00:21:12,860 in primitive animals. 344 00:21:12,860 --> 00:21:16,010 In development, you still see a lot of that. 345 00:21:16,010 --> 00:21:21,110 But then, as they form connections, 346 00:21:21,110 --> 00:21:23,720 as the connections increase in density, 347 00:21:23,720 --> 00:21:28,530 they tended to segregate from the other axons. 348 00:21:28,530 --> 00:21:31,790 And that's what I'm showing through these later stages. 349 00:21:31,790 --> 00:21:35,030 So here, they're almost completely segregated. 350 00:21:35,030 --> 00:21:38,380 Inferior colliculus going down here, 351 00:21:38,380 --> 00:21:42,390 the retina going more superficially in the thalamus 352 00:21:42,390 --> 00:21:46,830 there through the ventral part. 353 00:21:46,830 --> 00:21:50,220 Superior colliculus carrying visual information that 354 00:21:50,220 --> 00:21:54,810 did overlap in the geniculate body, 355 00:21:54,810 --> 00:21:59,656 but then it took over the parts of the LP. 356 00:21:59,656 --> 00:22:06,100 And in the pretectal, focusing on just specific sections 357 00:22:06,100 --> 00:22:07,870 of the LP. 358 00:22:07,870 --> 00:22:10,800 So you end up with this pattern. 359 00:22:10,800 --> 00:22:13,525 But that process where you get the segregation 360 00:22:13,525 --> 00:22:15,690 is called parcellation. 361 00:22:15,690 --> 00:22:19,890 Experimentally, in development, if we got the retina 362 00:22:19,890 --> 00:22:23,890 to send projections to the wrong side of the tectum, 363 00:22:23,890 --> 00:22:25,470 here's what they do developmentally. 364 00:22:25,470 --> 00:22:28,096 They grow in, and they just overlap with each other. 365 00:22:28,096 --> 00:22:30,510 They just intertwine. 366 00:22:30,510 --> 00:22:33,734 But then as they begin to form connections, 367 00:22:33,734 --> 00:22:35,650 the connections of one eye and the connections 368 00:22:35,650 --> 00:22:36,774 of the other eye segregate. 369 00:22:39,340 --> 00:22:42,330 As they get denser they tend to terminate in the areas 370 00:22:42,330 --> 00:22:45,380 closest to where they came in because that's where they 371 00:22:45,380 --> 00:22:47,470 formed denser connections first, you see. 372 00:22:47,470 --> 00:22:48,660 They got there first. 373 00:22:48,660 --> 00:22:51,110 That's where they form the connections first. 374 00:22:51,110 --> 00:22:54,530 And then they segregate. 375 00:22:54,530 --> 00:22:59,630 They pull away from each other, literally. 376 00:22:59,630 --> 00:23:03,350 They don't necessarily degenerate, but it withdraws. 377 00:23:18,142 --> 00:23:19,136 All right. 378 00:23:22,620 --> 00:23:25,670 So the idea here is that multimodal convergence 379 00:23:25,670 --> 00:23:28,405 was the primitive state of all of the thalamus. 380 00:23:28,405 --> 00:23:30,880 And then parcellation occurred. 381 00:23:30,880 --> 00:23:34,115 And correlated changes occurred within the neocortex. 382 00:23:34,115 --> 00:23:36,905 [PHONE RINGING] 383 00:23:36,905 --> 00:23:39,730 I'm getting reports on a member of the family that's 384 00:23:39,730 --> 00:23:41,173 in the hospital. 385 00:23:41,173 --> 00:23:44,540 [PHONE RINGING] 386 00:23:44,540 --> 00:23:47,418 I can wait a few minutes to look at that there. 387 00:23:55,860 --> 00:23:58,490 All right, so when you look across widely different 388 00:23:58,490 --> 00:24:02,200 animals, like, here's the [INAUDIBLE]. 389 00:24:02,200 --> 00:24:07,550 This is animals like the salamander or the frog. 390 00:24:07,550 --> 00:24:09,840 They have fewer thalamic areas. 391 00:24:09,840 --> 00:24:12,460 When you go up to reptiles, there's more. 392 00:24:12,460 --> 00:24:13,555 Birds, even more. 393 00:24:13,555 --> 00:24:16,100 And mammals, the most. 394 00:24:16,100 --> 00:24:22,710 If you look in the human compared with other primates, 395 00:24:22,710 --> 00:24:26,470 you'll find the same areas, but you 396 00:24:26,470 --> 00:24:28,350 can subdivide the areas more. 397 00:24:28,350 --> 00:24:31,030 It's like the brain, with evolution, 398 00:24:31,030 --> 00:24:32,600 becomes more specialized. 399 00:24:32,600 --> 00:24:36,610 There's more parcellation than there is earlier. 400 00:24:36,610 --> 00:24:39,200 And that's with this comparative data support. 401 00:24:39,200 --> 00:24:43,490 This is just a concept based on one 402 00:24:43,490 --> 00:24:46,630 that [? Streeter ?] published after reviewing 403 00:24:46,630 --> 00:24:47,790 a lot of this work. 404 00:24:55,210 --> 00:24:58,985 And then I talk about these three systems separately. 405 00:24:58,985 --> 00:25:00,950 These are all things that we did talk 406 00:25:00,950 --> 00:25:04,350 about when we talked about these systems. 407 00:25:04,350 --> 00:25:05,354 It's just a reminder. 408 00:25:08,140 --> 00:25:10,300 And then I talked about that segregation 409 00:25:10,300 --> 00:25:12,050 within the somatosensory system that 410 00:25:12,050 --> 00:25:14,800 led to the revolution of the motor cortex. 411 00:25:14,800 --> 00:25:17,190 And this is the picture that I had. 412 00:25:17,190 --> 00:25:19,620 This was from chapter 15. 413 00:25:19,620 --> 00:25:27,855 And it shows how you can define somatosensory cortex. 414 00:25:27,855 --> 00:25:31,550 You can define it in terms of thalamic projections. 415 00:25:31,550 --> 00:25:34,420 The part that gets input from the posterior 416 00:25:34,420 --> 00:25:38,980 nucleus because that's where the somatosensory input comes 417 00:25:38,980 --> 00:25:41,710 in from the spinal cord in the trigeminal system. 418 00:25:41,710 --> 00:25:46,490 And then, anterior through that, the ventrolateral nucleus 419 00:25:46,490 --> 00:25:52,010 projects, what we call, the primary motor cortex. 420 00:25:52,010 --> 00:25:55,530 The VA anterior just goes even more anterior, the premotor 421 00:25:55,530 --> 00:25:57,120 cortex. 422 00:25:57,120 --> 00:26:00,910 And it shows how these projections of those two nuclei 423 00:26:00,910 --> 00:26:04,170 are completely overlapping in the [INAUDIBLE]. 424 00:26:04,170 --> 00:26:08,120 So if you record from it, physiologically, you 425 00:26:08,120 --> 00:26:09,180 can't separate them. 426 00:26:09,180 --> 00:26:12,540 If you study the projections, you can't separate them. 427 00:26:12,540 --> 00:26:16,380 And then this is not the opossum, 428 00:26:16,380 --> 00:26:17,865 it's the brushtail possum. 429 00:26:17,865 --> 00:26:19,820 It's a different animal. 430 00:26:19,820 --> 00:26:23,350 And you find an area that doesn't overlap 431 00:26:23,350 --> 00:26:24,750 for each of these nuclei but then 432 00:26:24,750 --> 00:26:27,820 there's a fairly large area where they overlap. 433 00:26:27,820 --> 00:26:30,620 If you look at a rat, there's just 434 00:26:30,620 --> 00:26:32,850 an area of the hindlimb representation 435 00:26:32,850 --> 00:26:36,320 where there has not been a complete parcellation. 436 00:26:36,320 --> 00:26:38,545 But otherwise it's pretty segregated. 437 00:26:38,545 --> 00:26:46,380 If you look at a primate, just a galago, complete segregation. 438 00:26:46,380 --> 00:26:49,105 That's true of all the larger primates. 439 00:26:49,105 --> 00:26:50,700 In fact, I think all of the primates 440 00:26:50,700 --> 00:26:54,480 that I know about are like that. 441 00:26:54,480 --> 00:27:00,070 So the evidence is pretty good for this kind of parcellation 442 00:27:00,070 --> 00:27:01,990 in the somatosensory system, and how 443 00:27:01,990 --> 00:27:04,203 the motor cortex evolved out of it. 444 00:27:04,203 --> 00:27:06,780 OK, whereas the visual system, people 445 00:27:06,780 --> 00:27:10,770 have looked at widely different animals including marsupials. 446 00:27:10,770 --> 00:27:12,960 You always see a V1 and a V2. 447 00:27:16,070 --> 00:27:19,210 And in most of them, you see a third area 448 00:27:19,210 --> 00:27:22,630 that's always there, an area we call MT in the monkeys. 449 00:27:25,360 --> 00:27:27,570 And then you'll see varying numbers 450 00:27:27,570 --> 00:27:32,320 of additional visual areas. 451 00:27:32,320 --> 00:27:35,130 In some there are not many at all. 452 00:27:35,130 --> 00:27:37,940 There's not much cortex. 453 00:27:37,940 --> 00:27:39,720 But in the large primates and in humans, 454 00:27:39,720 --> 00:27:42,920 there is a very large number. 455 00:27:42,920 --> 00:27:44,533 So these are the methods of expansion 456 00:27:44,533 --> 00:27:46,700 that we've talked about. 457 00:27:46,700 --> 00:27:48,050 These are pictures of that. 458 00:27:51,090 --> 00:27:54,260 Primates, and here you see in the gray color 459 00:27:54,260 --> 00:27:57,790 here-- maybe that's a blueish gray-- 460 00:27:57,790 --> 00:27:59,680 you see what [? Nessalum ?] calls 461 00:27:59,680 --> 00:28:03,130 the heteromodal areas, the multimodal areas. 462 00:28:03,130 --> 00:28:07,800 And it's typical to picture rat and hedgehog, 463 00:28:07,800 --> 00:28:10,010 especially hedgehog-- you see how 464 00:28:10,010 --> 00:28:12,580 they picture it-- no multimodal areas. 465 00:28:16,110 --> 00:28:18,680 It'll be interesting to see how my colleagues that 466 00:28:18,680 --> 00:28:22,160 have published these kinds of pictures for a long time 467 00:28:22,160 --> 00:28:25,390 will react because I've looked really carefully 468 00:28:25,390 --> 00:28:28,121 at that literature, and that is not what you find. 469 00:28:28,121 --> 00:28:29,890 There's a lot of multimodal cortex, 470 00:28:29,890 --> 00:28:33,170 and this is-- so I have this line, 471 00:28:33,170 --> 00:28:37,090 multimodal regions do exist in between the major sensory areas 472 00:28:37,090 --> 00:28:39,375 in hedgehog, hamster, vole. 473 00:28:39,375 --> 00:28:42,880 It's been best studied in the vole. 474 00:28:42,880 --> 00:28:45,920 And unimodal and multimodal association areas 475 00:28:45,920 --> 00:28:50,600 are not so distinguishable as they are in the primates 476 00:28:50,600 --> 00:28:53,680 because they're all multimodal, and these two modalities 477 00:28:53,680 --> 00:28:56,356 will go into those areas. 478 00:28:56,356 --> 00:28:58,640 They might be dominated by one sense, 479 00:28:58,640 --> 00:29:05,880 but they're not really unimodal association areas. 480 00:29:05,880 --> 00:29:08,580 And then I talk about some multimodal inputs even 481 00:29:08,580 --> 00:29:09,940 in the primary sensory areas. 482 00:29:13,270 --> 00:29:16,300 And that just indicates that this parcellation 483 00:29:16,300 --> 00:29:19,790 isn't complete. 484 00:29:19,790 --> 00:29:24,240 Maybe in the large primates and in humans, 485 00:29:24,240 --> 00:29:27,080 it's about as complete as it can be. 486 00:29:27,080 --> 00:29:30,181 But not in many animals. 487 00:29:30,181 --> 00:29:33,940 So it's a neglected fact that gives us clues about evolution. 488 00:29:33,940 --> 00:29:37,994 And because of that I've paid a lot of attention to it. 489 00:29:37,994 --> 00:29:40,160 And then I have a little bit about axon trajectories 490 00:29:40,160 --> 00:29:43,820 that you should realize. 491 00:29:43,820 --> 00:29:45,690 This is for reptilian cortex, which 492 00:29:45,690 --> 00:29:51,365 you'll see the same thing for amphibians and fishes 493 00:29:51,365 --> 00:29:57,630 that where, in the cortex, the axons don't come in from below. 494 00:29:57,630 --> 00:30:00,520 Like in this picture, you'll see here 495 00:30:00,520 --> 00:30:03,330 for the hedgehog, the mammal, they 496 00:30:03,330 --> 00:30:05,790 come in through the white matter. 497 00:30:05,790 --> 00:30:10,150 Then they go up and terminate in the various layers including 498 00:30:10,150 --> 00:30:12,200 layer one there. 499 00:30:12,200 --> 00:30:16,660 Whereas in the reptiles and turtles 500 00:30:16,660 --> 00:30:20,380 and in the salamander and other amphibians, 501 00:30:20,380 --> 00:30:22,516 they come in like this. 502 00:30:22,516 --> 00:30:24,265 They don't come in through a white matter, 503 00:30:24,265 --> 00:30:26,030 they travel conventionally. 504 00:30:26,030 --> 00:30:31,620 So if you look, this is the way that it was pictured. 505 00:30:31,620 --> 00:30:37,540 And Allman, he used a picture here of Pedro Ramon y 506 00:30:37,540 --> 00:30:42,810 Cajal, Santiago Ramon y Cajal's brother. 507 00:30:42,810 --> 00:30:48,680 And this is from the American, CJ Herrick, 508 00:30:48,680 --> 00:30:53,160 where he shows a similar level where you see this beautifully 509 00:30:53,160 --> 00:30:58,155 thick medial pallium with this cortex next to it. 510 00:31:01,256 --> 00:31:05,130 It's a multimodal area of dorsal cortex. 511 00:31:05,130 --> 00:31:07,850 In most animals it's called dorsal pallium 512 00:31:07,850 --> 00:31:09,010 or dorsal cortex. 513 00:31:09,010 --> 00:31:12,960 And it projects heavily into the medial pallium, 514 00:31:12,960 --> 00:31:16,980 but it gets multimodal input from the thalamus. 515 00:31:16,980 --> 00:31:19,240 But you see how the axons travel. 516 00:31:19,240 --> 00:31:21,760 Here they come out of the lateral forebrain [INAUDIBLE] 517 00:31:21,760 --> 00:31:22,260 they travel. 518 00:31:22,260 --> 00:31:24,130 They don't travel through a white matter 519 00:31:24,130 --> 00:31:26,300 at the base like the mammals. 520 00:31:26,300 --> 00:31:30,390 OK, so then I point out that in the hamster, 521 00:31:30,390 --> 00:31:32,600 and this is true for hedgehog too, 522 00:31:32,600 --> 00:31:35,990 there are some neurons in the lateral thalamus. 523 00:31:35,990 --> 00:31:37,850 Some of the data indicates they might all 524 00:31:37,850 --> 00:31:39,892 be in the posterior nuclei group, 525 00:31:39,892 --> 00:31:42,000 but they're in the lateral thalamus. 526 00:31:42,000 --> 00:31:44,770 And they have a trajectory that's 527 00:31:44,770 --> 00:31:46,821 more alike those primitive animals. 528 00:31:46,821 --> 00:31:50,430 So here's, I call it, the type one axon 529 00:31:50,430 --> 00:31:52,345 coming in like from geniculate body 530 00:31:52,345 --> 00:31:55,640 and arborizing primarily in layer one and four. 531 00:31:55,640 --> 00:31:59,190 But they have some branches in the other layers as well. 532 00:31:59,190 --> 00:32:04,040 But then you have this other type that travel long distances 533 00:32:04,040 --> 00:32:06,010 and terminate-- it's as if they ignore 534 00:32:06,010 --> 00:32:11,510 the boundaries between cortical areas. 535 00:32:11,510 --> 00:32:17,060 They go-- even the primary visual cortex apparently 536 00:32:17,060 --> 00:32:18,520 carry multimodal input. 537 00:32:25,150 --> 00:32:28,600 It's an odd fact in neuroanatomy that such axons exist, 538 00:32:28,600 --> 00:32:31,500 and they have not been studied very well at all. 539 00:32:31,500 --> 00:32:33,870 OK, but they can account for some 540 00:32:33,870 --> 00:32:37,415 of the physiological results that we've been talking about. 541 00:32:45,770 --> 00:32:50,250 So I want to talk more specifically now about-- this 542 00:32:50,250 --> 00:32:54,910 is now stuff from chapter 33, which 543 00:32:54,910 --> 00:32:56,520 we'll talk about next time as well. 544 00:32:59,140 --> 00:33:02,620 We'll try to finish chapter 33 next time and maybe at least 545 00:33:02,620 --> 00:33:08,760 get started in the last chapter in the book. 546 00:33:08,760 --> 00:33:13,950 So I wanna say more about cell types and they're connections. 547 00:33:20,020 --> 00:33:23,200 Different regions-- how we name them-- there's 548 00:33:23,200 --> 00:33:26,200 different ways to talk about different regions. 549 00:33:26,200 --> 00:33:29,070 And then the major fiber routes which we brought up before, 550 00:33:29,070 --> 00:33:30,456 but I want to review them. 551 00:33:33,230 --> 00:33:36,665 So you should be able to contrast 552 00:33:36,665 --> 00:33:39,370 some of the major neural cell types. 553 00:33:39,370 --> 00:33:41,280 What are the two main cell types that you 554 00:33:41,280 --> 00:33:44,700 can think of if you just think of structure and talking 555 00:33:44,700 --> 00:33:47,196 about neocortex? 556 00:33:47,196 --> 00:33:49,020 When [INAUDIBLE] talked about these, 557 00:33:49,020 --> 00:33:52,380 he just mainly talked about these two cell types. 558 00:33:52,380 --> 00:33:56,380 The dominant cell type, parameter cells. 559 00:33:56,380 --> 00:33:59,370 With the apical dendrite going right up towards the surface 560 00:33:59,370 --> 00:34:03,550 and arborizing, OK. 561 00:34:03,550 --> 00:34:07,410 And the other type, you can lump them all together 562 00:34:07,410 --> 00:34:09,120 and call them stellate cells. 563 00:34:09,120 --> 00:34:14,143 There are other shapes-- a fusiform shape, for example, 564 00:34:14,143 --> 00:34:18,520 sort of a bipolar-looking neuron. 565 00:34:18,520 --> 00:34:23,030 But there's other ways to classify them. 566 00:34:23,030 --> 00:34:24,739 You can use neurotransmitters. 567 00:34:24,739 --> 00:34:30,147 You can use whether they're spiny or non-spiny, 568 00:34:30,147 --> 00:34:31,855 whether they're excitatory or inhibitory. 569 00:34:35,356 --> 00:34:37,409 So the criteria vary. 570 00:34:37,409 --> 00:34:40,429 And the nicest classification I've seen 571 00:34:40,429 --> 00:34:44,060 is in this picture, which I've put in the book, in which they 572 00:34:44,060 --> 00:34:48,555 separate these groups according to the spiny excitatory neurons 573 00:34:48,555 --> 00:34:51,570 all using glutamate as a transmitter, 574 00:34:51,570 --> 00:34:56,350 the non-spiny inhibitory or GABAergic interneurons. 575 00:34:56,350 --> 00:35:00,450 And notice that these are most all stellate in shape, 576 00:35:00,450 --> 00:35:03,485 a few of them might have a fusiform shape, but mostly 577 00:35:03,485 --> 00:35:07,650 the star-shaped cells that don't have an apical dendrite. 578 00:35:07,650 --> 00:35:11,770 Here are the pyramidal cells, with this apical dendrite. 579 00:35:11,770 --> 00:35:19,835 And this you see here, this is one in layer five. 580 00:35:19,835 --> 00:35:23,540 It's a big pyramidal cell. 581 00:35:23,540 --> 00:35:25,860 The apical dendrite goes right up 582 00:35:25,860 --> 00:35:28,910 and arborizes in the layer one. 583 00:35:28,910 --> 00:35:33,270 And these pictures lack a lot of the processes that are really 584 00:35:33,270 --> 00:35:35,570 there that are pretty complex. 585 00:35:35,570 --> 00:35:38,870 And it shows an enlargement here. 586 00:35:38,870 --> 00:35:41,735 You look at higher magnification of a Golgi stain 587 00:35:41,735 --> 00:35:44,800 or a cell that's been filled with the HRP 588 00:35:44,800 --> 00:35:46,540 or something like that, you'll see 589 00:35:46,540 --> 00:35:48,622 the little spines they can take. 590 00:35:52,980 --> 00:35:59,150 Sites that many of the synapses are formed in are spines. 591 00:35:59,150 --> 00:36:01,840 And then it shows where they go. 592 00:36:01,840 --> 00:36:04,280 Like these big cells in layer five 593 00:36:04,280 --> 00:36:10,865 go to the spinal cord, brainstem thalamus, striatum, and others 594 00:36:10,865 --> 00:36:14,140 of cortex, OK. 595 00:36:14,140 --> 00:36:17,440 The pyramidal cells in layer three and layer two 596 00:36:17,440 --> 00:36:21,750 are much smaller, but they're still pyramidally shaped. 597 00:36:21,750 --> 00:36:25,590 They're transcortical, so they're 598 00:36:25,590 --> 00:36:29,486 association cells of the cortex. 599 00:36:29,486 --> 00:36:31,820 The [? colloquial ?] cortical cells. 600 00:36:31,820 --> 00:36:35,940 A terms that's not usually used, but it's an appropriate term. 601 00:36:35,940 --> 00:36:39,040 And the only excitatory cell here 602 00:36:39,040 --> 00:36:44,310 that's not pyramidal in shape is a little stellate cell. 603 00:36:44,310 --> 00:36:49,030 We happen to call them granular cells in layer four. 604 00:36:49,030 --> 00:36:51,250 A lot of input from the thalamus comes in here. 605 00:36:51,250 --> 00:36:56,300 And the axons simply terminates within the same column, carries 606 00:36:56,300 --> 00:36:59,070 that information right up to the superficial layers, 607 00:36:59,070 --> 00:37:03,400 which we often call association layers, layers two and three, 608 00:37:03,400 --> 00:37:06,120 because they contain these neurons. 609 00:37:06,120 --> 00:37:10,090 They're getting input from these stellates 610 00:37:10,090 --> 00:37:16,190 and therefore they're projecting others areas of cortex. 611 00:37:16,190 --> 00:37:17,910 Now they do get other inputs. 612 00:37:17,910 --> 00:37:20,240 They get some direct input from the thalamus 613 00:37:20,240 --> 00:37:21,890 too, because the thalamus contacts 614 00:37:21,890 --> 00:37:28,610 those branches of the pyramidal [INAUDIBLE]. 615 00:37:28,610 --> 00:37:31,055 And then you'll see here for the non-spiny inhibitory 616 00:37:31,055 --> 00:37:33,560 interneurons, how many different shapes. 617 00:37:33,560 --> 00:37:37,850 And look at the way the axons form. 618 00:37:37,850 --> 00:37:45,490 You see cells like this that have an axon that 619 00:37:45,490 --> 00:37:49,540 distributes all the nearby columns. 620 00:37:49,540 --> 00:37:55,750 Here's one that all the axon distributes up and down 621 00:37:55,750 --> 00:37:56,680 the same column. 622 00:37:59,830 --> 00:38:02,590 They've all got local axons. 623 00:38:02,590 --> 00:38:05,760 Some of them covering a number of columns. 624 00:38:05,760 --> 00:38:08,112 Some of them covering only one column. 625 00:38:08,112 --> 00:38:11,460 But so two major divisions according 626 00:38:11,460 --> 00:38:14,160 to this classification, but if you do it just 627 00:38:14,160 --> 00:38:18,680 structurally you would say pyramidal and stellate 628 00:38:18,680 --> 00:38:21,310 are the two major types. 629 00:38:21,310 --> 00:38:23,250 And here's from [INAUDIBLE] book. 630 00:38:23,250 --> 00:38:26,550 He shows a small pyramidal cell in layer six, 631 00:38:26,550 --> 00:38:28,950 and then he shows a couple of stellates. 632 00:38:28,950 --> 00:38:31,330 And he has a more elaborate picture 633 00:38:31,330 --> 00:38:36,680 of both the dendrites and the axons. 634 00:38:36,680 --> 00:38:39,500 Whereas other anatomy books, like Brodal 635 00:38:39,500 --> 00:38:42,720 has a simplified picture of, in this case, 636 00:38:42,720 --> 00:38:45,696 interneurons where he's showing some of those same cells that 637 00:38:45,696 --> 00:38:47,700 are in the other picture. 638 00:38:47,700 --> 00:38:50,865 But he's put the axons in red like they did, simplified 639 00:38:50,865 --> 00:38:55,630 the dendritic tree a little bit and indicates 640 00:38:55,630 --> 00:38:56,760 how they terminate. 641 00:38:56,760 --> 00:39:02,865 These are all GABAergic cells, except this one. 642 00:39:02,865 --> 00:39:06,475 This is probably an excitatory cell therefore. 643 00:39:06,475 --> 00:39:14,340 So this would be the only one that is classified over here 644 00:39:14,340 --> 00:39:19,580 because it's a spiny excitatory cell. 645 00:39:19,580 --> 00:39:25,240 All right, and then I point out here 646 00:39:25,240 --> 00:39:28,005 that not all local interconnections 647 00:39:28,005 --> 00:39:31,540 within the neocortex are made by the short axon interneurons. 648 00:39:31,540 --> 00:39:34,860 And I'm talking about just locally. 649 00:39:34,860 --> 00:39:39,180 In the same column or between one column and nearby columns. 650 00:39:39,180 --> 00:39:43,070 They're made by axon collaterals. 651 00:39:43,070 --> 00:39:48,000 Almost all pictures that you see in textbooks 652 00:39:48,000 --> 00:39:53,360 never show this elaborate collateralization of the axon. 653 00:39:53,360 --> 00:39:55,950 But the Scheibels were very good anatomists. 654 00:39:55,950 --> 00:39:58,940 They published some of the best Golgi pictures 655 00:39:58,940 --> 00:40:03,270 in modern neuroanatomical literature. 656 00:40:03,270 --> 00:40:09,210 And here they're showing that the dendritic spread 657 00:40:09,210 --> 00:40:18,080 in the cat of neocortical cells averaged around 500 microns. 658 00:40:18,080 --> 00:40:21,905 Whereas the axon collaterals, collaterals 659 00:40:21,905 --> 00:40:24,860 of the initial segment of the axon, in this case, 660 00:40:24,860 --> 00:40:26,135 the axons are all going out. 661 00:40:29,220 --> 00:40:31,830 This one to other cortical areas. 662 00:40:31,830 --> 00:40:38,010 These two to the thalamus and brainstem and spinal cord. 663 00:40:38,010 --> 00:40:40,760 Look how much they cover, three thousand microns 664 00:40:40,760 --> 00:40:43,100 so three millimeters. 665 00:40:43,100 --> 00:40:46,280 So huge numbers of local connections 666 00:40:46,280 --> 00:40:48,034 are formed by these axon collaterals. 667 00:40:54,200 --> 00:40:58,680 Now you should be able to answer this, how neuroscientists 668 00:40:58,680 --> 00:41:02,940 define cortical layers and cortical columns. 669 00:41:02,940 --> 00:41:05,993 Divide it into anatomical methods 670 00:41:05,993 --> 00:41:09,585 where then this whole method and also the Golgi method, if it's 671 00:41:09,585 --> 00:41:13,780 so dominated, also [INAUDIBLE] stains. 672 00:41:13,780 --> 00:41:16,470 But what about the functional side, 673 00:41:16,470 --> 00:41:20,790 electrophysiology, our initial definition of columns 674 00:41:20,790 --> 00:41:25,050 came from electrophysiologists putting microelectrodes 675 00:41:25,050 --> 00:41:29,060 and seeing functional differences between one 676 00:41:29,060 --> 00:41:31,670 regional cortex in the immediately adjacent. 677 00:41:31,670 --> 00:41:35,350 Like in the visual cortex, you'd find that cells here 678 00:41:35,350 --> 00:41:38,570 respond to one eye, cells here respond to the next eye. 679 00:41:38,570 --> 00:41:43,740 And then back to the first eye and the second and so forth. 680 00:41:43,740 --> 00:41:48,320 So physiological methods and various anatomical methods. 681 00:41:48,320 --> 00:41:51,474 There are molecular methods in addition 682 00:41:51,474 --> 00:41:54,035 that have been applied, especially for layers. 683 00:41:54,035 --> 00:41:56,500 You look back in chapter 2, I had a picture 684 00:41:56,500 --> 00:41:58,770 where they had antibodies that bound 685 00:41:58,770 --> 00:42:04,050 to cells in specific laminae, specific layers 686 00:42:04,050 --> 00:42:04,875 of the neocortex. 687 00:42:04,875 --> 00:42:08,010 So that's still one more method. 688 00:42:08,010 --> 00:42:12,330 Molecular methods used for neuroanatomy. 689 00:42:12,330 --> 00:42:15,380 And this just summarizes these pictures. 690 00:42:15,380 --> 00:42:19,170 This is the one I used in the book, 691 00:42:19,170 --> 00:42:24,270 and this is the one that usually you see in books. 692 00:42:24,270 --> 00:42:26,330 And people will wonder, why did I 693 00:42:26,330 --> 00:42:32,130 choose this one by an American neuroanatomist and not 694 00:42:32,130 --> 00:42:33,700 the one that's always published? 695 00:42:33,700 --> 00:42:39,150 And that's because I insisted, with Amy's help, 696 00:42:39,150 --> 00:42:42,550 finding the sources. 697 00:42:42,550 --> 00:42:45,210 If I found people cited a certain source, 698 00:42:45,210 --> 00:42:47,600 I found the source. 699 00:42:47,600 --> 00:42:50,500 And I found out it was wrong again and again 700 00:42:50,500 --> 00:42:54,960 and again because people usually aren't 701 00:42:54,960 --> 00:42:57,100 that careful in their scholarship. 702 00:42:57,100 --> 00:42:59,100 I just wanted to point out to you 703 00:42:59,100 --> 00:43:01,046 that you can't believe everything 704 00:43:01,046 --> 00:43:05,320 you read even in science. 705 00:43:05,320 --> 00:43:10,060 Especially, scientists aren't always very good historians. 706 00:43:10,060 --> 00:43:13,730 Just thought you might like to know that. 707 00:43:13,730 --> 00:43:17,240 And we'll have to stop there. 708 00:43:17,240 --> 00:43:19,630 We'll come back and go through a few of these things. 709 00:43:19,630 --> 00:43:21,390 Now focus on the pictures. 710 00:43:21,390 --> 00:43:24,210 Make sure you're understanding the pictures, OK. 711 00:43:24,210 --> 00:43:26,260 They're all posted. 712 00:43:26,260 --> 00:43:29,320 It talks about cortical types, cortical columns, 713 00:43:29,320 --> 00:43:34,636 how you can define them anatomically, layers as well, 714 00:43:34,636 --> 00:43:37,910 and a few of the things that are commonly stated. 715 00:43:37,910 --> 00:43:48,190 OK, so we'll come back there in the next class. 716 00:43:48,190 --> 00:43:49,940 And I know we can get through these, 717 00:43:49,940 --> 00:43:52,100 and hopefully, we can get a little bit 718 00:43:52,100 --> 00:43:55,150 into the next chapter as well.