1 00:00:00,250 --> 00:00:01,800 The following content is provided 2 00:00:01,800 --> 00:00:04,040 under a Creative Commons license. 3 00:00:04,040 --> 00:00:06,890 Your support will help MIT OpenCourseWare continue 4 00:00:06,890 --> 00:00:10,740 to offer high quality educational resources for free. 5 00:00:10,740 --> 00:00:13,360 To make a donation or view additional materials 6 00:00:13,360 --> 00:00:17,241 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:17,241 --> 00:00:17,866 at ocw.mit.edu. 8 00:00:23,120 --> 00:00:27,960 PROFESSOR: I want these auditory system specializations. 9 00:00:27,960 --> 00:00:30,110 I'd like to say just a little bit about that. 10 00:00:33,720 --> 00:00:38,050 Earlier in chapter six, we talked about the echolocating 11 00:00:38,050 --> 00:00:42,060 animals-- the bats and dolphins-- 12 00:00:42,060 --> 00:00:47,170 and we pointed out then that they 13 00:00:47,170 --> 00:00:52,735 have this very large arbitrary midbrain, 14 00:00:52,735 --> 00:00:53,735 the inferior colliculus. 15 00:00:56,340 --> 00:00:58,440 In most animals-- the rodents we look 16 00:00:58,440 --> 00:01:04,750 at in the lab, any of the primates-- superior colliculus 17 00:01:04,750 --> 00:01:06,930 is much larger than the interior colliculus. 18 00:01:11,300 --> 00:01:13,670 Here's one primate-- the tarsier-- 19 00:01:13,670 --> 00:01:16,500 and here's an ungulate-- the ibex. 20 00:01:16,500 --> 00:01:20,540 And you see the superior colliculus being much larger, 21 00:01:20,540 --> 00:01:24,370 which is typical for an animal dominated by vision. 22 00:01:24,370 --> 00:01:30,530 Even if they don't have a huge visual cortical area, 23 00:01:30,530 --> 00:01:35,310 they will still have a large midbrain area for vision. 24 00:01:35,310 --> 00:01:36,900 But the echolocating animals have 25 00:01:36,900 --> 00:01:38,870 a much larger inferior colliculus 26 00:01:38,870 --> 00:01:43,060 because some of the processing is done cortically. 27 00:01:43,060 --> 00:01:46,840 And the inferior colliculus is the major route 28 00:01:46,840 --> 00:01:51,600 to the auditory thalamus. 29 00:01:51,600 --> 00:01:56,066 This is from an early study of a bat that uses echolocation. 30 00:02:00,040 --> 00:02:06,290 And there is a lot of cortex devoted to auditory processing. 31 00:02:06,290 --> 00:02:13,430 And early on, they knew the primary area was very large. 32 00:02:13,430 --> 00:02:17,050 They could map out different frequency representation. 33 00:02:17,050 --> 00:02:21,200 And there were areas like, at this point, they [INAUDIBLE] 34 00:02:21,200 --> 00:02:24,510 worked out three different areas where the units were 35 00:02:24,510 --> 00:02:27,880 responsive to various kinds of frequency modulation. 36 00:02:27,880 --> 00:02:32,800 And then he continued that work, and he found areas or units 37 00:02:32,800 --> 00:02:38,680 sensitive to range-- just how far away the animals were-- 38 00:02:38,680 --> 00:02:39,715 and to velocities. 39 00:02:39,715 --> 00:02:46,240 So they could detect a number of features of their prey 40 00:02:46,240 --> 00:02:47,300 that they were chasing. 41 00:02:53,230 --> 00:02:59,240 Now if we go to birds-- I'm asking here 42 00:02:59,240 --> 00:03:01,850 what is the area in bird that's comparable 43 00:03:01,850 --> 00:03:05,310 to the auditory neocortex of a mammal? 44 00:03:05,310 --> 00:03:07,070 Does a bird have a neocortex? 45 00:03:07,070 --> 00:03:09,078 AUDIENCE: [INAUDIBLE] 46 00:03:09,078 --> 00:03:09,930 PROFESSOR: Sorry? 47 00:03:09,930 --> 00:03:10,680 AUDIENCE: Pallium. 48 00:03:13,566 --> 00:03:14,690 PROFESSOR: What's the word? 49 00:03:14,690 --> 00:03:15,440 AUDIENCE: Pallium? 50 00:03:17,790 --> 00:03:21,650 PROFESSOR: They have areas in the thalamus that 51 00:03:21,650 --> 00:03:26,110 receive auditory input, just like they have areas there 52 00:03:26,110 --> 00:03:27,980 that receive visual input. 53 00:03:27,980 --> 00:03:32,010 Where do those areas project? 54 00:03:32,010 --> 00:03:34,240 They do have a kind of visual cortex too. 55 00:03:34,240 --> 00:03:36,750 But the area-- their geniculate body 56 00:03:36,750 --> 00:03:38,960 usually isn't called geniculate body, remember, 57 00:03:38,960 --> 00:03:42,620 but it's called other things-- but it does project 58 00:03:42,620 --> 00:03:45,890 to a cortex-like area that is called the hyperpallium. 59 00:03:48,590 --> 00:03:50,380 Pallium, of course, is just another name 60 00:03:50,380 --> 00:03:52,380 for a cortical region. 61 00:03:52,380 --> 00:03:57,540 And the hyperpallium is the most similar to the neocortex 62 00:03:57,540 --> 00:03:59,160 of mammals. 63 00:03:59,160 --> 00:04:01,690 But then, they have other nuclear 64 00:04:01,690 --> 00:04:07,180 in the thalamus that get input like the LP in mammals 65 00:04:07,180 --> 00:04:08,750 or the medial geniculate body. 66 00:04:08,750 --> 00:04:13,220 They get input from the midbrain. 67 00:04:13,220 --> 00:04:14,910 So in the case of the auditory system, 68 00:04:14,910 --> 00:04:19,820 they're getting projections from the bird's inferior colliculus 69 00:04:19,820 --> 00:04:23,945 region-- often, again, with a different name. 70 00:04:32,100 --> 00:04:34,790 In the birds, it's usually called nucleus ovoidalis. 71 00:04:38,300 --> 00:04:45,370 And that projects to this large region that for many years 72 00:04:45,370 --> 00:04:50,700 was called this neostriatum in birds. 73 00:04:50,700 --> 00:04:56,720 But now we know first from connection data gathered here 74 00:04:56,720 --> 00:05:00,890 at MIT by Karten, who was working with Nauta. 75 00:05:00,890 --> 00:05:04,050 And later, in the gene expression data, 76 00:05:04,050 --> 00:05:11,465 we know that that area is not equivalent, not homologous 77 00:05:11,465 --> 00:05:14,230 to the striatum of mammals. 78 00:05:14,230 --> 00:05:20,500 So it's called a nested pallium, or a neopallium. 79 00:05:20,500 --> 00:05:24,810 It is subcortical if you go by the ventricle. 80 00:05:24,810 --> 00:05:27,830 Here's where the ventricle is along here. 81 00:05:27,830 --> 00:05:31,362 And the hyperpallium is above it. 82 00:05:31,362 --> 00:05:36,490 And that would be where the equivalent 83 00:05:36,490 --> 00:05:40,560 of the lateral geniculate projects for the visual system. 84 00:05:40,560 --> 00:05:42,600 And a lot of it is visual. 85 00:05:42,600 --> 00:05:44,625 And the medial part is hippocampal. 86 00:05:47,240 --> 00:05:50,450 But the auditory region of the thalamus, 87 00:05:50,450 --> 00:05:54,965 nucleus ovadulus projects to the neopallium, the medial part 88 00:05:54,965 --> 00:05:57,866 in an area we call Field L. 89 00:05:57,866 --> 00:06:00,170 Now reptiles have something similar. 90 00:06:00,170 --> 00:06:03,670 We get the thalamic nucleus that gets auditory input 91 00:06:03,670 --> 00:06:10,230 a different name-- the medial reunions. 92 00:06:10,230 --> 00:06:15,540 It goes to that large dorsal ventricular ridge. 93 00:06:15,540 --> 00:06:18,245 And dorsal ventricular ridge becomes a neopallium 94 00:06:18,245 --> 00:06:21,530 if it's in bird development. 95 00:06:21,530 --> 00:06:23,360 We keep calling it dorsal ventricular 96 00:06:23,360 --> 00:06:25,090 ridge in the reptiles. 97 00:06:25,090 --> 00:06:27,660 And they have a auditory region, just like here 98 00:06:27,660 --> 00:06:32,880 more laterally in this region right there 99 00:06:32,880 --> 00:06:37,395 it gets visual input from a different nucleus 100 00:06:37,395 --> 00:06:43,020 in the thalamus, a nucleus that gets input from the tectum. 101 00:06:43,020 --> 00:06:46,100 And then, of course, here's the equivalent circuit in mammals. 102 00:06:46,100 --> 00:06:51,600 Medial geniculate body to these auditory critical regions. 103 00:06:51,600 --> 00:06:53,120 And this is what it looks like. 104 00:06:53,120 --> 00:06:56,870 This is from an atlas by Karten working 105 00:06:56,870 --> 00:07:00,570 with Bill Hodos in the late '60s. 106 00:07:00,570 --> 00:07:04,190 And they published this atlas showing the appearance 107 00:07:04,190 --> 00:07:07,290 of sections at various levels of the bird brain. 108 00:07:07,290 --> 00:07:10,230 And you can see just looking at the cells 109 00:07:10,230 --> 00:07:13,320 here, how Field L stands out. 110 00:07:13,320 --> 00:07:16,680 It's got several layers-- just a little layer down here, 111 00:07:16,680 --> 00:07:19,540 the main layer there, and another, 112 00:07:19,540 --> 00:07:20,880 more superficial layer. 113 00:07:20,880 --> 00:07:25,440 And here's the way it's diagrammed. 114 00:07:25,440 --> 00:07:31,620 And you can see that's all below this end-brain ventricle. 115 00:07:31,620 --> 00:07:34,490 And this would be where the hippocampal equivalent is, 116 00:07:34,490 --> 00:07:38,355 the medial pallium, and this whole region in many animals 117 00:07:38,355 --> 00:07:40,370 is just called dorsal cortex. 118 00:07:40,370 --> 00:07:42,655 But in birds, it's called the hyperpallium. 119 00:07:45,350 --> 00:07:45,850 All right. 120 00:07:45,850 --> 00:07:51,600 So if you trace the auditory pathway from the cochlear 121 00:07:51,600 --> 00:07:56,720 region, they don't have the coiled cochlea of mammals, 122 00:07:56,720 --> 00:08:01,240 but it's, instead of a basilar membrane, 123 00:08:01,240 --> 00:08:03,030 they have a basilar papilla. 124 00:08:03,030 --> 00:08:07,720 And where the auditory receptors are 125 00:08:07,720 --> 00:08:10,120 in contact with the eighth nerve, 126 00:08:10,120 --> 00:08:13,290 and you can see the eighth nerve comes in 127 00:08:13,290 --> 00:08:16,450 to contact the secondary sensory cells of the cochlear nuclei, 128 00:08:16,450 --> 00:08:18,230 just like in mammals. 129 00:08:18,230 --> 00:08:21,165 We saw that when we talked about spatial location, 130 00:08:21,165 --> 00:08:22,914 remember, for the [INAUDIBLE]. 131 00:08:25,670 --> 00:08:29,330 They're dorsally located. 132 00:08:29,330 --> 00:08:32,315 And the neurons there project to the inferior colliculus 133 00:08:32,315 --> 00:08:34,740 of the bird. 134 00:08:34,740 --> 00:08:39,249 It's got a different name-- the MLd-- mesencephalicus lateralis 135 00:08:39,249 --> 00:08:41,480 pars dorsalis. 136 00:08:41,480 --> 00:08:46,760 OK, and that then projects to the thalamus-- 137 00:08:46,760 --> 00:08:49,868 the ovoid nucleus-- nucleus ovoidalis. 138 00:08:49,868 --> 00:08:53,140 Which projects to Field L. OK, so that's just 139 00:08:53,140 --> 00:08:58,230 the simplest picture of the auditory pathway. 140 00:08:58,230 --> 00:09:03,430 But you can then follow things from the auditory pathway that 141 00:09:03,430 --> 00:09:07,120 are involved in controlling their vocalizations. 142 00:09:07,120 --> 00:09:10,995 And the most direct pathway goes from Field L 143 00:09:10,995 --> 00:09:18,510 to a so-called higher vocal center, which then projects 144 00:09:18,510 --> 00:09:23,210 to this nucleus robustus of the arcopallium. 145 00:09:23,210 --> 00:09:32,420 The arcopallium is homologous to the amygdala region of mammals. 146 00:09:32,420 --> 00:09:34,250 Remember the amygdala region, though, 147 00:09:34,250 --> 00:09:38,310 has many outputs to hypothalamus and to midbrain. 148 00:09:38,310 --> 00:09:44,420 And in birds, this nucleus robustus 149 00:09:44,420 --> 00:09:50,100 has a direct projection to the hypervisual nucleus, 150 00:09:50,100 --> 00:09:55,060 part of which controls the syrinx, which 151 00:09:55,060 --> 00:09:58,350 controls basically the voice box of the bird, 152 00:09:58,350 --> 00:10:00,900 controlling his vocalizations, together 153 00:10:00,900 --> 00:10:03,460 with breathing control. 154 00:10:03,460 --> 00:10:05,700 And then there's a less direct pathway 155 00:10:05,700 --> 00:10:11,410 that goes to an outer part of the inferior colliculus region, 156 00:10:11,410 --> 00:10:15,200 which then projects to the hypoglossal nucleus 157 00:10:15,200 --> 00:10:17,140 and controls the syrinx. 158 00:10:17,140 --> 00:10:19,650 Now there's a less direct pathway that in many ways 159 00:10:19,650 --> 00:10:22,620 is more interesting. 160 00:10:22,620 --> 00:10:26,230 From Field L and the higher vocal center, 161 00:10:26,230 --> 00:10:29,700 it projects to the striata of the bird. 162 00:10:29,700 --> 00:10:31,500 Now we're talking about the real striata. 163 00:10:34,270 --> 00:10:40,600 That is, it's equivalent to the dorsal striatum in a mammal. 164 00:10:40,600 --> 00:10:42,940 And like in mammals, the striatum 165 00:10:42,940 --> 00:10:45,900 has an output to the thalamus. 166 00:10:45,900 --> 00:10:49,370 And the thalamic structure it projects to then 167 00:10:49,370 --> 00:10:55,750 projects back to a pallial region. 168 00:10:55,750 --> 00:10:57,950 It's like a Broca's area in mammals. 169 00:10:57,950 --> 00:10:59,880 That is, they're very similar pathways 170 00:10:59,880 --> 00:11:02,130 controlling speech in humans. 171 00:11:02,130 --> 00:11:05,760 It's part of the nested pallium. 172 00:11:05,760 --> 00:11:11,100 Remember this, more caudally, the Field L, 173 00:11:11,100 --> 00:11:15,000 the auditory system, gets part of that nidopallium. 174 00:11:15,000 --> 00:11:22,110 Well, [INAUDIBLE], this nucleus, called LMAN, 175 00:11:22,110 --> 00:11:24,730 is also involved in vocalization. 176 00:11:24,730 --> 00:11:30,330 In fact, this circuit is what's involved in male birds learning 177 00:11:30,330 --> 00:11:32,730 the vocalization of their species. 178 00:11:32,730 --> 00:11:38,020 And they learn by imitation of listening to their father sing, 179 00:11:38,020 --> 00:11:41,170 and they develop. 180 00:11:41,170 --> 00:11:43,030 If they don't hear that singing, they 181 00:11:43,030 --> 00:11:46,650 don't develop as complex a vocal repertoire. 182 00:11:46,650 --> 00:11:50,200 Anyway, that nucleus projects to the robust nucleus, 183 00:11:50,200 --> 00:11:52,680 which gives rise to those outputs 184 00:11:52,680 --> 00:11:56,602 to control the vocal system of the bird, 185 00:11:56,602 --> 00:11:59,145 the syrinx in the throat. 186 00:11:59,145 --> 00:12:00,095 All right. 187 00:12:04,370 --> 00:12:05,960 You learn a lot about that if you 188 00:12:05,960 --> 00:12:07,710 work with Michael Fee in the building. 189 00:12:07,710 --> 00:12:12,040 And students that work with Michael probably 190 00:12:12,040 --> 00:12:14,640 become pretty familiar with that circuit. 191 00:12:14,640 --> 00:12:18,010 But now, I want to go through some, 192 00:12:18,010 --> 00:12:19,930 say a little bit about the forebrain 193 00:12:19,930 --> 00:12:23,240 before we become a little more specialized in covering 194 00:12:23,240 --> 00:12:24,070 the forebrain. 195 00:12:24,070 --> 00:12:29,260 We'll be talking about-- well, you'll see here. 196 00:12:29,260 --> 00:12:33,880 We've covered now-- the first five parts 197 00:12:33,880 --> 00:12:39,790 were all development and evolution 198 00:12:39,790 --> 00:12:45,840 of the brain explaining the basic organization of the CNS. 199 00:12:45,840 --> 00:12:48,390 And then, we went to specialized systems. 200 00:12:48,390 --> 00:12:54,760 And I began with three chapters on the motor system, 201 00:12:54,760 --> 00:12:59,980 then a single chapter on brain states, 202 00:12:59,980 --> 00:13:03,210 and then sensory systems, which should probably 203 00:13:03,210 --> 00:13:05,980 be called special century the because general sensories, 204 00:13:05,980 --> 00:13:10,380 and metasensory I didn't cover in that section. 205 00:13:10,380 --> 00:13:13,680 Because we talked a lot about somatosensory systems 206 00:13:13,680 --> 00:13:16,250 in the earlier parts of the book. 207 00:13:16,250 --> 00:13:20,680 So that's when we dealt with gustatory olfactory, visual, 208 00:13:20,680 --> 00:13:22,960 and then finally, auditory systems. 209 00:13:22,960 --> 00:13:25,390 So now, forebrain origins. 210 00:13:25,390 --> 00:13:29,160 And then we talk about the limbic system and hypothalamus. 211 00:13:29,160 --> 00:13:30,000 That'll be next. 212 00:13:30,000 --> 00:13:34,940 And then, a couple chapters on the corpus striatum of mammals, 213 00:13:34,940 --> 00:13:38,920 primarily, and then finally, several chapters 214 00:13:38,920 --> 00:13:41,350 on the neocortex. 215 00:13:41,350 --> 00:13:48,880 So what was most likely the earliest part of the forebrain? 216 00:13:48,880 --> 00:13:51,390 You first encountered a forebrain 217 00:13:51,390 --> 00:13:56,342 when we talked about amphyioxus, a cephalochordate-- simplest 218 00:13:56,342 --> 00:13:57,050 living chordates. 219 00:14:00,340 --> 00:14:02,970 And remember, you had pigmented cells there 220 00:14:02,970 --> 00:14:04,335 that respond to light. 221 00:14:04,335 --> 00:14:07,360 You had secretory cells secreting. 222 00:14:07,360 --> 00:14:10,996 Directly into the bloodstream of the animal. 223 00:14:10,996 --> 00:14:12,447 AUDIENCE: Olfactory bulb. 224 00:14:12,447 --> 00:14:13,155 PROFESSOR: Sorry? 225 00:14:13,155 --> 00:14:15,860 AUDIENCE: Olfactory bulb. 226 00:14:15,860 --> 00:14:18,890 PROFESSOR: That's a very interesting comment 227 00:14:18,890 --> 00:14:21,890 because you would think olfaction would probably 228 00:14:21,890 --> 00:14:23,970 be the earliest input. 229 00:14:23,970 --> 00:14:26,080 But in fact, we're not sure there's 230 00:14:26,080 --> 00:14:28,160 olfaction in amphyioxus. 231 00:14:28,160 --> 00:14:30,560 But we do know there are those secretory cells. 232 00:14:30,560 --> 00:14:33,650 And we do know they're getting effects of light 233 00:14:33,650 --> 00:14:35,610 through that pigmented cell region. 234 00:14:35,610 --> 00:14:38,800 And they have cells that are like retinal ganglion 235 00:14:38,800 --> 00:14:41,839 cells that provide input to the brain. 236 00:14:41,839 --> 00:14:43,630 Now we think the most primitive part is all 237 00:14:43,630 --> 00:14:44,930 equivalent to diencephalon. 238 00:14:44,930 --> 00:14:48,320 And the gene expression studies have supported that. 239 00:14:48,320 --> 00:14:52,890 It's actually like diencephalon, not like end-brain. 240 00:14:52,890 --> 00:14:55,220 So they don't have anything like cortex. 241 00:14:55,220 --> 00:15:02,320 They don't appear-- nothing for sure-- of olfaction. 242 00:15:02,320 --> 00:15:04,500 If they do have any olfaction, there 243 00:15:04,500 --> 00:15:08,380 are a couple of nerves that they don't know much about. 244 00:15:08,380 --> 00:15:11,470 One of them could be equivalent to olfactory. 245 00:15:11,470 --> 00:15:17,930 But it's going into the equivalent of a tween-brain. 246 00:15:17,930 --> 00:15:20,050 So that leads to this next question-- what 247 00:15:20,050 --> 00:15:23,652 are the cranial nerves that are attached to the forebrain? 248 00:15:23,652 --> 00:15:27,540 Now forebrain includes end-brain and tween-brain, remember. 249 00:15:27,540 --> 00:15:29,670 So I want all the cranial nerves that 250 00:15:29,670 --> 00:15:32,680 connect there-- now one of you've 251 00:15:32,680 --> 00:15:41,450 already mentioned-- number one-- olfaction, number two is what? 252 00:15:41,450 --> 00:15:47,390 the optic nerve-- OK-- which becomes optic tract, 253 00:15:47,390 --> 00:15:51,000 so it is a CNS tract, but we still call it a nerve 254 00:15:51,000 --> 00:15:53,550 before it gets to the chiasum. 255 00:15:53,550 --> 00:15:57,260 OK, so that's two of them. 256 00:15:57,260 --> 00:15:59,155 Those are the two that are among the twelve 257 00:15:59,155 --> 00:16:01,280 that we name for the human brain. 258 00:16:01,280 --> 00:16:03,750 But there's actually three others. 259 00:16:03,750 --> 00:16:06,690 OK, and here I list them. 260 00:16:06,690 --> 00:16:13,650 If you don't have a forebrain, he's missing these five nerves. 261 00:16:13,650 --> 00:16:19,120 Nerve one and two-- but nerve one-- the olfactory nerve 262 00:16:19,120 --> 00:16:22,520 we could include the vomeronasal nasal nerve and the terminal 263 00:16:22,520 --> 00:16:24,860 nerve. 264 00:16:24,860 --> 00:16:28,990 Terminal nerve innervates, apparently the nasal septum. 265 00:16:28,990 --> 00:16:32,534 It's found in humans-- at least in most humans. 266 00:16:32,534 --> 00:16:33,575 There's some variability. 267 00:16:37,760 --> 00:16:40,670 We think it may respond to olfactory input, 268 00:16:40,670 --> 00:16:43,970 but even that is not certain. 269 00:16:43,970 --> 00:16:46,500 You'll find it in human anatomy books. 270 00:16:50,030 --> 00:16:56,350 The vomeronasal organ is Jacobson's organ. 271 00:16:56,350 --> 00:16:59,200 It's in the nasal cavity. 272 00:16:59,200 --> 00:17:06,790 And animals that have this well-developed 273 00:17:06,790 --> 00:17:10,119 have an opening into the roof of the mouth. 274 00:17:10,119 --> 00:17:13,770 Ungulates have this very prominently. 275 00:17:13,770 --> 00:17:20,300 And they, for example, in mating, the male 276 00:17:20,300 --> 00:17:23,250 collects the urine from the female, 277 00:17:23,250 --> 00:17:28,359 brings it into his mouth to that organ in the roof of his mouth 278 00:17:28,359 --> 00:17:32,040 where there are receptors that respond to pheromones 279 00:17:32,040 --> 00:17:36,320 that change with the receptive state of the female. 280 00:17:36,320 --> 00:17:43,960 OK, so he can then tell from that preliminary mating action 281 00:17:43,960 --> 00:17:47,710 whether she's receptive, and whether it 282 00:17:47,710 --> 00:17:50,770 can be impregnated at that time. 283 00:17:50,770 --> 00:17:54,355 So it's part of the ritual they go through before mating. 284 00:17:58,930 --> 00:18:04,680 And the other animals still collect pheromones 285 00:18:04,680 --> 00:18:07,150 on their tongue-- snakes, for example. 286 00:18:07,150 --> 00:18:08,990 You see them flicking out their tongue. 287 00:18:08,990 --> 00:18:14,720 They're actually collecting substances from the air. 288 00:18:14,720 --> 00:18:17,100 And if that includes pheromones, they 289 00:18:17,100 --> 00:18:19,220 bring it to that vomeronasal organ. 290 00:18:19,220 --> 00:18:23,540 Where does the vomeronasal organ project? 291 00:18:23,540 --> 00:18:27,170 To part of the olfactory bulb-- remember, 292 00:18:27,170 --> 00:18:29,200 there's a main olfactory bulb and then 293 00:18:29,200 --> 00:18:32,990 there's an accessory olfactory bulb. 294 00:18:32,990 --> 00:18:38,110 And most mammals have that. 295 00:18:38,110 --> 00:18:41,225 And it specializes in responding to pheromones. 296 00:18:41,225 --> 00:18:47,250 It can come in through the olfactory epithelium also, 297 00:18:47,250 --> 00:18:50,670 not just through vomeronasal organ. 298 00:18:50,670 --> 00:18:53,100 And then, we have the optic nerve. 299 00:18:53,100 --> 00:18:56,170 And then there's another nerve that 300 00:18:56,170 --> 00:18:59,000 brings in information from light. 301 00:18:59,000 --> 00:19:01,930 The epiphyseal nerve-- this is the pineal-- 302 00:19:01,930 --> 00:19:07,850 the nerve can activate the pineal cells by light. 303 00:19:07,850 --> 00:19:10,940 And we know about the pineal eye. 304 00:19:10,940 --> 00:19:14,520 If animals have the pineal eye on the top of their head, 305 00:19:14,520 --> 00:19:19,580 they have a nerve that's called the epiphyseal nerve. 306 00:19:19,580 --> 00:19:24,440 The epiphysis is the name for that structure. 307 00:19:24,440 --> 00:19:27,490 OK, so five cranial nerves, but three of them 308 00:19:27,490 --> 00:19:29,935 associated with olfactory, and two 309 00:19:29,935 --> 00:19:39,192 of them responding to light-- OK, so if an animal doesn't 310 00:19:39,192 --> 00:19:41,400 have a forebrain, there's another thing he's missing. 311 00:19:41,400 --> 00:19:45,090 He doesn't have control of his pituitary gland. 312 00:19:45,090 --> 00:19:46,810 Because what controls the pituitary? 313 00:19:46,810 --> 00:19:50,710 Well, we're going to learn more about that after this class. 314 00:19:50,710 --> 00:19:54,970 We deal with hypothalamus, specifically. 315 00:19:54,970 --> 00:19:59,810 But we know the pituitary is connected to the hypothalamus 316 00:19:59,810 --> 00:20:02,960 in a very interesting way that we will discuss. 317 00:20:06,200 --> 00:20:10,800 It's possible, though, to disconnect the entire forebrain 318 00:20:10,800 --> 00:20:15,600 as we learn in-- I think it was chapter seven. 319 00:20:15,600 --> 00:20:20,980 You can disconnect the entire forebrain from the midbrain . 320 00:20:20,980 --> 00:20:22,900 But you could leave the hypothalamus 321 00:20:22,900 --> 00:20:24,270 connected to the pituitary. 322 00:20:24,270 --> 00:20:27,590 And if you do so, the animal maintains a lot more function 323 00:20:27,590 --> 00:20:30,450 than if you don't. 324 00:20:30,450 --> 00:20:33,080 Because pituitary, to function normally, 325 00:20:33,080 --> 00:20:37,420 needs the hypothalamus attached. 326 00:20:37,420 --> 00:20:41,050 And the controls that the hypothalamus 327 00:20:41,050 --> 00:20:46,110 exerts on the pituitary gland need to be intact. 328 00:20:46,110 --> 00:20:51,010 So in chapter seven, I went through studies 329 00:20:51,010 --> 00:20:54,800 where there was removal or disconnection 330 00:20:54,800 --> 00:20:58,800 of the forebrain from the midbrain. 331 00:20:58,800 --> 00:21:02,310 And I said that animals are missing major components 332 00:21:02,310 --> 00:21:06,670 of normal behavior, even if you leave the hypothalamus attached 333 00:21:06,670 --> 00:21:09,100 to pituitary. 334 00:21:09,100 --> 00:21:10,840 So what is missing? 335 00:21:10,840 --> 00:21:12,006 Anybody remember? 336 00:21:12,006 --> 00:21:13,290 Motivation. 337 00:21:13,290 --> 00:21:16,440 Motivation-- motivated behavior. 338 00:21:16,440 --> 00:21:20,460 So we called it appetitive behavior. 339 00:21:20,460 --> 00:21:27,100 So if an animal's hungry, his behavior that indicates he 340 00:21:27,100 --> 00:21:29,030 has an appetite for food. 341 00:21:29,030 --> 00:21:33,060 But you can use that term-- appetitive behaviour for other 342 00:21:33,060 --> 00:21:36,310 motivations too-- for example, if you're thirsting. 343 00:21:36,310 --> 00:21:41,005 Appetitive behaviour when an animal's thirsty, 344 00:21:41,005 --> 00:21:44,515 a behavior initiated by his motivational system, 345 00:21:44,515 --> 00:21:48,430 a hypothalamus that centers on hypothalamus will lead 346 00:21:48,430 --> 00:21:53,330 to locomotion and seeking of water. 347 00:21:53,330 --> 00:21:55,830 You can use the term, also, for mating behavior, 348 00:21:55,830 --> 00:21:57,755 for sexual motivations. 349 00:21:57,755 --> 00:22:02,320 You can use it for brood-tending behaviors 350 00:22:02,320 --> 00:22:05,960 if they're raising young. 351 00:22:05,960 --> 00:22:07,710 But there's a lot of other things missing, 352 00:22:07,710 --> 00:22:09,680 of course, that depend on forebrain-- 353 00:22:09,680 --> 00:22:12,740 all the cortical and corpus striatum functions. 354 00:22:12,740 --> 00:22:17,910 And I've listed major forebrain functions-- all of which 355 00:22:17,910 --> 00:22:20,720 we're going to be talking more about. 356 00:22:20,720 --> 00:22:26,780 First of all, acuity-- animals that develop a large forebrain 357 00:22:26,780 --> 00:22:32,650 have much better sensory acuity and much better 358 00:22:32,650 --> 00:22:36,785 manipulatory variability of their limbs. 359 00:22:40,911 --> 00:22:41,660 But wait a minute. 360 00:22:41,660 --> 00:22:45,180 Doesn't animals that have a very large optic tectum 361 00:22:45,180 --> 00:22:48,100 have good acuity? 362 00:22:48,100 --> 00:22:53,975 Well, they do, but only for unlearned behaviors. 363 00:22:57,270 --> 00:23:01,034 Acuity for learned behaviors depends on that forebrain. 364 00:23:04,670 --> 00:23:06,630 And of course, humans are so dominated 365 00:23:06,630 --> 00:23:10,290 by learning that often we're pretty 366 00:23:10,290 --> 00:23:14,070 unaware of the tectal controlled behavior, 367 00:23:14,070 --> 00:23:17,590 although it exists in primates too. 368 00:23:17,590 --> 00:23:19,530 OK, but then other things they lack 369 00:23:19,530 --> 00:23:22,790 that you need a forebrain for. 370 00:23:22,790 --> 00:23:24,820 You need an endbrain for. 371 00:23:24,820 --> 00:23:29,190 Lack of anticipation-- they're controlled 372 00:23:29,190 --> 00:23:31,540 by stimuli coming in, but they can't 373 00:23:31,540 --> 00:23:33,750 anticipate what's going to happen. 374 00:23:37,180 --> 00:23:40,090 They don't have good spatial memory. 375 00:23:40,090 --> 00:23:46,000 They don't learn the habits. 376 00:23:46,000 --> 00:23:50,470 The only learning of the midbrain and lower structures 377 00:23:50,470 --> 00:23:52,940 is very short-term. 378 00:23:52,940 --> 00:23:54,500 Many studies have shown this. 379 00:23:59,130 --> 00:24:02,470 What we know as long-term memory developed out of spatial memory 380 00:24:02,470 --> 00:24:08,150 system involving the medial pallium or hippocampus. 381 00:24:08,150 --> 00:24:12,220 And we know that habit learning developed very early 382 00:24:12,220 --> 00:24:18,980 in the olfactory system involving the striatum. 383 00:24:18,980 --> 00:24:24,690 OK, so what do they retain if they've lost all this? 384 00:24:24,690 --> 00:24:26,732 What can they still do? 385 00:24:26,732 --> 00:24:29,618 AUDIENCE: They can eat if they're-- [INAUDIBLE] They can 386 00:24:29,618 --> 00:24:30,789 eat if they're fed. 387 00:24:30,789 --> 00:24:33,330 PROFESSOR: Yeah, they can eat if you put food in their mouth. 388 00:24:33,330 --> 00:24:36,660 What do you call the eating? 389 00:24:36,660 --> 00:24:40,180 There's a general term we use for all drives for that output 390 00:24:40,180 --> 00:24:40,910 site. 391 00:24:40,910 --> 00:24:43,530 We call it consummatory behavior. 392 00:24:43,530 --> 00:24:45,160 It's very easy to remember for eating 393 00:24:45,160 --> 00:24:47,200 because it means consuming the food. 394 00:24:47,200 --> 00:24:48,470 OK? 395 00:24:48,470 --> 00:24:50,500 But you can refer to consummatory behavior 396 00:24:50,500 --> 00:24:52,046 for thirst. 397 00:24:52,046 --> 00:24:54,300 You can refer to it for sexual behavior 398 00:24:54,300 --> 00:25:00,140 where the consummatory behavior is mating, and so forth. 399 00:25:00,140 --> 00:25:02,546 So they retain consummatory behavior. 400 00:25:06,150 --> 00:25:08,180 They retain-- and I've listed some 401 00:25:08,180 --> 00:25:15,310 of those-- they do have pain-elicited aggression. 402 00:25:15,310 --> 00:25:19,670 So a cat without the forebrain-- if you cause him pain, 403 00:25:19,670 --> 00:25:23,910 like you pull his tail-- he will strike out. 404 00:25:23,910 --> 00:25:26,440 He'll unsheath his claws and strike out. 405 00:25:26,440 --> 00:25:28,700 But as soon as you let go, it's gone. 406 00:25:31,710 --> 00:25:33,420 So we call it sham rage. 407 00:25:33,420 --> 00:25:38,350 He acts like he's enraged, but it's not enduring. 408 00:25:38,350 --> 00:25:41,800 We know what we call rage in an animal 409 00:25:41,800 --> 00:25:47,104 outlasts the stimulus that triggers it. 410 00:25:47,104 --> 00:25:49,540 A human can be angry about something 411 00:25:49,540 --> 00:25:50,925 that happened hours before. 412 00:25:54,260 --> 00:25:59,880 It can be angry about something he's just thinking about. 413 00:25:59,880 --> 00:26:01,780 He can be angry about something-- 414 00:26:01,780 --> 00:26:03,915 if you hold a grudge, you could be angry for years. 415 00:26:06,750 --> 00:26:11,895 OK, an animal like that retains his sexual postures 416 00:26:11,895 --> 00:26:14,000 and reflexes. 417 00:26:14,000 --> 00:26:16,310 You can stimulate an animal like that, 418 00:26:16,310 --> 00:26:18,970 like a female cat if she's receptive, 419 00:26:18,970 --> 00:26:23,360 you can stimulate the lordosis response just 420 00:26:23,360 --> 00:26:26,790 by touching her in the right way, 421 00:26:26,790 --> 00:26:29,543 depending on the animal-- they have different regions. 422 00:26:29,543 --> 00:26:32,010 If you give them tactile input, they 423 00:26:32,010 --> 00:26:34,630 will assume that receptive posture. 424 00:26:34,630 --> 00:26:38,650 That's part of the-- you can call it a reflex, 425 00:26:38,650 --> 00:26:40,685 but it's a complicated reflex. 426 00:26:40,685 --> 00:26:42,572 It's part of their fixed action patterns 427 00:26:42,572 --> 00:26:43,530 that they've inherited. 428 00:26:46,768 --> 00:26:49,696 AUDIENCE: I'm just wondering, how about for fear-- 429 00:26:49,696 --> 00:26:51,650 a sense of fear? 430 00:26:51,650 --> 00:26:54,380 PROFESSOR: Like what kind of fear? 431 00:26:54,380 --> 00:26:58,560 AUDIENCE: Do they still retain the fear? 432 00:26:58,560 --> 00:27:02,210 PROFESSOR: They don't remember long-term. 433 00:27:02,210 --> 00:27:08,010 They don't retain the fear, and it doesn't last very long. 434 00:27:08,010 --> 00:27:13,800 It's all pretty short-term, very dependent on the stimulus. 435 00:27:13,800 --> 00:27:17,570 Like a pigeon will actually fly without a forebrain 436 00:27:17,570 --> 00:27:21,700 if you've left his optic nerve attached to the tectum 437 00:27:21,700 --> 00:27:23,880 Because all the stimuli are there. 438 00:27:23,880 --> 00:27:26,865 If you throw him into the air, all the stimuli 439 00:27:26,865 --> 00:27:28,860 that elicit flying are there. 440 00:27:28,860 --> 00:27:32,190 And he will flap his wings and be able to stay in the air. 441 00:27:32,190 --> 00:27:33,120 He will locomote. 442 00:27:33,120 --> 00:27:40,400 He will fly and he will actually avoid running into things. 443 00:27:40,400 --> 00:27:42,390 He will go around trees. 444 00:27:42,390 --> 00:27:47,770 He will land on horizontally placed things, 445 00:27:47,770 --> 00:27:49,750 land on a surface, land on a limb. 446 00:27:52,420 --> 00:27:55,000 He won't maintain the motivation, though. 447 00:27:55,000 --> 00:28:00,160 So once he lands, he won't have the incentive to take off again 448 00:28:00,160 --> 00:28:02,840 unless if he gets blown off the limb, 449 00:28:02,840 --> 00:28:04,710 then he will start flying again. 450 00:28:04,710 --> 00:28:06,480 And they will right themselves. 451 00:28:06,480 --> 00:28:08,250 If you tip them over, they will walk. 452 00:28:10,770 --> 00:28:14,380 But generally, they don't initiate much walking. 453 00:28:14,380 --> 00:28:17,570 They have to be nudged. 454 00:28:17,570 --> 00:28:22,389 So let's talk about primitive forebrains. 455 00:28:22,389 --> 00:28:24,180 We can look at the nonvertebrate chordates. 456 00:28:24,180 --> 00:28:27,570 The invertebrate chordates. 457 00:28:27,570 --> 00:28:30,700 That includes amphioxus. 458 00:28:30,700 --> 00:28:34,980 We could look at the proto mammals. 459 00:28:34,980 --> 00:28:38,990 But to do that-- the animals that led to mammals-- we'd 460 00:28:38,990 --> 00:28:41,725 have to use paleontology and look at skulls. 461 00:28:41,725 --> 00:28:42,600 And that's been done. 462 00:28:42,600 --> 00:28:44,900 We talked about that a little bit 463 00:28:44,900 --> 00:28:46,910 when we talked about auditory system. 464 00:28:46,910 --> 00:28:49,230 Because it's through those studies 465 00:28:49,230 --> 00:28:52,070 that we know about changes in the middle earbones 466 00:28:52,070 --> 00:28:54,650 and the bones around the eye which became 467 00:28:54,650 --> 00:28:58,650 reduced in the earliest mammals. 468 00:28:58,650 --> 00:29:00,750 And of course, we can use comparative anatomy 469 00:29:00,750 --> 00:29:01,650 to study the brain. 470 00:29:01,650 --> 00:29:04,280 That is studies of living animals. 471 00:29:04,280 --> 00:29:11,680 We can't do comparative anatomy very much with animals. 472 00:29:11,680 --> 00:29:13,850 Well, we only have the fossils because brain 473 00:29:13,850 --> 00:29:16,240 is retained in the fossils. 474 00:29:16,240 --> 00:29:18,317 And of course, we can study primitive mammals. 475 00:29:21,450 --> 00:29:26,140 Now we use cladistics to portray these different animals' 476 00:29:26,140 --> 00:29:26,640 groups. 477 00:29:26,640 --> 00:29:33,180 And this is a typical cladogram of the vertebrates 478 00:29:33,180 --> 00:29:37,560 drawn by R. Glenn Northcutt. 479 00:29:37,560 --> 00:29:41,100 And Glenn Northcutt has done a lot of different work 480 00:29:41,100 --> 00:29:43,305 in comparative neuroanatomoy. 481 00:29:43,305 --> 00:29:45,870 He's a little bit different from Karten 482 00:29:45,870 --> 00:29:48,630 in that he's sort of a systematizer, 483 00:29:48,630 --> 00:29:52,714 whereas Karten is a guy who studies connections and is 484 00:29:52,714 --> 00:29:57,320 interested in what led to what in evolution. 485 00:29:57,320 --> 00:29:59,530 I'm a little more like Karten. 486 00:29:59,530 --> 00:30:03,510 Karten was also a student of Nauda. 487 00:30:03,510 --> 00:30:08,120 But Northcutt and his students have done a lot of contribution 488 00:30:08,120 --> 00:30:10,870 to cladistics. 489 00:30:10,870 --> 00:30:14,030 In fact, Northcutt was probably the first neuroanatomist 490 00:30:14,030 --> 00:30:18,650 to use this way of portraying comparing animals. 491 00:30:18,650 --> 00:30:26,920 What he's showing here is how certain animals branched off 492 00:30:26,920 --> 00:30:28,680 from the main vertebrate tree. 493 00:30:28,680 --> 00:30:34,770 This is a chordate line action-- like the sea lamprey. 494 00:30:34,770 --> 00:30:42,130 Amphibians-- well, then the fish, and very early, 495 00:30:42,130 --> 00:30:46,610 the Elasmobranches, the cartilaginous fish 496 00:30:46,610 --> 00:30:47,170 branched off. 497 00:30:47,170 --> 00:30:54,470 That includes the sharks, skates, and the rays-- 498 00:30:54,470 --> 00:30:56,970 and then of course, later the bony fish. 499 00:30:56,970 --> 00:30:58,530 So if you're at the end of an era, 500 00:30:58,530 --> 00:31:00,620 he shows a brain of a living animal here, 501 00:31:00,620 --> 00:31:06,620 sort of where that line of evolution has led to. 502 00:31:06,620 --> 00:31:08,600 And here the bony vertebrate-- these 503 00:31:08,600 --> 00:31:12,610 are all bony vertebrates-- amphibians branching off 504 00:31:12,610 --> 00:31:18,660 the earliest, and then the Sauropsids, reptiles and birds. 505 00:31:18,660 --> 00:31:21,260 But even before they branched off that line, 506 00:31:21,260 --> 00:31:24,840 we see the mammals. 507 00:31:24,840 --> 00:31:27,790 OK, here's an earlier view. 508 00:31:27,790 --> 00:31:33,920 This was Ludwig Edinger, 1908. 509 00:31:33,920 --> 00:31:36,160 And he had a view that can easily 510 00:31:36,160 --> 00:31:39,640 be fitted to the cladogram, cladistic approach. 511 00:31:39,640 --> 00:31:44,470 But he didn't use it. 512 00:31:44,470 --> 00:31:47,880 We didn't have as many sources of data about evolution then. 513 00:31:50,950 --> 00:31:53,420 So he basically talked about this part 514 00:31:53,420 --> 00:31:59,210 that he saw similar to the neocortex of humans, 515 00:31:59,210 --> 00:32:02,330 much smaller in small mammals like the rabbit. 516 00:32:05,640 --> 00:32:08,900 What he doesn't show here is something major. 517 00:32:08,900 --> 00:32:11,530 What is the major difference in that end-brain 518 00:32:11,530 --> 00:32:14,390 of cartilaginous fish and lizards 519 00:32:14,390 --> 00:32:17,074 when compared with rabbits and humans? 520 00:32:19,800 --> 00:32:22,280 The neocortex-- and that's something 521 00:32:22,280 --> 00:32:23,816 that Northcutt stresses. 522 00:32:27,360 --> 00:32:33,390 But what he shows here is the cerebral hemisphere, 523 00:32:33,390 --> 00:32:38,160 which again we know is different in mammals 524 00:32:38,160 --> 00:32:39,690 than in all these other animals. 525 00:32:39,690 --> 00:32:44,420 Because only the mammals have the neocortex. 526 00:32:44,420 --> 00:32:49,500 But if we take a cladogram here and look at the creatures that 527 00:32:49,500 --> 00:32:52,990 are still living today that branched off the earliest, 528 00:32:52,990 --> 00:33:01,420 we find these three-- amphyioxus, sea lamprey, 529 00:33:01,420 --> 00:33:03,120 and hagfishes. 530 00:33:03,120 --> 00:33:07,340 And we looked at these once before. 531 00:33:07,340 --> 00:33:10,910 And you'll just notice very tiny telan cephalon 532 00:33:10,910 --> 00:33:16,355 in these animals-- non-existent, really, in amphyioxus. 533 00:33:16,355 --> 00:33:18,230 They just have a diencephalon-like structure. 534 00:33:21,070 --> 00:33:24,730 Very tiny, smaller than the olfactory bulbs in the sea 535 00:33:24,730 --> 00:33:30,560 lamprey-- and still very small in the hagfish. 536 00:33:30,560 --> 00:33:33,470 Here's a hagfish. 537 00:33:36,330 --> 00:33:38,460 There's the telan cephalon. 538 00:33:38,460 --> 00:33:41,170 There's the olfactory bulb. 539 00:33:41,170 --> 00:33:44,300 The whole telan cephalon is not that much bigger 540 00:33:44,300 --> 00:33:45,870 than the olfactory bulb. 541 00:33:53,470 --> 00:33:58,210 Then I show you here some of the bony fish-- 542 00:33:58,210 --> 00:34:01,940 the mormyrus with the huge cerebellum, a trout 543 00:34:01,940 --> 00:34:07,860 with a huge midbrain-- predatory fish, very tiny telencephalon. 544 00:34:07,860 --> 00:34:09,550 Here's a [? vicar ?], which is only 545 00:34:09,550 --> 00:34:11,530 slightly larger telencephalon. 546 00:34:15,699 --> 00:34:19,920 And here's a question that you don't see very much, 547 00:34:19,920 --> 00:34:22,610 but Georg Striedter treats it, and so does 548 00:34:22,610 --> 00:34:24,409 [INAUDIBLE] in his book. 549 00:34:24,409 --> 00:34:27,780 They say in most chordate groups, brain size increases 550 00:34:27,780 --> 00:34:31,920 in evolution, but in a few groups it decreases. 551 00:34:31,920 --> 00:34:34,510 So why would it ever decrease? 552 00:34:34,510 --> 00:34:36,830 For it to decrease in evolution, that 553 00:34:36,830 --> 00:34:41,210 means there had to be adaptive reasons why 554 00:34:41,210 --> 00:34:43,179 it would decrease in size. 555 00:34:43,179 --> 00:34:45,709 Can you think of an adaptive reason 556 00:34:45,709 --> 00:34:51,711 why a brain structure would decrease in size? 557 00:34:51,711 --> 00:34:56,691 AUDIENCE: Well one idea is just to make your head lighter. 558 00:34:56,691 --> 00:34:58,683 And this is actually going way back, 559 00:34:58,683 --> 00:35:03,663 but when I think of dinosaurs, sauropods had very long necks 560 00:35:03,663 --> 00:35:06,651 and that's just hard to support a heavy head. 561 00:35:06,651 --> 00:35:09,650 So they had very small brains. 562 00:35:09,650 --> 00:35:12,760 PROFESSOR: So even the weight could be a disadvantage. 563 00:35:12,760 --> 00:35:15,420 I would say one thing is even more important. 564 00:35:15,420 --> 00:35:19,770 And that brain tissue-- very demanding in energy 565 00:35:19,770 --> 00:35:21,610 consumption. 566 00:35:21,610 --> 00:35:25,673 Like our brain is hardly 20% of our body weight, 567 00:35:25,673 --> 00:35:28,000 but it uses 20% of the energy. 568 00:35:32,640 --> 00:35:35,502 Some people get a fever if they think too hard. 569 00:35:35,502 --> 00:35:40,410 I'm sorry-- couldn't resist that. 570 00:35:40,410 --> 00:35:43,960 It actually uses a lot of energy. 571 00:35:43,960 --> 00:35:47,550 You can't go without eating too long if you're working hard 572 00:35:47,550 --> 00:35:48,520 on homework problems. 573 00:35:52,080 --> 00:35:56,240 So it can decrease because of energy demands. 574 00:35:56,240 --> 00:35:58,770 Why is that so critical? 575 00:35:58,770 --> 00:36:00,950 With high energy demands, you've got 576 00:36:00,950 --> 00:36:05,050 to spend more time getting food. 577 00:36:05,050 --> 00:36:09,580 And it takes a lot of energy, depending 578 00:36:09,580 --> 00:36:10,960 on what you're eating, of course. 579 00:36:10,960 --> 00:36:13,940 You might be eating a high-energy food, 580 00:36:13,940 --> 00:36:16,590 like eating other animals. 581 00:36:16,590 --> 00:36:20,120 But then it takes energy to digest. 582 00:36:20,120 --> 00:36:23,100 So that's another big energy consumer. 583 00:36:23,100 --> 00:36:25,860 Brain, gut. 584 00:36:25,860 --> 00:36:29,780 What did humans develop that made possible 585 00:36:29,780 --> 00:36:33,850 the much larger brain using a lot more energy? 586 00:36:33,850 --> 00:36:36,520 How did humans decrease the demand 587 00:36:36,520 --> 00:36:38,180 on their digestive system? 588 00:36:38,180 --> 00:36:39,100 AUDIENCE: Cooking. 589 00:36:39,100 --> 00:36:41,230 PROFESSOR: Cooking-- exactly. 590 00:36:41,230 --> 00:36:46,090 So you see after the indications of fire being developed 591 00:36:46,090 --> 00:36:50,791 by humans, the last big surge of growth of the end-brain. 592 00:36:50,791 --> 00:36:51,291 OK? 593 00:36:52,782 --> 00:36:55,764 AUDIENCE: How does cooking help? 594 00:36:55,764 --> 00:36:56,758 PROFESSOR: I can't-- 595 00:36:56,758 --> 00:36:58,249 AUDIENCE: How does cooking help? 596 00:36:58,249 --> 00:37:01,730 Because I thought it actually took some of the-- 597 00:37:01,730 --> 00:37:06,530 PROFESSOR: It requires a lot more energy to digest raw meat 598 00:37:06,530 --> 00:37:09,390 than it does cooked meat. 599 00:37:09,390 --> 00:37:13,284 The energy alters the proteins in ways 600 00:37:13,284 --> 00:37:14,450 that assist their digestion. 601 00:37:17,650 --> 00:37:20,450 This is dealt with in a little more detail in Allman, 602 00:37:20,450 --> 00:37:22,940 but you can find discussions of it too online. 603 00:37:29,420 --> 00:37:31,700 AUDIENCE: Can I ask something? 604 00:37:31,700 --> 00:37:37,080 Can we say that the size of a brain 605 00:37:37,080 --> 00:37:41,580 means that it's more smart, or something? 606 00:37:41,580 --> 00:37:44,680 PROFESSOR: OK, you have to add to that 607 00:37:44,680 --> 00:37:46,470 that if brain size is decreasing, 608 00:37:46,470 --> 00:37:49,610 they must decrease the size of something that's 609 00:37:49,610 --> 00:37:52,570 not critical to their survival. 610 00:37:52,570 --> 00:37:53,750 You're quite right. 611 00:37:53,750 --> 00:37:56,840 We've talked about how the size of a structure 612 00:37:56,840 --> 00:37:59,790 increases if there's a lot of neural processing going on. 613 00:37:59,790 --> 00:38:03,900 He needs it for his hunting behavior or other things 614 00:38:03,900 --> 00:38:05,372 he's doing. 615 00:38:05,372 --> 00:38:08,430 You're right. 616 00:38:08,430 --> 00:38:12,740 Let's look at which animals-- these were brain versus body 617 00:38:12,740 --> 00:38:15,190 weights of the major animal groups, 618 00:38:15,190 --> 00:38:18,530 just to remind you where humans are. 619 00:38:18,530 --> 00:38:21,170 Remember it's relative size that increases-- 620 00:38:21,170 --> 00:38:22,830 this is whale up here. 621 00:38:22,830 --> 00:38:23,690 This is elephant. 622 00:38:23,690 --> 00:38:25,910 They have the largest brains. 623 00:38:25,910 --> 00:38:27,670 Humans are here-- smaller brains, 624 00:38:27,670 --> 00:38:31,480 but in relative to their body weight, it's the largest. 625 00:38:31,480 --> 00:38:35,150 And this is on a cladogram. 626 00:38:35,150 --> 00:38:39,540 Striedter drew this after figuring out 627 00:38:39,540 --> 00:38:42,670 where the increases in relative brain size occur, 628 00:38:42,670 --> 00:38:44,940 where the decreases occur. 629 00:38:44,940 --> 00:38:47,790 There's not decreases very many places. 630 00:38:47,790 --> 00:38:50,565 But you see here when salamanders evolved, 631 00:38:50,565 --> 00:38:55,200 there were decreases in relative size. 632 00:38:55,200 --> 00:38:56,805 The eels-- similar. 633 00:38:56,805 --> 00:38:58,820 There were decreases in size. 634 00:39:01,610 --> 00:39:03,970 All these others-- the red dots are 635 00:39:03,970 --> 00:39:07,625 for when there were marked increases in size. 636 00:39:14,730 --> 00:39:18,260 And remember, we talked about the very early forebrain 637 00:39:18,260 --> 00:39:21,760 and evidence that is dominated by olfaction. 638 00:39:21,760 --> 00:39:24,270 I emphasized that early in the book. 639 00:39:24,270 --> 00:39:27,970 And I talked about how olfaction dominated 640 00:39:27,970 --> 00:39:29,040 the primitive endbrain. 641 00:39:29,040 --> 00:39:31,300 We didn't have really good information on that 642 00:39:31,300 --> 00:39:35,970 until people fairly recently studied the olfactory bulb 643 00:39:35,970 --> 00:39:44,130 projections in those two animals that 644 00:39:44,130 --> 00:39:48,850 are members of the non-bony vertebrates. 645 00:39:48,850 --> 00:39:52,420 And that was the hagfishes and the sea lampreys. 646 00:39:52,420 --> 00:39:54,757 Probably the lamprey study is the most interesting 647 00:39:54,757 --> 00:39:56,340 because the lampreys are a little less 648 00:39:56,340 --> 00:39:59,000 specialized than the hagfish. 649 00:39:59,000 --> 00:40:03,970 This is a hagfish-- the Pacific hagfish. 650 00:40:03,970 --> 00:40:09,450 They injected tracers into the olfactory bulb here. 651 00:40:09,450 --> 00:40:13,160 This is BO-- bulbus olfactorious, sorry. 652 00:40:13,160 --> 00:40:18,850 A lot of times they like to use the Latin or Greek names, 653 00:40:18,850 --> 00:40:21,650 so they use it here for telencephelon, 654 00:40:21,650 --> 00:40:23,460 then diencephalon. 655 00:40:23,460 --> 00:40:25,365 And what is TM? 656 00:40:25,365 --> 00:40:27,780 Tectum mesencephali. 657 00:40:27,780 --> 00:40:31,870 So midbrain tectum-- and this is just 658 00:40:31,870 --> 00:40:35,482 a summary of olfactory bulb projections in the hagfish 659 00:40:35,482 --> 00:40:40,020 and lamprey when compared to amphibians, 660 00:40:40,020 --> 00:40:45,880 also the most primitive group of tetrapods. 661 00:40:45,880 --> 00:40:48,880 Notice that in the hagfish and also in the lamprey, 662 00:40:48,880 --> 00:40:52,540 the olfactory bulb projects to every end-brain structure 663 00:40:52,540 --> 00:40:56,980 that's there and some of the tween-brain structures. 664 00:40:56,980 --> 00:40:59,400 This is a projection to the tween brain. 665 00:40:59,400 --> 00:41:01,380 And some of these structures are tween brain. 666 00:41:01,380 --> 00:41:04,140 This is actually striatum here. 667 00:41:04,140 --> 00:41:07,370 In the lamprey, it goes into the striatum. 668 00:41:07,370 --> 00:41:10,610 It goes into the medial pallium here. 669 00:41:10,610 --> 00:41:11,910 This is a layered structure. 670 00:41:11,910 --> 00:41:15,990 It's going into one layer and other tween 671 00:41:15,990 --> 00:41:18,820 structures and diencephalic structures. 672 00:41:21,780 --> 00:41:24,430 But when you get to amphibians, you 673 00:41:24,430 --> 00:41:28,160 see it's going to the medial pallium, but only 674 00:41:28,160 --> 00:41:31,840 one edge of it. 675 00:41:31,840 --> 00:41:34,370 It's going into the dorsal pallium, which 676 00:41:34,370 --> 00:41:37,685 is like a parahippocampal area in those animals. 677 00:41:37,685 --> 00:41:41,502 And we know it projects into the medial pallium. 678 00:41:41,502 --> 00:41:46,840 It gets direct olfactory input, but only at one edge. 679 00:41:46,840 --> 00:41:48,770 And it goes into the striatum, but not 680 00:41:48,770 --> 00:41:51,860 throughout the entire striatum. 681 00:41:51,860 --> 00:41:55,517 Big areas then that don't get olfactory bulb projections 682 00:41:55,517 --> 00:41:57,350 the way they do in the lamphrey and hagfish. 683 00:42:01,020 --> 00:42:02,580 And it's already 4:00. 684 00:42:02,580 --> 00:42:04,110 I think I'd better stop here. 685 00:42:07,430 --> 00:42:09,240 I think we will finish this, and be 686 00:42:09,240 --> 00:42:12,940 able to start talking about the hypothalamus next time.