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 --> 00:00:10,710 to offer high quality educational resources for free. 5 00:00:10,710 --> 00:00:13,360 To make a donation or view additional materials 6 00:00:13,360 --> 00:00:17,241 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:17,241 --> 00:00:17,866 at ocw.mit.edu. 8 00:00:23,080 --> 00:00:28,160 PROFESSOR: I want to go over the homework I will post right 9 00:00:28,160 --> 00:00:29,210 after the class. 10 00:00:29,210 --> 00:00:32,220 I wanted to talk to you about it first. 11 00:00:32,220 --> 00:00:33,850 These are really worksheets. 12 00:00:33,850 --> 00:00:38,110 It's homework that you should all get everything right. 13 00:00:40,780 --> 00:00:42,510 I will do a separate homework that 14 00:00:42,510 --> 00:00:46,680 will make up for some of the bad quiz performances. 15 00:00:46,680 --> 00:00:48,440 I know you requested that. 16 00:00:48,440 --> 00:00:49,647 That's not what this is. 17 00:00:49,647 --> 00:00:51,940 This is to help you review. 18 00:00:51,940 --> 00:00:55,650 And I selected a bunch of pictures. 19 00:00:55,650 --> 00:00:58,200 I'm just giving you a [INAUDIBLE]. 20 00:00:58,200 --> 00:00:59,365 This will all be posted. 21 00:01:03,690 --> 00:01:09,475 I guess you all have access to printers. 22 00:01:12,630 --> 00:01:15,170 If you have problems printing it, 23 00:01:15,170 --> 00:01:18,360 just come with us after class. 24 00:01:18,360 --> 00:01:19,795 We'll print it. 25 00:01:19,795 --> 00:01:21,600 But I'm going to show you what it is. 26 00:01:21,600 --> 00:01:24,230 These are the worksheets. 27 00:01:24,230 --> 00:01:27,340 And you can see, if we look at one of them here, 28 00:01:27,340 --> 00:01:29,320 this is a pretty straightforward one, 29 00:01:29,320 --> 00:01:32,450 and you should remember now. 30 00:01:32,450 --> 00:01:38,445 Here you have places to write the names. 31 00:01:38,445 --> 00:01:43,220 And so, just to remind you what I want here, question on I 32 00:01:43,220 --> 00:01:44,930 say, in slide number one. 33 00:01:44,930 --> 00:01:48,467 That refers to the number of the slide is that. 34 00:01:51,820 --> 00:01:54,820 The number's actually written in the corner. 35 00:01:54,820 --> 00:01:59,780 And then I list A, B,C, D,E. I just want you to write 36 00:01:59,780 --> 00:02:04,390 the English and the Greek or Latin for each of those 37 00:02:04,390 --> 00:02:05,370 subdivision. 38 00:02:05,370 --> 00:02:09,199 That's what you do for that one. 39 00:02:09,199 --> 00:02:14,000 And for something like this, all of these are like that. 40 00:02:14,000 --> 00:02:20,890 Here I ask you to name the parts that are being pointed to. 41 00:02:20,890 --> 00:02:27,580 Here, I ask you to color in the pathway like I did in class. 42 00:02:27,580 --> 00:02:31,120 And I want the local reflex channel. 43 00:02:31,120 --> 00:02:37,220 Now, whereas this, the blank brain diagram. 44 00:02:37,220 --> 00:02:39,455 They're pretty similar to ones I used in class, 45 00:02:39,455 --> 00:02:45,290 but they match the text of the book very well. 46 00:02:45,290 --> 00:02:49,650 And then I ask you questions about them. 47 00:02:49,650 --> 00:02:54,520 But for those, because you have to-- if you have to draw them, 48 00:02:54,520 --> 00:02:57,420 notice I put it right in, most of the ones you would need 49 00:02:57,420 --> 00:02:57,920 printed . 50 00:03:01,750 --> 00:03:04,300 And for this one, too, because I'm asking for drawing. 51 00:03:08,100 --> 00:03:09,860 And then I ask a question up here. 52 00:03:09,860 --> 00:03:12,900 Here I want you to draw a primer sensor neuron. 53 00:03:12,900 --> 00:03:20,930 I've already drawn it for you on the horizontal diagram there, 54 00:03:20,930 --> 00:03:23,440 but I want you to do that here, too. 55 00:03:23,440 --> 00:03:26,660 And I want you to show these final [INAUDIBLE]. 56 00:03:26,660 --> 00:03:28,480 And then later, I do the same thing 57 00:03:28,480 --> 00:03:31,860 for the dorsal column and medial meniscus. 58 00:03:31,860 --> 00:03:35,070 And then I do the same thing for the corticospinal. 59 00:03:35,070 --> 00:03:37,030 So you can find those figures. 60 00:03:37,030 --> 00:03:38,080 They're all in the book. 61 00:03:38,080 --> 00:03:39,750 They were all on the slides, too. 62 00:03:44,110 --> 00:03:46,300 And I wanted you to draw them in. 63 00:03:46,300 --> 00:03:49,850 But if all you're going to do is find it and then go 64 00:03:49,850 --> 00:03:52,110 back and forth to get every detail right, 65 00:03:52,110 --> 00:03:53,800 you're not learning. 66 00:03:53,800 --> 00:03:58,192 You have to study it, then put it aside, and then try it. 67 00:03:58,192 --> 00:04:00,150 Try to draw it. 68 00:04:00,150 --> 00:04:02,600 And if you hand something in with all kinds of things 69 00:04:02,600 --> 00:04:05,280 crossed out because you didn't write it, that's all right. 70 00:04:05,280 --> 00:04:10,736 I want you to use this to learn about these things. 71 00:04:10,736 --> 00:04:13,200 AUDIENCE: [INAUDIBLE]? 72 00:04:13,200 --> 00:04:17,240 PROFESSOR: Some of these might be on the midterm. 73 00:04:17,240 --> 00:04:20,370 Or I might just ask questions about them. 74 00:04:20,370 --> 00:04:22,952 But, yeah, there might be things like this on the midterm, 75 00:04:22,952 --> 00:04:25,340 definitely. 76 00:04:25,340 --> 00:04:26,970 So that'll all be posted. 77 00:04:26,970 --> 00:04:29,575 And that is just to help you review. 78 00:04:38,270 --> 00:04:40,832 You can have it due Monday, I think. 79 00:04:40,832 --> 00:04:43,590 And I will get another one posted where you just have-- 80 00:04:43,590 --> 00:04:45,580 because these are all very straightforward. 81 00:04:45,580 --> 00:04:49,030 You just have to find and learn them. 82 00:04:49,030 --> 00:04:50,085 Try to do it. 83 00:04:52,660 --> 00:04:55,360 Many of them, I give you the diagram, 84 00:04:55,360 --> 00:05:00,820 and I want you to eliminate a lot of the labels. 85 00:05:00,820 --> 00:05:05,990 And so, like in the one with the meninges and the glia, 86 00:05:05,990 --> 00:05:10,180 you should know which ones here are the astrocytes, which 87 00:05:10,180 --> 00:05:18,320 is the dura, what is the pia, and what is the arachnoid? 88 00:05:18,320 --> 00:05:21,580 So you need to know those things, 89 00:05:21,580 --> 00:05:24,480 and it's good to have not just the words, 90 00:05:24,480 --> 00:05:27,820 but to have in your spatial memory, too. 91 00:05:27,820 --> 00:05:30,050 So that's why we're doing it. 92 00:05:30,050 --> 00:05:35,084 Use it to practise and review. 93 00:05:35,084 --> 00:05:36,750 And then I will give you some questions, 94 00:05:36,750 --> 00:05:39,380 I think, mostly on the motor system 95 00:05:39,380 --> 00:05:41,945 because you haven't had any homework on that. 96 00:05:41,945 --> 00:05:45,540 And I could give a little bit on development, 97 00:05:45,540 --> 00:05:47,800 things that I know you can find. 98 00:05:47,800 --> 00:05:51,990 And we'll use that, as I promised, 99 00:05:51,990 --> 00:05:55,900 to make up for bad quiz grades. 100 00:05:55,900 --> 00:05:57,970 We'll decide exactly how we're going to do that, 101 00:05:57,970 --> 00:05:58,970 but I think that's fine. 102 00:06:02,505 --> 00:06:04,130 AUDIENCE: [INAUDIBLE] how many chapters 103 00:06:04,130 --> 00:06:06,630 the midterm will be covering? 104 00:06:06,630 --> 00:06:08,630 Is it one through-- 105 00:06:08,630 --> 00:06:12,720 PROFESSOR: 17, through the brain states chapter. 106 00:06:17,340 --> 00:06:24,440 And then we start sensory systems afterwards, 107 00:06:24,440 --> 00:06:26,020 after the break. 108 00:06:26,020 --> 00:06:26,760 Or wait a minute. 109 00:06:26,760 --> 00:06:28,040 Do we have a Friday? 110 00:06:28,040 --> 00:06:32,560 I guess we started just before the break. 111 00:06:32,560 --> 00:06:35,720 All right, so this is where we were. 112 00:06:35,720 --> 00:06:42,140 It's a little bit more on the introductory chapter 113 00:06:42,140 --> 00:06:43,830 to the motor system, where we're talking 114 00:06:43,830 --> 00:06:48,500 about these multipurpose movements. 115 00:06:48,500 --> 00:06:52,270 There was a lot about locomotion last time. 116 00:06:52,270 --> 00:06:54,220 We've also talked about the other movements. 117 00:06:58,020 --> 00:07:01,190 All that I have of what remains is 118 00:07:01,190 --> 00:07:08,390 I discuss in a little bit about evolution of that ability. 119 00:07:08,390 --> 00:07:11,720 And just because we know that the tectum is 120 00:07:11,720 --> 00:07:17,820 the dominant structure now in most animals, 121 00:07:17,820 --> 00:07:21,550 except perhaps in animals like humans and even monkeys, 122 00:07:21,550 --> 00:07:24,180 where the cortex has become so dominant 123 00:07:24,180 --> 00:07:26,210 over most of these functions. 124 00:07:26,210 --> 00:07:29,080 But in most animals, it is still very important 125 00:07:29,080 --> 00:07:31,890 and it has an importance even in humans, 126 00:07:31,890 --> 00:07:32,985 more than people realize. 127 00:07:36,010 --> 00:07:43,169 So I do mention a little bit about some 128 00:07:43,169 --> 00:07:44,085 of the early controls. 129 00:07:47,660 --> 00:07:53,100 But I'm mostly emphasizing two very different functions 130 00:07:53,100 --> 00:07:56,630 of the tectum, one involving locomotion. 131 00:07:56,630 --> 00:07:58,196 We talked about escape movements. 132 00:08:01,130 --> 00:08:06,120 But normally, when animals are escaping, they also orient. 133 00:08:06,120 --> 00:08:10,520 They don't generally orient with respect to the animals 134 00:08:10,520 --> 00:08:11,650 their escaping from. 135 00:08:11,650 --> 00:08:14,670 They orient towards safe place. 136 00:08:14,670 --> 00:08:18,100 If they're near their tunnel, they head for their tunnel. 137 00:08:18,100 --> 00:08:20,930 If they're near any hiding place, 138 00:08:20,930 --> 00:08:24,560 any place they can crawl into to get away, they head for that. 139 00:08:24,560 --> 00:08:26,255 And they're extremely good at finding 140 00:08:26,255 --> 00:08:27,645 that very, very rapidly. 141 00:08:30,460 --> 00:08:33,039 And I say a little bit about the tectum and pretectum 142 00:08:33,039 --> 00:08:37,470 here because I go over this in the visual system later on. 143 00:08:37,470 --> 00:08:43,030 If I were you, I would just read this and use it. 144 00:08:43,030 --> 00:08:45,620 It does help prepare you for what's coming, 145 00:08:45,620 --> 00:08:49,520 but right now, you need to know this, 146 00:08:49,520 --> 00:08:51,433 the different nature outputs to the tectum. 147 00:08:55,600 --> 00:08:58,070 So a little bit more about grasping. 148 00:08:58,070 --> 00:08:59,556 We know why it's so important. 149 00:09:03,770 --> 00:09:05,500 We know what muscles are involved. 150 00:09:05,500 --> 00:09:07,900 We know that there's different kinds of grasping; 151 00:09:07,900 --> 00:09:10,220 grasping with the hands. 152 00:09:10,220 --> 00:09:14,790 We know in large primates, it's largely a neocortical function, 153 00:09:14,790 --> 00:09:20,390 but animals without neocortex can still feed themselves. 154 00:09:20,390 --> 00:09:23,390 They still have to grasp things, either with the mouth 155 00:09:23,390 --> 00:09:28,774 or with the hands, so structures evolve to do that, 156 00:09:28,774 --> 00:09:29,940 and they're in the midbrain. 157 00:09:34,105 --> 00:09:35,813 So that's what those questions are about. 158 00:09:44,949 --> 00:09:46,490 And we talked about this a little bit 159 00:09:46,490 --> 00:09:49,780 last time, so I'm not going to over it again. 160 00:09:49,780 --> 00:09:52,680 But I didn't talk about the red nucleus 161 00:09:52,680 --> 00:09:53,760 in a little more detail. 162 00:09:53,760 --> 00:09:57,230 There's two major parts of the red nucleus. 163 00:09:57,230 --> 00:09:59,840 It is quite interesting when you compare different animals. 164 00:09:59,840 --> 00:10:06,060 There's a large cell part that's the caudal part of the nucleus. 165 00:10:06,060 --> 00:10:09,350 And then there's a small cell part, 166 00:10:09,350 --> 00:10:15,540 so we refer to the magnocellular red part of the red nucleus. 167 00:10:15,540 --> 00:10:19,460 It's abbreviated NR for nucleus ruber, 168 00:10:19,460 --> 00:10:24,740 and then MC for magnocellular, or NR, nucleus ruber, 169 00:10:24,740 --> 00:10:27,860 PC for parvocellular. 170 00:10:27,860 --> 00:10:30,350 Parvo means small. 171 00:10:30,350 --> 00:10:31,770 So those are the two parts. 172 00:10:31,770 --> 00:10:39,950 And it's really interesting if you look across primates, even 173 00:10:39,950 --> 00:10:41,770 if you went here to primitive primates, 174 00:10:41,770 --> 00:10:45,310 it would be like the carnivore here. 175 00:10:45,310 --> 00:10:49,900 And humans, the parvocellular part, the rostral part, 176 00:10:49,900 --> 00:10:52,970 is by far the largest part. 177 00:10:52,970 --> 00:10:56,110 The magnocelluar part is smaller. 178 00:10:56,110 --> 00:10:58,370 So, what do these two parts do? 179 00:10:58,370 --> 00:11:00,640 Well, the outputs are very different. 180 00:11:00,640 --> 00:11:04,030 Of course, their inputs are different, too. 181 00:11:04,030 --> 00:11:05,810 Let's just deal with the outputs. 182 00:11:05,810 --> 00:11:10,100 The rubrospinal tract case. 183 00:11:10,100 --> 00:11:12,000 The output at the spinal cord, that 184 00:11:12,000 --> 00:11:14,460 comes from the large cells, the magnocyte 185 00:11:14,460 --> 00:11:16,990 are part of the red nucleus. 186 00:11:16,990 --> 00:11:19,190 So in animals where that pathway's 187 00:11:19,190 --> 00:11:28,400 more important than neocortex, it'll be like this. 188 00:11:28,400 --> 00:11:30,560 The caudal part is relatively larger. 189 00:11:30,560 --> 00:11:32,460 That's true and carnivores. 190 00:11:32,460 --> 00:11:36,730 It's true in rodents, true in most animals. 191 00:11:36,730 --> 00:11:40,650 But animals that are really developed, 192 00:11:40,650 --> 00:11:44,710 more endbrain control of their hands, 193 00:11:44,710 --> 00:11:46,840 then the parvocellular part is more. 194 00:11:46,840 --> 00:11:50,300 So why is that? 195 00:11:50,300 --> 00:11:51,930 Well, what does it project to? 196 00:11:51,930 --> 00:11:55,800 First of all, it projects forward, 197 00:11:55,800 --> 00:11:57,530 not like the rubrospinal tract. 198 00:11:57,530 --> 00:11:58,530 This projects rostrally. 199 00:11:58,530 --> 00:12:03,380 Parvocellular nucleus projects to the thalamus, 200 00:12:03,380 --> 00:12:07,850 mostly to the ventral lateral thalamus, 201 00:12:07,850 --> 00:12:11,135 the part of the thalamus that projects to the primary motor 202 00:12:11,135 --> 00:12:11,635 cortex. 203 00:12:19,180 --> 00:12:22,070 And it also projects to the precellebellar nucleus. 204 00:12:22,070 --> 00:12:26,480 So the inputs to the cerebellum and to the neocortex 205 00:12:26,480 --> 00:12:32,030 depend on that for controlling hand movements, 206 00:12:32,030 --> 00:12:34,380 both through that parvocellular part. 207 00:12:34,380 --> 00:12:36,340 And this also shows a correlation 208 00:12:36,340 --> 00:12:39,512 with a structure in the cerebellum. 209 00:12:39,512 --> 00:12:40,530 That's this structure. 210 00:12:40,530 --> 00:12:42,280 They just pick that out of the cerebellum. 211 00:12:42,280 --> 00:12:45,860 It's the lateral most deep nucleus. 212 00:12:45,860 --> 00:12:48,450 It's the part of the cerebellum that gets input 213 00:12:48,450 --> 00:12:53,556 from the very large hemispheres in human cerebellum. 214 00:12:53,556 --> 00:12:56,930 But any animal-- what they're not showing here 215 00:12:56,930 --> 00:12:58,490 is the whole cerebellar hemisphere 216 00:12:58,490 --> 00:13:02,970 in growing bigger in these animals at the right, 217 00:13:02,970 --> 00:13:07,230 in apes and humans and also monkeys. 218 00:13:07,230 --> 00:13:13,650 Whereas in other animals with less of this kind of control, 219 00:13:13,650 --> 00:13:18,510 that lateral cerebellar output nucleus is also smaller. 220 00:13:18,510 --> 00:13:22,650 So as the cerebellum evolves, so does the cortex, 221 00:13:22,650 --> 00:13:24,420 and the red nucleus changes also. 222 00:13:27,170 --> 00:13:29,670 AUDIENCE: [INAUDIBLE]. 223 00:13:29,670 --> 00:13:40,996 Does the red nucleus [INAUDIBLE] by having visual inputs? 224 00:13:40,996 --> 00:13:42,810 Because I read that-- 225 00:13:42,810 --> 00:13:45,840 PROFESSOR: Animals, no because animals 226 00:13:45,840 --> 00:13:49,380 can still be pretty dexterous without so much visual input, 227 00:13:49,380 --> 00:13:53,480 but there is a general correspondence. 228 00:13:53,480 --> 00:13:58,100 If you look, there are prosimians, for example, 229 00:13:58,100 --> 00:14:01,850 that where the red nucleus is more prominent than it is even 230 00:14:01,850 --> 00:14:06,580 in humans, that have incredible dexterity, 231 00:14:06,580 --> 00:14:08,340 but it's mostly fixed action patterns. 232 00:14:08,340 --> 00:14:10,430 They use it for grabbing bugs out of the air. 233 00:14:13,727 --> 00:14:16,082 AUDIENCE: [INAUDIBLE] magnocellular 234 00:14:16,082 --> 00:14:17,024 and parvocellular? 235 00:14:17,024 --> 00:14:18,450 I think the-- 236 00:14:18,450 --> 00:14:20,980 PROFESSOR: All the animals I mentioned that have a small one 237 00:14:20,980 --> 00:14:23,238 are less visual. 238 00:14:23,238 --> 00:14:24,988 AUDIENCE: Magnocellular and parvocellular, 239 00:14:24,988 --> 00:14:26,482 there's a distinction [INAUDIBLE]. 240 00:14:29,862 --> 00:14:31,570 PROFESSOR: You have these different types 241 00:14:31,570 --> 00:14:33,940 of cells in other systems, too. 242 00:14:33,940 --> 00:14:36,880 But, no, there's no real strict correlation. 243 00:14:36,880 --> 00:14:41,570 Animals can be very dexterous even without using vision. 244 00:14:41,570 --> 00:14:46,116 And humans without vision can have very, very dexterous hand 245 00:14:46,116 --> 00:14:46,616 movements. 246 00:14:55,170 --> 00:15:00,430 There's an interesting study of the projections 247 00:15:00,430 --> 00:15:04,940 of the red nucleus because they're 248 00:15:04,940 --> 00:15:07,770 concerned with control of distal muscles. 249 00:15:07,770 --> 00:15:10,190 Well, there's distal muscles in the forelimbs, 250 00:15:10,190 --> 00:15:12,380 but also in the hindlimbs. 251 00:15:12,380 --> 00:15:16,150 The question is, are those kept separate in the red nucleus? 252 00:15:16,150 --> 00:15:20,810 So you look at the projections to the cervical enlargement 253 00:15:20,810 --> 00:15:22,850 and the lumbar enlargement . 254 00:15:22,850 --> 00:15:27,140 It's just a cartoon to illustrate those two 255 00:15:27,140 --> 00:15:31,200 parts of the spinal cord and then the red nucleus 256 00:15:31,200 --> 00:15:31,830 projections. 257 00:15:31,830 --> 00:15:35,820 And what this shows is neurons that 258 00:15:35,820 --> 00:15:39,630 project to the cervical enlargement, 259 00:15:39,630 --> 00:15:42,100 neurons the projected to the lumbar enlargement, 260 00:15:42,100 --> 00:15:49,990 and neurons that project to both; a branch to both nuclei. 261 00:15:49,990 --> 00:15:52,320 So if you look at the opossum, you'll 262 00:15:52,320 --> 00:15:55,690 see that there is some inter-mixture here. 263 00:15:55,690 --> 00:16:00,770 The topographic separation of the representation 264 00:16:00,770 --> 00:16:02,730 for hand control and foot control 265 00:16:02,730 --> 00:16:04,960 is it's not all that good. 266 00:16:04,960 --> 00:16:08,040 In the rat, it's a little better and in the cat, 267 00:16:08,040 --> 00:16:10,680 the separation is really good. 268 00:16:10,680 --> 00:16:14,200 And of course, in primates it is, too. 269 00:16:14,200 --> 00:16:17,040 Just an interesting thing about how 270 00:16:17,040 --> 00:16:25,650 you find these correspondences with function and anatomy 271 00:16:25,650 --> 00:16:29,500 in these descending projections. 272 00:16:29,500 --> 00:16:33,170 So now I want to talk about the outputs. 273 00:16:33,170 --> 00:16:35,205 And I want to start with the motor neurons. 274 00:16:37,950 --> 00:16:39,860 So then we can talk about the pathways 275 00:16:39,860 --> 00:16:41,840 that connect to those motor neurons, 276 00:16:41,840 --> 00:16:45,650 and how the pathways, say, from the cortex and brainstem 277 00:16:45,650 --> 00:16:49,460 connect to the motor neurons to the spinal cord. 278 00:16:49,460 --> 00:16:56,730 And we're talking here about somatic motor neurons. 279 00:16:56,730 --> 00:16:59,730 We talked earlier about autonomic, 280 00:16:59,730 --> 00:17:02,530 and we said a little bit about neuroendocrine controls 281 00:17:02,530 --> 00:17:03,736 to the hypothalamus. 282 00:17:03,736 --> 00:17:05,670 We've talked a lot more about that, 283 00:17:05,670 --> 00:17:09,020 when we talked specifically about hypothalamus. 284 00:17:09,020 --> 00:17:12,520 We're just talking about the somatic system 285 00:17:12,520 --> 00:17:16,550 with synaptic connections to muscles, 286 00:17:16,550 --> 00:17:19,690 not paracrine, as in the autonomic system, 287 00:17:19,690 --> 00:17:23,014 and not endocrine, as in the endocrine systems. 288 00:17:25,920 --> 00:17:28,870 This is Larry Swanson's characterization 289 00:17:28,870 --> 00:17:33,130 of the entire motor system, he says, the three motor systems. 290 00:17:33,130 --> 00:17:36,870 This is the somatic, number 3 here. 291 00:17:36,870 --> 00:17:38,770 Number one is the endocrine. 292 00:17:38,770 --> 00:17:40,765 And he shows this. 293 00:17:40,765 --> 00:17:43,390 The Dashed line indicates connections. 294 00:17:43,390 --> 00:17:46,670 There's no synapse at all. 295 00:17:46,670 --> 00:17:48,920 They're just through the bloodstream. 296 00:17:48,920 --> 00:17:51,600 And then the paracrine innervation 297 00:17:51,600 --> 00:17:53,910 of the autonomic system, parasympathetic and 298 00:17:53,910 --> 00:17:54,540 sympathetic. 299 00:17:54,540 --> 00:17:57,655 That's motor system two and motor system three. 300 00:17:57,655 --> 00:17:59,530 And when he discusses that, it's interesting. 301 00:17:59,530 --> 00:18:07,185 He says, we don't know what are the pattern generators that 302 00:18:07,185 --> 00:18:09,380 are coordinating these three systems. 303 00:18:09,380 --> 00:18:13,390 And my comment about that is just 304 00:18:13,390 --> 00:18:18,130 that, we don't know if there is very much direct coordination 305 00:18:18,130 --> 00:18:21,620 central to these systems, but there probably is some, 306 00:18:21,620 --> 00:18:25,680 but it's not been specifically-- we know a lot less about that 307 00:18:25,680 --> 00:18:29,340 than we know about controlled pattern movements. 308 00:18:29,340 --> 00:18:32,660 And this distribution of somatic motor 309 00:18:32,660 --> 00:18:37,380 neurons, I've had that in other pictures 310 00:18:37,380 --> 00:18:39,330 that I showed you earlier on. 311 00:18:39,330 --> 00:18:42,110 You probably didn't pay much attention, 312 00:18:42,110 --> 00:18:45,620 except I always show the motor neurons ventrally. 313 00:18:45,620 --> 00:18:49,710 So I asked this question here, this is a horizontal view, 314 00:18:49,710 --> 00:18:52,450 it doesn't indicate anything about dorsal and ventral. 315 00:18:52,450 --> 00:18:54,180 So I say, where are these neurons 316 00:18:54,180 --> 00:18:57,460 located in frontal sections? 317 00:18:57,460 --> 00:18:59,960 So here, this is all spinal cord, 318 00:18:59,960 --> 00:19:03,580 where most of those neurons are, and you can see most of them 319 00:19:03,580 --> 00:19:05,840 are in the enlargements. 320 00:19:05,840 --> 00:19:08,960 Because we've many more muscles ti control in the limbs, 321 00:19:08,960 --> 00:19:12,010 we need finer controls, so we've got more motor neurons 322 00:19:12,010 --> 00:19:13,420 controlling them. 323 00:19:13,420 --> 00:19:15,490 They're always in the ventral horn. 324 00:19:15,490 --> 00:19:19,210 And that's what we're going to talk about next, 325 00:19:19,210 --> 00:19:21,195 but these are the groups of neurons. 326 00:19:24,730 --> 00:19:26,590 And these columns that aren't directly 327 00:19:26,590 --> 00:19:28,600 connected with each other, that we 328 00:19:28,600 --> 00:19:32,090 talked about when we talked about hindbrain and midbrain. 329 00:19:32,090 --> 00:19:36,300 And notice, the most rostral ones are in the midbrain. 330 00:19:36,300 --> 00:19:38,145 It did come up a couple times in a class. 331 00:19:38,145 --> 00:19:40,000 If you didn't remember, fine. 332 00:19:40,000 --> 00:19:42,150 But with the help of the quiz, you'll 333 00:19:42,150 --> 00:19:47,120 probably remember it now; the most rostral somatic motor 334 00:19:47,120 --> 00:19:49,280 neurons. 335 00:19:49,280 --> 00:19:54,950 If you include the endocrine system as motor, 336 00:19:54,950 --> 00:19:56,594 like Swanson does, then you could say, 337 00:19:56,594 --> 00:19:58,260 well there's another kind a motor neuron 338 00:19:58,260 --> 00:20:04,240 in the hypothalamus and even further forward. 339 00:20:04,240 --> 00:20:08,230 Secretory cells-- we're not talking about secretory cells 340 00:20:08,230 --> 00:20:11,804 now at all, just control of somatic motor neurons. 341 00:20:23,830 --> 00:20:26,860 So I want to talk about-- it's a chapter centered 342 00:20:26,860 --> 00:20:29,540 on the studies of descending pathways, 343 00:20:29,540 --> 00:20:32,060 the anatomy, and their function. 344 00:20:32,060 --> 00:20:35,336 And these are the ones we just saw. 345 00:20:35,336 --> 00:20:37,290 I want to answer this question now. 346 00:20:37,290 --> 00:20:40,690 What's the basic spatial layout of motor neurons, 347 00:20:40,690 --> 00:20:43,090 and what are the spinal cord enlargements? 348 00:20:43,090 --> 00:20:44,630 How is it organized? 349 00:20:44,630 --> 00:20:50,630 And then we'll talk about what connects to those motor 350 00:20:50,630 --> 00:20:54,720 neurons, and the main type of neuron that connects to them 351 00:20:54,720 --> 00:20:57,510 is interneurons in the intermediate layers 352 00:20:57,510 --> 00:20:59,770 of the spinal cord. 353 00:20:59,770 --> 00:21:02,570 Yes, there are coming directly from cortex, too. 354 00:21:02,570 --> 00:21:05,300 And we'll talk about those. 355 00:21:05,300 --> 00:21:09,860 Those connections connect mainly to those interneurons. 356 00:21:09,860 --> 00:21:12,725 And this is the kind of figure you often 357 00:21:12,725 --> 00:21:14,400 will see in a medical school book. 358 00:21:14,400 --> 00:21:15,570 What does that mean? 359 00:21:18,260 --> 00:21:20,180 Is that Atlas holding the world up? 360 00:21:20,180 --> 00:21:22,325 No, it's he's holding a spinal cord up. 361 00:21:22,325 --> 00:21:24,580 But why do they have him pictured like that, 362 00:21:24,580 --> 00:21:27,830 with his arms like this? 363 00:21:27,830 --> 00:21:31,260 Because it's showing that the motor neurons 364 00:21:31,260 --> 00:21:34,710 in the ventral horns here, the motor 365 00:21:34,710 --> 00:21:37,130 neurons controlling the axial muscles, 366 00:21:37,130 --> 00:21:41,100 so the muscles of the neck or along the back, those 367 00:21:41,100 --> 00:21:46,700 are the axial muscles, very important in postural control. 368 00:21:46,700 --> 00:21:52,740 And they're most medial. 369 00:21:52,740 --> 00:21:56,900 And then we talk about the girder muscles, the muscles 370 00:21:56,900 --> 00:22:00,860 that control shoulders or hips, separate 371 00:22:00,860 --> 00:22:03,410 from the muscles controlling the limbs. 372 00:22:06,080 --> 00:22:11,420 You find those next, moving laterally, and then the arms, 373 00:22:11,420 --> 00:22:15,120 and finally, the hands and feet, depending 374 00:22:15,120 --> 00:22:19,470 on whether you're in the cervical or lumbar enlargement. 375 00:22:19,470 --> 00:22:23,400 So this is the picture from the Lawrence and Kuypers 376 00:22:23,400 --> 00:22:25,075 study that I use in the book. 377 00:22:27,780 --> 00:22:31,930 It shows a section of the spinal cord. 378 00:22:35,060 --> 00:22:37,455 By just putting in a few neurons, 379 00:22:37,455 --> 00:22:39,710 they're showing you groups of neurons 380 00:22:39,710 --> 00:22:43,375 that are located medially and then more and more laterally. 381 00:22:47,090 --> 00:22:51,530 So axial muscles, medially, then the girder muscles, 382 00:22:51,530 --> 00:22:54,510 and then the distal muscles. 383 00:22:54,510 --> 00:22:56,790 And there is some separation that you 384 00:22:56,790 --> 00:23:01,570 see in that other picture of the flexors and extensors as well. 385 00:23:04,230 --> 00:23:08,015 You don't need to worry about flexor and extensor separation 386 00:23:08,015 --> 00:23:10,290 because it is fairly complex. 387 00:23:10,290 --> 00:23:13,500 There's no need to memorize it. 388 00:23:13,500 --> 00:23:17,360 But you need to know about the relation 389 00:23:17,360 --> 00:23:21,020 of the typography in the cord and the control 390 00:23:21,020 --> 00:23:24,780 of different muscles in the body. 391 00:23:24,780 --> 00:23:28,550 So now we know about proximal and distal representation 392 00:23:28,550 --> 00:23:29,450 in the cord. 393 00:23:29,450 --> 00:23:34,140 The next question, back to this one, is the interneurons. 394 00:23:34,140 --> 00:23:37,100 And, yes, they are radially arranged, 395 00:23:37,100 --> 00:23:39,460 so the interneurons way out laterally 396 00:23:39,460 --> 00:23:42,660 here do connect to the lateral-most motor neurons. 397 00:23:42,660 --> 00:23:44,760 Whereas the ones located medially, 398 00:23:44,760 --> 00:23:47,830 connect to the medial ones, controlling axial muscles. 399 00:23:47,830 --> 00:23:50,260 And there's another difference. 400 00:23:50,260 --> 00:23:51,490 It's quite important. 401 00:23:51,490 --> 00:23:55,010 Some of those interneurons that connect to the medial motor 402 00:23:55,010 --> 00:23:59,410 neurons, project to both sides of the cord. 403 00:23:59,410 --> 00:24:01,320 Because when you control axial muscles, 404 00:24:01,320 --> 00:24:03,000 you're always dealing with movements 405 00:24:03,000 --> 00:24:07,760 that never-- they always involve both sides of the body. 406 00:24:07,760 --> 00:24:12,100 So both sides the cord tend to be involved. 407 00:24:12,100 --> 00:24:14,560 And the same thing is true for descending connections. 408 00:24:14,560 --> 00:24:18,710 Connections that are for the control of axial muscles, 409 00:24:18,710 --> 00:24:20,740 tend to be bilateral. 410 00:24:20,740 --> 00:24:23,890 That's a very important point if you're 411 00:24:23,890 --> 00:24:27,260 doing lesion studies, the function. 412 00:24:27,260 --> 00:24:34,620 So then, in this study by-- it's a classic study by Hans Kuypers 413 00:24:34,620 --> 00:24:37,110 is a very well known neuronanatomist, 414 00:24:37,110 --> 00:24:41,780 a Dutch neuronanatomist, a colleague of [INAUDIBLE]. 415 00:24:41,780 --> 00:24:44,160 And his student Lawrence, that did this study back 416 00:24:44,160 --> 00:24:48,742 in the '60s, published it in Brain. 417 00:24:48,742 --> 00:24:50,730 And everything they found, applies 418 00:24:50,730 --> 00:24:52,360 pretty much to humans, as well, and 419 00:24:52,360 --> 00:24:55,680 corresponds to many findings in the clinic. 420 00:24:55,680 --> 00:24:58,050 But what this, the upper section, 421 00:24:58,050 --> 00:25:04,190 show here are the patterns of termination of , first of all, 422 00:25:04,190 --> 00:25:06,480 at the left, the corticospinal tract, 423 00:25:06,480 --> 00:25:09,310 or the part of the corticospinal tract coming from precentral 424 00:25:09,310 --> 00:25:12,670 gyrus, the motor cortex. 425 00:25:12,670 --> 00:25:15,590 And it shows that it goes everywhere. 426 00:25:15,590 --> 00:25:17,460 If we include the postcentral gyrus, 427 00:25:17,460 --> 00:25:20,472 then you'll see it goes to the dorsal horn, too. 428 00:25:20,472 --> 00:25:23,475 So, pretty much everything in it also crosses the midline. 429 00:25:23,475 --> 00:25:27,010 This is just the left corticospinal tract. 430 00:25:27,010 --> 00:25:33,560 It goes to both sides, but only in that ventral medial area, 431 00:25:33,560 --> 00:25:38,420 the part that controls the axial muscles. 432 00:25:38,420 --> 00:25:42,220 So then he's got pathways that travel through the-- come 433 00:25:42,220 --> 00:25:45,020 from the lateral brainstem, including 434 00:25:45,020 --> 00:25:47,360 the red nucleus, the midbrain. 435 00:25:47,360 --> 00:25:49,700 And they travel laterally through the hindbrain. 436 00:25:49,700 --> 00:25:53,830 They're joined by the axons from lateral reticular formation 437 00:25:53,830 --> 00:26:00,210 cells, and they terminate in this dorsal lateral part 438 00:26:00,210 --> 00:26:03,100 of the interneuronal group. 439 00:26:03,100 --> 00:26:07,350 They tend to spare the ventral medial area, for the most part, 440 00:26:07,350 --> 00:26:12,190 and they generally don't cross the midline. 441 00:26:12,190 --> 00:26:15,430 Then, if you look at the medial pathways, 442 00:26:15,430 --> 00:26:21,190 medial brainstem-- I'm calling ventral medial here 443 00:26:21,190 --> 00:26:24,115 because they're terminating ventral medially in the cord. 444 00:26:26,800 --> 00:26:29,530 That's where you find the [? vectro ?] spinal pathway 445 00:26:29,530 --> 00:26:32,630 terminating, the vestibulospinal, the ones 446 00:26:32,630 --> 00:26:36,040 from the cerebellum, the vestigial spinal, 447 00:26:36,040 --> 00:26:37,625 and medial reticulospinal. 448 00:26:37,625 --> 00:26:41,620 There's a lot of different groups of axons. 449 00:26:41,620 --> 00:26:45,190 Center axons, always down in these medial regions 450 00:26:45,190 --> 00:26:50,190 of the ventral column, and they terminate in that pattern. 451 00:26:50,190 --> 00:26:57,220 Again, if you just look at projections from the left side 452 00:26:57,220 --> 00:27:00,999 here, they terminate more on the left than the right, 453 00:27:00,999 --> 00:27:02,290 but they terminate bilaterally. 454 00:27:07,480 --> 00:27:11,590 So now we can draw pictures like this 455 00:27:11,590 --> 00:27:13,640 to represent these three descending 456 00:27:13,640 --> 00:27:17,430 pathways from cortex, in the lateral brainstem, 457 00:27:17,430 --> 00:27:20,010 and the medial brainstem. 458 00:27:20,010 --> 00:27:24,890 And I have this in color in the book, so a little easier. 459 00:27:24,890 --> 00:27:28,070 But all I do is show in a monkey brain 460 00:27:28,070 --> 00:27:33,430 with an enlarged spinal cord so we can see it a little better. 461 00:27:33,430 --> 00:27:37,940 Just separate the ones coming from the representation 462 00:27:37,940 --> 00:27:41,180 in the motor cortex of the body axis. 463 00:27:41,180 --> 00:27:44,220 That is the back and neck, and then, 464 00:27:44,220 --> 00:27:45,435 representation at the limbs. 465 00:27:48,630 --> 00:27:55,420 AUDIENCE: So these aren't [? traumatic ?] motor neurons. 466 00:27:55,420 --> 00:27:56,390 They terminate in the-- 467 00:27:56,390 --> 00:27:57,900 PROFESSOR: These are not. 468 00:27:57,900 --> 00:28:02,840 This is a common mistake that most of your compatriots 469 00:28:02,840 --> 00:28:05,220 that don't take this class will make. 470 00:28:05,220 --> 00:28:07,890 These are not motor neurons. 471 00:28:07,890 --> 00:28:12,270 Remember the-- how do we define a motor neuron? 472 00:28:12,270 --> 00:28:14,930 And axon that leaves the central nervous system 473 00:28:14,930 --> 00:28:19,790 and terminates on an effector organ, usually a muscle. 474 00:28:19,790 --> 00:28:21,840 Those are the true motor neurons. 475 00:28:21,840 --> 00:28:25,017 These are pathways that, among other things, 476 00:28:25,017 --> 00:28:26,850 connect with motor neurons, but most of them 477 00:28:26,850 --> 00:28:28,550 go to interneurons. 478 00:28:28,550 --> 00:28:30,850 And if it's motor cortex, they usually 479 00:28:30,850 --> 00:28:34,080 concerned with movement, but they go other places, too. 480 00:28:34,080 --> 00:28:35,550 They go to the cerebellum. 481 00:28:35,550 --> 00:28:38,870 They go to part of the interneuronal, 482 00:28:38,870 --> 00:28:43,580 the great network that now to describe. 483 00:28:43,580 --> 00:28:46,930 So I separate them on these two diagrams. 484 00:28:46,930 --> 00:28:49,750 And you just notice the ones controlling distal muscles, 485 00:28:49,750 --> 00:28:51,570 which I've drawn in solid line here. 486 00:28:54,760 --> 00:28:56,210 I shall show them. 487 00:28:56,210 --> 00:28:58,690 I show them in blue in the book. 488 00:28:58,690 --> 00:29:01,070 They're terminating mainly in the enlargements. 489 00:29:01,070 --> 00:29:04,690 So the two enlargements, you see them here, too. 490 00:29:04,690 --> 00:29:06,807 And see, the color helps a lot. 491 00:29:06,807 --> 00:29:08,390 It's a little harder to separate here. 492 00:29:08,390 --> 00:29:11,800 But the concept is very simple. 493 00:29:11,800 --> 00:29:16,730 And then I show here the position 494 00:29:16,730 --> 00:29:19,480 of those corticospinal axons. 495 00:29:19,480 --> 00:29:21,485 Here they are throughout the pyramidal tract 496 00:29:21,485 --> 00:29:23,000 and the hindbrain. 497 00:29:23,000 --> 00:29:25,160 Here in the midbrain, they're in the middle portion 498 00:29:25,160 --> 00:29:27,560 of the [INAUDIBLE]. 499 00:29:27,560 --> 00:29:29,550 The other ones are going to terminate 500 00:29:29,550 --> 00:29:31,780 before they get to the spinal cord, a lot of them 501 00:29:31,780 --> 00:29:35,510 in pontine gray. 502 00:29:35,510 --> 00:29:43,600 So here I show the rubrospinal axons, which cross and travel. 503 00:29:43,600 --> 00:29:46,250 Then they move laterally as they descend. 504 00:29:46,250 --> 00:29:48,750 And here they are in the hindbrain, 505 00:29:48,750 --> 00:29:51,690 right out here at the lateral edge. 506 00:29:51,690 --> 00:29:55,610 So now, the axons controlling the more distal muscles, 507 00:29:55,610 --> 00:29:58,160 if the anatomy is giving us the right idea, 508 00:29:58,160 --> 00:30:01,550 can be found in those two places; here and here. 509 00:30:07,170 --> 00:30:12,320 Except, if I want these to correspond, 510 00:30:12,320 --> 00:30:18,320 I have to say, here and here because these 511 00:30:18,320 --> 00:30:20,139 haven't crossed yet. 512 00:30:20,139 --> 00:30:20,930 These have crossed. 513 00:30:23,870 --> 00:30:26,055 That's a detail to keep in mind. 514 00:30:28,710 --> 00:30:30,730 And then here, for the medial pathways, 515 00:30:30,730 --> 00:30:38,215 I show the tectospinal crossing, and then the vestibulospinal. 516 00:30:38,215 --> 00:30:46,510 They're uncrossed because they're hindbrain. 517 00:30:46,510 --> 00:30:50,740 And I could've added the ones from cerebellum. 518 00:30:50,740 --> 00:30:53,120 I do show a few from reticular formation here, 519 00:30:53,120 --> 00:30:55,650 that are joining that pathway. 520 00:30:55,650 --> 00:30:59,280 And those are the ones that go down through the cord 521 00:30:59,280 --> 00:31:02,435 and terminate in that ventromedial region. 522 00:31:02,435 --> 00:31:10,590 And here I show them in the cross-sections; tectospinal. 523 00:31:10,590 --> 00:31:15,400 I just show the tectospinal and the reticulospinal origins 524 00:31:15,400 --> 00:31:17,360 here. 525 00:31:17,360 --> 00:31:19,180 The vestibulospinal is only on this one. 526 00:31:24,550 --> 00:31:28,740 So then, what are the three lesions 527 00:31:28,740 --> 00:31:32,300 that Lawrence and Kuypers made? 528 00:31:32,300 --> 00:31:35,250 Let's just go through the logic of Lawrence 529 00:31:35,250 --> 00:31:37,545 and Kuypers' study, very straightforward. 530 00:31:40,210 --> 00:31:43,830 They did try just eliminating the medial hindbrain 531 00:31:43,830 --> 00:31:48,170 pathways or the lateral pathways in otherwise intact monkeys. 532 00:31:48,170 --> 00:31:52,560 They didn't get long-lasting effects at all. 533 00:31:52,560 --> 00:31:55,510 So they reasoned that probably that's 534 00:31:55,510 --> 00:31:58,650 because the cortex is so dominant, 535 00:31:58,650 --> 00:32:02,220 they had spared the whole corticospinal pathway. 536 00:32:02,220 --> 00:32:06,295 So they all we started by eliminating the pathways 537 00:32:06,295 --> 00:32:07,280 from cortex. 538 00:32:07,280 --> 00:32:09,050 They cut the pyramidal tract. 539 00:32:09,050 --> 00:32:10,785 Yes? 540 00:32:10,785 --> 00:32:11,972 AUDIENCE: [INAUDIBLE]. 541 00:32:11,972 --> 00:32:13,430 PROFESSOR: You have to talk louder. 542 00:32:13,430 --> 00:32:15,780 This ventilation is pretty rough. 543 00:32:15,780 --> 00:32:20,262 AUDIENCE: So in the book, I remember 544 00:32:20,262 --> 00:32:23,748 [INAUDIBLE] there was a [INAUDIBLE]. 545 00:32:26,250 --> 00:32:28,830 PROFESSOR: The type, yes, you do get some recovery. 546 00:32:28,830 --> 00:32:32,020 But remember, there's a lot of different pathways involved 547 00:32:32,020 --> 00:32:34,982 here and it's very difficult to get all of them. 548 00:32:34,982 --> 00:32:36,280 AUDIENCE: OK, so the-- 549 00:32:36,280 --> 00:32:38,740 PROFESSOR: And also, so there's various ways 550 00:32:38,740 --> 00:32:41,610 the brain can compensate, but it's remarkable 551 00:32:41,610 --> 00:32:43,350 how little the compensation is when 552 00:32:43,350 --> 00:32:46,060 they do a really good lesion. 553 00:32:46,060 --> 00:32:50,070 And then I ask the functions of these three major pathways. 554 00:32:50,070 --> 00:32:53,860 Well, when I introduced it with the output, 555 00:32:53,860 --> 00:32:56,330 you can pretty much predict the function, 556 00:32:56,330 --> 00:33:00,050 so we're going to go through that. 557 00:33:00,050 --> 00:33:04,090 And I want to know why would diaschisis effects of lesions 558 00:33:04,090 --> 00:33:07,670 of one of the descending pathways in the study 559 00:33:07,670 --> 00:33:13,160 be greater in humans than in monkeys. 560 00:33:13,160 --> 00:33:15,260 So, we'll come back to that when we 561 00:33:15,260 --> 00:33:19,750 talk about functional effects of the lesions. 562 00:33:19,750 --> 00:33:22,190 This is their logic. 563 00:33:22,190 --> 00:33:24,810 You eliminate the corticospinal projections. 564 00:33:24,810 --> 00:33:27,890 They did that at the hindbrain level 565 00:33:27,890 --> 00:33:30,510 by coming in through the roof of the mouth. 566 00:33:30,510 --> 00:33:34,597 I've done this also in hamsters with a student, 567 00:33:34,597 --> 00:33:36,930 [? Katherine ?] [? Kalo, ?] who's been at the University 568 00:33:36,930 --> 00:33:38,425 of Wisconsin now for many years. 569 00:33:41,040 --> 00:33:43,160 I don't know if anybody else has attempted 570 00:33:43,160 --> 00:33:44,990 that on these little animals, but we did, 571 00:33:44,990 --> 00:33:48,055 and we succeeded to do it at least unilaterally. 572 00:33:51,330 --> 00:33:53,110 You see this in sheep brain dissection. 573 00:33:53,110 --> 00:33:54,965 You can see the pyramidal tract. 574 00:33:54,965 --> 00:33:59,550 The problem is, you also see this huge artery called 575 00:33:59,550 --> 00:34:00,680 the basilar artery. 576 00:34:00,680 --> 00:34:04,340 So what we do-- and also, there's other problems. 577 00:34:04,340 --> 00:34:07,510 When you're doing that kind of surgery, 578 00:34:07,510 --> 00:34:11,840 you tend to stretch nerves in the neck, 579 00:34:11,840 --> 00:34:16,790 and that can cause them to hold their breath in and hold it 580 00:34:16,790 --> 00:34:19,069 because you're eliminating normal pathways involved 581 00:34:19,069 --> 00:34:19,610 in breathing. 582 00:34:19,610 --> 00:34:22,969 So what we found is if we just flood the whole area 583 00:34:22,969 --> 00:34:26,940 with ice-cold saline, we reduce the conduction 584 00:34:26,940 --> 00:34:30,420 so much in those nerves that they keep breathing just fine. 585 00:34:30,420 --> 00:34:36,170 And then, we take a little spatula, 586 00:34:36,170 --> 00:34:39,389 nudge the basilar artery over. 587 00:34:39,389 --> 00:34:43,205 And we have a little spatula-like knife, very sharp. 588 00:34:43,205 --> 00:34:45,679 We know exactly how deep to go. 589 00:34:45,679 --> 00:34:48,360 And we can do what Lawrence and Kuypers did here. 590 00:34:48,360 --> 00:34:52,110 Here's their lesions; cut the pyramidal tract. 591 00:34:52,110 --> 00:34:55,070 This is the level they cut it. 592 00:34:55,070 --> 00:34:59,260 They're making a cut from the ventral side, 593 00:34:59,260 --> 00:35:01,130 just cutting the pyramidal tracts. 594 00:35:01,130 --> 00:35:05,270 And usually, just above the pyramidal tract 595 00:35:05,270 --> 00:35:06,960 is the medial lemniscus. 596 00:35:06,960 --> 00:35:11,350 So they often did cut, damage, medial lemniscus fibers. 597 00:35:11,350 --> 00:35:14,470 So because of that, they had to have controls 598 00:35:14,470 --> 00:35:17,460 where they had lesions, for example, the dorsal column 599 00:35:17,460 --> 00:35:18,860 nuclei. 600 00:35:18,860 --> 00:35:21,450 So they got rid of the medial lemniscus 601 00:35:21,450 --> 00:35:23,787 fibers so they could see that the functional effects 602 00:35:23,787 --> 00:35:25,370 that they were seeing in their monkeys 603 00:35:25,370 --> 00:35:29,540 weren't caused by the medial lemniscus damage. 604 00:35:29,540 --> 00:35:33,310 And then they allowed them to recover from that lesion 605 00:35:33,310 --> 00:35:34,990 as much as they could. 606 00:35:34,990 --> 00:35:39,000 And then they did one of these two situations. 607 00:35:39,000 --> 00:35:42,080 Either they cut the lateral pathways on one side. 608 00:35:44,820 --> 00:35:48,430 And remember, that doesn't-- it stays on one side so you can 609 00:35:48,430 --> 00:35:51,370 compare the two sides of the animal. 610 00:35:51,370 --> 00:35:53,530 Or they did the medial pathways. 611 00:35:53,530 --> 00:35:57,230 They tried it unilaterally, didn't get much effect. 612 00:35:57,230 --> 00:36:02,620 But if they did it bilaterally, then they got drastic effects. 613 00:36:02,620 --> 00:36:04,630 This is what they're doing. 614 00:36:04,630 --> 00:36:08,440 They're going right through the damaged pyramidal tract. 615 00:36:08,440 --> 00:36:10,370 I mean, it's already degenerating, remember, 616 00:36:10,370 --> 00:36:12,340 from the earlier lesion. 617 00:36:12,340 --> 00:36:14,210 And they cut all those medial pathways. 618 00:36:14,210 --> 00:36:17,000 They all descend right near the midline. 619 00:36:17,000 --> 00:36:17,790 Yes? 620 00:36:17,790 --> 00:36:20,190 AUDIENCE: I think Lawrence [INAUDIBLE]? 621 00:36:24,174 --> 00:36:25,840 PROFESSOR: Yeah, that's a good question. 622 00:36:25,840 --> 00:36:28,850 There's is a little bit, and it's somewhat variable. 623 00:36:28,850 --> 00:36:31,490 It's not as much as in humans, but there 624 00:36:31,490 --> 00:36:32,860 is some lateral dominance. 625 00:36:32,860 --> 00:36:36,950 There is some asymmetry in the brains, too. 626 00:36:36,950 --> 00:36:41,300 The most drastic asymmetry they found on animals is in fish 627 00:36:41,300 --> 00:36:42,920 and you have venular nuclei. 628 00:36:42,920 --> 00:36:47,120 And they just still don't know a lot about why that is. 629 00:36:47,120 --> 00:36:48,970 So here's what happens. 630 00:36:48,970 --> 00:36:51,480 You start with a pyramidotomy, get 631 00:36:51,480 --> 00:36:53,189 rid of those corticospinal fibers. 632 00:36:53,189 --> 00:36:54,105 You do it bilaterally. 633 00:36:57,070 --> 00:36:59,940 Initially, they seem almost paralyzed. 634 00:36:59,940 --> 00:37:05,167 And if you do this-- and here the question refers to-- this 635 00:37:05,167 --> 00:37:06,750 is the diaschisis effect, because they 636 00:37:06,750 --> 00:37:08,560 recover a lot from it. 637 00:37:08,560 --> 00:37:12,110 But why is that effect so much greater in humans? 638 00:37:12,110 --> 00:37:14,680 Remember, it's just quantitative. 639 00:37:14,680 --> 00:37:17,332 The pathway's bigger in humans. 640 00:37:17,332 --> 00:37:21,070 The motor cortex is even more important in humans. 641 00:37:21,070 --> 00:37:25,330 So humans, after a pyramidal tract section, 642 00:37:25,330 --> 00:37:28,760 losing even their spinal reflexes for awhile. 643 00:37:28,760 --> 00:37:31,604 That's just like spinal shock, transection of the spinal cord. 644 00:37:35,300 --> 00:37:38,030 But the monkeys lose speed and strength 645 00:37:38,030 --> 00:37:40,040 and they never completely recover 646 00:37:40,040 --> 00:37:43,970 normal speed and normal strength, 647 00:37:43,970 --> 00:37:47,210 but they do recover a lot. 648 00:37:47,210 --> 00:37:50,110 Humans recover their strength. 649 00:37:50,110 --> 00:37:56,130 They never recover full coordination, but strength, 650 00:37:56,130 --> 00:37:56,980 they do pretty well. 651 00:37:56,980 --> 00:38:00,220 In fact, sometimes the reflexes become overactive, stronger 652 00:38:00,220 --> 00:38:02,930 than normal, because of sprouting 653 00:38:02,930 --> 00:38:06,470 that happens in the spinal cord. 654 00:38:06,470 --> 00:38:11,100 But the one thing they do lose that's a qualitative difference 655 00:38:11,100 --> 00:38:15,510 from normal, is they can't do that anymore. 656 00:38:15,510 --> 00:38:19,710 They can't pick something up with single digits. 657 00:38:19,710 --> 00:38:25,150 They have to use their whole hand together. 658 00:38:25,150 --> 00:38:27,600 So apparently, those lateral brainstem pathways 659 00:38:27,600 --> 00:38:32,620 are quite capable of controlling fairly organized hand 660 00:38:32,620 --> 00:38:33,890 movements. 661 00:38:33,890 --> 00:38:37,245 But when it involves separation, separate control of the digits, 662 00:38:37,245 --> 00:38:38,460 they never really recover. 663 00:38:48,130 --> 00:38:52,100 I mention here a question that I think 664 00:38:52,100 --> 00:38:54,820 I should give as a homework, but you 665 00:38:54,820 --> 00:38:58,420 will see a discussion in the book. 666 00:38:58,420 --> 00:39:01,700 I'll try to remember this as I'm telling it to you now. 667 00:39:01,700 --> 00:39:04,735 There is a discussion of fixed action patterns. 668 00:39:04,735 --> 00:39:09,310 It comes-- the only study I know of I did with a student, 669 00:39:09,310 --> 00:39:13,420 [? Katherine ?] [? Kalo, ?] the woman I mentioned. 670 00:39:13,420 --> 00:39:16,720 We found that they need the pyramidal tract coming 671 00:39:16,720 --> 00:39:20,150 from cortex to do their fixed action 672 00:39:20,150 --> 00:39:22,770 patterns of seed-shelling. 673 00:39:22,770 --> 00:39:26,329 So read about that, and then answer this question. 674 00:39:35,892 --> 00:39:36,808 AUDIENCE: [INAUDIBLE]? 675 00:39:41,810 --> 00:39:43,970 PROFESSOR: The corpus striatum for any kind 676 00:39:43,970 --> 00:39:45,940 learned movements, yes. 677 00:39:45,940 --> 00:39:48,000 But in this hamster study, we were 678 00:39:48,000 --> 00:39:50,460 looking at unlearned movements. 679 00:39:50,460 --> 00:39:52,350 The first time they ever see. 680 00:39:52,350 --> 00:39:55,170 We raised them in the lab, so you can-- 681 00:39:55,170 --> 00:39:57,040 they only see food pellets. 682 00:39:57,040 --> 00:39:59,150 They never see seeds. 683 00:39:59,150 --> 00:40:01,245 And yet, the first time I give a hamster 684 00:40:01,245 --> 00:40:03,880 a seed-- I can let them become an adult, 685 00:40:03,880 --> 00:40:06,755 and I can give them a seed, and they can pick it up and shell 686 00:40:06,755 --> 00:40:11,288 it faster than you can because it's inborn. 687 00:40:11,288 --> 00:40:18,274 AUDIENCE: I thought [INAUDIBLE] fixed patterns 688 00:40:18,274 --> 00:40:21,267 of moving [INAUDIBLE] pattern. 689 00:40:21,267 --> 00:40:21,767 [INAUDIBLE]? 690 00:40:25,280 --> 00:40:28,070 PROFESSOR: There are aspects of the sequence that are learned, 691 00:40:28,070 --> 00:40:32,030 but most grooming is unlearned, and so 692 00:40:32,030 --> 00:40:35,990 you don't get a permanent disruption. 693 00:40:35,990 --> 00:40:38,410 There's some very good studies by John Fentress. 694 00:40:38,410 --> 00:40:39,720 If you look his name up. 695 00:40:39,720 --> 00:40:40,970 He's at Dalhousie University. 696 00:40:40,970 --> 00:40:42,673 He's done many studies of grooming 697 00:40:42,673 --> 00:40:51,055 in mice, genetic effects as well as lesion effects, 698 00:40:51,055 --> 00:40:52,805 and showing that are fixed action patters. 699 00:40:56,680 --> 00:40:59,070 This second question, number seven, 700 00:40:59,070 --> 00:41:03,750 here, it refers to a study of motor system 701 00:41:03,750 --> 00:41:07,550 by [INAUDIBLE] lab here at MIT. 702 00:41:07,550 --> 00:41:12,720 So to read that, and see if you can figure out. 703 00:41:12,720 --> 00:41:16,180 I think I make it clear there in the book. 704 00:41:16,180 --> 00:41:19,930 And this one, we can deal with right now. 705 00:41:19,930 --> 00:41:22,686 You should know what Betz cells are. 706 00:41:22,686 --> 00:41:25,140 Does anybody remember? 707 00:41:25,140 --> 00:41:26,710 And I want to know how it's related 708 00:41:26,710 --> 00:41:29,030 to the discovery of Fritsch and Hitzig. 709 00:41:29,030 --> 00:41:30,030 Who are they? 710 00:41:30,030 --> 00:41:36,450 1870, the first guys to study motor cortex 711 00:41:36,450 --> 00:41:38,720 by electrical stimulation. 712 00:41:38,720 --> 00:41:44,117 They defined it as the area, which when stimulated-- 713 00:41:44,117 --> 00:41:45,700 it was a horrible time in neuroscience 714 00:41:45,700 --> 00:41:49,200 because they didn't have good anesthesia at all. 715 00:41:49,200 --> 00:41:51,880 So it was very difficult to do these experiments. 716 00:41:51,880 --> 00:41:54,360 They actually did some of it on humans; 717 00:41:54,360 --> 00:41:59,890 men in the Franco-Prussian War who had their skulls blown off, 718 00:41:59,890 --> 00:42:03,200 so they were dying soldiers. 719 00:42:03,200 --> 00:42:05,590 They still did some of this work. 720 00:42:05,590 --> 00:42:09,590 Their first purpose was medical, but then they 721 00:42:09,590 --> 00:42:12,050 were able to do a little bit of this at the same time. 722 00:42:12,050 --> 00:42:14,470 But most of the work was done on dogs, 723 00:42:14,470 --> 00:42:18,140 and they were able to map out the motor cortex. 724 00:42:18,140 --> 00:42:21,095 It's where, with the smallest electrical currents, 725 00:42:21,095 --> 00:42:22,470 you can get movement. 726 00:42:22,470 --> 00:42:24,260 It doesn't mean you can't get movement 727 00:42:24,260 --> 00:42:25,760 from other places in the cortex. 728 00:42:25,760 --> 00:42:27,172 You can. 729 00:42:27,172 --> 00:42:30,570 There are descending connections from visual cortex, too. 730 00:42:30,570 --> 00:42:33,260 They don't all go to motor cortex. 731 00:42:33,260 --> 00:42:36,570 Most of them, they don't go at all to motor cortex. 732 00:42:36,570 --> 00:42:38,080 But they do go to the brainstem. 733 00:42:38,080 --> 00:42:40,680 They go to the tectum, for example. 734 00:42:40,680 --> 00:42:43,070 So they control, orienting with this, directly 735 00:42:43,070 --> 00:42:46,410 from visual cortex by projecting to the tectum. 736 00:42:46,410 --> 00:42:48,310 So that's a type of motor cortex, too. 737 00:42:48,310 --> 00:42:50,450 But what we call the motor cortex 738 00:42:50,450 --> 00:42:54,990 is this specialized somatosensory area rostral 739 00:42:54,990 --> 00:43:00,090 to the primary somatosensory cortex in mammals. 740 00:43:00,090 --> 00:43:04,260 Betz cells are the giant pyramidal cells 741 00:43:04,260 --> 00:43:08,216 that you find in that area that Fritsch and Hitzig mapped out 742 00:43:08,216 --> 00:43:10,780 as the motor cortex. 743 00:43:10,780 --> 00:43:17,390 It was four years later, 1874 that that Betz 744 00:43:17,390 --> 00:43:19,470 described these giant cells. 745 00:43:19,470 --> 00:43:21,550 They are the cells that give rise 746 00:43:21,550 --> 00:43:24,660 to the very long axons that go all 747 00:43:24,660 --> 00:43:28,390 the way down the spinal cord, and they no doubt 748 00:43:28,390 --> 00:43:33,268 include neurons that project directly to motor neurons. 749 00:43:33,268 --> 00:43:37,530 AUDIENCE: Are Betz cells are cells in the [INAUDIBLE] area? 750 00:43:37,530 --> 00:43:39,530 PROFESSOR: No, they're just the really big ones. 751 00:43:39,530 --> 00:43:42,470 Some of them are much bigger than others. 752 00:43:47,180 --> 00:43:50,380 You see Betz cells even in the hamster. 753 00:43:50,380 --> 00:43:52,840 When we did those sections of the pyramidal tract 754 00:43:52,840 --> 00:43:56,720 and we looked at the motor cortex, 755 00:43:56,720 --> 00:44:00,340 we wanted to know if the Betz-- the big cells or any cells 756 00:44:00,340 --> 00:44:02,220 degenerate. 757 00:44:02,220 --> 00:44:04,090 And they didn't degenerate. 758 00:44:04,090 --> 00:44:05,180 They just lose weight. 759 00:44:05,180 --> 00:44:06,152 They get smaller. 760 00:44:06,152 --> 00:44:09,050 They don't look as much like Betz cells. 761 00:44:09,050 --> 00:44:10,800 But we did cell counts, so we know 762 00:44:10,800 --> 00:44:12,990 that all the cells were still there. 763 00:44:12,990 --> 00:44:14,610 They just get smaller when they don't 764 00:44:14,610 --> 00:44:16,310 support a long axon anymore. 765 00:44:19,030 --> 00:44:21,590 Just very quickly, the medial lesions, 766 00:44:21,590 --> 00:44:23,680 this is described in the book. 767 00:44:23,680 --> 00:44:26,180 You've got to do the lesion bilaterally. 768 00:44:26,180 --> 00:44:30,280 Remember the reason's because they crossover, 769 00:44:30,280 --> 00:44:31,910 And many axons do cross over. 770 00:44:31,910 --> 00:44:37,510 But you get drastic effects on writing. 771 00:44:37,510 --> 00:44:39,157 They did get some recovery. 772 00:44:39,157 --> 00:44:40,490 Why do you think they recovered? 773 00:44:40,490 --> 00:44:42,110 You asked me this earlier. 774 00:44:42,110 --> 00:44:49,380 Even after as much as 40 days, because there's other ways 775 00:44:49,380 --> 00:44:54,030 to write just with spinal reflexes. 776 00:44:54,030 --> 00:44:58,550 The input from the somatosensory system and from the joints 777 00:44:58,550 --> 00:45:01,510 can support some writing. 778 00:45:01,510 --> 00:45:07,430 but for the vestibulospinal tract is gone so they can use-- 779 00:45:07,430 --> 00:45:10,970 do the normal-- or tectospinal also. 780 00:45:10,970 --> 00:45:17,410 They can't use visual, and they can't use vestibular input 781 00:45:17,410 --> 00:45:20,510 to write anymore. 782 00:45:20,510 --> 00:45:22,570 So when they walk, they stumble around. 783 00:45:22,570 --> 00:45:26,160 They don't know which way to go. 784 00:45:26,160 --> 00:45:27,550 I shouldn't say that. 785 00:45:27,550 --> 00:45:30,611 They know which way to go because they still 786 00:45:30,611 --> 00:45:33,110 control eye movements and you can see where they're looking. 787 00:45:33,110 --> 00:45:35,010 You can see where they're trying to get to. 788 00:45:35,010 --> 00:45:38,970 But yet, they can't make their body do it. 789 00:45:38,970 --> 00:45:41,760 It's a very interesting kind of, you don't really call it 790 00:45:41,760 --> 00:45:45,490 a paralysis, but they clearly can't control those movements 791 00:45:45,490 --> 00:45:48,180 well at all. 792 00:45:48,180 --> 00:45:50,340 And then the lateral pathways they lose. 793 00:45:50,340 --> 00:45:54,340 We'll come back to this and talk a little bit next time, 794 00:45:54,340 --> 00:45:55,590 the way they did it. 795 00:45:55,590 --> 00:45:58,430 I actually have films of this, but I 796 00:45:58,430 --> 00:46:02,930 need to see if we can find something online so I 797 00:46:02,930 --> 00:46:05,260 can show it in class. 798 00:46:05,260 --> 00:46:07,620 The video, the film's, take forever 799 00:46:07,620 --> 00:46:11,740 to set up and show in the classroom. 800 00:46:11,740 --> 00:46:13,942 But it was a very nice study. 801 00:46:13,942 --> 00:46:22,380 AUDIENCE: [INAUDIBLE] somatic [INAUDIBLE]? 802 00:46:22,380 --> 00:46:24,175 PROFESSOR: Sorry? 803 00:46:24,175 --> 00:46:32,800 AUDIENCE: [INAUDIBLE] motor neuron pool, 804 00:46:32,800 --> 00:46:36,050 were you looking for midbrain or the ocular motor? 805 00:46:36,050 --> 00:46:38,695 PROFESSOR: They're both true because the ocular motor, 806 00:46:38,695 --> 00:46:42,720 the most rostral ocular motor nuclei are in the midbrain. 807 00:46:42,720 --> 00:46:45,080 So either one is correct.