1 00:00:00,040 --> 00:00:02,050 NARRATOR: The following content is provided under a 2 00:00:02,050 --> 00:00:03,870 Creative Commons license. 3 00:00:03,870 --> 00:00:06,910 Your support will help MIT OpenCourseWare continue to 4 00:00:06,910 --> 00:00:10,560 offer high quality educational resources for free. 5 00:00:10,560 --> 00:00:13,460 To make a donation or view additional materials from 6 00:00:13,460 --> 00:00:19,290 hundreds of MIT courses, visit MIT OpenCourseWare at 7 00:00:19,290 --> 00:00:20,540 ocw.mit.edu. 8 00:00:28,299 --> 00:00:32,280 PROFESSOR JOHN GABRIELI: Last time we discussed how people 9 00:00:32,280 --> 00:00:34,720 can approach psychological issues in terms of 10 00:00:34,720 --> 00:00:38,650 experiments, and at least correlations in some cases or 11 00:00:38,650 --> 00:00:40,600 causal studies through experiments. 12 00:00:40,600 --> 00:00:43,400 And we discovered that if you think 13 00:00:43,400 --> 00:00:46,640 about money, what happens? 14 00:00:46,640 --> 00:00:51,463 On average, you become more self-reliant or less willing 15 00:00:51,463 --> 00:00:52,760 to help, right? 16 00:00:52,760 --> 00:00:55,810 We discovered that if you just change the way that men and 17 00:00:55,810 --> 00:01:00,440 women approach each other at a dating event, you change their 18 00:01:00,440 --> 00:01:03,670 internal feelings and their external behaviors simply by 19 00:01:03,670 --> 00:01:06,660 who's approaching whom. 20 00:01:06,660 --> 00:01:09,330 So we learned all kinds of things that you might or might 21 00:01:09,330 --> 00:01:12,304 not have known unless you did the experiments. 22 00:01:12,304 --> 00:01:15,502 And for all these things that are our mental life-- our 23 00:01:15,502 --> 00:01:16,896 thoughts, our feelings, they are all 24 00:01:16,896 --> 00:01:18,920 supported by our brains. 25 00:01:18,920 --> 00:01:21,054 And so for me personally as a neuroscientist, I've always 26 00:01:21,054 --> 00:01:24,006 thought that the brain is one of the three amazing things 27 00:01:24,006 --> 00:01:25,482 out there in the natural world. 28 00:01:25,482 --> 00:01:29,750 With the origins of the universe, the origin of life. 29 00:01:29,750 --> 00:01:32,704 And the brain that allow us to think and feel, to see, that 30 00:01:32,704 --> 00:01:39,190 remember, really everything that we do comes from that. 31 00:01:39,190 --> 00:01:39,860 OK. 32 00:01:39,860 --> 00:01:42,540 So here's this device. 33 00:01:42,540 --> 00:01:44,970 And I want to share with you just this phrase that people 34 00:01:44,970 --> 00:01:48,420 sometimes use, which is that your mind is 35 00:01:48,420 --> 00:01:49,890 what your brain does. 36 00:01:49,890 --> 00:01:54,140 That your mind is what your brain does And so the readings 37 00:01:54,140 --> 00:01:59,500 from Oliver Sacks for today kind of remind you of that. 38 00:01:59,500 --> 00:02:04,910 So there are two women who have 39 00:02:04,910 --> 00:02:06,820 seizures of various kinds. 40 00:02:06,820 --> 00:02:07,970 And what happens in them? 41 00:02:07,970 --> 00:02:10,160 So one is Mrs. OC, 88-year-old woman. 42 00:02:10,160 --> 00:02:13,190 And what starts to happen to her? 43 00:02:13,190 --> 00:02:15,940 She starts to hear songs. 44 00:02:15,940 --> 00:02:19,910 And so powerfully, not just when you have a little song in 45 00:02:19,910 --> 00:02:23,140 your head, that it's hard for her to hear conversations. 46 00:02:23,140 --> 00:02:25,652 For her, a conversation like we're having now, it's as if 47 00:02:25,652 --> 00:02:28,090 the music stayed on really loud. 48 00:02:28,090 --> 00:02:30,220 Turns out she's having temporal lobe seizures. 49 00:02:30,220 --> 00:02:32,420 The temporal lobes are the parts of the brain that are 50 00:02:32,420 --> 00:02:35,340 terribly important for hearing. 51 00:02:35,340 --> 00:02:37,970 So music is something that we hear. 52 00:02:37,970 --> 00:02:40,390 And then she has a right temporal lobe infarction. 53 00:02:40,390 --> 00:02:43,350 She's had an injury in the right temporal lobe. 54 00:02:43,350 --> 00:02:47,250 Music, for most of us, is more dependent on right hemisphere 55 00:02:47,250 --> 00:02:48,230 processes than the left. 56 00:02:48,230 --> 00:02:50,800 So that makes it unusual. 57 00:02:50,800 --> 00:02:55,280 And how does she feel about the whole process? 58 00:02:55,280 --> 00:02:57,980 So what's generating the songs, though? 59 00:02:57,980 --> 00:03:02,890 What's generating the songs that she hears? 60 00:03:02,890 --> 00:03:04,630 Yeah, her memory. 61 00:03:04,630 --> 00:03:05,910 Her brain, right? 62 00:03:05,910 --> 00:03:07,300 Because in epilepsy, what's happening? 63 00:03:07,300 --> 00:03:08,930 Neurons are firing. 64 00:03:08,930 --> 00:03:11,970 When neurons fire in organized patterns, those are memories, 65 00:03:11,970 --> 00:03:14,560 desires, physical actions, thoughts. 66 00:03:14,560 --> 00:03:17,760 When they're firing for no good reason like an epilepsy 67 00:03:17,760 --> 00:03:20,110 because of some brain difficulty, 68 00:03:20,110 --> 00:03:21,090 they just start firing. 69 00:03:21,090 --> 00:03:24,710 But the neurons that happen to be firing will drive certain 70 00:03:24,710 --> 00:03:26,620 mental processes that they normally support. 71 00:03:26,620 --> 00:03:29,710 In this case, the neurons that are firing away are ones that 72 00:03:29,710 --> 00:03:32,560 are involved in memory or songs and 73 00:03:32,560 --> 00:03:34,280 perception for songs. 74 00:03:34,280 --> 00:03:37,810 And when they fire, it's as if you heard the song itself. 75 00:03:37,810 --> 00:03:41,350 Because when you hear my voice or when you hear a song, 76 00:03:41,350 --> 00:03:43,600 you're never hearing the song. 77 00:03:43,600 --> 00:03:46,730 You're always hearing what your neurons are interpreting 78 00:03:46,730 --> 00:03:48,520 the sound that comes to your ear. 79 00:03:48,520 --> 00:03:50,980 Your mind is what your brain does in that sense, and in a 80 00:03:50,980 --> 00:03:52,670 very central way. 81 00:03:52,670 --> 00:03:54,680 If you had an injury in that part of the brain, you can be 82 00:03:54,680 --> 00:03:57,460 cortically deaf and never hear a sound, even though all the 83 00:03:57,460 --> 00:03:59,260 information came through your ear. 84 00:03:59,260 --> 00:04:02,390 So without your brain interpreting the environment, 85 00:04:02,390 --> 00:04:03,340 you wouldn't know what it is. 86 00:04:03,340 --> 00:04:06,820 But if your brain starts to fire on its own, that's just 87 00:04:06,820 --> 00:04:09,870 as good a signal as if you heard a song itself. 88 00:04:09,870 --> 00:04:12,550 Because that is the stuff of hearing songs. 89 00:04:12,550 --> 00:04:14,080 So she enjoyed it, actually. 90 00:04:14,080 --> 00:04:17,000 She declined taking anti-convulsive medications. 91 00:04:17,000 --> 00:04:20,459 Because she felt it was a portal to her past, right? 92 00:04:20,459 --> 00:04:22,820 The songs that she heard were ones that reminded her of her 93 00:04:22,820 --> 00:04:24,590 life and were kind of pleasant to hear. 94 00:04:24,590 --> 00:04:28,490 It was like being on a nonstop highlight film of for life, or 95 00:04:28,490 --> 00:04:31,280 a highlight MP3. 96 00:04:31,280 --> 00:04:34,900 So now an opposite response to a similar phenomenon comes 97 00:04:34,900 --> 00:04:36,270 from a Mrs. OM in her 80s. 98 00:04:36,270 --> 00:04:38,620 She hears songs, but she also hears a lot 99 00:04:38,620 --> 00:04:40,030 of ringing and hissing. 100 00:04:40,030 --> 00:04:42,330 It's not limited to the song itself. 101 00:04:42,330 --> 00:04:45,720 She doesn't mention any of this for how long? 102 00:04:45,720 --> 00:04:47,240 Four years. 103 00:04:47,240 --> 00:04:51,380 She's hearing ringing, hissing, songs. 104 00:04:51,380 --> 00:04:54,350 She knows because her mind is fine that they're coming from 105 00:04:54,350 --> 00:04:56,150 nowhere but inside her head. 106 00:04:56,150 --> 00:04:57,330 But she doesn't tell anybody. 107 00:04:57,330 --> 00:04:59,390 That's a huge burden, right? 108 00:04:59,390 --> 00:05:02,614 And why doesn't she tell them? 109 00:05:02,614 --> 00:05:03,600 Yeah, yeah. 110 00:05:03,600 --> 00:05:05,850 And especially if you're in your 80s, and you're going 111 00:05:05,850 --> 00:05:08,220 around saying, I'm hearing things, people go, OK. 112 00:05:08,220 --> 00:05:10,090 Were putting you in the old age home, right? 113 00:05:10,090 --> 00:05:12,430 You're out of it. 114 00:05:12,430 --> 00:05:15,860 So she doesn't want to give up her freedom. 115 00:05:15,860 --> 00:05:20,780 And she gets a short playlist, just three songs, and hears 116 00:05:20,780 --> 00:05:22,620 them over and over and over again. 117 00:05:22,620 --> 00:05:25,050 You may have had the experience that some songs you 118 00:05:25,050 --> 00:05:25,500 hear for a while. 119 00:05:25,500 --> 00:05:27,670 You like them more, and then you get tired of them. 120 00:05:27,670 --> 00:05:30,730 If you had only three all the time, every day, and a bad 121 00:05:30,730 --> 00:05:32,760 version that was hissing and ringing, you would get pretty 122 00:05:32,760 --> 00:05:35,440 tired of the songs too. 123 00:05:35,440 --> 00:05:38,640 That stops by anti-convulsive medications and medications 124 00:05:38,640 --> 00:05:41,640 that stops the seizures, stop the songs. 125 00:05:41,640 --> 00:05:45,420 And so it's sort of a beautiful story, when two 126 00:05:45,420 --> 00:05:49,090 opposite emotional responses for how your mind is what your 127 00:05:49,090 --> 00:05:50,470 brain does. 128 00:05:50,470 --> 00:05:53,700 Now from this, the fact that songs are played back as if 129 00:05:53,700 --> 00:05:57,270 you had pulled out songs from your computer or shelf 130 00:05:57,270 --> 00:05:59,860 somewhere, you might think that the brain retains these 131 00:05:59,860 --> 00:06:02,410 records perfectly throughout life and epilepsy 132 00:06:02,410 --> 00:06:03,160 would just sort them. 133 00:06:03,160 --> 00:06:05,430 But we'll come back to that later on, and say that in very 134 00:06:05,430 --> 00:06:07,360 much, we don't think memory is that way. 135 00:06:07,360 --> 00:06:10,390 But we do remember songs that are important for us. 136 00:06:10,390 --> 00:06:12,780 And if our brain just starts firing in the same place where 137 00:06:12,780 --> 00:06:17,720 we store those songs, we hear them just as real as your 138 00:06:17,720 --> 00:06:20,970 cortex hears it when it hears the actual song itself. 139 00:06:20,970 --> 00:06:23,000 Because that's the place where you hear it. 140 00:06:23,000 --> 00:06:25,950 So this is the kind of evidence that at least in some 141 00:06:25,950 --> 00:06:27,940 sense, your mind is what your brain does. 142 00:06:27,940 --> 00:06:29,340 And so here's this amazing brain. 143 00:06:29,340 --> 00:06:32,320 It's about two to three pounds. 144 00:06:32,320 --> 00:06:34,300 But every thought and feeling you'll ever have, or every 145 00:06:34,300 --> 00:06:37,130 physical movement, every desire, every thing that 146 00:06:37,130 --> 00:06:39,710 you're proud of or ashamed of that crosses your mind will be 147 00:06:39,710 --> 00:06:43,020 supported by this structure. 148 00:06:43,020 --> 00:06:45,350 So I'm going to talk a little bit about the neurons, just a 149 00:06:45,350 --> 00:06:47,700 little bit about the neurons that compose the brain, and a 150 00:06:47,700 --> 00:06:51,050 little bit about a quick tour through the gross organization 151 00:06:51,050 --> 00:06:51,470 of the brain. 152 00:06:51,470 --> 00:06:54,020 We'll come back to many of these structures as they're 153 00:06:54,020 --> 00:06:56,430 relevant to different things like memory or emotion or 154 00:06:56,430 --> 00:06:58,390 personality later in the course. 155 00:06:58,390 --> 00:07:00,760 Talk a little bit about the enterprise of trying to say 156 00:07:00,760 --> 00:07:03,660 which parts of our brain support which 157 00:07:03,660 --> 00:07:05,910 parts of our mind. 158 00:07:05,910 --> 00:07:09,540 Missteps about that, famous cases about that, that have 159 00:07:09,540 --> 00:07:13,010 turned out to have roughly the right message. 160 00:07:13,010 --> 00:07:15,380 And we'll focus on hemispheric specialization, the thing in 161 00:07:15,380 --> 00:07:17,840 humans where our left hemisphere and our right 162 00:07:17,840 --> 00:07:22,340 hemisphere are organized to accomplish different things, 163 00:07:22,340 --> 00:07:24,380 to support different mental functions. 164 00:07:24,380 --> 00:07:27,510 And the surprise from split brain or commissurotomy 165 00:07:27,510 --> 00:07:31,790 patients, that these different mental lives that support our 166 00:07:31,790 --> 00:07:32,930 different parts of the brain, that 167 00:07:32,930 --> 00:07:34,290 they can live in isolation. 168 00:07:34,290 --> 00:07:36,880 They don't even know they're there one to the other. 169 00:07:36,880 --> 00:07:38,380 So let me rephrase this. 170 00:07:38,380 --> 00:07:44,500 As you sit there, the thought is you might have independent 171 00:07:44,500 --> 00:07:46,870 parts of your mind supported by independent 172 00:07:46,870 --> 00:07:48,420 part of your brain. 173 00:07:48,420 --> 00:07:51,870 And at any one moment, your consciousness might be in one 174 00:07:51,870 --> 00:07:54,550 part, and then it might move to another. 175 00:07:54,550 --> 00:07:56,810 And just like there's all these people in this room, 176 00:07:56,810 --> 00:07:59,410 your brain might be all these things having their own 177 00:07:59,410 --> 00:08:02,100 independent thinking lives. 178 00:08:02,100 --> 00:08:03,560 They have to interact a lot. 179 00:08:03,560 --> 00:08:06,490 But how much might there be independent modules in your 180 00:08:06,490 --> 00:08:09,010 brain that are doing their own thing. 181 00:08:09,010 --> 00:08:11,940 And now you're thinking about music, and those turn on, and 182 00:08:11,940 --> 00:08:13,440 that's where your consciousness is. 183 00:08:13,440 --> 00:08:14,830 Now you're thinking about history. 184 00:08:14,830 --> 00:08:17,070 Now you're thinking about dinner tonight. 185 00:08:17,070 --> 00:08:19,190 And different parts of your brain turn on and that's when 186 00:08:19,190 --> 00:08:21,540 your consciousness is moving from one part of your 187 00:08:21,540 --> 00:08:22,580 brain to the other. 188 00:08:22,580 --> 00:08:25,150 But the other parts keep going. 189 00:08:25,150 --> 00:08:28,630 So we'll see how plausible is that. 190 00:08:28,630 --> 00:08:31,180 So it took a long time for people to decide that the 191 00:08:31,180 --> 00:08:34,510 brain actually is the stuff of the mind. 192 00:08:34,510 --> 00:08:40,220 Smart philosophers like Plato said, well, it's part of the 193 00:08:40,220 --> 00:08:41,860 body that's closest to the heavens. 194 00:08:41,860 --> 00:08:44,300 That's where the gods might reside, so that's a good place 195 00:08:44,300 --> 00:08:46,210 to have your mind and that's where your brain is. 196 00:08:46,210 --> 00:08:50,310 A sort of GPS approach to locating where 197 00:08:50,310 --> 00:08:51,540 the mind might be. 198 00:08:51,540 --> 00:08:53,040 Aristotle said, wait a minute. 199 00:08:53,040 --> 00:08:55,090 It's the warm and active heart-- the heart was very 200 00:08:55,090 --> 00:08:57,280 impressive in post-mortem examination of people who have 201 00:08:57,280 --> 00:08:58,210 passed away-- 202 00:08:58,210 --> 00:09:00,040 that houses the mind. 203 00:09:00,040 --> 00:09:02,520 And that it cools, and there's an inner brain. 204 00:09:02,520 --> 00:09:04,860 So the brain was kind of a radiator that would sort of 205 00:09:04,860 --> 00:09:07,630 cool stuff off to keep the heart in optimal. 206 00:09:07,630 --> 00:09:09,110 And even now, we talk about people having 207 00:09:09,110 --> 00:09:10,580 a big heart, right? 208 00:09:10,580 --> 00:09:12,250 A cold heart, a warm heart. 209 00:09:12,250 --> 00:09:15,950 We still talk about human personality or character in 210 00:09:15,950 --> 00:09:17,700 terms of heart. 211 00:09:17,700 --> 00:09:20,230 Galen said that the brain was surrounded-- there's 212 00:09:20,230 --> 00:09:22,070 ventricles in the middle of the brain that have fluid, 213 00:09:22,070 --> 00:09:23,400 cerebral spinal fluid. 214 00:09:23,400 --> 00:09:27,000 And he hypothesized that the brain was the packing material 215 00:09:27,000 --> 00:09:28,580 that protects that fluid. 216 00:09:28,580 --> 00:09:30,560 Hang on to that fluid, that's all your stuff. 217 00:09:30,560 --> 00:09:32,410 We're going to cram a lot of stuff around it, right? 218 00:09:32,410 --> 00:09:34,890 Like the bubble pack that comes in the boxes. 219 00:09:34,890 --> 00:09:36,720 And of course now we know it's the opposite way around. 220 00:09:36,720 --> 00:09:39,370 The mind is in the physical, the dense part of 221 00:09:39,370 --> 00:09:40,420 the brain, not that. 222 00:09:40,420 --> 00:09:43,270 And then ideas from Descartes, the pineal body is one of the 223 00:09:43,270 --> 00:09:46,660 very few structures that's in the midline of the brain, that 224 00:09:46,660 --> 00:09:49,210 doesn't have a thing on the left and a thing on the right. 225 00:09:49,210 --> 00:09:52,560 And so he thought maybe that's where things get unified in 226 00:09:52,560 --> 00:09:53,180 the whole brain. 227 00:09:53,180 --> 00:09:55,290 It all comes together as the place that 228 00:09:55,290 --> 00:09:56,390 runs the whole brain. 229 00:09:56,390 --> 00:09:57,290 And that's a wrong idea. 230 00:09:57,290 --> 00:10:00,530 But people were trying to figure out what was going on. 231 00:10:00,530 --> 00:10:03,670 In modern neuroscience, there's many levels of 232 00:10:03,670 --> 00:10:05,300 analysis of the brain. 233 00:10:05,300 --> 00:10:08,480 So if you go to any neuroscience program, like 234 00:10:08,480 --> 00:10:09,880 Department of Brain and Cognitive Science, you will 235 00:10:09,880 --> 00:10:12,440 actually see scientists who study things like molecules 236 00:10:12,440 --> 00:10:15,830 and synapses, molecular neurobiology, how neurons 237 00:10:15,830 --> 00:10:18,870 work, how neurons form networks, little organizations 238 00:10:18,870 --> 00:10:22,270 of things that solve problems at a higher level, maps, 239 00:10:22,270 --> 00:10:24,330 systems in the brain as a whole. 240 00:10:24,330 --> 00:10:27,060 In this course, we mostly have to operate at this level. 241 00:10:27,060 --> 00:10:29,590 That's the place where it's easy for us to relate in some 242 00:10:29,590 --> 00:10:32,700 ways parts of the mind as we understand it, of human nature 243 00:10:32,700 --> 00:10:34,720 as we understand it, and physical parts of the brain. 244 00:10:34,720 --> 00:10:36,400 It's very hard for us to get that to 245 00:10:36,400 --> 00:10:37,920 molecules at the moment. 246 00:10:37,920 --> 00:10:40,910 But lots of neuroscience is working to connect these 247 00:10:40,910 --> 00:10:41,940 things at different levels. 248 00:10:41,940 --> 00:10:44,970 And I can't resist talking for one second, too, about the 249 00:10:44,970 --> 00:10:46,730 fact that we know our brains were not 250 00:10:46,730 --> 00:10:48,760 designed from scratch. 251 00:10:48,760 --> 00:10:52,680 You are not humans 3.0 or 98.0, right? 252 00:10:52,680 --> 00:10:56,180 Everything in us in some way evolved from other species 253 00:10:56,180 --> 00:10:58,270 that were similar to us, and far enough back, 254 00:10:58,270 --> 00:10:59,440 dissimilar to us. 255 00:10:59,440 --> 00:11:02,450 So there's lots of speculation about how it is that we 256 00:11:02,450 --> 00:11:05,360 balance parts of the brain that are ancient in their 257 00:11:05,360 --> 00:11:07,540 evolutionary roots, that are more recent in their 258 00:11:07,540 --> 00:11:09,830 evolutionary basis, and what that means about us. 259 00:11:09,830 --> 00:11:13,520 Another sense in which we're comprised of multiple society 260 00:11:13,520 --> 00:11:16,940 of brain systems in between our ears. 261 00:11:16,940 --> 00:11:21,110 So we know the cells in the brain are glia support cells 262 00:11:21,110 --> 00:11:22,760 and neurons, that a neuron-- 263 00:11:22,760 --> 00:11:23,900 and I know you all know all this. 264 00:11:23,900 --> 00:11:25,990 Oh, let me say a word about notes. 265 00:11:25,990 --> 00:11:30,610 So we sent PDFs of the lecture notes from the first two 266 00:11:30,610 --> 00:11:32,370 lectures and the third one just recently. 267 00:11:32,370 --> 00:11:35,930 Starting tomorrow, we'll send you the PDF of each lecture, 268 00:11:35,930 --> 00:11:37,890 the latest by the night before the lecture. 269 00:11:37,890 --> 00:11:40,820 So you will be able to print it out or look 270 00:11:40,820 --> 00:11:42,230 at it on the computer. 271 00:11:42,230 --> 00:11:44,990 But neurons have a soma or cell body. 272 00:11:44,990 --> 00:11:47,930 Those make up the grey matter when we look at the brain. 273 00:11:47,930 --> 00:11:50,570 They have an axon that can be covered with myelin that makes 274 00:11:50,570 --> 00:11:52,330 the white matter. 275 00:11:52,330 --> 00:11:55,540 The dendrite is the extensions of the neurons that have the 276 00:11:55,540 --> 00:11:57,700 input to the neuron. 277 00:11:57,700 --> 00:11:59,300 We know that neurons communicate by 278 00:11:59,300 --> 00:12:03,660 neurotransmitters across synapses, junctions between 279 00:12:03,660 --> 00:12:06,140 different parts of neurons. 280 00:12:06,140 --> 00:12:07,610 When you have a collection of cell bodies, 281 00:12:07,610 --> 00:12:09,110 people call it a nucleus. 282 00:12:09,110 --> 00:12:11,490 When you have a collection of axons, they call it a tract. 283 00:12:11,490 --> 00:12:12,860 It's just vocabulary and stuff. 284 00:12:12,860 --> 00:12:15,360 And you know this from other courses, just reminding you 285 00:12:15,360 --> 00:12:16,190 about them. 286 00:12:16,190 --> 00:12:18,650 And then you get these unbelievably startling kinds 287 00:12:18,650 --> 00:12:21,090 of numbers, which are always huge estimates. 288 00:12:21,090 --> 00:12:25,180 But they show you how amazing your brain is, and how hard it 289 00:12:25,180 --> 00:12:30,560 is for us to deeply understand how the brain works. 290 00:12:30,560 --> 00:12:33,150 I mean, we understand incredibly more than we did 10 291 00:12:33,150 --> 00:12:35,440 years ago, 20 years ago, 30 years ago. 292 00:12:35,440 --> 00:12:37,950 We're incredibly far from understanding how your brain 293 00:12:37,950 --> 00:12:40,950 accomplishes the amazing things it accomplishes. 294 00:12:40,950 --> 00:12:43,360 So it has about 100 billion neurons. 295 00:12:43,360 --> 00:12:46,810 It has about 100 trillion synapses, connections among 296 00:12:46,810 --> 00:12:48,500 neurons and dendrites. 297 00:12:48,500 --> 00:12:52,410 If you were to lay out the very thin myelinated axons in 298 00:12:52,410 --> 00:12:55,870 your brain, just the big axons that get myelin, it's 299 00:12:55,870 --> 00:13:00,090 estimated that you'd have 62,000 miles of axons. 300 00:13:00,090 --> 00:13:01,020 That's pretty good, right? 301 00:13:01,020 --> 00:13:04,270 Now you really want to wear helmets when you go 302 00:13:04,270 --> 00:13:05,740 skateboarding or anything, right? 303 00:13:05,740 --> 00:13:09,370 And about 100,000 miles of dendrites in each of you. 304 00:13:09,370 --> 00:13:11,650 So this is why the brain is amazing and hard. 305 00:13:11,650 --> 00:13:15,080 It's fantastic in its complexity. 306 00:13:15,080 --> 00:13:19,200 An average neuron may have up to 15,000 connections, 1,000 307 00:13:19,200 --> 00:13:24,430 synapses, and up to 1,000 neurons. 308 00:13:24,430 --> 00:13:25,680 There's different ways of thinking about the 309 00:13:25,680 --> 00:13:27,160 computational power of a neuron. 310 00:13:27,160 --> 00:13:30,780 But they estimate that these might have, each one the 311 00:13:30,780 --> 00:13:33,200 computational power of something like a 312 00:13:33,200 --> 00:13:34,310 medium-sized computer. 313 00:13:34,310 --> 00:13:38,460 So it's not the best computer, but you've got 314 00:13:38,460 --> 00:13:40,760 100 billion of them. 315 00:13:40,760 --> 00:13:42,780 Now, that's the easy part. 316 00:13:42,780 --> 00:13:45,190 Take 100 billion neurons and your computer's in your head. 317 00:13:45,190 --> 00:13:47,040 The hard part is to get them all working together 318 00:13:47,040 --> 00:13:47,660 efficiently. 319 00:13:47,660 --> 00:13:51,030 And you're not sitting around going, "Computer 33, get up to 320 00:13:51,030 --> 00:13:52,720 speed here. 321 00:13:52,720 --> 00:13:54,620 Something's wrong here." You don't even think about them. 322 00:13:54,620 --> 00:13:56,110 You just go about your business. 323 00:13:56,110 --> 00:13:58,400 The time for information to go from neuron to neuron is 324 00:13:58,400 --> 00:14:01,250 pretty slow compared to fast computers, pretty fast for 325 00:14:01,250 --> 00:14:02,800 biology, 10 milliseconds. 326 00:14:02,800 --> 00:14:05,100 And everybody thinks the secret of the brain, whatever 327 00:14:05,100 --> 00:14:07,960 it will turn out to be in many ways, is that you can run a 328 00:14:07,960 --> 00:14:11,330 fantastic number of computations simultaneously 329 00:14:11,330 --> 00:14:12,930 and collaboratively. 330 00:14:12,930 --> 00:14:14,640 But we don't have a deep understanding of how 331 00:14:14,640 --> 00:14:15,715 that all plays out. 332 00:14:15,715 --> 00:14:20,000 So here's a cartoon of this amazing axon, the cell body, 333 00:14:20,000 --> 00:14:21,600 and the dendrites to get inputs to it. 334 00:14:21,600 --> 00:14:24,865 The axon is the output signal of a typical neuron. 335 00:14:24,865 --> 00:14:27,770 Neurons can have these beautiful arborizations, 336 00:14:27,770 --> 00:14:30,500 tree-like properties of dendrites. 337 00:14:30,500 --> 00:14:32,850 Neurons have all kinds of different shapes in different 338 00:14:32,850 --> 00:14:35,070 parts of the brain, presumably reflecting their different 339 00:14:35,070 --> 00:14:38,416 missions, what they have to accomplish. 340 00:14:38,416 --> 00:14:42,400 An incredibly complicated cellular factory inside all of 341 00:14:42,400 --> 00:14:44,980 them is producing different things. 342 00:14:44,980 --> 00:14:46,600 This is a big overview. 343 00:14:46,600 --> 00:14:48,850 This is not for you to learn a specific fact. 344 00:14:48,850 --> 00:14:51,000 And this, here's an actual neuron that's injected in the 345 00:14:51,000 --> 00:14:54,780 fantastic tree of connections it makes within the neurons to 346 00:14:54,780 --> 00:14:56,930 accomplish its mission. 347 00:14:56,930 --> 00:14:59,670 Here's a cartoon of a synapse, places where neurotransmitters 348 00:14:59,670 --> 00:15:03,750 signal from one axon to one dendrite, for example. 349 00:15:03,750 --> 00:15:05,370 Here's an actual picture. 350 00:15:05,370 --> 00:15:09,010 Here's the package of vesicles that house the 351 00:15:09,010 --> 00:15:11,230 neurotransmitters in them, making a connection or a 352 00:15:11,230 --> 00:15:13,390 synapse onto a dendrite. 353 00:15:13,390 --> 00:15:15,420 And you just have a fantastic number of these. 354 00:15:15,420 --> 00:15:18,140 And as you're sitting in you right now an unbelievable 355 00:15:18,140 --> 00:15:21,090 amount of stuff is going on-- releasing them, cleaning them 356 00:15:21,090 --> 00:15:23,720 away so they don't hang around too long, building new ones to 357 00:15:23,720 --> 00:15:24,640 get ready to go. 358 00:15:24,640 --> 00:15:28,780 It's just an unbelievable story per neuron, never mind 359 00:15:28,780 --> 00:15:30,050 the whole of them. 360 00:15:30,050 --> 00:15:32,430 So now we take a step back to the brain as a whole. 361 00:15:32,430 --> 00:15:34,050 Here's the front of the brain, top of the 362 00:15:34,050 --> 00:15:35,210 brain, back of the brain. 363 00:15:35,210 --> 00:15:37,210 I'm going to say a word about the cerebellum, which we'll 364 00:15:37,210 --> 00:15:39,840 talk very little about in this course. 365 00:15:39,840 --> 00:15:42,120 The cellular organization of the cerebellum is so 366 00:15:42,120 --> 00:15:45,190 consistent that people estimate that half of all the 367 00:15:45,190 --> 00:15:47,460 cortical neurons in the brain are in the cerebellum. 368 00:15:47,460 --> 00:15:50,480 And if you see this cerebellar size is small, not that large, 369 00:15:50,480 --> 00:15:52,990 it's because it's packed so tightly. 370 00:15:52,990 --> 00:15:55,250 And it's so consistent in its organization that people 371 00:15:55,250 --> 00:15:57,830 thought, that's the first part of the brain we'll crack. 372 00:15:57,830 --> 00:16:01,110 Because the organization is so clear that we'll be able to 373 00:16:01,110 --> 00:16:03,060 figure out what it's computing and how it does it. 374 00:16:03,060 --> 00:16:05,450 And it's turned out to be about as mysterious a 375 00:16:05,450 --> 00:16:07,030 structure as any. 376 00:16:07,030 --> 00:16:08,730 I can't tell you the number of debates about what people-- we 377 00:16:08,730 --> 00:16:11,140 know it's involved in motor control, but in many other 378 00:16:11,140 --> 00:16:12,760 things, as well. 379 00:16:12,760 --> 00:16:16,080 The wiring diagram, knowing it, what's connected to who, 380 00:16:16,080 --> 00:16:19,270 turns out to be only a tiny step in understanding how what 381 00:16:19,270 --> 00:16:21,610 part of the brain does what it does. 382 00:16:21,610 --> 00:16:24,800 So here's this mysterious cerebellum. 383 00:16:24,800 --> 00:16:28,550 And then here's a basal ganglia that we know is 384 00:16:28,550 --> 00:16:30,280 involved in movement. 385 00:16:30,280 --> 00:16:31,620 Parkinson's Disease affects it. 386 00:16:31,620 --> 00:16:33,530 Huntington's Disease affects it. 387 00:16:33,530 --> 00:16:37,410 It's also involved in learning habits of all kinds. 388 00:16:37,410 --> 00:16:40,240 It's also involved in the reward systems of the brain. 389 00:16:40,240 --> 00:16:42,420 What have we found delightful and important? 390 00:16:42,420 --> 00:16:45,290 What did we want to do because the reward 391 00:16:45,290 --> 00:16:47,240 system is turned on? 392 00:16:47,240 --> 00:16:49,110 We'll come back to that later on. 393 00:16:49,110 --> 00:16:51,210 And then the limbic system, the part of the brain that's 394 00:16:51,210 --> 00:16:54,060 involved in emotion and memory-- 395 00:16:54,060 --> 00:16:55,200 amygdala and hippocampus. 396 00:16:55,200 --> 00:16:55,950 We'll come back to that. 397 00:16:55,950 --> 00:16:58,440 If you don't have this structure intact, you can't 398 00:16:58,440 --> 00:17:00,340 form new memories ever again. 399 00:17:00,340 --> 00:17:04,190 We'll talk about patients like that. 400 00:17:04,190 --> 00:17:06,010 And then we'll come to the smarts of the brain, the 401 00:17:06,010 --> 00:17:08,520 cerebral cortex, four lobes-- 402 00:17:08,520 --> 00:17:11,839 frontal, parietal, occipital, and temporal. 403 00:17:11,839 --> 00:17:16,550 You have four on the left and four on the right. 404 00:17:16,550 --> 00:17:18,540 These lobes are comprised of gyri. 405 00:17:18,540 --> 00:17:20,369 That's the part of the brain that sticks out. 406 00:17:20,369 --> 00:17:22,640 And then there's this sort of indentation where it dives 407 00:17:22,640 --> 00:17:25,000 deep into a sulcus. 408 00:17:25,000 --> 00:17:27,510 Comes back up, it's the next gyrus, dives deep into the 409 00:17:27,510 --> 00:17:28,540 next sulcus. 410 00:17:28,540 --> 00:17:30,620 A huge sulcus is called a fissure. 411 00:17:30,620 --> 00:17:34,020 Here's a Sylvian fissure that separates the temporal and 412 00:17:34,020 --> 00:17:35,600 frontal cortices. 413 00:17:35,600 --> 00:17:37,900 And one of the reasons that people have speculated about 414 00:17:37,900 --> 00:17:39,640 why do we have a thing like that? 415 00:17:39,640 --> 00:17:44,380 Why do we have these waves of a gyrus going up and then 416 00:17:44,380 --> 00:17:48,230 plunging into the depths, then coming back up like this again 417 00:17:48,230 --> 00:17:52,040 and plunging from sulcus to sulcus? 418 00:17:52,040 --> 00:17:53,840 And nobody really knows. 419 00:17:53,840 --> 00:17:55,330 But there's kind of a speculation 420 00:17:55,330 --> 00:17:58,510 that's fun and plausible. 421 00:17:58,510 --> 00:18:03,160 One thing we know is that bigger cortices are good, not 422 00:18:03,160 --> 00:18:05,050 so much one person to another, but across species. 423 00:18:05,050 --> 00:18:06,820 Your smarts are in your cortices-- 424 00:18:06,820 --> 00:18:09,090 language, higher-level thought, and so on. 425 00:18:09,090 --> 00:18:11,980 So on the whole, a species that has bigger cortices has a 426 00:18:11,980 --> 00:18:14,670 lot of opportunities for thought and social 427 00:18:14,670 --> 00:18:16,840 development and so on. 428 00:18:16,840 --> 00:18:21,380 So you could imagine having babies with heads this big. 429 00:18:21,380 --> 00:18:24,850 They'd be really smart, maybe. 430 00:18:24,850 --> 00:18:26,555 But what would be the problem? 431 00:18:30,710 --> 00:18:33,830 What would be the big problem? 432 00:18:33,830 --> 00:18:37,240 Think about it not from your perspective, perhaps, if most 433 00:18:37,240 --> 00:18:41,740 of you are sort of teenagers or young 20s or something like 434 00:18:41,740 --> 00:18:43,220 that, most of you. 435 00:18:43,220 --> 00:18:46,900 So you don't remember your birth experience directly. 436 00:18:46,900 --> 00:18:49,730 But who remembers your birth experience pretty well? 437 00:18:49,730 --> 00:18:50,320 Your parents? 438 00:18:50,320 --> 00:18:50,820 OK. 439 00:18:50,820 --> 00:18:51,060 All right. 440 00:18:51,060 --> 00:18:53,770 It's your mother, especially. 441 00:18:53,770 --> 00:18:55,540 Giving birth is a pretty painful, 442 00:18:55,540 --> 00:18:57,730 specific, challenging process. 443 00:18:57,730 --> 00:19:00,340 So if a head this big came out, it would be 444 00:19:00,340 --> 00:19:01,725 incommensurate with the birth canal that 445 00:19:01,725 --> 00:19:02,530 the mother can afford. 446 00:19:02,530 --> 00:19:04,020 It's already pretty challenging with your head as 447 00:19:04,020 --> 00:19:05,550 big as it is when it comes out. 448 00:19:05,550 --> 00:19:06,450 That's the challenge of birth. 449 00:19:06,450 --> 00:19:07,890 It's not getting the arms and legs out. 450 00:19:07,890 --> 00:19:11,150 Its the head that's too big. 451 00:19:11,150 --> 00:19:14,060 So now we have a problem that the mother's birth canal is 452 00:19:14,060 --> 00:19:14,790 only so big. 453 00:19:14,790 --> 00:19:17,755 We want as much brain and smartness in our species and 454 00:19:17,755 --> 00:19:19,050 in ourselves as possible. 455 00:19:19,050 --> 00:19:20,850 So how are we going to get a lot of neocortex in there? 456 00:19:23,370 --> 00:19:26,890 We're going to fold it. 457 00:19:26,890 --> 00:19:30,720 A lot of neocortex in there, but a smaller volume to get 458 00:19:30,720 --> 00:19:32,070 out through the birth canal. 459 00:19:32,070 --> 00:19:35,170 And that's thought to be why the brain has this elaborate 460 00:19:35,170 --> 00:19:39,180 plunging from sulcus to sulcus, and this sort of 461 00:19:39,180 --> 00:19:43,620 convolved physical structure. 462 00:19:43,620 --> 00:19:47,070 And if we think about the brain, we can think about 463 00:19:47,070 --> 00:19:49,770 things that go into our brains, about the outer world. 464 00:19:49,770 --> 00:19:54,220 So when you see, vision enters through this area, or when you 465 00:19:54,220 --> 00:19:55,800 hear, it enters here. 466 00:19:55,800 --> 00:19:58,640 When you touch or when you move your body, these are the 467 00:19:58,640 --> 00:19:59,680 motor cortical neurons. 468 00:19:59,680 --> 00:20:02,250 So it's either sort of major inputs or major output. 469 00:20:02,250 --> 00:20:02,840 That's in blue. 470 00:20:02,840 --> 00:20:05,900 That's the areas that are devoted to specific perception 471 00:20:05,900 --> 00:20:08,320 or modalities or sensories. 472 00:20:08,320 --> 00:20:09,905 And then we have areas in yellow here. 473 00:20:09,905 --> 00:20:11,470 They are the areas that are sort of 474 00:20:11,470 --> 00:20:13,760 closely tied to one modality. 475 00:20:13,760 --> 00:20:16,690 But already, they're interpreting what's going on. 476 00:20:16,690 --> 00:20:19,290 And then you have areas in pink here that are sort of not 477 00:20:19,290 --> 00:20:23,070 tied to any modality and are devoted to what we might call 478 00:20:23,070 --> 00:20:24,100 abstract thought. 479 00:20:24,100 --> 00:20:26,950 And you can see the prefrontal cortex, the part of the cortex 480 00:20:26,950 --> 00:20:28,930 that's in front of the motor cortex. 481 00:20:28,930 --> 00:20:30,510 There's a huge swath like that. 482 00:20:30,510 --> 00:20:31,370 We'll come back to that. 483 00:20:31,370 --> 00:20:33,180 We think it's terribly important for thinking, 484 00:20:33,180 --> 00:20:35,680 problem solving, and many aspects of the 485 00:20:35,680 --> 00:20:39,570 highest human mentation. 486 00:20:39,570 --> 00:20:43,090 Now we're a huge believer in the end that form follows 487 00:20:43,090 --> 00:20:44,430 function in the brain. 488 00:20:44,430 --> 00:20:46,250 And if we understood the correct relationship between 489 00:20:46,250 --> 00:20:48,240 form and function, we'd be very far. 490 00:20:48,240 --> 00:20:51,170 And a neuroanatomist named [? Broadbent ?] 491 00:20:51,170 --> 00:20:53,340 made the following heroic effort. 492 00:20:53,340 --> 00:20:54,830 What he did is he sectioned brains into 493 00:20:54,830 --> 00:20:56,370 lots of thin slices. 494 00:20:56,370 --> 00:20:58,570 And he followed them through a microscope. 495 00:20:58,570 --> 00:21:02,170 And every time the brain tissue changed, the neurons 496 00:21:02,170 --> 00:21:06,220 looked different, he would change the number of the area. 497 00:21:06,220 --> 00:21:08,880 So he started in something like Area One. 498 00:21:08,880 --> 00:21:10,230 And the neurons look pretty similar. 499 00:21:10,230 --> 00:21:11,570 And he's moving, moving, moving. 500 00:21:11,570 --> 00:21:12,450 And then all of a sudden they start to look 501 00:21:12,450 --> 00:21:13,720 different, the neurons. 502 00:21:13,720 --> 00:21:16,540 And then that becomes something like Area Three. 503 00:21:16,540 --> 00:21:17,920 Moving, moving, Area Four. 504 00:21:17,920 --> 00:21:19,095 Moving, moving, Area Six. 505 00:21:19,095 --> 00:21:23,410 So every time the neurons looked different to his eye, 506 00:21:23,410 --> 00:21:24,530 it gets a new number. 507 00:21:24,530 --> 00:21:27,105 The idea being when the neurons look different, they 508 00:21:27,105 --> 00:21:28,380 have a different job to do. 509 00:21:28,380 --> 00:21:30,490 And that part of the brain does something different. 510 00:21:30,490 --> 00:21:33,020 And there's lots of debates about the best way to do this, 511 00:21:33,020 --> 00:21:34,090 or different interpretations. 512 00:21:34,090 --> 00:21:36,560 But something like this holds true in a striking way. 513 00:21:36,560 --> 00:21:40,210 The cellular organization of the brain reflects in some way 514 00:21:40,210 --> 00:21:42,180 what that part of the brain is accomplishing, what part of 515 00:21:42,180 --> 00:21:44,150 your mind it supports. 516 00:21:44,150 --> 00:21:47,040 And then we have simplified color pictures of this. 517 00:21:47,040 --> 00:21:50,520 And we'll come back to neuroimaging next time. 518 00:21:50,520 --> 00:21:53,880 But it's turned out to have a second life in neuroimaging. 519 00:21:53,880 --> 00:21:56,940 Because when scientists across the world want to compare 520 00:21:56,940 --> 00:21:59,620 their neuroimaging results, they'll talk about, well, I 521 00:21:59,620 --> 00:22:03,610 got activation in Area 46, or I got it in Area 21. 522 00:22:03,610 --> 00:22:06,520 It's become a nomenclature for the organization of the human 523 00:22:06,520 --> 00:22:09,480 brain that allows you to integrate all kinds of imaging 524 00:22:09,480 --> 00:22:12,100 data about the human species. 525 00:22:12,100 --> 00:22:14,310 And here's a view from the inside of the brain. 526 00:22:14,310 --> 00:22:16,420 And here's a structure chord, the corpus callosum, that 527 00:22:16,420 --> 00:22:20,500 we'll come back to in the next few minutes. 528 00:22:20,500 --> 00:22:25,790 So how much are functions localized or distributed? 529 00:22:25,790 --> 00:22:26,700 How much is-- 530 00:22:26,700 --> 00:22:28,970 you have a specific thing your mind does, and it's in one 531 00:22:28,970 --> 00:22:31,600 place in the brain versus it's spread over a range. 532 00:22:31,600 --> 00:22:34,110 And this idea of how much things are distributed or 533 00:22:34,110 --> 00:22:36,560 localized for mental functions in the brain has been a source 534 00:22:36,560 --> 00:22:38,900 of huge debate. 535 00:22:38,900 --> 00:22:41,130 And I'll show you a misstep, and then I'll show you some 536 00:22:41,130 --> 00:22:43,510 things where we think we have it more correctly. 537 00:22:43,510 --> 00:22:45,280 The misstep is a phrenology. 538 00:22:45,280 --> 00:22:49,240 And the most famous name in this is from Gall. 539 00:22:49,240 --> 00:22:50,700 Spurzheim is another one. 540 00:22:50,700 --> 00:22:54,950 And in the 19th century-- that's the 1800s-- 541 00:22:54,950 --> 00:22:56,800 the phrenology took hold a lot. 542 00:22:56,800 --> 00:22:59,340 And there's a sort of a Freudian story. 543 00:22:59,340 --> 00:23:01,650 If you want to call it that, of Gall, which is that 544 00:23:01,650 --> 00:23:05,090 apparently when he was a student, he viewed himself as 545 00:23:05,090 --> 00:23:07,750 a very effortful and fastidious student who took 546 00:23:07,750 --> 00:23:09,800 all the notes you're supposed to take, and worked very hard 547 00:23:09,800 --> 00:23:12,580 for exams and did everything you were supposed to do. 548 00:23:12,580 --> 00:23:14,520 But shock of shocks, some students did 549 00:23:14,520 --> 00:23:16,470 better than he did. 550 00:23:16,470 --> 00:23:17,690 And he looked around the classroom. 551 00:23:17,690 --> 00:23:18,940 He said, who are these students doing 552 00:23:18,940 --> 00:23:19,700 better than I am? 553 00:23:19,700 --> 00:23:21,050 Because I'm trying as hard as I can. 554 00:23:21,050 --> 00:23:22,180 And some students are doing better. 555 00:23:22,180 --> 00:23:24,360 And he said, hey, one thing I notice about these students is 556 00:23:24,360 --> 00:23:26,320 they all seem to have big foreheads. 557 00:23:26,320 --> 00:23:26,766 OK? 558 00:23:26,766 --> 00:23:27,212 [CHUCKLES] 559 00:23:27,212 --> 00:23:30,030 Now, I don't know how accurate he was scientifically. 560 00:23:30,030 --> 00:23:32,920 But apparently, this was a emotionally transformative 561 00:23:32,920 --> 00:23:33,670 moment for Gall. 562 00:23:33,670 --> 00:23:34,900 And you'll see in what way this ended 563 00:23:34,900 --> 00:23:37,990 up guiding his science. 564 00:23:37,990 --> 00:23:41,560 So Gall and Spurzheim were actually good neuroanatomists. 565 00:23:41,560 --> 00:23:43,680 They describe lots of things about the brain that were 566 00:23:43,680 --> 00:23:46,290 correct that were kind of unknown at the time. 567 00:23:46,290 --> 00:23:49,440 For example, the pyramidal tracts, the tracts that move 568 00:23:49,440 --> 00:23:51,780 from your motor cortex-- say on your left to control your 569 00:23:51,780 --> 00:23:54,970 right hand, or on your right to control your left hand-- 570 00:23:54,970 --> 00:23:58,110 they describe those very well. 571 00:23:58,110 --> 00:23:59,400 But here's where they got kind of funny. 572 00:23:59,400 --> 00:24:01,080 They said, OK, we can describe the physical 573 00:24:01,080 --> 00:24:02,090 organization of the brain. 574 00:24:02,090 --> 00:24:03,760 But now let's say which part of the brain is 575 00:24:03,760 --> 00:24:04,990 which part of the mind. 576 00:24:04,990 --> 00:24:08,140 And in a way that we now consider a bit willy-nilly, 577 00:24:08,140 --> 00:24:10,940 they began to assign different mental processes to different 578 00:24:10,940 --> 00:24:11,660 parts of the brain. 579 00:24:11,660 --> 00:24:14,330 And the way they did it was they said, I'm going to look 580 00:24:14,330 --> 00:24:14,820 at somebody. 581 00:24:14,820 --> 00:24:18,540 And let's pretend somebody you know is very combative. 582 00:24:18,540 --> 00:24:20,830 What they began to figure was this. 583 00:24:20,830 --> 00:24:23,190 Well, maybe the part of the brain that's involved in being 584 00:24:23,190 --> 00:24:24,250 combative-- 585 00:24:24,250 --> 00:24:27,710 the more combative you are, the more you have of it. 586 00:24:27,710 --> 00:24:30,840 So if I feel your skull above the part of the brain that I 587 00:24:30,840 --> 00:24:34,070 think goes with being combative, if you have a big 588 00:24:34,070 --> 00:24:36,400 rise there, if I feel your head-- and most of our heads 589 00:24:36,400 --> 00:24:39,410 are a little bumpy-- 590 00:24:39,410 --> 00:24:40,830 the person who's really combative is going to have a 591 00:24:40,830 --> 00:24:43,170 lot of bump there. 592 00:24:43,170 --> 00:24:45,960 And the person who's very meek will have none. 593 00:24:45,960 --> 00:24:47,030 OK, does that make sense? 594 00:24:47,030 --> 00:24:48,470 They have these little categories as they just 595 00:24:48,470 --> 00:24:49,630 thought about people. 596 00:24:49,630 --> 00:24:56,180 And they developed this idea that they could find where 597 00:24:56,180 --> 00:24:59,790 cautiousness was, or precociousness, or 598 00:24:59,790 --> 00:25:00,850 secretiveness. 599 00:25:00,850 --> 00:25:02,260 You'd give it a big bump there. 600 00:25:02,260 --> 00:25:03,140 Let me show you this picture. 601 00:25:03,140 --> 00:25:06,440 Here's a device you would step into that would have springs 602 00:25:06,440 --> 00:25:08,280 go down, and then it would go up, and they would say, where 603 00:25:08,280 --> 00:25:09,170 do you have the high bumps? 604 00:25:09,170 --> 00:25:10,640 And where do you have the little bumps? 605 00:25:10,640 --> 00:25:13,770 Now all of this is wrong. 606 00:25:13,770 --> 00:25:18,610 Because it's a naive way and not a scientific way to do it. 607 00:25:18,610 --> 00:25:21,460 Weirdly enough, look at what they put below the eye-- 608 00:25:21,460 --> 00:25:23,260 language. 609 00:25:23,260 --> 00:25:24,930 Now that's a weird place to put it. 610 00:25:24,930 --> 00:25:27,310 And what they saw was a soldier who had a wound that 611 00:25:27,310 --> 00:25:30,250 went his eye and into his brain. 612 00:25:30,250 --> 00:25:32,930 And they said, OK, he had trouble producing language. 613 00:25:32,930 --> 00:25:34,860 And they said, well, that's where language is. 614 00:25:34,860 --> 00:25:37,900 Language is not below your eye. 615 00:25:37,900 --> 00:25:41,200 But they didn't realize that the wound went up into what's 616 00:25:41,200 --> 00:25:42,080 something called Broca's area. 617 00:25:42,080 --> 00:25:43,870 We'll talk about that in a couple minutes. 618 00:25:43,870 --> 00:25:46,580 And so they weren't that wrong. 619 00:25:46,580 --> 00:25:48,540 They just didn't think through where the end 620 00:25:48,540 --> 00:25:49,800 of the injury was. 621 00:25:49,800 --> 00:25:52,760 All the other ones, we completely dismiss these days. 622 00:25:52,760 --> 00:25:56,380 But we have to worry about naive ways in which we link 623 00:25:56,380 --> 00:25:58,770 the life of the mind to the stuff of the brain. 624 00:25:58,770 --> 00:26:00,950 And they did a control experiment. "The famous 625 00:26:00,950 --> 00:26:03,540 physiologist, Magendie, preserved with veneration the 626 00:26:03,540 --> 00:26:04,945 brain of Laplace," who's a big name in 627 00:26:04,945 --> 00:26:06,340 the history of chemistry. 628 00:26:06,340 --> 00:26:08,290 "Spurzheim had the natural wish to see the brain." 629 00:26:08,290 --> 00:26:09,640 Spurzheim was the phrenologist. 630 00:26:09,640 --> 00:26:12,330 "To test the science of phrenologist, Magendie showed 631 00:26:12,330 --> 00:26:14,400 him instead the brain of an imbecile. 632 00:26:14,400 --> 00:26:16,670 Spurzheim, who had already worked up his enthusiasm, 633 00:26:16,670 --> 00:26:19,400 admired the brain of the imbecile as he would have 634 00:26:19,400 --> 00:26:21,290 admired that of Laplace." 635 00:26:21,290 --> 00:26:22,350 So this was a control assess. 636 00:26:22,350 --> 00:26:24,030 I give you a brain of somebody who's not a genius in 637 00:26:24,030 --> 00:26:25,510 chemistry, and you go, oh my gosh. 638 00:26:25,510 --> 00:26:27,750 This chemistry part of the brain is unbelievable. 639 00:26:27,750 --> 00:26:31,230 And this is the old idea we talked about, that if you have 640 00:26:31,230 --> 00:26:34,220 an idea you believe in as a scientist, you will always 641 00:26:34,220 --> 00:26:38,420 find positive evidence for it everywhere you look. 642 00:26:38,420 --> 00:26:40,580 Back to the brain, and let's talk about this part, the 643 00:26:40,580 --> 00:26:42,610 lower part of the orbital frontal cortex. 644 00:26:42,610 --> 00:26:44,720 It sits right above your eyes. 645 00:26:44,720 --> 00:26:48,080 Your eyes would be something like here. 646 00:26:48,080 --> 00:26:50,710 And we know something about what that part of the brain 647 00:26:50,710 --> 00:26:54,070 does from the famous case of Phineas Gage. 648 00:26:54,070 --> 00:26:56,920 He was involved in railroad construction in Vermont. 649 00:26:56,920 --> 00:26:59,980 And that involved exploding rocks to level the area so 650 00:26:59,980 --> 00:27:01,260 they could put in train tracks. 651 00:27:01,260 --> 00:27:02,880 They would drill a hole, put in some 652 00:27:02,880 --> 00:27:03,850 fuse, put in the powder. 653 00:27:03,850 --> 00:27:07,290 And they would use a tamping iron to push down the sand and 654 00:27:07,290 --> 00:27:10,670 powder so there would be a big explosion to flatten the rock. 655 00:27:10,670 --> 00:27:14,760 And at age 25 in 1848, he has a mind who was described as 656 00:27:14,760 --> 00:27:16,640 well-balanced, energetic, and persistent. 657 00:27:16,640 --> 00:27:20,970 He was the ideal employee, resourceful, hardworking. 658 00:27:20,970 --> 00:27:22,880 He was made a foreman, a leader. 659 00:27:22,880 --> 00:27:24,610 He was the most efficient and capable in the group. 660 00:27:24,610 --> 00:27:28,970 And on September 13, 1848, something big happened. 661 00:27:28,970 --> 00:27:30,420 There was a miscommunication. 662 00:27:30,420 --> 00:27:32,990 An iron that was three feet, seven inches in length-- 663 00:27:32,990 --> 00:27:35,130 I'll show you a picture in a moment, because even if you've 664 00:27:35,130 --> 00:27:37,190 heard this story, until you see a picture of it, you can't 665 00:27:37,190 --> 00:27:40,870 grasp how big this was compared to a human being. 666 00:27:40,870 --> 00:27:43,310 There was a miscommunication, the explosion went off early. 667 00:27:43,310 --> 00:27:44,710 He was directly over it. 668 00:27:44,710 --> 00:27:47,670 The rod flew up, went through his head, all the 669 00:27:47,670 --> 00:27:48,740 way through his head. 670 00:27:48,740 --> 00:27:53,340 And it had the power to land 30 yards away after exploding 671 00:27:53,340 --> 00:27:54,860 up into the air. 672 00:27:54,860 --> 00:27:59,040 And by March of the next year, he was back at work. 673 00:27:59,040 --> 00:28:02,200 Not too long a vacation, a recovery period for that big a 674 00:28:02,200 --> 00:28:03,190 thing going through your head. 675 00:28:03,190 --> 00:28:06,250 But his personality had fundamentally changed. 676 00:28:06,250 --> 00:28:11,130 So here's his cast of his actual head and his skull. 677 00:28:11,130 --> 00:28:13,220 Here's where it shot up through here 678 00:28:13,220 --> 00:28:15,660 and out this hole. 679 00:28:15,660 --> 00:28:17,630 Here's the actual rod compared to that. 680 00:28:17,630 --> 00:28:21,330 So if you haven't seen this, you can underestimate the 681 00:28:21,330 --> 00:28:23,050 amazingness of this thing. 682 00:28:23,050 --> 00:28:27,370 And at the time he was famous not for the reason we now 683 00:28:27,370 --> 00:28:28,180 think of him. 684 00:28:28,180 --> 00:28:31,930 He was just a Ripley's believe it or not story of that a 685 00:28:31,930 --> 00:28:34,750 human survived at all. 686 00:28:34,750 --> 00:28:38,120 So Antonio Damasio has attempted to reconstruct by 687 00:28:38,120 --> 00:28:42,540 computer where this rod shot up through here and out into 688 00:28:42,540 --> 00:28:44,250 30 yards away. 689 00:28:44,250 --> 00:28:46,770 They're that big compared to him. 690 00:28:46,770 --> 00:28:48,970 And the amazing thing, and described by a physician who 691 00:28:48,970 --> 00:28:51,580 worked with him at the time, is "the equilibrium to his 692 00:28:51,580 --> 00:28:54,130 intellectual faculties and animal propensities seems to 693 00:28:54,130 --> 00:28:54,630 have destroyed. 694 00:28:54,630 --> 00:28:57,085 He is fitful, irreverent, indulging at times in the 695 00:28:57,085 --> 00:28:58,510 grossest profanity. 696 00:28:58,510 --> 00:29:00,360 Little deference for his fellows, impatient of 697 00:29:00,360 --> 00:29:02,610 restraint, conflicting with his desires. 698 00:29:02,610 --> 00:29:05,130 At times pertinaciously obstinate, capricious and 699 00:29:05,130 --> 00:29:08,150 vacillating, devising many plans of future operations, 700 00:29:08,150 --> 00:29:10,450 which are no sooner arranged than they are abandoned in 701 00:29:10,450 --> 00:29:12,310 turn for others appearing more feasible." 702 00:29:12,310 --> 00:29:14,500 Exactly the opposite of who he was before. 703 00:29:14,500 --> 00:29:16,900 He was a responsible, efficient leader. 704 00:29:16,900 --> 00:29:20,680 And now he's a totally irresponsible person doing all 705 00:29:20,680 --> 00:29:22,110 kinds of things that make no sense. 706 00:29:22,110 --> 00:29:24,710 "A child in his intellectual capacity, he has the animal 707 00:29:24,710 --> 00:29:27,030 passions of a strong man." So he completely 708 00:29:27,030 --> 00:29:28,090 changed who he was. 709 00:29:28,090 --> 00:29:31,030 In this regard, his mind was so radically changed that his 710 00:29:31,030 --> 00:29:34,210 friends and acquaintances said that "he was no longer Gage." 711 00:29:34,210 --> 00:29:37,540 So here's a physical insult to the brain that changes the 712 00:29:37,540 --> 00:29:39,940 character of a person, that changes what we would think of 713 00:29:39,940 --> 00:29:41,520 as the moral judgments. 714 00:29:41,520 --> 00:29:45,010 Of when is it right to tell the truth, having plans and 715 00:29:45,010 --> 00:29:47,980 being a responsible, trustworthy person, completely 716 00:29:47,980 --> 00:29:49,650 changed by this injury. 717 00:29:52,180 --> 00:29:54,860 One interpretation is this part of the brain is essential 718 00:29:54,860 --> 00:29:59,210 for making moral judgments and being of good character. 719 00:29:59,210 --> 00:30:01,940 What would be another interpretation of why he might 720 00:30:01,940 --> 00:30:07,080 have changed, just common sense besides that this part 721 00:30:07,080 --> 00:30:08,300 of the brain does that? 722 00:30:08,300 --> 00:30:11,620 We want to not be for phrenologists, OK? 723 00:30:11,620 --> 00:30:16,140 So the first thought is, this part of the brain supports 724 00:30:16,140 --> 00:30:19,400 what we think of as moral reasoning and character. 725 00:30:19,400 --> 00:30:22,040 Well, what else could you imagine might have happened? 726 00:30:24,980 --> 00:30:26,174 Yeah. 727 00:30:26,174 --> 00:30:29,443 AUDIENCE: He had a giant spike driven though his skull and is 728 00:30:29,443 --> 00:30:30,377 upset about it? 729 00:30:30,377 --> 00:30:31,790 PROFESSOR JOHN GABRIELI: Yeah. 730 00:30:31,790 --> 00:30:34,220 I'll make up something like that. 731 00:30:34,220 --> 00:30:37,070 But a more psychological and different interpretation, let 732 00:30:37,070 --> 00:30:39,120 me try this one. 733 00:30:39,120 --> 00:30:41,120 He was getting ready for the future. 734 00:30:41,120 --> 00:30:43,270 I'll be a foreman today, and then next week, I'll be 735 00:30:43,270 --> 00:30:45,300 executive vice president, and then I'll be associate 736 00:30:45,300 --> 00:30:47,170 executive president. 737 00:30:47,170 --> 00:30:48,610 And a rod goes through his head, and he 738 00:30:48,610 --> 00:30:49,170 goes, wait a minute. 739 00:30:49,170 --> 00:30:49,810 Life is short. 740 00:30:49,810 --> 00:30:51,250 It could end at any moment. 741 00:30:51,250 --> 00:30:53,530 Why not just do what I want to do all the time? 742 00:30:53,530 --> 00:30:57,020 Because the next rod could come who knows when. 743 00:30:57,020 --> 00:31:00,110 And I had all these plans, and I was promising people things 744 00:31:00,110 --> 00:31:01,670 next week that I delivered on. 745 00:31:01,670 --> 00:31:04,070 But that's a sucker's life, because your life 746 00:31:04,070 --> 00:31:05,080 can end like that. 747 00:31:05,080 --> 00:31:09,710 So forget all the stuff about-- just enjoy the moment. 748 00:31:09,710 --> 00:31:11,160 That's a possible thing, OK? 749 00:31:11,160 --> 00:31:12,690 You see movies like that, where people are told, you 750 00:31:12,690 --> 00:31:15,300 have so long to live, and they change. 751 00:31:15,300 --> 00:31:17,800 What would you want to convince yourself that it 752 00:31:17,800 --> 00:31:19,850 wasn't something like that, which is not an unreasonable 753 00:31:19,850 --> 00:31:21,100 interpretation? 754 00:31:23,560 --> 00:31:27,120 What you would want to see, at a minimum, is that if you have 755 00:31:27,120 --> 00:31:30,540 brain injuries other places in the brain, you don't see that. 756 00:31:30,540 --> 00:31:32,240 And if you have other people with brain injuries in the 757 00:31:32,240 --> 00:31:33,990 same part of the brain, you see that consistently. 758 00:31:33,990 --> 00:31:35,100 At a minimum, you want to say it's not 759 00:31:35,100 --> 00:31:37,130 just a big brain injury. 760 00:31:37,130 --> 00:31:39,620 But it's consistently a brain injury in this part of the 761 00:31:39,620 --> 00:31:41,460 brain that leads to this kind of behavior. 762 00:31:41,460 --> 00:31:43,970 And for at least this example, that's true. 763 00:31:43,970 --> 00:31:46,490 Other patients with similar injuries behaved similarly. 764 00:31:46,490 --> 00:31:49,750 People with very big injuries elsewhere in the brain don't 765 00:31:49,750 --> 00:31:50,660 behave similarly. 766 00:31:50,660 --> 00:31:54,060 So there's a lot of reason in the end for us to believe that 767 00:31:54,060 --> 00:31:55,640 this part of the brain is essential for something that 768 00:31:55,640 --> 00:31:57,790 we consider almost metaphysical. 769 00:31:57,790 --> 00:32:01,920 Character has this incredibly physical dependence. 770 00:32:01,920 --> 00:32:04,280 And relatively recently, just a few years ago, they 771 00:32:04,280 --> 00:32:09,700 discovered a picture of Phineas Gage himself. 772 00:32:09,700 --> 00:32:11,380 Here's the rod. 773 00:32:11,380 --> 00:32:14,560 Here's the injury to his eye, his eye is damaged. 774 00:32:14,560 --> 00:32:17,330 So one more example, and then we'll switch this refrain. 775 00:32:17,330 --> 00:32:19,010 Paul Broca. 776 00:32:19,010 --> 00:32:22,150 And Broca's area in the brain, here's Paul Broca. 777 00:32:22,150 --> 00:32:24,510 Here's a brain of a patient named Mr. Tan. 778 00:32:24,510 --> 00:32:26,280 And let me say a word about the story. 779 00:32:26,280 --> 00:32:29,230 So in France, a number of people observing patients with 780 00:32:29,230 --> 00:32:32,140 injuries had talked about that the left side of the brain is 781 00:32:32,140 --> 00:32:33,600 important for speech. 782 00:32:33,600 --> 00:32:35,820 Until then there had not been much ideas that the left and 783 00:32:35,820 --> 00:32:38,270 right were fundamentally different. 784 00:32:38,270 --> 00:32:39,700 So there's always sort of a 785 00:32:39,700 --> 00:32:41,390 background before the discovery. 786 00:32:41,390 --> 00:32:44,350 And there's a talk in 1861 which describes a man who lost 787 00:32:44,350 --> 00:32:46,710 his speech but understood everything said to him. 788 00:32:46,710 --> 00:32:47,660 He couldn't produce speech. 789 00:32:47,660 --> 00:32:48,955 He could understand speech. 790 00:32:48,955 --> 00:32:50,980 His intelligence is still unimpaired. 791 00:32:50,980 --> 00:32:53,390 His speech is gone. 792 00:32:53,390 --> 00:32:55,610 And then Broca heard that talk, and he went back, and 793 00:32:55,610 --> 00:32:58,360 five days later a patient named LeBorgne, who had lost 794 00:32:58,360 --> 00:33:01,220 his speech-- he could only say two things, "tan," and he 795 00:33:01,220 --> 00:33:03,850 could swear like crazy. 796 00:33:03,850 --> 00:33:07,950 And our current thought about that is swearing that's 797 00:33:07,950 --> 00:33:11,150 emotional and intuitive, not the one where you think, OK, 798 00:33:11,150 --> 00:33:12,640 I'm going to swear now to scare somebody. 799 00:33:12,640 --> 00:33:14,530 But the one-- you stub your toe in the middle of the 800 00:33:14,530 --> 00:33:16,460 night, and you really let out a curse-- 801 00:33:16,460 --> 00:33:18,790 we think that's guided like an animal cry 802 00:33:18,790 --> 00:33:21,110 by the basal ganglia. 803 00:33:21,110 --> 00:33:25,610 Those heartfelt, really emotional cursing is not 804 00:33:25,610 --> 00:33:26,500 really language. 805 00:33:26,500 --> 00:33:29,950 It's actually the same cry an animal makes on injury. 806 00:33:29,950 --> 00:33:32,040 And it uses some of the same neurocircuitry. 807 00:33:32,040 --> 00:33:34,500 But for higher level cortical stuff, the only word he could 808 00:33:34,500 --> 00:33:37,160 say was "tan." He died in 1871. 809 00:33:37,160 --> 00:33:39,470 They looked at his brain, and they found this change in the 810 00:33:39,470 --> 00:33:41,190 left frontal cortex. 811 00:33:41,190 --> 00:33:44,410 And we now call that Broca's aphasia, the inability to 812 00:33:44,410 --> 00:33:46,950 speak despite the presence of-- 813 00:33:46,950 --> 00:33:49,040 your mouth can move, and you can understand 814 00:33:49,040 --> 00:33:49,850 language pretty well. 815 00:33:49,850 --> 00:33:51,140 We'll come back to that. 816 00:33:51,140 --> 00:33:54,080 So we talk about Broca's area, and then Wernicke-- 817 00:33:54,080 --> 00:33:56,890 the Broca's area's important for production. 818 00:33:56,890 --> 00:33:58,900 And here's the kind of damage. 819 00:33:58,900 --> 00:34:02,270 And we'll come back to Broca's aphasia later in the course. 820 00:34:02,270 --> 00:34:04,140 So this was a big hint that there's something different 821 00:34:04,140 --> 00:34:07,740 between the right and the left hemispheres. 822 00:34:07,740 --> 00:34:10,900 Now in what percentage of people is language, especially 823 00:34:10,900 --> 00:34:13,770 speech production, predominantly in the left? 824 00:34:13,770 --> 00:34:15,830 And our best answer for that comes from a thing 825 00:34:15,830 --> 00:34:17,340 called the Wada Test. 826 00:34:17,340 --> 00:34:19,739 So this is a test given to patients who are undergoing 827 00:34:19,739 --> 00:34:22,620 neurosurgery for something like epilepsy, 828 00:34:22,620 --> 00:34:24,159 sometimes for tumors. 829 00:34:24,159 --> 00:34:28,050 And they want to know for you personally with great 830 00:34:28,050 --> 00:34:30,780 certainty, which hemisphere is the eloquent or speaking 831 00:34:30,780 --> 00:34:31,320 hemisphere? 832 00:34:31,320 --> 00:34:35,630 Because they want to remove more tissue if they're away 833 00:34:35,630 --> 00:34:39,485 from your language areas, and less tissue if they're near 834 00:34:39,485 --> 00:34:40,219 your language areas. 835 00:34:40,219 --> 00:34:42,290 Maybe they won't even do a certain surgery if they're too 836 00:34:42,290 --> 00:34:44,360 much in the middle of your language areas. 837 00:34:44,360 --> 00:34:47,449 Because in many cases, it's so frustrating for people to lose 838 00:34:47,449 --> 00:34:50,730 their ability to speak their thoughts, that they'd rather 839 00:34:50,730 --> 00:34:52,570 have the seizures, for epilepsy, than 840 00:34:52,570 --> 00:34:54,060 be unable to speak. 841 00:34:54,060 --> 00:34:56,350 So physicians and neurosurgeons are very worried 842 00:34:56,350 --> 00:34:57,170 about that. 843 00:34:57,170 --> 00:34:59,250 So what they give you is, they give you a test where they put 844 00:34:59,250 --> 00:35:01,470 in a drug called sodium amytal. 845 00:35:01,470 --> 00:35:04,810 And they inject it into your femoral or carotid artery. 846 00:35:04,810 --> 00:35:06,140 It feeds up. 847 00:35:06,140 --> 00:35:08,580 And the way that the vasculatures between the two 848 00:35:08,580 --> 00:35:12,340 hemispheres-- it mostly shuts down the operation of one 849 00:35:12,340 --> 00:35:12,680 atmosphere. 850 00:35:12,680 --> 00:35:14,950 If you're injected in this femoral artery, it'll mostly 851 00:35:14,950 --> 00:35:16,280 shut down your left. 852 00:35:16,280 --> 00:35:19,170 In this one, it will mostly shut down your right. 853 00:35:19,170 --> 00:35:22,520 And while the patient has one hemisphere turned off, and 854 00:35:22,520 --> 00:35:24,390 they know this because for example, let's say they shut 855 00:35:24,390 --> 00:35:26,350 down this hemisphere with the injection. 856 00:35:26,350 --> 00:35:27,270 You're waving your arm. 857 00:35:27,270 --> 00:35:29,730 It falls down because your motor system can no longer 858 00:35:29,730 --> 00:35:30,650 control your arm. 859 00:35:30,650 --> 00:35:31,780 You're blind in this field. 860 00:35:31,780 --> 00:35:32,850 We'll talk about that. 861 00:35:32,850 --> 00:35:35,175 Many of the mental processes done by this half of the brain 862 00:35:35,175 --> 00:35:36,180 are shut down. 863 00:35:36,180 --> 00:35:38,330 And then they'll test you like crazy to see if you can talk. 864 00:35:38,330 --> 00:35:39,610 They'll say, what are the days of the week? 865 00:35:39,610 --> 00:35:40,550 What's your name? 866 00:35:40,550 --> 00:35:41,360 Name these pictures. 867 00:35:41,360 --> 00:35:41,750 OK? 868 00:35:41,750 --> 00:35:43,420 Until the drug wears off. 869 00:35:43,420 --> 00:35:45,570 And then you come back two days later or a day later, and 870 00:35:45,570 --> 00:35:47,230 they'll inject the other side. 871 00:35:47,230 --> 00:35:50,690 And they'll know with near certainty in you which is the 872 00:35:50,690 --> 00:35:52,780 side of your brain that does the speaking. 873 00:35:52,780 --> 00:35:57,620 And best estimates are that something like 90% to 99% of 874 00:35:57,620 --> 00:35:59,260 people speak from their left. 875 00:35:59,260 --> 00:36:04,320 Even left-handers mostly speak from the left hemisphere. 876 00:36:04,320 --> 00:36:06,230 Because these are patients with epilepsy, we're not quite 877 00:36:06,230 --> 00:36:07,560 sure how they generalize to everybody. 878 00:36:07,560 --> 00:36:09,080 We wouldn't do this with typical people. 879 00:36:09,080 --> 00:36:12,370 Because these kinds of tests are invasive and a bit risky. 880 00:36:12,370 --> 00:36:14,850 But our best estimates are that if you're right-handed, 881 00:36:14,850 --> 00:36:18,320 it's almost certain you speak from your left hemisphere. 882 00:36:18,320 --> 00:36:20,880 And if you're left-handed, about 80% of left-handed 883 00:36:20,880 --> 00:36:23,750 people also speak from the left hemisphere. 884 00:36:23,750 --> 00:36:25,250 So it doesn't go by handedness, which makes 885 00:36:25,250 --> 00:36:27,910 handedness a bit more of a mystery. 886 00:36:27,910 --> 00:36:33,150 So now switch from grey matter discussions to white matter. 887 00:36:33,150 --> 00:36:34,630 In the middle of your brain is something 888 00:36:34,630 --> 00:36:36,500 called the corpus callosum. 889 00:36:36,500 --> 00:36:38,190 Here it's viewed from the middle, if we cut 890 00:36:38,190 --> 00:36:39,160 the brain this way. 891 00:36:39,160 --> 00:36:44,240 200 million myelinated fibers that connect the similar areas 892 00:36:44,240 --> 00:36:45,510 from the left and the right. 893 00:36:45,510 --> 00:36:48,530 This is what hooks up the left and right hemisphere 894 00:36:48,530 --> 00:36:50,760 from spot to spot. 895 00:36:50,760 --> 00:36:52,150 Here it is connecting-- 896 00:36:52,150 --> 00:36:54,470 and this is from the side view-- so it's a huge white 897 00:36:54,470 --> 00:36:55,830 matter area. 898 00:36:55,830 --> 00:36:57,330 Corpus callosum. 899 00:36:57,330 --> 00:36:59,260 And people noticed it because it was so striking. 900 00:36:59,260 --> 00:37:01,590 But they couldn't figure out what it does. 901 00:37:01,590 --> 00:37:03,470 And it kind of started to figure a little bit in 902 00:37:03,470 --> 00:37:04,860 philosophical debates. 903 00:37:04,860 --> 00:37:06,410 Would a divided brain-- if you cut the 904 00:37:06,410 --> 00:37:07,660 brain down the middle-- 905 00:37:07,660 --> 00:37:09,500 would it read to separate stores of mood, 906 00:37:09,500 --> 00:37:10,710 predisposition, knowledge, and memory? 907 00:37:10,710 --> 00:37:13,060 That is, if your two halves of your brain were divided from 908 00:37:13,060 --> 00:37:16,470 one other, would you be sort of two people? 909 00:37:16,470 --> 00:37:18,690 Now, we're not going to do that to you. 910 00:37:18,690 --> 00:37:21,590 But the fascinating thing is, are you two people to start 911 00:37:21,590 --> 00:37:24,210 with, who talk to one another sometimes 912 00:37:24,210 --> 00:37:26,890 across your corpus callosum? 913 00:37:26,890 --> 00:37:28,760 And William McDougall said, well, the unity of 914 00:37:28,760 --> 00:37:31,180 consciousness does not depend on the unity 915 00:37:31,180 --> 00:37:32,170 of the nervous system. 916 00:37:32,170 --> 00:37:34,550 And he volunteered for commissurotomy to cut the 917 00:37:34,550 --> 00:37:35,880 corpus callosum. 918 00:37:35,880 --> 00:37:39,790 Erickson noted in 1940 that epileptic seizures would 919 00:37:39,790 --> 00:37:43,640 become generalized convulsions often in animal models-- 920 00:37:43,640 --> 00:37:46,800 if the seizure began here, it would spread to the 921 00:37:46,800 --> 00:37:49,540 corresponding part of the opposite side of the brain, 922 00:37:49,540 --> 00:37:51,040 and become a much worse seizure. 923 00:37:51,040 --> 00:37:53,150 So they got the idea that if they cut the corpus callosum 924 00:37:53,150 --> 00:37:55,870 in patients with severe epilepsy who did not respond 925 00:37:55,870 --> 00:37:58,060 to medications that maybe that would make the 926 00:37:58,060 --> 00:37:59,700 seizures less severe. 927 00:37:59,700 --> 00:38:00,370 Does that make sense? 928 00:38:00,370 --> 00:38:02,460 Because you wouldn't transmit the seizure from the left to 929 00:38:02,460 --> 00:38:04,760 the right or the right to left. 930 00:38:04,760 --> 00:38:06,790 But people were sort of almost making jokes 931 00:38:06,790 --> 00:38:08,220 about the corpus callosum. 932 00:38:08,220 --> 00:38:09,770 Because they couldn't figure out what it does. 933 00:38:09,770 --> 00:38:11,300 They said, "The corpus callosum is hardly connected 934 00:38:11,300 --> 00:38:12,680 with the psychological functions at all. 935 00:38:12,680 --> 00:38:15,160 It is for transmitting seizure activity from one hemisphere 936 00:38:15,160 --> 00:38:19,070 to the other." That's kind of a neurology joke. 937 00:38:19,070 --> 00:38:21,170 Or Karl Lashley at Harvard, "to keep hemispheres from 938 00:38:21,170 --> 00:38:24,150 collapsing into one another." You do have to have structure 939 00:38:24,150 --> 00:38:25,780 to keep things from collapsing. 940 00:38:25,780 --> 00:38:28,570 So now I need to tell you a word for the next couple 941 00:38:28,570 --> 00:38:30,960 minutes for this to make sense, about how your visual 942 00:38:30,960 --> 00:38:33,030 system is organized. 943 00:38:33,030 --> 00:38:35,320 So here's the world out there. 944 00:38:35,320 --> 00:38:37,550 And if you're looking straight ahead, everything to the left 945 00:38:37,550 --> 00:38:39,650 people call the left visual field, everything to the right 946 00:38:39,650 --> 00:38:41,660 people call the right visual field. 947 00:38:41,660 --> 00:38:44,610 And we'll look at this more next week a little bit. 948 00:38:44,610 --> 00:38:47,190 But weirdly, your eyes are not set up in that way. 949 00:38:47,190 --> 00:38:49,690 You could think this eye looks at this half, and this eye 950 00:38:49,690 --> 00:38:50,710 looks at that half. 951 00:38:50,710 --> 00:38:55,200 The way it's set up, each eye looks at both fields. 952 00:38:55,200 --> 00:38:58,410 Each eye looks at both fields. 953 00:38:58,410 --> 00:39:02,860 And then the neurons that leave the eye get organized 954 00:39:02,860 --> 00:39:04,610 here in the optic chiasm. 955 00:39:04,610 --> 00:39:08,530 So by the time they move out towards the brain, everything 956 00:39:08,530 --> 00:39:10,830 in the opposite half of the world is reflected. 957 00:39:10,830 --> 00:39:14,090 So everything that's in the right visual field starts in 958 00:39:14,090 --> 00:39:15,940 your brain in the left hemisphere. 959 00:39:15,940 --> 00:39:18,510 Everything that's in the left visual field starts in your 960 00:39:18,510 --> 00:39:20,290 brain in the right hemisphere. 961 00:39:20,290 --> 00:39:21,660 Does that make sense? 962 00:39:21,660 --> 00:39:24,690 So the first part of your smart neocortex that knows 963 00:39:24,690 --> 00:39:27,210 what's out there as you're looking at a face, a word, a 964 00:39:27,210 --> 00:39:28,550 scene, anything-- 965 00:39:28,550 --> 00:39:31,540 the right occipital cortex notices what's on the left, 966 00:39:31,540 --> 00:39:34,410 and the left occipital cortex notices on the right. 967 00:39:34,410 --> 00:39:37,720 Things are so seamlessly integrated in the brain that 968 00:39:37,720 --> 00:39:39,230 you don't ever have that feeling. 969 00:39:39,230 --> 00:39:41,230 You almost never have like, we're getting bad signals on 970 00:39:41,230 --> 00:39:42,560 the left here. 971 00:39:42,560 --> 00:39:44,470 If you didn't have a course like this, you wouldn't know 972 00:39:44,470 --> 00:39:45,080 that exists. 973 00:39:45,080 --> 00:39:47,050 And you could wonder, why on Earth is it like that? 974 00:39:47,050 --> 00:39:50,230 Is it just to torture students and confuse them about fields, 975 00:39:50,230 --> 00:39:52,390 eyes, and brains? 976 00:39:52,390 --> 00:39:54,240 And people debate about some evolutionary 977 00:39:54,240 --> 00:39:55,020 history behind this. 978 00:39:55,020 --> 00:39:56,980 But it's a great big mystery-- 979 00:39:56,980 --> 00:39:59,660 why we don't organize things much more simply and just go 980 00:39:59,660 --> 00:40:01,020 all the way this way. 981 00:40:01,020 --> 00:40:01,700 Quite the opposite. 982 00:40:01,700 --> 00:40:05,130 We have in the left posterior areas, that's where we see the 983 00:40:05,130 --> 00:40:06,290 right half of the world. 984 00:40:06,290 --> 00:40:07,790 And then things get integrated. 985 00:40:07,790 --> 00:40:09,190 Is that OK? 986 00:40:09,190 --> 00:40:11,080 Keep in mind also that our left hemisphere moves our 987 00:40:11,080 --> 00:40:12,900 right hand, and our right hemisphere 988 00:40:12,900 --> 00:40:13,540 moves our left hand. 989 00:40:13,540 --> 00:40:15,550 So at least that's the same story-- 990 00:40:15,550 --> 00:40:19,170 opposite hemisphere seeing the opposite field, controlling 991 00:40:19,170 --> 00:40:21,030 the opposite hand. 992 00:40:21,030 --> 00:40:25,500 So imagine these kinds of patients who had the surgery 993 00:40:25,500 --> 00:40:28,720 that divided the corpus callosum or 994 00:40:28,720 --> 00:40:30,590 treatment of epilepsy. 995 00:40:30,590 --> 00:40:31,410 Let me tell you a couple things. 996 00:40:31,410 --> 00:40:34,030 Clinically, it was pretty rarely done. 997 00:40:34,030 --> 00:40:35,200 There weren't that many of them. 998 00:40:35,200 --> 00:40:37,960 It's pretty rarely done nowadays, first. 999 00:40:37,960 --> 00:40:41,210 Second, the first thing that people noticed was, it didn't 1000 00:40:41,210 --> 00:40:43,450 have much an effect on the patients. 1001 00:40:43,450 --> 00:40:44,750 It's a fascinating story. 1002 00:40:44,750 --> 00:40:48,890 Nobody noticed anything for decades. 1003 00:40:48,890 --> 00:40:51,790 Because they didn't have the right questions to ask. 1004 00:40:51,790 --> 00:40:55,320 So these patients are not like astounding patients, I can't 1005 00:40:55,320 --> 00:40:56,830 believe when I see them. 1006 00:40:56,830 --> 00:40:58,920 They seem pretty much like the same as they were. 1007 00:40:58,920 --> 00:41:02,300 I'll show you a video in a couple minutes of two of them. 1008 00:41:02,300 --> 00:41:05,230 They're not looking unusual in most ways. 1009 00:41:05,230 --> 00:41:07,990 But when people figured out what to ask of them, they saw 1010 00:41:07,990 --> 00:41:08,960 remarkable things. 1011 00:41:08,960 --> 00:41:12,980 They saw two minds in one head. 1012 00:41:12,980 --> 00:41:15,530 And here's how they saw that. 1013 00:41:15,530 --> 00:41:18,560 If they showed them a picture, let's say of a spoon and a 1014 00:41:18,560 --> 00:41:21,300 picture of a cup simultaneously in the two 1015 00:41:21,300 --> 00:41:23,440 fields, they would be up briefly and go. 1016 00:41:23,440 --> 00:41:27,400 But it's easy for you to say, I saw a spoon and I saw a cup. 1017 00:41:27,400 --> 00:41:29,340 They would say, what did you see? 1018 00:41:29,340 --> 00:41:32,240 And the person would say, a cup. 1019 00:41:32,240 --> 00:41:34,610 And that would be it. 1020 00:41:34,610 --> 00:41:35,300 What did you see? 1021 00:41:35,300 --> 00:41:35,710 A cup. 1022 00:41:35,710 --> 00:41:40,170 Because the information in the right visual field goes into 1023 00:41:40,170 --> 00:41:41,730 the left hemisphere. 1024 00:41:41,730 --> 00:41:43,560 That's the speaking hemisphere. 1025 00:41:43,560 --> 00:41:47,630 So left hemisphere says, I saw a cup. 1026 00:41:47,630 --> 00:41:50,780 The right hemisphere saw this perfectly well. 1027 00:41:50,780 --> 00:41:53,420 It's typically not the speaking hemisphere. 1028 00:41:53,420 --> 00:41:57,040 So that information is locked in the right hemisphere, and 1029 00:41:57,040 --> 00:41:59,710 it doesn't have access to the speaking part of the brain in 1030 00:41:59,710 --> 00:42:00,730 the left hemisphere. 1031 00:42:00,730 --> 00:42:03,670 So each hemisphere had its own experience, and only the left 1032 00:42:03,670 --> 00:42:05,150 hemisphere could speak. 1033 00:42:05,150 --> 00:42:08,260 You would integrate this information instantly via the 1034 00:42:08,260 --> 00:42:10,000 corpus callosum. 1035 00:42:10,000 --> 00:42:12,690 But each hemisphere only knew what it saw. 1036 00:42:12,690 --> 00:42:16,340 And so here's another example, which is not only that each 1037 00:42:16,340 --> 00:42:17,870 hemisphere only knows what it knows. 1038 00:42:17,870 --> 00:42:19,400 But it's completely ignorant that the 1039 00:42:19,400 --> 00:42:21,170 other one knows anything. 1040 00:42:21,170 --> 00:42:25,220 It's as if the two of you were sitting next to each other and 1041 00:42:25,220 --> 00:42:26,810 don't know each other, are not passing notes 1042 00:42:26,810 --> 00:42:29,790 or tweeting or whatever. 1043 00:42:29,790 --> 00:42:32,220 It's as if like, do you know exactly what the person next 1044 00:42:32,220 --> 00:42:33,450 to you is thinking? 1045 00:42:33,450 --> 00:42:35,260 No, not necessarily. 1046 00:42:35,260 --> 00:42:37,640 So that's exactly what it is like, like you're in one 1047 00:42:37,640 --> 00:42:39,560 person in their brain, in their skull. 1048 00:42:39,560 --> 00:42:42,270 So they would show them a square in the left visual 1049 00:42:42,270 --> 00:42:44,480 field and a triangle in the right visual field. 1050 00:42:44,480 --> 00:42:46,150 You would say, I saw a square, I saw a triangle. 1051 00:42:46,150 --> 00:42:47,710 What do you want? 1052 00:42:47,710 --> 00:42:48,780 Here's what happens. 1053 00:42:48,780 --> 00:42:51,880 If they're asked to say, say what did you see? 1054 00:42:51,880 --> 00:42:55,590 And then behind a board, draw what you saw. 1055 00:42:55,590 --> 00:42:58,970 The board is there so it's not confusing them. 1056 00:42:58,970 --> 00:42:59,660 So here's what they say. 1057 00:42:59,660 --> 00:43:00,180 What did you see? 1058 00:43:00,180 --> 00:43:01,090 I saw a triangle. 1059 00:43:01,090 --> 00:43:03,060 Because it's in the right field, it goes into their 1060 00:43:03,060 --> 00:43:04,800 visual area in the left hemisphere. 1061 00:43:04,800 --> 00:43:06,810 That's the speaking hemisphere. 1062 00:43:06,810 --> 00:43:08,930 But if they're drawing with their left hand, 1063 00:43:08,930 --> 00:43:11,190 what do they draw? 1064 00:43:11,190 --> 00:43:12,520 The square. 1065 00:43:12,520 --> 00:43:15,000 Because the right hemisphere saw a square, so the left hand 1066 00:43:15,000 --> 00:43:16,160 is drawing, it draws the square. 1067 00:43:16,160 --> 00:43:19,270 So simultaneously they will say, a triangle, and the hand 1068 00:43:19,270 --> 00:43:21,590 behind the board will draw a square. 1069 00:43:21,590 --> 00:43:25,280 And the patient is not bothered in the least. 1070 00:43:25,280 --> 00:43:27,950 Because each hemisphere only knows what it knows. 1071 00:43:27,950 --> 00:43:31,640 The reason they have the board there is if they didn't have 1072 00:43:31,640 --> 00:43:33,220 the board there, then the left hemisphere would see you 1073 00:43:33,220 --> 00:43:34,320 drawing a square. 1074 00:43:34,320 --> 00:43:35,800 And you go like, why am I drawing a square? 1075 00:43:35,800 --> 00:43:36,720 I saw a triangle. 1076 00:43:36,720 --> 00:43:37,940 And the person would be weirded out. 1077 00:43:37,940 --> 00:43:39,190 Does that make sense? 1078 00:43:42,010 --> 00:43:43,010 But here's the thing. 1079 00:43:43,010 --> 00:43:46,570 The amazing thing is both of them have a lot of smarts by 1080 00:43:46,570 --> 00:43:47,180 themselves. 1081 00:43:47,180 --> 00:43:49,120 And they're completely unaware of what the 1082 00:43:49,120 --> 00:43:50,620 other hemisphere knows. 1083 00:43:50,620 --> 00:43:52,960 Again, the idea is in you, the hemispheres are 1084 00:43:52,960 --> 00:43:53,710 talking all the time. 1085 00:43:53,710 --> 00:43:55,630 But at lots of moments, different parts of your brain 1086 00:43:55,630 --> 00:43:57,270 might be knowing different things. 1087 00:43:57,270 --> 00:43:58,680 And we have a lot of belief for that. 1088 00:43:58,680 --> 00:44:00,690 But this is the most striking demonstration. 1089 00:44:00,690 --> 00:44:04,230 So here's a patient who was asked to say what he saw and 1090 00:44:04,230 --> 00:44:05,156 pick it up. 1091 00:44:05,156 --> 00:44:06,980 He had one instruction. 1092 00:44:06,980 --> 00:44:10,640 Read what you see, and pick it up with your left hand. 1093 00:44:10,640 --> 00:44:12,280 So he sees the word ring. 1094 00:44:12,280 --> 00:44:14,620 In the speaking hemisphere, he says ring. 1095 00:44:14,620 --> 00:44:17,250 His left hemisphere sees the word key, has enough language 1096 00:44:17,250 --> 00:44:18,040 to read that. 1097 00:44:18,040 --> 00:44:20,925 And it picks up the key behind the board. 1098 00:44:20,925 --> 00:44:23,980 And it never says, I saw two things or anything like that 1099 00:44:23,980 --> 00:44:25,660 in most cases. 1100 00:44:25,660 --> 00:44:29,630 So let me stop here. 1101 00:44:29,630 --> 00:44:31,570 And can we do the first video? 1102 00:44:31,570 --> 00:44:33,970 So you're going to see an example of a patient named 1103 00:44:33,970 --> 00:44:37,760 Vicky who's going to be tested by Mike Gazzaniga. 1104 00:44:37,760 --> 00:44:39,890 You're going to see two videos with Mike Gazzaniga when he 1105 00:44:39,890 --> 00:44:40,720 was younger and when he was older. 1106 00:44:40,720 --> 00:44:42,870 He did a lot of the work with these split brain patients. 1107 00:44:42,870 --> 00:44:45,820 Plus, Alan Alda from MASH will visit Mike Gazzaniga in the 1108 00:44:45,820 --> 00:44:47,070 second one. 1109 00:44:58,600 --> 00:45:01,040 So one of the really interesting things is these 1110 00:45:01,040 --> 00:45:03,810 split brain patients have given us a chance to ask, you 1111 00:45:03,810 --> 00:45:07,000 and I, what are some different ways in which the right 1112 00:45:07,000 --> 00:45:09,395 hemisphere and left hemisphere are your own minds? 1113 00:45:09,395 --> 00:45:12,141 And what are the things they seem to care about, and that 1114 00:45:12,141 --> 00:45:13,300 are useful? 1115 00:45:13,300 --> 00:45:14,425 So here's one example from Jerre Levy. 1116 00:45:14,425 --> 00:45:16,250 It's a very clever experiment. 1117 00:45:16,250 --> 00:45:18,600 She would show in the left or right visual field 1118 00:45:18,600 --> 00:45:20,330 something like this. 1119 00:45:20,330 --> 00:45:24,060 And then say, in free view, which of these two things is 1120 00:45:24,060 --> 00:45:25,340 more similar? 1121 00:45:25,340 --> 00:45:28,630 And on purpose it's ambiguous. 1122 00:45:28,630 --> 00:45:30,850 On purpose you could say, well, this is more similar 1123 00:45:30,850 --> 00:45:33,630 because it has a similar shape or appearance. 1124 00:45:33,630 --> 00:45:36,600 This is more similar because I use a spoon and a fork to eat 1125 00:45:36,600 --> 00:45:38,470 a piece of cake. 1126 00:45:38,470 --> 00:45:42,390 And if this was seen by the left hemisphere, people would 1127 00:45:42,390 --> 00:45:44,450 pick by function. 1128 00:45:44,450 --> 00:45:47,440 If this was seen by the right hemisphere, the patients would 1129 00:45:47,440 --> 00:45:49,770 pick by appearance. 1130 00:45:49,770 --> 00:45:53,460 So the ideas is that the left-- and this is the power 1131 00:45:53,460 --> 00:45:56,590 of having two hemispheres in parallel figuring out what's 1132 00:45:56,590 --> 00:46:00,480 going on-- one is figuring out what's the information I need 1133 00:46:00,480 --> 00:46:02,930 about shape and things like that in the world? 1134 00:46:02,930 --> 00:46:05,160 And what's the information I need about function? 1135 00:46:05,160 --> 00:46:08,230 And because you have two semi-independent brains in 1136 00:46:08,230 --> 00:46:11,840 you, you're constantly figuring out form and function 1137 00:46:11,840 --> 00:46:14,430 and then using whatever you need to use to solve the 1138 00:46:14,430 --> 00:46:15,720 problem in front of you. 1139 00:46:15,720 --> 00:46:16,780 Does that make sense? 1140 00:46:16,780 --> 00:46:17,990 So here's another nice one. 1141 00:46:17,990 --> 00:46:21,390 Here's scissors projected into left visual field. 1142 00:46:21,390 --> 00:46:24,280 The right hemisphere, that would pick the 1143 00:46:24,280 --> 00:46:24,990 spoon and the fork. 1144 00:46:24,990 --> 00:46:27,940 Because the crossing shape is resembling that. 1145 00:46:27,940 --> 00:46:30,980 In the right visual field, left hemisphere, people would 1146 00:46:30,980 --> 00:46:32,360 pick the needle and thread. 1147 00:46:32,360 --> 00:46:34,090 Because that functionally goes with scissors. 1148 00:46:34,090 --> 00:46:37,740 So your mind is seeing the same thing, but in one case 1149 00:46:37,740 --> 00:46:40,570 it's tuned, in the left hemisphere, to functions, and 1150 00:46:40,570 --> 00:46:43,110 the right hemisphere to appearance. 1151 00:46:43,110 --> 00:46:46,050 So these are just notes for you going over what I said. 1152 00:46:46,050 --> 00:46:49,240 So they talked about, would you have two different 1153 00:46:49,240 --> 00:46:50,190 consciousnesses in you? 1154 00:46:50,190 --> 00:46:51,730 It's hard really to tell. 1155 00:46:51,730 --> 00:46:53,740 They did one experiment with Vicky, where they would 1156 00:46:53,740 --> 00:46:56,150 present a nude picture in the left visual field 1157 00:46:56,150 --> 00:46:56,836 unexpectedly-- 1158 00:46:56,836 --> 00:46:59,790 and this was a long time ago, it was a shocking thing. 1159 00:46:59,790 --> 00:47:01,920 And the patient would blush and giggle. 1160 00:47:01,920 --> 00:47:05,480 When asked to explain why you were blushing and giggling, 1161 00:47:05,480 --> 00:47:08,680 all she could say is, oh doctor, you have some machine. 1162 00:47:08,680 --> 00:47:10,780 She knows something funny happened and inappropriate. 1163 00:47:10,780 --> 00:47:13,270 She can't tell you just in the language in the hemisphere 1164 00:47:13,270 --> 00:47:13,820 that saw it. 1165 00:47:13,820 --> 00:47:16,120 And so she gives this other kind of description. 1166 00:47:16,120 --> 00:47:18,320 Another kind of a favorite one is the dresses one. 1167 00:47:18,320 --> 00:47:21,120 There was one patient who went back to work in his father's 1168 00:47:21,120 --> 00:47:21,870 grocery store. 1169 00:47:21,870 --> 00:47:25,430 And this could be frustrating, early on after his treatment. 1170 00:47:25,430 --> 00:47:28,300 He would stock things onto a shelf with one hand and remove 1171 00:47:28,300 --> 00:47:28,860 it with the other. 1172 00:47:28,860 --> 00:47:31,870 You could imagine that would be a slow work day. 1173 00:47:31,870 --> 00:47:34,630 These kinds of weird behaviors pretty much 1174 00:47:34,630 --> 00:47:36,240 clear up within weeks. 1175 00:47:36,240 --> 00:47:38,480 After that, you have to test to see the difference. 1176 00:47:38,480 --> 00:47:40,830 Another one, they presented the instructions -- walk 1177 00:47:40,830 --> 00:47:43,090 across the room to the left visual field, right 1178 00:47:43,090 --> 00:47:43,480 hemisphere. 1179 00:47:43,480 --> 00:47:45,600 Person gets up, walks across the room. 1180 00:47:45,600 --> 00:47:48,190 That person's asked, why did you walk across the room? 1181 00:47:48,190 --> 00:47:49,490 Person doesn't know why. 1182 00:47:49,490 --> 00:47:52,090 Because their speaking hemisphere didn't see it. 1183 00:47:52,090 --> 00:47:53,930 And they'll just say something like, I was thirsty. 1184 00:47:53,930 --> 00:47:56,260 So interestingly, they fill in motivations. 1185 00:47:56,260 --> 00:47:59,050 They don't say, I don't know why, or I have a split brain. 1186 00:47:59,050 --> 00:48:00,940 What do you expect? 1187 00:48:00,940 --> 00:48:03,080 I mean they're being tested for that, right? 1188 00:48:03,080 --> 00:48:05,290 But they seem like they want to fill in some other 1189 00:48:05,290 --> 00:48:05,770 explanation. 1190 00:48:05,770 --> 00:48:07,830 And I'll show you another example for that. 1191 00:48:07,830 --> 00:48:09,440 And social psychologists have said-- 1192 00:48:09,440 --> 00:48:10,810 because they like this-- 1193 00:48:10,810 --> 00:48:13,870 they said, this is an example that people are desperate 1194 00:48:13,870 --> 00:48:15,240 rationalizers for ourselves. 1195 00:48:15,240 --> 00:48:17,220 We'll come back to this in social psychology. 1196 00:48:17,220 --> 00:48:19,620 You could think about whether it's true for yourself or not. 1197 00:48:19,620 --> 00:48:22,360 That when things are contradictory, we don't say, 1198 00:48:22,360 --> 00:48:23,810 oh, things are contradictory. 1199 00:48:23,810 --> 00:48:28,240 We say, well, here's why, as we explain our own behavior, 1200 00:48:28,240 --> 00:48:31,370 that we have to rationalize our own behavior. 1201 00:48:31,370 --> 00:48:33,720 So here's the example. 1202 00:48:33,720 --> 00:48:34,650 Here's the picture. 1203 00:48:34,650 --> 00:48:36,830 So here's a split brain patient. 1204 00:48:36,830 --> 00:48:44,930 And he's shown pairs of pictures in visual fields. 1205 00:48:44,930 --> 00:48:46,900 And he's supposed to pick two of them in free vision, then 1206 00:48:46,900 --> 00:48:49,890 relate to what he sees. 1207 00:48:49,890 --> 00:48:51,010 Here's the picture that he sees. 1208 00:48:51,010 --> 00:48:53,490 Boom, this goes up and goes away. 1209 00:48:53,490 --> 00:48:57,180 Now both hands go and pick something related to what the 1210 00:48:57,180 --> 00:48:58,450 person just saw. 1211 00:48:58,450 --> 00:49:00,420 OK So this is shown briefly. 1212 00:49:00,420 --> 00:49:01,860 It disappears. 1213 00:49:01,860 --> 00:49:03,860 This hand-- 1214 00:49:03,860 --> 00:49:05,770 let me do this right-- 1215 00:49:05,770 --> 00:49:07,610 the chicken went to this part of the brain that 1216 00:49:07,610 --> 00:49:08,480 controls this hand. 1217 00:49:08,480 --> 00:49:12,130 So the claw goes to the rooster. 1218 00:49:12,130 --> 00:49:15,372 This hemisphere saw a snowy scene, controls this hand and 1219 00:49:15,372 --> 00:49:18,290 it goes for the shovel. 1220 00:49:18,290 --> 00:49:20,620 So now they're going to make the patient confront the 1221 00:49:20,620 --> 00:49:23,820 weirdness of what he just did. 1222 00:49:23,820 --> 00:49:24,780 His hand went out. 1223 00:49:24,780 --> 00:49:27,010 Each hemisphere points to what it saw. 1224 00:49:27,010 --> 00:49:29,480 And again, his answer could be, I'm in an experiment. 1225 00:49:29,480 --> 00:49:30,850 You're constantly tricking me. 1226 00:49:30,850 --> 00:49:31,720 I know that. 1227 00:49:31,720 --> 00:49:34,790 Basically they know that, they're in an experiment. 1228 00:49:34,790 --> 00:49:37,480 But his answer is, I saw a claw-- 1229 00:49:37,480 --> 00:49:38,780 that's the speaking hemisphere. 1230 00:49:38,780 --> 00:49:39,980 I picked the chicken. 1231 00:49:39,980 --> 00:49:43,880 OK, that's fine, left hemisphere is speaking. 1232 00:49:43,880 --> 00:49:45,050 And then you have to clean out the 1233 00:49:45,050 --> 00:49:46,820 chicken shed with a shovel. 1234 00:49:46,820 --> 00:49:48,210 OK You understand? 1235 00:49:48,210 --> 00:49:54,210 He's creating a story to make his behavior seem coherent. 1236 00:49:54,210 --> 00:49:56,890 Rather than just saying, I'm an experimental subject and 1237 00:49:56,890 --> 00:49:58,700 that's why you're testing me. 1238 00:49:58,700 --> 00:50:00,490 Here's the last thing I want to show you for two minutes. 1239 00:50:00,490 --> 00:50:02,630 And then I'm going to show you a film that touches on this. 1240 00:50:02,630 --> 00:50:05,740 Psychologists are interested in understanding also in what 1241 00:50:05,740 --> 00:50:08,460 way we see the forests and the trees. 1242 00:50:08,460 --> 00:50:12,230 You see the bumper stickers, think globally, act locally. 1243 00:50:12,230 --> 00:50:15,560 Let's talk about global and local, or parts and wholes. 1244 00:50:15,560 --> 00:50:19,510 So the whole here is H. And the locals are S. Does that 1245 00:50:19,510 --> 00:50:20,000 makes sense? 1246 00:50:20,000 --> 00:50:24,440 It's a way to operationalize an experiment looking at the 1247 00:50:24,440 --> 00:50:27,190 forest versus the trees of S's. 1248 00:50:27,190 --> 00:50:31,500 Here the whole is the C, and the local elements are O's. 1249 00:50:31,500 --> 00:50:34,290 And there's a painter who did beautiful pictures. 1250 00:50:34,290 --> 00:50:35,990 You'll see another example. 1251 00:50:35,990 --> 00:50:40,370 But he made whole faces out of vegetable parts. 1252 00:50:40,370 --> 00:50:41,760 OK, do you see that? 1253 00:50:41,760 --> 00:50:44,940 Every part here of this face, if you look at it piece by 1254 00:50:44,940 --> 00:50:49,540 piece, is a different vegetable or fruit. 1255 00:50:49,540 --> 00:50:51,770 So it's a sort of play on this thing, and you'll see the 1256 00:50:51,770 --> 00:50:52,400 movie that way. 1257 00:50:52,400 --> 00:50:54,980 He made the whole face of the parts of this. 1258 00:50:54,980 --> 00:50:57,360 But here's what split brain patients do. 1259 00:50:57,360 --> 00:50:58,810 And I'll show you something else in a moment. 1260 00:50:58,810 --> 00:51:02,280 They're asked shortly after surgery to copy this. 1261 00:51:02,280 --> 00:51:04,970 It's right in front of them all the time. 1262 00:51:04,970 --> 00:51:06,300 It's right in front of them all the time. 1263 00:51:06,300 --> 00:51:09,100 Just copy what's right in front of you. 1264 00:51:09,100 --> 00:51:12,190 If they do it with their left hand, right hemisphere, you 1265 00:51:12,190 --> 00:51:15,830 see that you get the forest but not the trees. 1266 00:51:15,830 --> 00:51:16,740 Here's the trees, and then they don't 1267 00:51:16,740 --> 00:51:18,710 look that good, honestly. 1268 00:51:18,710 --> 00:51:23,360 But still, there's some Y-ish thing there. 1269 00:51:23,360 --> 00:51:24,010 Copy this. 1270 00:51:24,010 --> 00:51:24,890 It's right in front of you. 1271 00:51:24,890 --> 00:51:27,870 If it's the left hand, you get the forest but not the parts. 1272 00:51:27,870 --> 00:51:29,620 If it's the right hand, you get the 1273 00:51:29,620 --> 00:51:31,050 parts but not the forest. 1274 00:51:31,050 --> 00:51:31,890 Does that make sense? 1275 00:51:31,890 --> 00:51:34,530 It's as if each hemisphere is one hemisphere-- the left 1276 00:51:34,530 --> 00:51:37,240 hemisphere is seeing the parts, and the right 1277 00:51:37,240 --> 00:51:38,830 hemisphere is seeing the whole. 1278 00:51:38,830 --> 00:51:39,660 So that's awesome. 1279 00:51:39,660 --> 00:51:41,850 Because you don't have to be global or local. 1280 00:51:41,850 --> 00:51:45,970 Your mind is simultaneously figuring out the local parts 1281 00:51:45,970 --> 00:51:47,270 and the global parts. 1282 00:51:47,270 --> 00:51:50,010 And then you can use whatever is the useful information. 1283 00:51:50,010 --> 00:51:53,870 Your mind, because you have multiple brains in you, is 1284 00:51:53,870 --> 00:51:55,790 sort of figuring out what it needs to do. 1285 00:51:55,790 --> 00:51:58,690 Last thing I'll show you, and then we'll do one more video. 1286 00:51:58,690 --> 00:52:03,370 Here are patients who have injuries after stroke. 1287 00:52:03,370 --> 00:52:04,670 It's the same idea, though. 1288 00:52:04,670 --> 00:52:06,390 So here's what they have to copy. 1289 00:52:06,390 --> 00:52:07,770 It's right in front of them. 1290 00:52:07,770 --> 00:52:08,960 Just copy it exactly. 1291 00:52:08,960 --> 00:52:10,350 That's all they have to do. 1292 00:52:10,350 --> 00:52:16,970 If the patient has damage on the right, he loses his sense 1293 00:52:16,970 --> 00:52:18,540 of wholeness. 1294 00:52:18,540 --> 00:52:21,890 You see there's lots of Z's, that's the parts perceived by 1295 00:52:21,890 --> 00:52:23,580 the intact left hemisphere. 1296 00:52:23,580 --> 00:52:25,400 But the right hemisphere is not giving very much 1297 00:52:25,400 --> 00:52:28,010 information about the whole. 1298 00:52:28,010 --> 00:52:30,540 Here's another patient with left hemisphere damage. 1299 00:52:30,540 --> 00:52:32,940 That person fails to appreciate the parts, 1300 00:52:32,940 --> 00:52:33,770 but gets the whole. 1301 00:52:33,770 --> 00:52:35,210 Here's the same thing down here. 1302 00:52:35,210 --> 00:52:37,990 A patient with right hemisphere damage appreciates 1303 00:52:37,990 --> 00:52:42,440 the parts in the intact left hemisphere, but doesn't 1304 00:52:42,440 --> 00:52:45,910 appreciate the whole in the injured right hemisphere. 1305 00:52:45,910 --> 00:52:48,680 Conversely, here's the injured left hemisphere. 1306 00:52:48,680 --> 00:52:50,110 That patient copies the whole. 1307 00:52:50,110 --> 00:52:51,900 The right hemisphere gets it, left hemisphere 1308 00:52:51,900 --> 00:52:54,820 is missing the parts. 1309 00:52:54,820 --> 00:52:55,820 The amazing thing? 1310 00:52:55,820 --> 00:52:57,220 It's right in front of them. 1311 00:52:57,220 --> 00:52:58,430 They're copying it. 1312 00:52:58,430 --> 00:53:02,820 But if your brain is injured, it no longer appreciates that 1313 00:53:02,820 --> 00:53:06,580 the whole exists or that a part exists. 1314 00:53:06,580 --> 00:53:08,880 It's as if it wasn't there. 1315 00:53:08,880 --> 00:53:10,720 So that's how much our mind is what our brain 1316 00:53:10,720 --> 00:53:12,030 does in this regard. 1317 00:53:12,030 --> 00:53:14,110 And so if we do the last video you'll see that again. 1318 00:53:25,288 --> 00:53:27,250 Any questions on what you saw? 1319 00:53:27,250 --> 00:53:29,860 So I would say neurons are unbelievably-- 1320 00:53:29,860 --> 00:53:31,730 we can't even begin to figure out your brain 1321 00:53:31,730 --> 00:53:32,560 at the neuron level. 1322 00:53:32,560 --> 00:53:34,740 We're so far from that. 1323 00:53:34,740 --> 00:53:37,410 The big message from this last part besides hemispheric 1324 00:53:37,410 --> 00:53:40,420 specialization is that your brain-- 1325 00:53:40,420 --> 00:53:41,660 and we'll show you this over and over 1326 00:53:41,660 --> 00:53:42,790 again in this course-- 1327 00:53:42,790 --> 00:53:46,840 is a society of semi-independent brains doing 1328 00:53:46,840 --> 00:53:50,500 their own thing, sharing information as needed. 1329 00:53:50,500 --> 00:53:53,400 And the more we study the brain, the more we understand 1330 00:53:53,400 --> 00:53:56,860 how many parts of you there are that are semi-independent 1331 00:53:56,860 --> 00:53:57,860 and autonomous. 1332 00:53:57,860 --> 00:53:59,110 Thanks.