1 00:00:00,825 --> 00:00:02,785 We see with the eyes, 2 00:00:02,809 --> 00:00:05,254 but we see with the brain as well. 3 00:00:06,000 --> 00:00:09,839 And seeing with the brain is often called imagination. 4 00:00:10,982 --> 00:00:15,165 And we are familiar with the landscapes of our own imagination, 5 00:00:15,189 --> 00:00:16,559 our inscapes. 6 00:00:16,583 --> 00:00:18,583 We've lived with them all our lives. 7 00:00:19,306 --> 00:00:22,799 But there are also hallucinations as well. 8 00:00:23,332 --> 00:00:25,976 And hallucinations are completely different. 9 00:00:26,000 --> 00:00:28,110 They don't seem to be of our creation. 10 00:00:28,134 --> 00:00:30,174 They don't seem to be under control. 11 00:00:30,198 --> 00:00:34,488 They seem to come from the outside and to mimic perception. 12 00:00:34,960 --> 00:00:39,031 So I am going to be talking about hallucinations 13 00:00:39,055 --> 00:00:42,166 and a particular sort of visual hallucination, 14 00:00:43,658 --> 00:00:46,705 which I see among my patients. 15 00:00:48,594 --> 00:00:54,006 A few months ago, I got a phone call from a nursing home where I work. 16 00:00:54,496 --> 00:00:59,229 They told me that one of their residents, an old lady in her 90s, 17 00:00:59,253 --> 00:01:00,743 was seeing things, 18 00:01:01,602 --> 00:01:04,288 and they wondered if she'd gone bonkers 19 00:01:04,312 --> 00:01:05,858 or, because she was an old lady, 20 00:01:05,882 --> 00:01:09,170 whether she'd had a stroke, or whether she had Alzheimer's. 21 00:01:09,194 --> 00:01:13,375 And so they asked me if I would come and see Rosalie, 22 00:01:14,478 --> 00:01:15,700 the old lady. 23 00:01:16,327 --> 00:01:17,976 I went in to see her. 24 00:01:18,358 --> 00:01:22,948 It was evident straightaway that she was perfectly sane 25 00:01:22,972 --> 00:01:26,764 and lucid and of good intelligence, 26 00:01:26,788 --> 00:01:30,153 but she'd been very startled and very bewildered, 27 00:01:30,177 --> 00:01:32,187 because she'd been seeing things. 28 00:01:33,672 --> 00:01:37,976 And she told me -- the nurses hadn't mentioned this -- 29 00:01:38,000 --> 00:01:40,276 that she was blind, 30 00:01:40,300 --> 00:01:45,121 that she had been completely blind from macular degeneration for five years. 31 00:01:45,145 --> 00:01:48,695 But now, for the last few days, she'd been seeing things. 32 00:01:48,719 --> 00:01:50,716 So I said, "What sort of things?" 33 00:01:50,740 --> 00:01:54,457 And she said, "People in Eastern dress, 34 00:01:54,481 --> 00:01:57,475 in drapes, walking up and down stairs. 35 00:01:58,290 --> 00:02:01,449 A man who turns towards me and smiles, 36 00:02:01,473 --> 00:02:04,812 but he has huge teeth on one side of his mouth. 37 00:02:05,510 --> 00:02:06,845 Animals too. 38 00:02:07,597 --> 00:02:10,605 I see a white building. It's snowing, a soft snow. 39 00:02:10,629 --> 00:02:14,614 I see this horse with a harness, dragging the snow away. 40 00:02:15,527 --> 00:02:18,802 Then, one night, the scene changes. 41 00:02:18,826 --> 00:02:21,380 I see cats and dogs walking towards me. 42 00:02:21,404 --> 00:02:24,038 They come to a certain point and then stop. 43 00:02:24,570 --> 00:02:26,133 Then it changes again. 44 00:02:26,157 --> 00:02:29,279 I see a lot of children. They're walking up and down stairs. 45 00:02:29,303 --> 00:02:32,240 They wear bright colors, rose and blue, 46 00:02:32,264 --> 00:02:33,854 like Eastern dress." 47 00:02:34,857 --> 00:02:38,434 Sometimes, she said, before the people come on, 48 00:02:38,458 --> 00:02:41,976 she may hallucinate pink and blue squares on the floor, 49 00:02:42,000 --> 00:02:43,888 which seem to go up to the ceiling. 50 00:02:44,856 --> 00:02:49,454 I said, "Is this like a dream?" 51 00:02:49,478 --> 00:02:52,837 And she said, "No, it's not like a dream. It's like a movie." 52 00:02:52,861 --> 00:02:55,500 She said, "It's got color. It's got motion. 53 00:02:55,524 --> 00:02:58,976 But it's completely silent, like a silent movie." 54 00:02:59,000 --> 00:03:01,254 And she said it's a rather boring movie. 55 00:03:01,278 --> 00:03:02,279 (Laughter) 56 00:03:02,303 --> 00:03:04,508 She said, "All these people with Eastern dress, 57 00:03:04,532 --> 00:03:08,526 walking up and down, very repetitive, very limited." 58 00:03:08,550 --> 00:03:09,952 (Laughter) 59 00:03:09,976 --> 00:03:12,747 And she had a sense of humor. 60 00:03:12,771 --> 00:03:16,073 She knew it was a hallucination, but she was frightened. 61 00:03:16,097 --> 00:03:17,461 She had lived 95 years, 62 00:03:17,485 --> 00:03:19,762 and she'd never had a hallucination before. 63 00:03:20,247 --> 00:03:25,303 She said that the hallucinations were unrelated to anything she was thinking 64 00:03:25,327 --> 00:03:27,921 or feeling or doing, 65 00:03:27,945 --> 00:03:31,712 that they seemed to come on by themselves, or disappear. 66 00:03:31,736 --> 00:03:33,936 She had no control over them. 67 00:03:33,960 --> 00:03:37,478 She said she didn't recognize any of the people or places 68 00:03:37,502 --> 00:03:39,248 in the hallucinations, 69 00:03:39,272 --> 00:03:41,521 and none of the people or the animals -- 70 00:03:41,545 --> 00:03:44,350 well, they all seemed oblivious of her. 71 00:03:45,223 --> 00:03:47,240 And she didn't know what was going on. 72 00:03:47,264 --> 00:03:51,196 She wondered if she was going mad or losing her mind. 73 00:03:51,220 --> 00:03:53,729 Well, I examined her carefully. 74 00:03:53,753 --> 00:03:56,142 She was a bright old lady, 75 00:03:56,166 --> 00:03:57,507 perfectly sane. 76 00:03:57,531 --> 00:03:59,441 She had no medical problems. 77 00:03:59,465 --> 00:04:03,061 She wasn't on any medications which could produce hallucinations. 78 00:04:03,085 --> 00:04:04,566 But she was blind. 79 00:04:05,657 --> 00:04:09,460 And I then said to her, "I think I know what you have." 80 00:04:09,484 --> 00:04:13,101 I said, "There is a special form of visual hallucination 81 00:04:13,125 --> 00:04:17,077 which may go with deteriorating vision or blindness. 82 00:04:17,640 --> 00:04:19,857 This was originally described," I said, 83 00:04:19,881 --> 00:04:22,103 "right back in the 18th century, 84 00:04:22,127 --> 00:04:25,082 by a man called Charles Bonnet. 85 00:04:25,106 --> 00:04:27,953 And you have Charles Bonnet syndrome. 86 00:04:27,977 --> 00:04:31,637 There's nothing wrong with your brain. There's nothing wrong with your mind. 87 00:04:31,661 --> 00:04:33,493 You have Charles Bonnet syndrome." 88 00:04:33,517 --> 00:04:36,342 And she was very relieved at this, 89 00:04:36,366 --> 00:04:39,112 that there was nothing seriously the matter, 90 00:04:39,136 --> 00:04:42,603 and also rather curious. 91 00:04:42,627 --> 00:04:45,610 She said, "Who is this Charles Bonnet?" 92 00:04:45,634 --> 00:04:47,607 She said, "Did he have them himself?" 93 00:04:48,107 --> 00:04:53,579 And she said, "Tell all the nurses that I have Charles Bonnet syndrome." 94 00:04:53,603 --> 00:04:55,103 (Laughter) 95 00:04:55,127 --> 00:04:59,164 "I'm not crazy. I'm not demented. I have Charles Bonnet syndrome." 96 00:05:00,000 --> 00:05:02,101 Well, so, I did tell the nurses. 97 00:05:02,125 --> 00:05:04,976 Now this, for me, is a common situation. 98 00:05:05,000 --> 00:05:07,746 I work in old-age homes, largely. 99 00:05:07,770 --> 00:05:09,937 I see a lot of elderly people 100 00:05:09,961 --> 00:05:12,918 who are hearing-impaired or visually impaired. 101 00:05:12,942 --> 00:05:15,594 About 10 percent of the hearing-impaired people 102 00:05:15,618 --> 00:05:18,188 get musical hallucinations. 103 00:05:18,212 --> 00:05:21,193 And about 10 percent of the visually impaired people 104 00:05:21,217 --> 00:05:23,114 get visual hallucinations. 105 00:05:23,138 --> 00:05:25,399 You don't have to be completely blind, 106 00:05:25,423 --> 00:05:27,693 only sufficiently impaired. 107 00:05:27,717 --> 00:05:31,604 Now, with the original description in the 18th century, 108 00:05:31,628 --> 00:05:33,443 Charles Bonnet did not have them. 109 00:05:33,467 --> 00:05:36,209 His grandfather had these hallucinations. 110 00:05:36,233 --> 00:05:39,573 His grandfather was a magistrate, an elderly man. 111 00:05:39,597 --> 00:05:41,830 He'd had cataract surgery. 112 00:05:41,854 --> 00:05:44,105 His vision was pretty poor. 113 00:05:44,129 --> 00:05:49,294 And in 1759, he described to his grandson 114 00:05:49,318 --> 00:05:51,635 various things he was seeing. 115 00:05:51,659 --> 00:05:55,107 The first thing he said was he saw a handkerchief in midair. 116 00:05:55,131 --> 00:05:58,976 It was a large blue handkerchief with four orange circles. 117 00:05:59,456 --> 00:06:01,827 And he knew it was a hallucination. 118 00:06:01,851 --> 00:06:04,214 You don't have handkerchiefs in midair. 119 00:06:04,238 --> 00:06:07,525 And then he saw a big wheel in midair. 120 00:06:08,327 --> 00:06:13,277 But sometimes he wasn't sure whether he was hallucinating or not, 121 00:06:13,301 --> 00:06:16,976 because the hallucinations would fit in the context of the visions. 122 00:06:17,000 --> 00:06:20,821 So on one occasion, when his granddaughters were visiting them, 123 00:06:20,845 --> 00:06:23,988 he said, "And who are these handsome young men with you?" 124 00:06:24,012 --> 00:06:25,027 (Laughter) 125 00:06:25,051 --> 00:06:29,685 And they said, "Alas, Grandpapa, there are no handsome young men." 126 00:06:29,709 --> 00:06:32,102 And then the handsome young men disappeared. 127 00:06:33,459 --> 00:06:35,976 It's typical of these hallucinations 128 00:06:36,000 --> 00:06:38,976 that they may come in a flash and disappear in a flash. 129 00:06:39,000 --> 00:06:41,568 They don't usually fade in and out. 130 00:06:41,592 --> 00:06:44,935 They are rather sudden, and they change suddenly. 131 00:06:44,959 --> 00:06:46,976 Charles Lullin, the grandfather, 132 00:06:47,000 --> 00:06:49,976 saw hundreds of different figures, 133 00:06:50,000 --> 00:06:52,611 different landscapes of all sorts. 134 00:06:52,635 --> 00:06:56,448 On one occasion, he saw a man in a bathrobe smoking a pipe, 135 00:06:56,472 --> 00:06:58,544 and realized it was himself. 136 00:06:59,306 --> 00:07:01,976 That was the only figure he recognized. 137 00:07:02,694 --> 00:07:05,976 On one occasion, when he was walking in the streets of Paris, 138 00:07:06,000 --> 00:07:09,039 he saw -- this was real -- a scaffolding. 139 00:07:09,063 --> 00:07:12,577 But when he got back home, he saw a miniature of the scaffolding, 140 00:07:12,601 --> 00:07:14,327 six inches high, 141 00:07:14,351 --> 00:07:16,119 on his study table. 142 00:07:16,143 --> 00:07:20,975 This repetition of perception is sometimes called "palinopsia." 143 00:07:22,445 --> 00:07:26,372 With him and with Rosalie, 144 00:07:26,396 --> 00:07:27,976 what seems to be going on -- 145 00:07:28,000 --> 00:07:30,148 and Rosalie said, "What's going on?" -- 146 00:07:30,172 --> 00:07:32,976 and I said that as you lose vision, 147 00:07:33,000 --> 00:07:36,048 as the visual parts of the brain are no longer getting any input, 148 00:07:36,072 --> 00:07:39,154 they become hyperactive and excitable, 149 00:07:39,178 --> 00:07:41,879 and they start to fire spontaneously. 150 00:07:41,903 --> 00:07:44,053 And you start to see things. 151 00:07:44,077 --> 00:07:48,607 The things you see can be very complicated indeed. 152 00:07:48,631 --> 00:07:53,681 With another patient of mine who also had some vision, 153 00:07:54,829 --> 00:07:57,365 the visions she had could be disturbing. 154 00:07:57,389 --> 00:08:02,976 On one occasion, she said she saw a man in a striped shirt in a restaurant. 155 00:08:03,000 --> 00:08:04,296 And he turned round, 156 00:08:04,320 --> 00:08:08,423 and then he divided into six figures in striped shirts, 157 00:08:08,447 --> 00:08:10,857 who started walking towards her. 158 00:08:10,881 --> 00:08:14,290 And then the six figures came together, like a concertina. 159 00:08:14,314 --> 00:08:16,036 Once, when she was driving, 160 00:08:16,060 --> 00:08:17,976 or rather, her husband was driving, 161 00:08:18,000 --> 00:08:20,292 the road divided into four 162 00:08:20,316 --> 00:08:24,192 and she felt herself going simultaneously up four roads. 163 00:08:24,859 --> 00:08:29,650 She had very mobile hallucinations as well. 164 00:08:29,674 --> 00:08:31,844 A lot of them had to do with a car. 165 00:08:31,868 --> 00:08:36,698 Sometimes she would see a teenage boy sitting on the hood of the car. 166 00:08:36,722 --> 00:08:38,219 He was very tenacious, 167 00:08:38,243 --> 00:08:41,543 and he moved rather gracefully when the car turned. 168 00:08:41,567 --> 00:08:43,976 And then when they came to a stop, 169 00:08:44,000 --> 00:08:47,537 the boy would do a sudden vertical takeoff, 100 foot in the air, 170 00:08:47,561 --> 00:08:48,973 and then disappear. 171 00:08:50,377 --> 00:08:54,976 Another patient of mine had a different sort of hallucination. 172 00:08:55,000 --> 00:08:57,887 This was a woman who didn't have trouble with her eyes 173 00:08:57,911 --> 00:08:59,976 but the visual parts of her brain, 174 00:09:00,000 --> 00:09:03,658 a little tumor in the occipital cortex. 175 00:09:03,682 --> 00:09:07,463 And, above all, she would see cartoons. 176 00:09:08,288 --> 00:09:12,795 And these cartoons would be transparent, 177 00:09:12,819 --> 00:09:16,782 and would cover half the visual field, like a screen. 178 00:09:16,806 --> 00:09:21,585 And especially, she saw cartoons of Kermit the Frog. 179 00:09:21,609 --> 00:09:23,061 (Laughter) 180 00:09:23,085 --> 00:09:27,791 Now, I don't watch Sesame Street, 181 00:09:27,815 --> 00:09:29,586 but she made a point of saying, 182 00:09:29,610 --> 00:09:32,976 "Why Kermit?" she said, "Kermit the Frog means nothing to me." 183 00:09:33,000 --> 00:09:38,111 You know, I was wondering about Freudian determinants: Why Kermit? 184 00:09:38,135 --> 00:09:40,500 "Kermit the Frog means nothing to me." 185 00:09:40,524 --> 00:09:42,706 She didn't mind the cartoons too much. 186 00:09:42,730 --> 00:09:44,318 But what did disturb her 187 00:09:44,342 --> 00:09:48,912 was she got very persistent images or hallucinations of faces, 188 00:09:48,936 --> 00:09:52,423 and as with Rosalie, the faces were often deformed, 189 00:09:52,447 --> 00:09:55,585 with very large teeth or very large eyes. 190 00:09:56,000 --> 00:09:58,254 And these frightened her. 191 00:09:59,262 --> 00:10:03,040 Well, what is going on with these people? 192 00:10:03,064 --> 00:10:06,678 As a physician, I have to try and define what's going on 193 00:10:06,702 --> 00:10:08,408 and to reassure people, 194 00:10:08,432 --> 00:10:11,976 especially to reassure them that they're not going insane. 195 00:10:13,019 --> 00:10:15,244 Something like 10 percent, as I said, 196 00:10:15,268 --> 00:10:18,221 of visually impaired people get these. 197 00:10:18,245 --> 00:10:21,976 But no more than one percent of the people acknowledge them, 198 00:10:22,000 --> 00:10:25,356 because they are afraid they will be seen as insane or something. 199 00:10:25,380 --> 00:10:27,828 And if they do mention them to their own doctors, 200 00:10:27,852 --> 00:10:29,707 they may be misdiagnosed. 201 00:10:30,080 --> 00:10:33,596 In particular, the notion is that if you see things or hear things, 202 00:10:33,620 --> 00:10:34,846 you're going mad. 203 00:10:34,870 --> 00:10:37,895 But the psychotic hallucinations are quite different. 204 00:10:37,919 --> 00:10:41,118 Psychotic hallucinations, whether they are visual or vocal, 205 00:10:41,142 --> 00:10:42,318 they address you. 206 00:10:42,342 --> 00:10:47,052 They accuse you, they seduce you, they humiliate you, they jeer at you. 207 00:10:48,072 --> 00:10:49,657 You interact with them. 208 00:10:50,643 --> 00:10:53,614 There is none of this quality of being addressed 209 00:10:53,638 --> 00:10:56,099 with these Charles Bonnet hallucinations. 210 00:10:56,123 --> 00:11:00,726 There is a film. You're seeing a film which has nothing to do with you -- 211 00:11:00,750 --> 00:11:03,292 or that's how people think about it. 212 00:11:03,728 --> 00:11:07,537 There is also a rare thing called temporal lobe epilepsy, 213 00:11:07,561 --> 00:11:09,976 and sometimes, if one has this, 214 00:11:10,000 --> 00:11:15,025 one may feel oneself transported back to a time and place in the past. 215 00:11:15,049 --> 00:11:17,518 You're at a particular road junction. 216 00:11:17,542 --> 00:11:19,569 You smell chestnuts roasting. 217 00:11:19,593 --> 00:11:22,839 You hear the traffic. All the senses are involved. 218 00:11:22,863 --> 00:11:24,573 And you're waiting for your girl. 219 00:11:24,597 --> 00:11:28,786 And it's that Tuesday evening back in 1982. 220 00:11:28,810 --> 00:11:32,708 The temporal lobe hallucinations are all sense hallucinations, 221 00:11:32,732 --> 00:11:35,269 full of feeling, full of familiarity, 222 00:11:35,293 --> 00:11:37,360 located in space and time, 223 00:11:37,384 --> 00:11:39,088 coherent, dramatic. 224 00:11:39,722 --> 00:11:41,976 The Charles Bonnet ones are quite different. 225 00:11:42,516 --> 00:11:47,847 In the Charles Bonnet hallucinations, you have all sorts of levels, 226 00:11:47,871 --> 00:11:49,976 from the geometrical hallucinations -- 227 00:11:50,000 --> 00:11:53,264 the pink and blue squares the woman had -- 228 00:11:53,288 --> 00:11:57,735 up to quite elaborate hallucinations 229 00:11:57,759 --> 00:12:00,440 with figures and especially faces. 230 00:12:00,464 --> 00:12:03,576 Faces, and sometimes deformed faces, 231 00:12:03,600 --> 00:12:08,038 are the single commonest thing in these hallucinations. 232 00:12:08,062 --> 00:12:10,976 And one of the second commonest is cartoons. 233 00:12:11,404 --> 00:12:14,240 So, what is going on? 234 00:12:14,264 --> 00:12:16,255 Fascinatingly, in the last few years, 235 00:12:16,279 --> 00:12:20,198 it's been possible to do functional brain imagery, 236 00:12:20,222 --> 00:12:24,975 to do fMRI on people as they are hallucinating, 237 00:12:24,999 --> 00:12:31,164 and, in fact, to find that different parts of the visual brain are activated 238 00:12:31,188 --> 00:12:33,024 as they are hallucinating. 239 00:12:33,048 --> 00:12:36,398 When people have these simple, geometrical hallucinations, 240 00:12:36,422 --> 00:12:39,976 the primary visual cortex is activated. 241 00:12:40,000 --> 00:12:43,736 This is the part of the brain which perceives edges and patterns. 242 00:12:43,760 --> 00:12:47,768 You don't form images with your primary visual cortex. 243 00:12:47,792 --> 00:12:50,114 When images are formed, 244 00:12:50,138 --> 00:12:55,725 a higher part of the visual cortex is involved, in the temporal lobe. 245 00:12:55,749 --> 00:12:58,818 And in particular, one area of the temporal lobe 246 00:12:58,842 --> 00:13:01,691 is called the fusiform gyrus. 247 00:13:01,715 --> 00:13:05,362 And it's known that if people have damage in the fusiform gyrus, 248 00:13:05,386 --> 00:13:08,795 they may lose the ability to recognize faces. 249 00:13:09,533 --> 00:13:13,105 But if there's an abnormal activity in the fusiform gyrus, 250 00:13:13,129 --> 00:13:15,287 they may hallucinate faces, 251 00:13:15,311 --> 00:13:18,513 and this is exactly what you find in some of these people. 252 00:13:18,537 --> 00:13:22,720 There is an area in the anterior part of this gyrus 253 00:13:22,744 --> 00:13:26,976 where teeth and eyes are represented, 254 00:13:27,000 --> 00:13:30,612 and that part of the gyrus is activated 255 00:13:30,636 --> 00:13:34,405 when people get the deformed hallucinations. 256 00:13:34,429 --> 00:13:38,226 There is another part of the brain which is especially activated 257 00:13:38,250 --> 00:13:40,226 when one sees cartoons. 258 00:13:40,713 --> 00:13:43,598 It's activated when one recognizes cartoons, 259 00:13:43,622 --> 00:13:46,852 when one draws cartoons and when one hallucinates them. 260 00:13:46,876 --> 00:13:50,132 It's very interesting that that should be specific. 261 00:13:50,156 --> 00:13:53,284 There are other parts of the brain which are specifically involved 262 00:13:53,308 --> 00:13:57,795 with the recognition and hallucination of buildings and landscapes. 263 00:13:57,819 --> 00:14:01,757 Around 1970, it was found that there were not only parts of the brain, 264 00:14:01,781 --> 00:14:03,661 but particular cells. 265 00:14:03,685 --> 00:14:07,869 "Face cells" were discovered around 1970. 266 00:14:07,893 --> 00:14:11,979 And now we know that there are hundreds of other sorts of cells, 267 00:14:12,003 --> 00:14:14,257 which can be very, very specific. 268 00:14:14,281 --> 00:14:21,253 So you may not only have "car" cells, you may have "Aston Martin" cells. 269 00:14:21,277 --> 00:14:23,551 (Laughter) 270 00:14:23,575 --> 00:14:26,797 I saw an Aston Martin this morning. I had to bring it in. 271 00:14:26,821 --> 00:14:27,844 (Laughter) 272 00:14:27,868 --> 00:14:30,684 And now it's in there, somewhere. 273 00:14:30,708 --> 00:14:31,866 So -- 274 00:14:31,890 --> 00:14:33,354 (Laughter) 275 00:14:33,378 --> 00:14:38,107 now, at this level, in what's called the inferotemporal cortex, 276 00:14:38,131 --> 00:14:40,417 there are only visual images, 277 00:14:40,441 --> 00:14:43,013 or figments or fragments. 278 00:14:43,037 --> 00:14:48,074 It's only at higher levels that the other senses join in 279 00:14:48,098 --> 00:14:51,023 and there are connections with memory and emotion. 280 00:14:51,047 --> 00:14:52,748 And in the Charles Bonnet syndrome, 281 00:14:52,772 --> 00:14:54,987 you don't go to those higher levels. 282 00:14:55,011 --> 00:14:58,022 You're in these levels of inferior visual cortex, 283 00:14:58,046 --> 00:15:00,722 where you have thousands and tens of thousands 284 00:15:00,746 --> 00:15:03,063 and millions of images, 285 00:15:03,087 --> 00:15:05,493 or figments or fragmentary figments, 286 00:15:05,517 --> 00:15:11,314 all neurally encoded in particular cells or small clusters of cells. 287 00:15:11,687 --> 00:15:17,076 Normally, these are all part of the integrated stream of perception, 288 00:15:17,100 --> 00:15:18,773 or imagination, 289 00:15:18,797 --> 00:15:20,835 and one is not conscious of them. 290 00:15:20,859 --> 00:15:24,934 It is only if one is visually impaired or blind 291 00:15:24,958 --> 00:15:27,528 that the process is interrupted. 292 00:15:27,552 --> 00:15:30,025 And instead of getting normal perception, 293 00:15:30,049 --> 00:15:32,588 you're getting an anarchic, 294 00:15:32,612 --> 00:15:35,601 convulsive stimulation, or release, 295 00:15:35,625 --> 00:15:39,492 of all of these visual cells in the inferotemporal cortex. 296 00:15:39,516 --> 00:15:42,305 So, suddenly, you see a face. Suddenly, you see a car. 297 00:15:42,329 --> 00:15:45,043 Suddenly this and suddenly that. 298 00:15:45,067 --> 00:15:47,440 The mind does its best to organize 299 00:15:47,464 --> 00:15:50,142 and to give some sort of coherence to this, 300 00:15:50,166 --> 00:15:52,705 but not terribly successfully. 301 00:15:52,729 --> 00:15:54,377 When these were first described, 302 00:15:54,401 --> 00:15:57,966 it was thought that they could be interpreted like dreams. 303 00:15:57,990 --> 00:15:59,816 But, in fact, people say, 304 00:15:59,840 --> 00:16:04,252 "I don't recognize the people. I can't form any associations. 305 00:16:04,276 --> 00:16:06,226 Kermit means nothing to me." 306 00:16:06,250 --> 00:16:11,901 You don't get anywhere, thinking of them as dreams. 307 00:16:11,925 --> 00:16:16,226 Well, I've more or less said what I wanted. 308 00:16:16,250 --> 00:16:21,164 I think I just want to recapitulate and say this is common. 309 00:16:21,188 --> 00:16:22,967 Think of the number of blind people. 310 00:16:22,991 --> 00:16:25,582 There must be hundreds of thousands of blind people 311 00:16:25,606 --> 00:16:27,320 who have these hallucinations 312 00:16:27,344 --> 00:16:29,465 but are too scared to mention them. 313 00:16:29,489 --> 00:16:34,977 So this sort of thing needs to be brought into notice, 314 00:16:35,001 --> 00:16:37,432 for patients, for doctors, for the public. 315 00:16:37,813 --> 00:16:42,839 Finally, I think they are infinitely interesting and valuable, 316 00:16:42,863 --> 00:16:47,137 for giving one some insight as to how the brain works. 317 00:16:47,161 --> 00:16:50,758 Charles Bonnet said, 250 years ago -- 318 00:16:50,782 --> 00:16:54,226 he wondered how, thinking of these hallucinations, 319 00:16:54,250 --> 00:16:56,930 how, as he put it, the theater of the mind 320 00:16:56,954 --> 00:17:00,304 could be generated by the machinery of the brain. 321 00:17:00,804 --> 00:17:03,226 Now, 250 years later, 322 00:17:03,250 --> 00:17:06,536 I think we're beginning to glimpse how this is done. 323 00:17:06,560 --> 00:17:07,760 Thanks very much. 324 00:17:07,784 --> 00:17:10,761 (Applause) 325 00:17:10,785 --> 00:17:13,762 Chris Anderson: That was superb. Thank you so much. 326 00:17:13,786 --> 00:17:16,756 You speak about these things with so much insight 327 00:17:16,780 --> 00:17:19,231 and empathy for your patients. 328 00:17:19,623 --> 00:17:23,443 Have you yourself experienced any of the syndromes you write about? 329 00:17:23,467 --> 00:17:25,684 Oliver Sacks: I was afraid you would ask that. 330 00:17:25,708 --> 00:17:27,536 (Laughter) 331 00:17:27,560 --> 00:17:29,928 Well, yeah, a lot of them. 332 00:17:29,952 --> 00:17:33,019 And, actually, I'm a little visually impaired myself. 333 00:17:33,043 --> 00:17:36,226 I'm blind in one eye and not terribly good in the other. 334 00:17:36,250 --> 00:17:40,300 And I see the geometrical hallucinations. 335 00:17:40,324 --> 00:17:41,797 But they stop there. 336 00:17:41,821 --> 00:17:43,714 CA: And they don't disturb you? 337 00:17:43,738 --> 00:17:46,977 Because you understand what's doing it, it doesn't make you worried? 338 00:17:47,001 --> 00:17:50,226 OS: Well, they don't disturb me any more than my tinnitus, 339 00:17:50,250 --> 00:17:53,355 which I ignore. 340 00:17:53,379 --> 00:17:55,067 They occasionally interest me, 341 00:17:55,091 --> 00:17:58,000 and I have many pictures of them in my notebooks. 342 00:17:58,024 --> 00:18:00,876 I've gone and had an fMRI myself, 343 00:18:00,900 --> 00:18:03,955 to see how my visual cortex is ticking over. 344 00:18:03,979 --> 00:18:08,133 And when I see all these hexagons 345 00:18:08,157 --> 00:18:10,226 and complex things, which I also have, 346 00:18:10,250 --> 00:18:12,013 in visual migraine, 347 00:18:12,037 --> 00:18:14,489 I wonder whether everyone sees things like this 348 00:18:14,513 --> 00:18:17,463 and whether things like cave art or ornamental art 349 00:18:17,487 --> 00:18:19,561 may have been derived from them a bit. 350 00:18:20,059 --> 00:18:22,481 CA: That was an utterly, utterly fascinating talk. 351 00:18:22,505 --> 00:18:24,317 Thank you so much for sharing. 352 00:18:24,341 --> 00:18:25,921 OS: Thank you. Thank you. 353 00:18:25,945 --> 00:18:27,833 (Applause)