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 --> 00:00:10,750 to offer high-quality educational resources for free. 5 00:00:10,750 --> 00:00:13,360 To make a donation or view additional materials 6 00:00:13,360 --> 00:00:17,239 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:17,239 --> 00:00:17,864 at ocw.mit.edu. 8 00:00:22,736 --> 00:00:24,610 PROFESSOR: A little more about the hindbrain. 9 00:00:27,740 --> 00:00:33,600 I want to talk about the changes that sort of distorted 10 00:00:33,600 --> 00:00:38,720 that simple picture of the embryonic hindbrain. 11 00:00:38,720 --> 00:00:41,550 We know it becomes a lot more complicated looking 12 00:00:41,550 --> 00:00:45,000 in the adult, but there's also this idea 13 00:00:45,000 --> 00:00:48,370 of changes in relative size of parts. 14 00:00:48,370 --> 00:00:51,250 And more than that, there are migrations 15 00:00:51,250 --> 00:00:54,670 of cells from the other plate that form the cerebellum 16 00:00:54,670 --> 00:00:57,610 and really distort things. 17 00:00:57,610 --> 00:01:00,525 And we talked before about some of these changes 18 00:01:00,525 --> 00:01:02,790 that you see in specialized creatures, 19 00:01:02,790 --> 00:01:07,920 like these fish specialized for taste 20 00:01:07,920 --> 00:01:10,790 like the buffalo fish and the catfish, 21 00:01:10,790 --> 00:01:14,660 the catfish that tastes with his whole body. 22 00:01:14,660 --> 00:01:18,260 And then the huge cerebellum develops 23 00:01:18,260 --> 00:01:22,330 in some of the electric fish, animals with electroreception. 24 00:01:26,387 --> 00:01:30,170 But we want to talk now about cerebellum. 25 00:01:30,170 --> 00:01:33,604 So first of all, what's the meaning of the word pons? 26 00:01:37,400 --> 00:01:42,920 And what's the major input and output of the pons? 27 00:01:42,920 --> 00:01:43,610 Where is it? 28 00:01:46,380 --> 00:01:49,230 In the rostral hindbrain, what part? 29 00:01:53,960 --> 00:01:56,680 Remember what pons means? 30 00:01:56,680 --> 00:01:57,430 It means bridge. 31 00:02:02,265 --> 00:02:04,190 Why do they call it a bridge? 32 00:02:04,190 --> 00:02:07,900 Well, if you look at the brain from the ventral side, 33 00:02:07,900 --> 00:02:09,860 it's a really obvious structure. 34 00:02:09,860 --> 00:02:13,880 It's wider than the rest of the hindbrain. 35 00:02:13,880 --> 00:02:17,736 It's way up at the top of the rostral part of the hindbrain. 36 00:02:17,736 --> 00:02:20,065 It's white because of myelinated fibers. 37 00:02:22,940 --> 00:02:26,340 What are all those fibers doing? 38 00:02:26,340 --> 00:02:29,250 There's a lot of cells there, and there's a lot of fibers. 39 00:02:29,250 --> 00:02:34,463 The cells we call the pontine gray, the pontine gray matter. 40 00:02:40,380 --> 00:02:45,082 And it projects to what? 41 00:02:45,082 --> 00:02:45,955 The cerebellum. 42 00:02:48,860 --> 00:02:53,272 So it gets very big in animals with a big cerebellum. 43 00:02:53,272 --> 00:02:55,355 Well, what is its major input? 44 00:02:59,160 --> 00:03:03,210 I showed it once in this picture. 45 00:03:06,990 --> 00:03:08,870 This is a picture that was originally 46 00:03:08,870 --> 00:03:12,080 of the primitive brain, and then I added the neocortex to it 47 00:03:12,080 --> 00:03:16,320 to show some of the long pathways going up 48 00:03:16,320 --> 00:03:21,240 this neocortex, and then in this one coming down from neocortex. 49 00:03:21,240 --> 00:03:26,310 And I'm showing axons here that generally go on 50 00:03:26,310 --> 00:03:31,301 into the spinal cord, but they have collaterals 51 00:03:31,301 --> 00:03:33,267 that terminate there in the pons. 52 00:03:33,267 --> 00:03:37,110 And you can see here what the output of the pons is. 53 00:03:39,822 --> 00:03:41,820 It goes to the cerebellar cortex. 54 00:03:50,360 --> 00:03:52,350 So that's the answer to number 16. 55 00:04:00,890 --> 00:04:04,120 If you wanted to give a general answer to that next question, 56 00:04:04,120 --> 00:04:07,500 what causes quantitative distortions 57 00:04:07,500 --> 00:04:09,930 of the basic structural layout of the hindbrain? 58 00:04:13,910 --> 00:04:16,005 What's the major distortion that occurs 59 00:04:16,005 --> 00:04:17,879 in the development of the hindbrain of humans 60 00:04:17,879 --> 00:04:20,649 and other primates? 61 00:04:20,649 --> 00:04:24,490 And that's mainly what I want to talk about here. 62 00:04:24,490 --> 00:04:31,310 The distortion has to do with the size of structures. 63 00:04:31,310 --> 00:04:34,530 Just like you saw the hindbrain distortions caused 64 00:04:34,530 --> 00:04:39,750 by these fish with a very specialized taste input. 65 00:04:39,750 --> 00:04:44,590 What were the cell groups that grew so much, became so big 66 00:04:44,590 --> 00:04:50,810 and distorted the brain stem in those animals like this? 67 00:04:50,810 --> 00:04:53,540 That's a hindbrain distortion, yet it's 68 00:04:53,540 --> 00:04:57,440 become the biggest part of the brain. 69 00:04:57,440 --> 00:04:58,520 What's the cell group? 70 00:05:01,040 --> 00:05:04,950 What kind of neuron are they? 71 00:05:04,950 --> 00:05:05,538 Sorry? 72 00:05:05,538 --> 00:05:06,760 AUDIENCE: Gustatory. 73 00:05:06,760 --> 00:05:08,550 PROFESSOR: Gustatory, yes-- taste. 74 00:05:08,550 --> 00:05:11,720 They have specialized taste, so a lot of them 75 00:05:11,720 --> 00:05:16,810 must be secondary sensory cells representing taste. 76 00:05:16,810 --> 00:05:21,000 Now, there are other cells in that lobe too, because they 77 00:05:21,000 --> 00:05:27,830 actually in their specialized taste organ in the palate, 78 00:05:27,830 --> 00:05:31,730 way in the back of the throat, they also 79 00:05:31,730 --> 00:05:36,230 have some contractile organs there, 80 00:05:36,230 --> 00:05:38,430 so that it has a motor component that's 81 00:05:38,430 --> 00:05:40,080 included in that huge lobe. 82 00:05:45,110 --> 00:05:45,610 OK. 83 00:05:45,610 --> 00:05:57,000 So why is that the cerebellum gets so large in the primates? 84 00:05:57,000 --> 00:06:01,860 It has to do with a very large neocortex. 85 00:06:01,860 --> 00:06:07,292 The neocortex seems to need a cerebellum 86 00:06:07,292 --> 00:06:10,040 to coordinate its output. 87 00:06:10,040 --> 00:06:14,950 For one thing, output isn't controlled just by neocortex. 88 00:06:14,950 --> 00:06:17,960 It's controlled by sending inputs 89 00:06:17,960 --> 00:06:22,770 that also go the cerebellum-- mainly proprioceptive, but also 90 00:06:22,770 --> 00:06:31,810 somatosensory and visual, even some auditory input. 91 00:06:31,810 --> 00:06:35,140 So all these different senses with slightly different timing 92 00:06:35,140 --> 00:06:38,010 getting there have to be adjusted and coordinated 93 00:06:38,010 --> 00:06:41,460 so they can get to the output at the right time, 94 00:06:41,460 --> 00:06:44,000 and that's what the cerebellum is largely about. 95 00:06:48,090 --> 00:06:51,295 That's not what most neuroscience classes will teach 96 00:06:51,295 --> 00:06:54,770 you, but that's what I'm teaching. 97 00:06:54,770 --> 00:06:58,400 I have to see why that appeared, why 98 00:06:58,400 --> 00:07:01,980 it was so important throughout development. 99 00:07:01,980 --> 00:07:02,929 Yeah? 100 00:07:02,929 --> 00:07:03,845 AUDIENCE: [INAUDIBLE]. 101 00:07:14,594 --> 00:07:16,010 PROFESSOR: That's a good question. 102 00:07:16,010 --> 00:07:18,760 Is there a correlation between proprioceptive 103 00:07:18,760 --> 00:07:21,800 input-- you mean in quantitative terms, the amount 104 00:07:21,800 --> 00:07:23,520 of proprioception, the amount of it? 105 00:07:23,520 --> 00:07:26,240 Well, you could look at vestibular input 106 00:07:26,240 --> 00:07:29,370 as a kind of proprioception. 107 00:07:29,370 --> 00:07:32,950 It's affected by our movements all the time. 108 00:07:32,950 --> 00:07:37,020 It's giving us feedback on our movement, just like feedback 109 00:07:37,020 --> 00:07:42,050 from the joints, feedback from the muscles. 110 00:07:42,050 --> 00:07:45,220 They all give feedback, monitoring our movements. 111 00:07:49,280 --> 00:07:52,230 So I would expect some correlation. 112 00:07:52,230 --> 00:07:55,240 But it's interesting that the cerebellum develops very early, 113 00:07:55,240 --> 00:08:01,560 and it develops as basically a vestibular organ. 114 00:08:01,560 --> 00:08:06,420 And then later it acquires all these other inputs. 115 00:08:06,420 --> 00:08:09,910 As they expanded, they all seem to want 116 00:08:09,910 --> 00:08:13,480 to get to the cerebellum as well as into the forebrain. 117 00:08:18,280 --> 00:08:23,440 Then I introduce another term in question 18 here. 118 00:08:23,440 --> 00:08:26,090 What is the role of the rhombic lip? 119 00:08:26,090 --> 00:08:28,884 It's a structure seen during the development 120 00:08:28,884 --> 00:08:29,925 of the rostral hindbrain. 121 00:08:33,250 --> 00:08:35,600 You remember what the rhombic lip is? 122 00:08:35,600 --> 00:08:37,610 Did you read the chapter? 123 00:08:37,610 --> 00:08:40,720 I realize you're getting some of these concepts 124 00:08:40,720 --> 00:08:42,820 for the first time. 125 00:08:42,820 --> 00:08:45,990 We're going to talk a lot more about development 126 00:08:45,990 --> 00:08:50,770 in a couple of the later sections of the class. 127 00:08:50,770 --> 00:08:54,350 One coming up pretty soon, where we'll talk about axon growth. 128 00:08:54,350 --> 00:08:57,800 But here we're talking about-- and we'll 129 00:08:57,800 --> 00:09:00,790 talk about this actually in the very next class when 130 00:09:00,790 --> 00:09:01,790 we talk about forebrain. 131 00:09:05,370 --> 00:09:08,130 So what is the rhombic lip? 132 00:09:08,130 --> 00:09:09,655 It's a transient structure. 133 00:09:12,260 --> 00:09:19,420 There are very large numbers of neuroblasts there 134 00:09:19,420 --> 00:09:25,989 that migrate from that region into the cerebellum, 135 00:09:25,989 --> 00:09:27,530 into the roof plate of the hindbrain, 136 00:09:27,530 --> 00:09:30,800 forming the cerebellum at the rostral end of the hindbrain. 137 00:09:30,800 --> 00:09:35,932 But they also migrate from there to other positions 138 00:09:35,932 --> 00:09:36,640 in the hindbrain. 139 00:09:39,300 --> 00:09:45,870 They form the structures that project to the cerebellar 140 00:09:45,870 --> 00:09:46,370 cortex. 141 00:09:49,050 --> 00:09:52,846 Those structures all seem to arise in the rhombic lip. 142 00:09:56,650 --> 00:10:02,340 Basically, the rhombic lip is in the [INAUDIBLE] plate, 143 00:10:02,340 --> 00:10:05,370 cells migrate from that region, and that's 144 00:10:05,370 --> 00:10:08,200 what leads to these distortions. 145 00:10:08,200 --> 00:10:10,005 They migrate into the cerebellum. 146 00:10:10,005 --> 00:10:12,870 They migrate into cell groups. 147 00:10:12,870 --> 00:10:15,080 This is where it is. 148 00:10:15,080 --> 00:10:16,575 This is where the cerebellum forms. 149 00:10:19,140 --> 00:10:21,855 And the rhombic lip is huge numbers 150 00:10:21,855 --> 00:10:28,650 of neuroblasts that form [INAUDIBLE] here. 151 00:10:28,650 --> 00:10:33,780 And that's what leads to the formation of the cerebellum. 152 00:10:33,780 --> 00:10:35,900 And here, if you look at this picture 153 00:10:35,900 --> 00:10:41,550 where I've sort of depicted-- I don't have an animation, 154 00:10:41,550 --> 00:10:43,970 so you've got to use your imagination. 155 00:10:43,970 --> 00:10:48,480 Here's the original embryonic rostral hindbrain. 156 00:10:48,480 --> 00:10:50,070 And there with the red arrows I'm 157 00:10:50,070 --> 00:10:53,240 showing migration cells from the rhombic lip 158 00:10:53,240 --> 00:10:55,320 into the roof plate, so those are 159 00:10:55,320 --> 00:11:00,120 going to form the cerebellum itself. 160 00:11:00,120 --> 00:11:04,650 But they also migrate down to form the pons. 161 00:11:04,650 --> 00:11:06,610 And then some of them migrate more caudally 162 00:11:06,610 --> 00:11:12,710 and form the inferior olive, another major source of input. 163 00:11:12,710 --> 00:11:14,610 These are really the two major sources 164 00:11:14,610 --> 00:11:20,060 of input from the hindbrain into the cerebellum, from the pons 165 00:11:20,060 --> 00:11:22,170 and from the inferior olive. 166 00:11:25,130 --> 00:11:28,500 And then as these migrations occur, 167 00:11:28,500 --> 00:11:34,190 as the cerebellar cortex grows, you can see in relative terms, 168 00:11:34,190 --> 00:11:35,710 it gets very, very large. 169 00:11:35,710 --> 00:11:39,040 I've not even shown its full size in a human. 170 00:11:42,350 --> 00:11:47,790 And it grows on the ventral side too as the pons forms. 171 00:11:47,790 --> 00:11:50,260 And here I'm just showing that the projections 172 00:11:50,260 --> 00:11:54,280 from the pontine cells are decussating. 173 00:11:54,280 --> 00:12:00,210 They cross there within the pons and go to the cerebellum. 174 00:12:00,210 --> 00:12:01,110 on the opposite side. 175 00:12:10,500 --> 00:12:13,270 You say, well, why did they have to cross? 176 00:12:13,270 --> 00:12:15,170 Remember, we talked about decussations 177 00:12:15,170 --> 00:12:18,886 and how the sensory world comes to be represented 178 00:12:18,886 --> 00:12:23,450 on the opposite side in the midbrain and forebrain. 179 00:12:23,450 --> 00:12:26,100 But this is hindbrain. 180 00:12:26,100 --> 00:12:29,330 So why are they crossing? 181 00:12:29,330 --> 00:12:33,820 Well, that projection from the neocortex 182 00:12:33,820 --> 00:12:36,300 is not a cross projection. 183 00:12:36,300 --> 00:12:40,620 So the right hemisphere projects to the right side of the pons. 184 00:12:40,620 --> 00:12:43,640 The right side of the midbrain tectum, for example, 185 00:12:43,640 --> 00:12:45,830 projects to the right side of the pons. 186 00:12:48,592 --> 00:12:52,950 But the cerebellum is not a crossed system. 187 00:12:52,950 --> 00:12:59,820 So they'd have to cross there in order 188 00:12:59,820 --> 00:13:01,870 to match the inputs they're getting 189 00:13:01,870 --> 00:13:04,960 from the spinal cord and more caudal hindbrain. 190 00:13:10,940 --> 00:13:18,610 This is a picture of a human rostral hindbrain. 191 00:13:18,610 --> 00:13:22,020 So here's the original cross-section, 192 00:13:22,020 --> 00:13:24,080 and look what's happened to the roof plate. 193 00:13:24,080 --> 00:13:26,240 Here, you're just seeing the deepest part. 194 00:13:26,240 --> 00:13:28,590 There's only a little bit of cortex even showing there. 195 00:13:31,230 --> 00:13:35,630 It would go way out to here someplace and way up 196 00:13:35,630 --> 00:13:40,110 above the seal, if you saw the whole thing. 197 00:13:40,110 --> 00:13:43,220 What you're seeing there is the output structures 198 00:13:43,220 --> 00:13:44,680 of the cerebellum. 199 00:13:44,680 --> 00:13:48,410 These are called the deep nuclei. 200 00:13:48,410 --> 00:13:51,326 The one that looks like it's corrugated 201 00:13:51,326 --> 00:13:54,498 is the dentate nucleus. 202 00:13:54,498 --> 00:13:58,330 The animals with the largest cerebral hemispheres 203 00:13:58,330 --> 00:14:01,120 have the largest dentate nucleus. 204 00:14:01,120 --> 00:14:03,320 So it's very large in humans. 205 00:14:03,320 --> 00:14:08,190 And then there's an intermediate one, the emboliform nucleus. 206 00:14:08,190 --> 00:14:15,170 And then medial ones here, the fastigial nucleus, 207 00:14:15,170 --> 00:14:18,570 more concerned with axial muscle control. 208 00:14:18,570 --> 00:14:21,280 And the most primitive parts of the cerebellum 209 00:14:21,280 --> 00:14:25,680 are those, this medial area here. 210 00:14:25,680 --> 00:14:26,180 OK. 211 00:14:26,180 --> 00:14:30,500 So all of this is pontine gray, the light areas, 212 00:14:30,500 --> 00:14:32,960 because this is a fiber stain. 213 00:14:32,960 --> 00:14:35,270 And then the corticospinal tract, 214 00:14:35,270 --> 00:14:37,960 which is at the base of the midbrain, 215 00:14:37,960 --> 00:14:41,570 it penetrates right through the middle of the pons. 216 00:14:41,570 --> 00:14:45,312 So here you see those axons, the corticospinal tract axons, 217 00:14:45,312 --> 00:14:46,400 cut in cross-section. 218 00:14:49,030 --> 00:14:52,430 They form a more compact bundle, again, 219 00:14:52,430 --> 00:14:55,480 at the very base of the hindbrain. 220 00:14:55,480 --> 00:14:57,360 They form the pyramidal tract there. 221 00:15:02,986 --> 00:15:05,720 So we'll come back to that again in a little bit 222 00:15:05,720 --> 00:15:07,530 when we talk about the motor system. 223 00:15:11,180 --> 00:15:15,666 Right now, we want to talk about the midbrain. 224 00:15:21,650 --> 00:15:25,800 This question, why a midbrain, occurred to me 225 00:15:25,800 --> 00:15:31,710 when I thought about traditional neuroanatomy textbooks 226 00:15:31,710 --> 00:15:34,880 and the way they treat the midbrain. 227 00:15:34,880 --> 00:15:38,790 It generally is given pretty short shrift. 228 00:15:38,790 --> 00:15:45,050 They treat it as basically a reflex center, controlling eye 229 00:15:45,050 --> 00:15:52,040 movements, the pupillary light reflex, auditory reflexes, 230 00:15:52,040 --> 00:15:54,972 and it serves as a relay of auditory information 231 00:15:54,972 --> 00:15:55,680 to the forebrain. 232 00:15:58,520 --> 00:16:03,840 And it serves as a very important visual center 233 00:16:03,840 --> 00:16:07,320 in primitive animals. 234 00:16:07,320 --> 00:16:12,540 But there's been enough studies now 235 00:16:12,540 --> 00:16:17,690 of the membrane and especially motor control 236 00:16:17,690 --> 00:16:20,860 that we can say a lot more about it now 237 00:16:20,860 --> 00:16:26,990 than the information that led to those medical school 238 00:16:26,990 --> 00:16:27,780 traditions. 239 00:16:27,780 --> 00:16:32,705 So we get a good idea about the evolution of the midbrain 240 00:16:32,705 --> 00:16:35,790 and forebrain from animals resembling the most primitive 241 00:16:35,790 --> 00:16:38,640 chordates that we discussed earlier. 242 00:16:38,640 --> 00:16:41,420 And of course we get many ideas from comparative studies 243 00:16:41,420 --> 00:16:42,045 of vertebrates. 244 00:16:44,670 --> 00:16:46,850 We don't get much information from skulls 245 00:16:46,850 --> 00:16:54,390 because the midbrain is-- primitive skulls, of course, 246 00:16:54,390 --> 00:16:56,180 can tell us something because they 247 00:16:56,180 --> 00:17:00,340 will be the shape of the midbrain, 248 00:17:00,340 --> 00:17:03,816 will be visible in some skills, where the forebrain is not 249 00:17:03,816 --> 00:17:04,315 so huge. 250 00:17:09,440 --> 00:17:12,109 So these are my initial answers to why 251 00:17:12,109 --> 00:17:15,722 we have a midbrain as well as the forebrain. 252 00:17:15,722 --> 00:17:18,770 So I say the midbrain together with early components 253 00:17:18,770 --> 00:17:21,125 of the forebrain, there's a kind of rostral extension 254 00:17:21,125 --> 00:17:24,630 of the hindbrain that enabled visual and olfactory control 255 00:17:24,630 --> 00:17:27,690 of the motor patterns, because olfaction 256 00:17:27,690 --> 00:17:29,970 develops at the very rostral end. 257 00:17:29,970 --> 00:17:32,240 That was the reason the endbrain started 258 00:17:32,240 --> 00:17:36,350 to form-- the olfactory input there. 259 00:17:36,350 --> 00:17:39,630 Otherwise, think of amphioxus before-- it probably 260 00:17:39,630 --> 00:17:42,400 doesn't even have olfaction. 261 00:17:42,400 --> 00:17:46,810 But it's got a forebrain, and it's mainly just a diencephalon 262 00:17:46,810 --> 00:17:52,220 with some secretory cells, important in endocrine control 263 00:17:52,220 --> 00:17:55,090 and probably control of motivation, 264 00:17:55,090 --> 00:17:58,120 just like it remains important in vertebrates. 265 00:18:02,350 --> 00:18:05,010 But for vision-- and vision comes in. 266 00:18:05,010 --> 00:18:05,560 Where? 267 00:18:05,560 --> 00:18:09,740 Even amphioxus has the pigmented cells right here. 268 00:18:09,740 --> 00:18:11,490 We already said it was diencephalon. 269 00:18:11,490 --> 00:18:14,370 That's where the visual inputs come in. 270 00:18:14,370 --> 00:18:18,490 OK, so for vision and olfaction ought to affect movement, 271 00:18:18,490 --> 00:18:23,730 they formed links in the midbrain. 272 00:18:23,730 --> 00:18:26,840 Generally, when connections first evolve, 273 00:18:26,840 --> 00:18:31,360 they're not long connections, because connections start out 274 00:18:31,360 --> 00:18:34,050 from structures that are small. 275 00:18:34,050 --> 00:18:36,880 Then, as they grow larger, the largest structures 276 00:18:36,880 --> 00:18:38,320 become more connected. 277 00:18:38,320 --> 00:18:41,800 There's a general rule in comparative anatomy-- 278 00:18:41,800 --> 00:18:45,054 larger is more connected. 279 00:18:45,054 --> 00:18:46,845 So we have these huge cerebral hemispheres. 280 00:18:46,845 --> 00:18:51,800 It's got connections to all parts of the spinal cord, 281 00:18:51,800 --> 00:18:56,370 hindbrain, midbrain, diencephalon, as well 282 00:18:56,370 --> 00:18:59,920 as many connections within the hemisphere. 283 00:18:59,920 --> 00:19:04,860 But animals who are very small, cerebral hemispheres 284 00:19:04,860 --> 00:19:06,800 do not have these long connections. 285 00:19:09,820 --> 00:19:13,560 They also added controlled by motivational states, 286 00:19:13,560 --> 00:19:16,820 and we will see, the midbrain can 287 00:19:16,820 --> 00:19:19,430 include structures that are involved 288 00:19:19,430 --> 00:19:20,670 in motivational control. 289 00:19:20,670 --> 00:19:23,280 It's not only the hypothalamus that does it. 290 00:19:23,280 --> 00:19:27,750 Remember, we talked about the hierarchy of control, 291 00:19:27,750 --> 00:19:31,610 or autonomic functions like temperature. 292 00:19:31,610 --> 00:19:35,880 So it's not just the hypothalamus that does that. 293 00:19:35,880 --> 00:19:37,720 The midbrain does it, the hindbrain does it, 294 00:19:37,720 --> 00:19:39,940 the spinal cord does it. 295 00:19:39,940 --> 00:19:44,080 So we'll look at that in the midbrain. 296 00:19:44,080 --> 00:19:46,565 And then this is just about those structures. 297 00:19:46,565 --> 00:19:50,710 There had to be visual and olfactory pathways 298 00:19:50,710 --> 00:19:57,770 from those systems, from the tweenbrain and endbrain, as 299 00:19:57,770 --> 00:20:00,440 well of inputs, of course, from more caudal structures, 300 00:20:00,440 --> 00:20:03,730 including the cerebellum that come into the midbrain. 301 00:20:03,730 --> 00:20:05,580 So first of all, what are the two inputs 302 00:20:05,580 --> 00:20:08,560 carrying information about light levels 303 00:20:08,560 --> 00:20:11,554 into the central nervous system? 304 00:20:11,554 --> 00:20:13,970 So we're going to talk a little bit about primitive vision 305 00:20:13,970 --> 00:20:16,550 here, and then about primitive olfaction. 306 00:20:16,550 --> 00:20:18,903 So for vision, what are the two inputs? 307 00:20:29,770 --> 00:20:33,280 Lateral eyes, that's one of them. 308 00:20:33,280 --> 00:20:36,430 What's the other one? 309 00:20:36,430 --> 00:20:38,850 What's it called-- the eye on top of the head. 310 00:20:38,850 --> 00:20:41,426 Yeah, you don't have it, I know. 311 00:20:41,426 --> 00:20:44,340 The pineal eye. 312 00:20:44,340 --> 00:20:47,870 It's an actual eye in many creatures. 313 00:20:47,870 --> 00:20:50,060 Many amphibians have a pineal eye. 314 00:20:56,440 --> 00:21:02,210 An early role of that optic input-- no doubt, 315 00:21:02,210 --> 00:21:07,130 before even their image forming eyes were present, 316 00:21:07,130 --> 00:21:10,400 just detection of light levels-- was 317 00:21:10,400 --> 00:21:15,290 control of the rhythm of activity, which was different 318 00:21:15,290 --> 00:21:16,950 in day and night, because it made 319 00:21:16,950 --> 00:21:18,600 a big difference in efficiency. 320 00:21:18,600 --> 00:21:21,170 It made a big difference in survival of the animals. 321 00:21:21,170 --> 00:21:23,460 They were active during certain periods of the day. 322 00:21:26,430 --> 00:21:29,860 And we know now that cells developed there 323 00:21:29,860 --> 00:21:35,840 that had an endogenous rhythm, a circadian rhythm, 324 00:21:35,840 --> 00:21:37,870 but it was affected by light levels. 325 00:21:37,870 --> 00:21:42,255 They were active either during the day or during the night. 326 00:21:42,255 --> 00:21:49,840 So here are the two inputs, pineal eye and retinal input, 327 00:21:49,840 --> 00:21:54,000 from lateral eyes coming right into the hypothalamus, the most 328 00:21:54,000 --> 00:21:55,350 primitive visual connection. 329 00:21:59,610 --> 00:22:04,990 And in that hypothalamus that we see those two visual inputs, 330 00:22:04,990 --> 00:22:08,446 there was mechanisms for controlling 331 00:22:08,446 --> 00:22:12,100 the sleep-waking cycle, altering physiology 332 00:22:12,100 --> 00:22:16,940 and behavior, involved both the epithalamus or the pineal eye 333 00:22:16,940 --> 00:22:22,430 connected, and the anterior parts of the hypothalamus. 334 00:22:22,430 --> 00:22:27,710 And in a modern mammal, if you damage that anterior part 335 00:22:27,710 --> 00:22:31,330 of the hypothalamus, as Nauta did many years ago-- before he 336 00:22:31,330 --> 00:22:35,350 even was a neuroanatomist and doing a PhD thesis, 337 00:22:35,350 --> 00:22:39,760 he made lesions in hypothalamus, because he studied and he 338 00:22:39,760 --> 00:22:46,050 realized, these must be crucial for important controls 339 00:22:46,050 --> 00:22:47,480 of the animal's life. 340 00:22:47,480 --> 00:22:54,460 And he found major centers for controlling wakefulness 341 00:22:54,460 --> 00:22:56,950 and sleep. 342 00:22:59,490 --> 00:23:03,820 He's still cited for those findings. 343 00:23:03,820 --> 00:23:08,300 But other, we could say, the cyclical motivational states 344 00:23:08,300 --> 00:23:10,860 are influenced by this biological clock. 345 00:23:10,860 --> 00:23:13,540 They're regulated by mostly the hypothalamus. 346 00:23:16,520 --> 00:23:19,960 Cyclical forging, feeding, drinking, nesting, 347 00:23:19,960 --> 00:23:20,924 and other things. 348 00:23:24,780 --> 00:23:26,860 But in order for the visual inputs, 349 00:23:26,860 --> 00:23:29,420 we just deal with vision now. 350 00:23:29,420 --> 00:23:32,680 In order for those inputs to control local mode responses 351 00:23:32,680 --> 00:23:35,810 more directly-- that is, not just through controlling 352 00:23:35,810 --> 00:23:39,360 the circadian rhythm-- then they had 353 00:23:39,360 --> 00:23:42,930 to have links to the midbrain. 354 00:23:42,930 --> 00:23:46,290 Now, when it comes to olfaction, it 355 00:23:46,290 --> 00:23:50,520 was and remains an important control of behavioral state. 356 00:23:50,520 --> 00:23:52,080 And these are the two main things 357 00:23:52,080 --> 00:23:59,530 olfaction did for animals-- learning object identities, 358 00:23:59,530 --> 00:24:02,620 remembering them, altering behavior 359 00:24:02,620 --> 00:24:05,140 according to what those objects were, 360 00:24:05,140 --> 00:24:09,100 so they could detect sexual identity and individual 361 00:24:09,100 --> 00:24:11,030 differences. 362 00:24:11,030 --> 00:24:13,105 They could discriminate what was good to eat 363 00:24:13,105 --> 00:24:15,790 and what was bad to eat-- they learned that just 364 00:24:15,790 --> 00:24:16,540 through olfaction. 365 00:24:20,010 --> 00:24:23,470 Why was it so important to do it through olfaction and not just 366 00:24:23,470 --> 00:24:25,770 with taste? 367 00:24:25,770 --> 00:24:28,740 Well, to identify food, if you had to taste it, 368 00:24:28,740 --> 00:24:32,124 well, you'd have to come right up and touch it. 369 00:24:32,124 --> 00:24:35,150 But with olfaction, you might be able to do it at a distance, 370 00:24:35,150 --> 00:24:41,940 so there was a big advantage-- no doubt 371 00:24:41,940 --> 00:24:45,075 promoted the evolution of the olfaction, olfactory system. 372 00:24:49,840 --> 00:24:52,970 For the olfaction to control behavior 373 00:24:52,970 --> 00:24:55,810 on the basis of those object identifications, 374 00:24:55,810 --> 00:25:01,765 you needed pathways going down to the motor system. 375 00:25:01,765 --> 00:25:04,680 And I point that out here at the bottom, 376 00:25:04,680 --> 00:25:07,170 and I point out the structures that were involved. 377 00:25:07,170 --> 00:25:10,196 We call them ventral striatum and the amygdala, 378 00:25:10,196 --> 00:25:12,085 are the precursors to those structures. 379 00:25:14,600 --> 00:25:19,180 Their main outputs were to the hypothalamus. 380 00:25:19,180 --> 00:25:22,290 But the hypothalamus likewise, to influence movement, 381 00:25:22,290 --> 00:25:25,160 most of the pathways went through the midbrain. 382 00:25:25,160 --> 00:25:27,960 And then, of course, it was important for detecting 383 00:25:27,960 --> 00:25:31,120 places too-- good places, bad places. 384 00:25:31,120 --> 00:25:35,650 They had to learn them, remember them, direct their behavior, 385 00:25:35,650 --> 00:25:41,670 according to whether they were something desirable or not. 386 00:25:41,670 --> 00:25:43,540 And that led to the evolution of what 387 00:25:43,540 --> 00:25:46,050 we call the medial pallium, which 388 00:25:46,050 --> 00:25:50,590 became the hippocampus in mammals. 389 00:25:50,590 --> 00:25:53,740 Outputs went through the ventral striatum and hypothalamus, 390 00:25:53,740 --> 00:25:57,450 and then of course to the midbrain. 391 00:25:57,450 --> 00:25:59,480 And this just expands on that a little bit. 392 00:25:59,480 --> 00:26:05,890 I talk about the approach avoidance movements 393 00:26:05,890 --> 00:26:10,740 that involves both of these kinds of control. 394 00:26:10,740 --> 00:26:19,540 And so for odors to influence locomotion, 395 00:26:19,540 --> 00:26:23,830 the projections went to specific places in the hypothalamus 396 00:26:23,830 --> 00:26:27,225 and the midbrain that had been studied, especially 397 00:26:27,225 --> 00:26:29,400 by the electrophysiologist, and I'm 398 00:26:29,400 --> 00:26:33,250 going to identify those areas for you in a minute here, 399 00:26:33,250 --> 00:26:34,840 and we'll come back to it when we 400 00:26:34,840 --> 00:26:39,850 start talking about the motor system, locomotor control. 401 00:26:39,850 --> 00:26:43,550 So escape from predator threat we've talked about before. 402 00:26:46,160 --> 00:26:52,480 Now we'll see what that's led to in locomotor 403 00:26:52,480 --> 00:26:54,570 areas of the brain. 404 00:26:54,570 --> 00:26:59,100 And then the other function for controlling orienting, 405 00:26:59,100 --> 00:27:00,970 how is olfaction involved in orienting? 406 00:27:00,970 --> 00:27:02,720 Olfaction doesn't really give you 407 00:27:02,720 --> 00:27:07,920 a sense of place except if you're near a good place 408 00:27:07,920 --> 00:27:12,510 or near a bad place and they smell different. 409 00:27:12,510 --> 00:27:16,130 It certainly will affect the motivation of the animal. 410 00:27:16,130 --> 00:27:18,560 And that will affect the response of the animal 411 00:27:18,560 --> 00:27:21,860 to visual, auditory, and somatosensory inputs. 412 00:27:21,860 --> 00:27:23,670 So that's how it affects orienting. 413 00:27:23,670 --> 00:27:26,050 You can trace those pathways. 414 00:27:26,050 --> 00:27:28,110 So here's the midbrain. 415 00:27:28,110 --> 00:27:32,180 This is the structure we're talking about. 416 00:27:32,180 --> 00:27:37,650 And now some more specific questions-- 417 00:27:37,650 --> 00:27:48,080 what are the three major types of multipurpose movements 418 00:27:48,080 --> 00:27:49,870 controlled by descending pathways that 419 00:27:49,870 --> 00:27:52,390 originate in the midbrain? 420 00:27:52,390 --> 00:27:55,340 Multipurpose movements you have to separate 421 00:27:55,340 --> 00:27:58,110 from specialized movements. 422 00:27:58,110 --> 00:28:01,410 Give me an example of each. 423 00:28:01,410 --> 00:28:09,690 A multipurpose movement is used in various motivational states. 424 00:28:09,690 --> 00:28:11,670 We use it when we want food. 425 00:28:11,670 --> 00:28:13,500 We use it when we want sex. 426 00:28:13,500 --> 00:28:15,660 We use it when we want to do this 427 00:28:15,660 --> 00:28:17,480 or that or the other thing. 428 00:28:17,480 --> 00:28:19,620 There are certain kinds of movements 429 00:28:19,620 --> 00:28:22,890 that are used for many different purposes. 430 00:28:22,890 --> 00:28:26,150 There's other movements that are very specialized-- courtship 431 00:28:26,150 --> 00:28:28,480 movements, for example, sexual movements. 432 00:28:28,480 --> 00:28:31,770 They're very particular. 433 00:28:31,770 --> 00:28:35,210 And there are many movements like that. 434 00:28:35,210 --> 00:28:38,070 In an evolution, fixed action patterns, 435 00:28:38,070 --> 00:28:41,740 meaning genetically controlled patterns of behavior, 436 00:28:41,740 --> 00:28:49,850 evolve both types, multipurpose and special purpose. 437 00:28:49,850 --> 00:28:52,640 So there's three major types of multipurpose movements 438 00:28:52,640 --> 00:28:58,295 controlled by the midbrain and pathways from it. 439 00:28:58,295 --> 00:29:00,420 We want to know what the structures in the midbrain 440 00:29:00,420 --> 00:29:05,500 are that gave rise to those pathways. 441 00:29:05,500 --> 00:29:09,700 Can anybody name one of them, either the structure 442 00:29:09,700 --> 00:29:10,790 or the type of movement? 443 00:29:13,930 --> 00:29:17,010 Orienting, turning movements-- that's 444 00:29:17,010 --> 00:29:18,300 a general purpose movement. 445 00:29:18,300 --> 00:29:22,570 We use it for all kinds of behaviors. 446 00:29:22,570 --> 00:29:26,900 We need to be able to orient our senses, 447 00:29:26,900 --> 00:29:30,290 orient our heads and eyes towards something. 448 00:29:30,290 --> 00:29:32,170 That's one of the general purpose movements. 449 00:29:32,170 --> 00:29:35,137 And what's the structure so important for controlling that? 450 00:29:37,819 --> 00:29:40,430 You say, well, the visual cortex. 451 00:29:40,430 --> 00:29:42,670 Well, that came much later. 452 00:29:42,670 --> 00:29:45,520 Let's talk about the midbrain. 453 00:29:45,520 --> 00:29:49,510 What was the midbrain structure so important in orienting? 454 00:29:49,510 --> 00:29:52,460 And most animals, even if they have a large cortex, 455 00:29:52,460 --> 00:29:54,070 still use that structure. 456 00:29:54,070 --> 00:29:57,025 The pathway simply goes from the cortex down to the structure 457 00:29:57,025 --> 00:29:59,780 to control orienting. 458 00:29:59,780 --> 00:30:05,180 It's the surface of the superior colliculus, or midbrain tectum. 459 00:30:05,180 --> 00:30:10,240 We saw a picture a while back of a predatory fish 460 00:30:10,240 --> 00:30:12,860 with enormous optic tectum. 461 00:30:12,860 --> 00:30:15,230 Remember the barracuda I showed you? 462 00:30:15,230 --> 00:30:19,930 Enormous tectum, bigger than any structure in the brain. 463 00:30:26,250 --> 00:30:29,990 Well, we're very visual animals too. 464 00:30:29,990 --> 00:30:33,360 Why isn't it so big in us in relative terms? 465 00:30:36,610 --> 00:30:41,080 Because some animals, the types of orienting they do 466 00:30:41,080 --> 00:30:46,840 are much more under the control of learning. 467 00:30:46,840 --> 00:30:50,120 And the midbrain is only good for very short-term kinds 468 00:30:50,120 --> 00:30:52,890 of learning. 469 00:30:52,890 --> 00:30:56,920 And we'll talk about that again in a minute. 470 00:30:56,920 --> 00:31:00,140 I want you to be able to name two pathways that originate 471 00:31:00,140 --> 00:31:02,310 in the midbrain and descend to the spinal cord. 472 00:31:02,310 --> 00:31:03,625 Why aren't there three? 473 00:31:03,625 --> 00:31:06,210 Because the third one we don't know as much 474 00:31:06,210 --> 00:31:07,220 about anatomically. 475 00:31:07,220 --> 00:31:09,064 We know about it from physiology. 476 00:31:09,064 --> 00:31:10,355 It's some very nice physiology. 477 00:31:13,500 --> 00:31:17,290 And I use the physiology data as well as anatomical data 478 00:31:17,290 --> 00:31:20,695 in coming to these descriptions. 479 00:31:23,390 --> 00:31:27,020 So here's a typical picture of a midbrain 480 00:31:27,020 --> 00:31:30,915 of an animal like a rat or a mouse or a hamster. 481 00:31:33,860 --> 00:31:35,920 When I first drew these, I drew them from memory. 482 00:31:35,920 --> 00:31:38,720 And the animal I'd use the most was the hamster. 483 00:31:38,720 --> 00:31:42,710 I had also done work with rats and mice 484 00:31:42,710 --> 00:31:44,025 and a number of other animals. 485 00:31:47,350 --> 00:31:51,812 So here is that optic tectum, except we usually 486 00:31:51,812 --> 00:31:56,360 call it the superior colliculus in a mammal. 487 00:31:56,360 --> 00:32:00,050 We think of it as a visual structure, 488 00:32:00,050 --> 00:32:05,460 but the visual layers are just these superficial layers. 489 00:32:05,460 --> 00:32:07,780 What are the axons down below? 490 00:32:10,710 --> 00:32:12,580 Well, it must be the input coming 491 00:32:12,580 --> 00:32:19,887 in from the eye, the retina, and from posterior visual areas 492 00:32:19,887 --> 00:32:20,470 of the cortex. 493 00:32:24,050 --> 00:32:28,350 This is all superior colliculus down here too. 494 00:32:28,350 --> 00:32:30,700 You don't need that much colliculus just 495 00:32:30,700 --> 00:32:35,670 to get output to the lower brain stem 496 00:32:35,670 --> 00:32:41,390 and to the upper spinal cord to control head and eye movements. 497 00:32:41,390 --> 00:32:43,755 Other sensory inputs come in there too, 498 00:32:43,755 --> 00:32:47,630 and they tend to match the visual inputs. 499 00:32:47,630 --> 00:32:52,620 They match them in representing the same parts of space. 500 00:32:52,620 --> 00:32:56,450 So auditory and somatosensory inputs come out of here. 501 00:32:56,450 --> 00:33:01,040 If I am working with a rat, say, and I'm 502 00:33:01,040 --> 00:33:06,050 looking at the part of that optic layer that's 503 00:33:06,050 --> 00:33:09,110 responding to this visual field right out here-- remember, 504 00:33:09,110 --> 00:33:13,560 the rat's eyes are looking up here this way, 60 degrees out, 505 00:33:13,560 --> 00:33:16,330 30 degrees up, at least for the hamster, very similar 506 00:33:16,330 --> 00:33:17,250 for the mouse. 507 00:33:17,250 --> 00:33:18,970 So here's the two eyes looking up. 508 00:33:18,970 --> 00:33:22,930 And I show him something up here, 509 00:33:22,930 --> 00:33:25,450 and I get a response from the colliculus 510 00:33:25,450 --> 00:33:32,900 in the upper temporal field, somewhere in here, 511 00:33:32,900 --> 00:33:36,270 fairly far back from the tectum. 512 00:33:36,270 --> 00:33:40,630 Now, if I come close to him, what am I going to do? 513 00:33:40,630 --> 00:33:42,876 I'm going to touch whiskers here. 514 00:33:42,876 --> 00:33:48,280 If I stimulate those whiskers, this activates the same region 515 00:33:48,280 --> 00:33:51,590 but in the deeper layers. 516 00:33:51,590 --> 00:33:54,780 And in the middle, there's auditory input. 517 00:33:54,780 --> 00:33:57,410 And the auditory input in many animals 518 00:33:57,410 --> 00:34:02,280 also gives you a pretty good map of space. 519 00:34:02,280 --> 00:34:06,570 Like the cat, the owl-- very, very good at auditory 520 00:34:06,570 --> 00:34:07,963 localization too. 521 00:34:07,963 --> 00:34:13,630 The owl can hear rustling on the forest floor below his tree 522 00:34:13,630 --> 00:34:16,685 and know where that mouse is even though he never sees it. 523 00:34:16,685 --> 00:34:17,810 He just hears the rustling. 524 00:34:20,449 --> 00:34:26,586 And the cat is pretty similar in localized sounds really well. 525 00:34:26,586 --> 00:34:30,540 I'll try to go a little faster here. 526 00:34:30,540 --> 00:34:35,909 So the three output systems, I list them structurally here, 527 00:34:35,909 --> 00:34:37,699 functionally here. 528 00:34:37,699 --> 00:34:40,839 Descending axons from the midbrain locomotor area 529 00:34:40,839 --> 00:34:42,985 is the first output system. 530 00:34:42,985 --> 00:34:47,245 It controls locomotion involved in approach, avoidance, 531 00:34:47,245 --> 00:34:52,460 in exploring, foraging, seeking behavior or various types. 532 00:34:52,460 --> 00:34:54,179 It's a general purpose movement. 533 00:34:54,179 --> 00:34:57,430 That's the axon system, studied physiologically 534 00:34:57,430 --> 00:34:59,620 in some beautiful experiments by a number 535 00:34:59,620 --> 00:35:01,060 of different investigators. 536 00:35:01,060 --> 00:35:05,490 Then the tectospinal tract from the deep layers 537 00:35:05,490 --> 00:35:08,400 of the superior colliculus or optic tectum. 538 00:35:08,400 --> 00:35:10,090 It's controlling orienting movements-- 539 00:35:10,090 --> 00:35:14,150 that means turning of the eyes and head. 540 00:35:14,150 --> 00:35:17,790 And finally, rubrospinal tract. 541 00:35:17,790 --> 00:35:22,020 Rubro in Latin means red. 542 00:35:22,020 --> 00:35:26,290 So rubrospinal means a pathway from the red nucleus 543 00:35:26,290 --> 00:35:31,210 to the spinal cord, and that's controlling limb movements 544 00:35:31,210 --> 00:35:33,740 involved in exploring or reaching and grasping. 545 00:35:36,820 --> 00:35:38,835 Those are the three multipurpose movements 546 00:35:38,835 --> 00:35:43,270 we're talking about-- locomotion, orienting, 547 00:35:43,270 --> 00:35:46,195 and we'll just use that term, grasping. 548 00:35:52,960 --> 00:35:54,612 We'll come back to those again when 549 00:35:54,612 --> 00:35:56,250 we talk about motor system. 550 00:35:56,250 --> 00:35:59,510 Now, this is from a physiological study 551 00:35:59,510 --> 00:36:02,950 using electrical stimulation to define 552 00:36:02,950 --> 00:36:05,290 locomotor areas in the brain. 553 00:36:05,290 --> 00:36:08,830 This was done in the cat by the Russian, Orlovsky, who 554 00:36:08,830 --> 00:36:11,310 did some very nice work on this. 555 00:36:11,310 --> 00:36:15,950 And what I did is I traced two of his drawings 556 00:36:15,950 --> 00:36:19,000 where he was showing the stimulation sites. 557 00:36:19,000 --> 00:36:23,820 And he outlined the most areas where he most easily elicited 558 00:36:23,820 --> 00:36:26,320 locomotion from the hypothalamus, 559 00:36:26,320 --> 00:36:29,150 and that was called the hypothalamic locomotor area. 560 00:36:29,150 --> 00:36:31,780 There is a nearby area in the subthalamus 561 00:36:31,780 --> 00:36:33,880 where you can also get locomotion. 562 00:36:33,880 --> 00:36:36,600 People talk much less about it, but it's there. 563 00:36:36,600 --> 00:36:38,845 And here is the area in the caudal midbrain. 564 00:36:38,845 --> 00:36:41,770 Now, this is the sagittal section. 565 00:36:41,770 --> 00:36:44,070 So there's thalamus. 566 00:36:44,070 --> 00:36:48,190 There's the inferior colliculus, the caudal part 567 00:36:48,190 --> 00:36:50,900 of the colliculus. 568 00:36:50,900 --> 00:36:52,290 And that's the region. 569 00:36:52,290 --> 00:36:56,570 It centers in an area just in the reticular formation 570 00:36:56,570 --> 00:36:58,595 below the inferior colliculus. 571 00:36:58,595 --> 00:37:01,340 And here it is in a section. 572 00:37:01,340 --> 00:37:05,360 This is a section at this level. 573 00:37:05,360 --> 00:37:08,165 There's the inferior colliculus. 574 00:37:08,165 --> 00:37:10,270 That means lateral lemniscus, which 575 00:37:10,270 --> 00:37:11,560 we haven't talked about yet. 576 00:37:11,560 --> 00:37:14,155 It's an auditory pathway carrying auditory information 577 00:37:14,155 --> 00:37:16,970 from the hypothalamus up to the inferior colliculus. 578 00:37:16,970 --> 00:37:21,580 But there's the area centered in this area right 579 00:37:21,580 --> 00:37:24,500 below the inferior colliculus-- it's part of the reticular 580 00:37:24,500 --> 00:37:28,445 formation-- that when you stimulate you get locomotion. 581 00:37:34,090 --> 00:37:34,970 Sorry? 582 00:37:34,970 --> 00:37:37,620 AUDIENCE: [INAUDIBLE]. 583 00:37:37,620 --> 00:37:39,670 PROFESSOR: Yes, it does get input. 584 00:37:39,670 --> 00:37:44,740 If we just draw-- here are some major pathways-- 585 00:37:44,740 --> 00:37:49,700 I'll just sketch them here-- from the hypothalamic locomotor 586 00:37:49,700 --> 00:37:55,900 area to the midbrain locomotor area, 587 00:37:55,900 --> 00:38:01,480 from superior colliculus to the midbrain locomotor area. 588 00:38:01,480 --> 00:38:10,640 And from the striatum way up here, 589 00:38:10,640 --> 00:38:16,370 there are also pathways that go to that structure. 590 00:38:16,370 --> 00:38:18,380 Remember how I talked about how olfaction 591 00:38:18,380 --> 00:38:20,150 can affect locomotion, well, that's 592 00:38:20,150 --> 00:38:21,770 how it does it-- through the striatum. 593 00:38:33,920 --> 00:38:37,040 If you want, I'll put another slide in and draw those back 594 00:38:37,040 --> 00:38:39,580 when I put this online. 595 00:38:39,580 --> 00:38:41,810 All right, I just defined the terms 596 00:38:41,810 --> 00:38:43,770 because some people get very frustrated when 597 00:38:43,770 --> 00:38:46,345 I use abbreviations, and they don't know what they mean. 598 00:38:46,345 --> 00:38:49,120 But in fact, you can understand the basic thing here 599 00:38:49,120 --> 00:38:51,460 without knowing what all these things are. 600 00:38:51,460 --> 00:38:54,190 It doesn't hurt to read them, because the more you encounter 601 00:38:54,190 --> 00:38:57,380 them, the more likely you are to remember something 602 00:38:57,380 --> 00:39:00,620 later on when we study them more specifically. 603 00:39:00,620 --> 00:39:02,455 We didn't talk about the pons. 604 00:39:02,455 --> 00:39:05,730 There it is in the car. 605 00:39:05,730 --> 00:39:08,250 There it is in the cross-section. 606 00:39:08,250 --> 00:39:11,052 So this is actually rostral hypothalamus down here. 607 00:39:11,052 --> 00:39:12,260 That's all midbrain up there. 608 00:39:19,670 --> 00:39:22,030 This is just what we talked about. 609 00:39:22,030 --> 00:39:24,520 Now about the other two types of movement-- 610 00:39:24,520 --> 00:39:29,785 orienting and reaching and grasping. 611 00:39:29,785 --> 00:39:31,630 Here are the pathways for orienting. 612 00:39:31,630 --> 00:39:35,580 This is an output cell from the superior colliculus. 613 00:39:35,580 --> 00:39:36,970 It's a very large cell. 614 00:39:36,970 --> 00:39:41,680 There's many of them in the intermediate and deep layers 615 00:39:41,680 --> 00:39:42,610 here. 616 00:39:42,610 --> 00:39:47,350 And here, the axon crosses over to this position 617 00:39:47,350 --> 00:39:51,090 and descends to the caudal hypothalamus 618 00:39:51,090 --> 00:39:54,320 and to the rostral spinal cord, the cervical spinal cord. 619 00:39:54,320 --> 00:39:57,850 And here is a cell in the caudal part of the red nucleus, 620 00:39:57,850 --> 00:39:59,420 the output part of the red nucleus-- 621 00:39:59,420 --> 00:40:02,840 large cells that send their axon across the midline, 622 00:40:02,840 --> 00:40:06,140 they go to a more lateral position, and as they descend, 623 00:40:06,140 --> 00:40:08,060 they go more and more lateral. 624 00:40:08,060 --> 00:40:11,650 So in the hindbrain, they're way out at the lateral edge. 625 00:40:11,650 --> 00:40:15,390 From the red nucleus, descends to where, 626 00:40:15,390 --> 00:40:17,510 if it's going to control this kind of movement? 627 00:40:17,510 --> 00:40:18,551 Where does it have to go? 628 00:40:20,920 --> 00:40:28,080 From the red nucleus to spinal cord enlargements, where 629 00:40:28,080 --> 00:40:32,840 the neurons are controlling those movements. 630 00:40:32,840 --> 00:40:35,260 Movements of the what, too? 631 00:40:35,260 --> 00:40:36,575 To the spinal enlargements. 632 00:40:40,700 --> 00:40:43,490 So I'm not showing the locomotor area there. 633 00:40:43,490 --> 00:40:46,140 That's defined just physiologically. 634 00:40:46,140 --> 00:40:51,240 And then I have a slide just showing all the sensory systems 635 00:40:51,240 --> 00:40:53,360 in or passing through the midbrain. 636 00:40:53,360 --> 00:40:55,340 So visual inputs up here. 637 00:40:58,180 --> 00:41:00,930 Auditory inputs coming from inferior colliculus 638 00:41:00,930 --> 00:41:02,890 at this level are just seen out here. 639 00:41:02,890 --> 00:41:04,874 They're on their way to the thalamus. 640 00:41:04,874 --> 00:41:10,820 The somatosensory inputs are passing through, 641 00:41:10,820 --> 00:41:17,430 so the spinothalamic tract also goes to the tectum there. 642 00:41:17,430 --> 00:41:22,910 These are the medial lemniscus and trigeminal lemniscus. 643 00:41:22,910 --> 00:41:25,260 They'll stay in approximately that position. 644 00:41:25,260 --> 00:41:26,950 They'll enter the caudal thalamus 645 00:41:26,950 --> 00:41:30,208 and terminate in the ventral part of the caudal thalamus. 646 00:41:33,990 --> 00:41:35,820 Visceral inputs would be up here. 647 00:41:41,090 --> 00:41:48,120 And then the pathways descending from the spinal cord 648 00:41:48,120 --> 00:41:49,910 are in blue there. 649 00:41:49,910 --> 00:41:52,780 That's the cerebral peduncle. 650 00:41:52,780 --> 00:41:55,125 I name it here, cerebral peduncle. 651 00:41:55,125 --> 00:41:57,779 They're fibers from the cortex. 652 00:41:57,779 --> 00:42:00,070 They're going not only to the spinal cord and hindbrain 653 00:42:00,070 --> 00:42:01,398 but also to the pons. 654 00:42:07,140 --> 00:42:10,490 So we talked about this before, the roof of the midbrain 655 00:42:10,490 --> 00:42:14,530 with these little hills, the colliculi. 656 00:42:14,530 --> 00:42:18,200 I said, it shows great variations in size, remember? 657 00:42:18,200 --> 00:42:20,331 Here was the picture. 658 00:42:20,331 --> 00:42:24,610 If animals are more specialized for using audition, 659 00:42:24,610 --> 00:42:27,660 they tend to have very large inferior colliculi, 660 00:42:27,660 --> 00:42:33,610 like in the bat and the dolphin here, the echolocating bat. 661 00:42:33,610 --> 00:42:36,720 Whereas if they're more specialized for especially 662 00:42:36,720 --> 00:42:45,380 innate visual reactions, like in the wild goat or the prosimian 663 00:42:45,380 --> 00:42:50,406 primate, the tarsier, then the optic tectum is larger. 664 00:42:50,406 --> 00:42:54,480 And as I mentioned, some animals are specialized in vision. 665 00:42:54,480 --> 00:43:00,660 We've gone huge visual cortex, as in the higher primates. 666 00:43:00,660 --> 00:43:03,550 The optic tectum is often well developed 667 00:43:03,550 --> 00:43:04,840 in these primates too. 668 00:43:04,840 --> 00:43:07,820 But in some, like humans, we're so 669 00:43:07,820 --> 00:43:10,510 dominated by learned visual reactions 670 00:43:10,510 --> 00:43:13,680 that the colliculus is still very important, 671 00:43:13,680 --> 00:43:16,360 but it is not as expanded as it is in these animals. 672 00:43:19,970 --> 00:43:20,470 OK. 673 00:43:22,990 --> 00:43:25,200 I'm going to just show you this very quickly. 674 00:43:25,200 --> 00:43:26,820 I'd like you to read it. 675 00:43:26,820 --> 00:43:32,660 I divide the midbrain into two main regions. 676 00:43:32,660 --> 00:43:36,860 First of all, what are the limbic midbrain regions? 677 00:43:36,860 --> 00:43:41,610 The central gray and the ventral tegmental area. 678 00:43:41,610 --> 00:43:45,832 If you stimulate these areas in the central gray, 679 00:43:45,832 --> 00:43:48,070 you can get a lot of different behaviors. 680 00:43:48,070 --> 00:43:50,620 But it's dominated by behavior that 681 00:43:50,620 --> 00:43:55,620 indicates they don't like being stimulated there. 682 00:43:55,620 --> 00:43:59,180 Quite a bit of the central gray is involved in responses 683 00:43:59,180 --> 00:44:01,810 to pain-- not only, though. 684 00:44:01,810 --> 00:44:04,550 There's other functional areas in that, 685 00:44:04,550 --> 00:44:07,950 just like there is in the hypothalamus. 686 00:44:07,950 --> 00:44:10,315 There's an area concerned with sexual behavior, 687 00:44:10,315 --> 00:44:13,260 there's areas concerned with temperature regulation, 688 00:44:13,260 --> 00:44:14,660 and so forth. 689 00:44:14,660 --> 00:44:16,820 But a lot of it will give you, they'll 690 00:44:16,820 --> 00:44:18,760 react like they're in pain. 691 00:44:18,760 --> 00:44:22,080 Whereas down here, it's the opposite. 692 00:44:22,080 --> 00:44:26,220 They like to be stimulated down there. 693 00:44:26,220 --> 00:44:33,200 So if they respond to taste, if it's a very good taste, 694 00:44:33,200 --> 00:44:37,840 taste system projects directly into that area. 695 00:44:37,840 --> 00:44:40,990 Again, an animal with a very large cortex, more of the input 696 00:44:40,990 --> 00:44:43,790 comes from above, but there are direct projections 697 00:44:43,790 --> 00:44:47,300 from the taste nucleus there. 698 00:44:47,300 --> 00:44:49,020 Very bad tastes, though, are going 699 00:44:49,020 --> 00:44:51,030 to reach the central gray more. 700 00:44:51,030 --> 00:44:52,700 OK. 701 00:44:52,700 --> 00:44:55,050 You can divide the entire midbrain 702 00:44:55,050 --> 00:44:58,180 into these two systems. 703 00:44:58,180 --> 00:45:02,010 Those two structures I just talked about we say 704 00:45:02,010 --> 00:45:04,380 are limbic related areas, because they 705 00:45:04,380 --> 00:45:09,510 get heavy connections from the fringes of the hemisphere, 706 00:45:09,510 --> 00:45:12,780 the limbic areas related to hypothalamus. 707 00:45:12,780 --> 00:45:16,200 Remember, I defined it that way before. 708 00:45:16,200 --> 00:45:19,210 So these are the areas related to the hypothalamus. 709 00:45:19,210 --> 00:45:22,690 The somatic areas are all the other areas. 710 00:45:22,690 --> 00:45:25,390 And here they are, colored for you. 711 00:45:25,390 --> 00:45:29,730 The limbic areas, central gray and ventral tegmental area-- 712 00:45:29,730 --> 00:45:32,010 all the rest are somatic. 713 00:45:32,010 --> 00:45:36,880 Except down here, we look at the substantia nigra. 714 00:45:36,880 --> 00:45:39,610 I've shown that the medial area is really limbic. 715 00:45:42,240 --> 00:45:46,123 It should be lumped together with the ventral tegmental area 716 00:45:46,123 --> 00:45:48,340 in its connections. 717 00:45:48,340 --> 00:45:53,380 And if you follow these regions forward into the tweenbrain, 718 00:45:53,380 --> 00:45:56,610 you see that the limbic areas are 719 00:45:56,610 --> 00:45:59,240 interconnected with the epithalamus-- that's 720 00:45:59,240 --> 00:46:04,910 where the pineal eye comes in-- and the hypothalamus, 721 00:46:04,910 --> 00:46:08,200 whereas the other regions, if you follow them forward, 722 00:46:08,200 --> 00:46:10,140 you're in the thalamus and subthalamus. 723 00:46:12,780 --> 00:46:13,956 Those are the two regions. 724 00:46:17,130 --> 00:46:19,590 So we'll deal with these questions a little bit 725 00:46:19,590 --> 00:46:25,200 next time and just review some of these connections, 726 00:46:25,200 --> 00:46:28,458 talk about the variations across species. 727 00:46:28,458 --> 00:46:31,740 And that's it. 728 00:46:31,740 --> 00:46:34,300 This is just a summary of all the long connections 729 00:46:34,300 --> 00:46:36,150 going through.