WEBVTT - Ep11 "What does dreaming have to do with the rotation of the planet?" 0:00:05.040 --> 0:00:08.239 What do your nightly dreams have to do with the 0:00:08.360 --> 0:00:12.680 rotation of the planet. Why are so many musicians blind? 0:00:13.080 --> 0:00:16.160 Can blind people learn how to echolocate like a bat? 0:00:16.480 --> 0:00:19.759 Once we find alien life on other planets, should we 0:00:19.800 --> 0:00:27.040 expect that aliens have dreams at night? Welcome to Inner 0:00:27.120 --> 0:00:32.000 Cosmos with me, David Eagleman. I'm a neuroscientist and an 0:00:32.040 --> 0:00:36.600 author at Stanford University, and I've spent my whole career 0:00:37.040 --> 0:00:41.880 studying the intersection between how the brain works and how 0:00:41.960 --> 0:00:52.920 we experience life. I sort of personally have a love 0:00:52.960 --> 0:00:58.000 hate relationship with dreaming because we take it so seriously. 0:00:58.120 --> 0:01:01.639 We find ourselves in some biziz situation that doesn't make 0:01:01.680 --> 0:01:06.240 any sense, but while you are there, you buy it, 0:01:06.360 --> 0:01:11.200 hook line and sinker. You are emotionally tossed around and 0:01:11.840 --> 0:01:16.160 buffeted in the winds of situations that the moment after 0:01:16.200 --> 0:01:20.040 you wake up you realize weren't real, and more importantly, 0:01:20.360 --> 0:01:23.640 they typically make no sense at all. So why were 0:01:23.640 --> 0:01:27.520 you so caught up in that situation? I've always called 0:01:27.640 --> 0:01:31.160 dreaming sticking my head in the night blender, by which 0:01:31.240 --> 0:01:34.679 I simply mean that I don't necessarily look forward to 0:01:34.720 --> 0:01:36.760 it because I don't know where it's going to take me, 0:01:37.120 --> 0:01:40.280 and I generally feel that all that emotional energy I 0:01:40.319 --> 0:01:44.280 expend isn't that useful. But whatever your take on dreaming is, 0:01:44.920 --> 0:01:50.080 it's one of those absolutely insanely bizarre facts about our 0:01:50.160 --> 0:01:55.200 existence that we totally take for granted. You wake up 0:01:55.360 --> 0:01:58.280 and you say, oh, wow, I was just having a 0:01:58.400 --> 0:02:01.920 dance party with a pack of why monkeys. Or I 0:02:02.000 --> 0:02:03.960 was just at work where I forgot to put on 0:02:04.120 --> 0:02:06.240 pants and I was trying to hide behind my desk. 0:02:06.440 --> 0:02:09.800 Or I was on a river cruise and begging a 0:02:09.840 --> 0:02:11.960 person not to break up with me even though we're 0:02:11.960 --> 0:02:17.080 not even dating. And I find this absolutely stunning that 0:02:17.160 --> 0:02:21.239 it doesn't even bother us that we've just transitioned from 0:02:21.280 --> 0:02:25.079 one reality to another, Like in one second, you went 0:02:25.120 --> 0:02:29.320 from being in some bizarre situation to lying horizontal in 0:02:29.360 --> 0:02:32.400 your bed, and we're so used to it that we 0:02:32.560 --> 0:02:36.160 just say, oh, that was interesting. I just dreamed that 0:02:36.240 --> 0:02:38.840 I was on a hang glider riding over Istanbul and 0:02:38.880 --> 0:02:41.080 I was trying to figure out how not to crash 0:02:41.120 --> 0:02:43.800 because there were a lot of pigeons swirling around me. 0:02:44.240 --> 0:02:47.200 And if there's somebody there, then maybe we tell them. 0:02:47.080 --> 0:02:50.520 Our dream and Otherwise, we just get up and we 0:02:50.639 --> 0:02:53.600 brush our teeth and go about our day without even 0:02:53.680 --> 0:02:57.639 giving a second thought about what just happened. We were 0:02:57.760 --> 0:03:01.560 in one reality and totally emotional invested in it, and 0:03:01.600 --> 0:03:04.400 then a moment later we said, hmm, I guess I'm 0:03:04.400 --> 0:03:07.799 in this other reality now. Now this is a testament 0:03:08.200 --> 0:03:13.480 to the human mind's ability to accept the absolutely amazing 0:03:13.560 --> 0:03:17.119 and bizarre as something not even worth investigating. 0:03:17.360 --> 0:03:18.320 Think about it this way. 0:03:18.520 --> 0:03:21.840 Just imagine if dreams happened right in the middle of 0:03:21.880 --> 0:03:24.760 your day. So you're on a walk, or you're sitting 0:03:24.760 --> 0:03:27.320 at your desk or eating at a restaurant with friends, 0:03:27.760 --> 0:03:33.680 and suddenly your reality morphs to a completely bizarre other reality, 0:03:34.200 --> 0:03:37.320 and now you're on a street you've never seen before, 0:03:37.920 --> 0:03:41.480 or you're flying, or you're falling from a building, or 0:03:41.520 --> 0:03:45.120 you're being chased by a monster. You would be terrified 0:03:45.200 --> 0:03:48.560 by this lack of cohesion in your reality, the fact 0:03:48.560 --> 0:03:51.440 that you just flipped from one to another. And as 0:03:51.440 --> 0:03:54.480 soon as you were back in this reality, you'd presumably 0:03:54.600 --> 0:03:57.080 run to your doctor and say you just had this 0:03:57.160 --> 0:04:01.120 bizarre hallucination and thought you were somewhere else or maybe 0:04:01.160 --> 0:04:04.840 someone else, and you'd be terrified, But because we're so 0:04:05.280 --> 0:04:08.200 used to dreaming, we wake up and we think, oh, 0:04:08.200 --> 0:04:09.400 that was weird, and then we go. 0:04:09.400 --> 0:04:11.040 About our new reality. 0:04:11.560 --> 0:04:15.800 And in fact, one of the evergreen questions among philosophers 0:04:16.279 --> 0:04:19.840 is whether we live in a simulation. And I'm going 0:04:19.920 --> 0:04:22.599 to dive deep into that question in a different episode, 0:04:22.640 --> 0:04:25.279 but for now, I'll just mention the question, which is, 0:04:25.320 --> 0:04:28.000 how would you know if you are a brain in 0:04:28.080 --> 0:04:31.240 a vat who is being stimulated in just the right 0:04:31.240 --> 0:04:34.440 way to think that you're listening to a podcast and 0:04:34.560 --> 0:04:36.839 seeing the world around you and eating. 0:04:36.520 --> 0:04:37.760 Delicious food and so on. 0:04:38.200 --> 0:04:40.520 Or the modern version of that is whether we are 0:04:40.560 --> 0:04:45.559 living in a computer simulation. So I suggest the mere 0:04:46.160 --> 0:04:51.880 existence of dreams is sufficient to prove that all this 0:04:52.000 --> 0:04:56.240 could be a simulation, because dreams demonstrate to us so 0:04:56.520 --> 0:05:01.560 clearly that we completely buy what ever reality we find 0:05:01.560 --> 0:05:04.600 ourselves in, and when we find ourselves in another reality, 0:05:04.640 --> 0:05:07.080 we say, oh, I guess that one wasn't real. 0:05:07.120 --> 0:05:09.159 I was fooled, but this is real. 0:05:09.360 --> 0:05:11.279 But let me leave that as a teaser for the 0:05:11.440 --> 0:05:13.920 episode on whether we're living in a simulation and how 0:05:13.960 --> 0:05:18.240 we'd know. For today, I want to dive into dreaming 0:05:18.720 --> 0:05:21.880 in particular, and from the brain's point. 0:05:21.600 --> 0:05:23.240 Of view, why do we dream? 0:05:23.600 --> 0:05:28.159 Why does our consciousness go on these bizarre flights every 0:05:28.240 --> 0:05:31.360 ninety minutes during the night. So as a neuroscientist, I've 0:05:31.440 --> 0:05:34.120 always been fascinated by dreaming, by what. 0:05:34.080 --> 0:05:35.240 The heck this is all about. 0:05:35.640 --> 0:05:38.479 So in this episode, we're going to talk about the why, 0:05:39.000 --> 0:05:41.800 and I'm going to tell you about some hypotheses that 0:05:41.839 --> 0:05:44.880 people have proposed over the centuries, and then I'm going 0:05:44.920 --> 0:05:49.320 to tell you about a new hypothesis that makes quantitative 0:05:49.360 --> 0:05:54.680 predictions across animal species. So let's start with an interesting fact, 0:05:55.000 --> 0:05:59.279 which is that all animals appear to have dream sleep, 0:05:59.520 --> 0:06:04.720 also as REM sleep. REM is spelled r EM, and 0:06:04.760 --> 0:06:09.240 it stands for rapid eye movement. So in this stage 0:06:09.240 --> 0:06:12.560 of sleep, the eyes are darting back and forth under 0:06:12.600 --> 0:06:16.000 the eyelids. And if you haven't really watched someone while 0:06:16.000 --> 0:06:20.280 they're sleeping, you should in a respectful manner because you'll 0:06:20.279 --> 0:06:23.360 see how amazing this is. Every ninety minutes or so, 0:06:23.440 --> 0:06:27.279 their eyes start jiggling back and forth. Now here's the 0:06:27.320 --> 0:06:30.039 cool part. If you wake them up right when this 0:06:30.160 --> 0:06:33.640 is happening and you say, quick, what were you just 0:06:33.880 --> 0:06:36.599 thinking about? They will tell you that they were just 0:06:37.200 --> 0:06:39.599 riding a camel in a shopping mall, or they were 0:06:39.880 --> 0:06:42.640 running from a pack of leprechauns, or they were flying 0:06:42.640 --> 0:06:45.400 around their house or whatever. And this is how we know, 0:06:46.120 --> 0:06:49.240 from years of experiments of waking people up at different 0:06:49.279 --> 0:06:52.359 stages of sleep, this is how we know that rem 0:06:52.600 --> 0:06:57.400 sleep is when dreams happen. Because if you wake someone 0:06:57.480 --> 0:07:01.120 up during a deeper stage of sleep, what we call 0:07:01.200 --> 0:07:03.400 stage one or two or three, when their eyes are 0:07:03.440 --> 0:07:06.599 not moving, and you say, quick, what were you just 0:07:06.640 --> 0:07:10.640 thinking about, they'll generally say nothing at all, there was 0:07:10.880 --> 0:07:14.640 nothing going on in my consciousness. Now, for completeness, I'll 0:07:14.680 --> 0:07:17.280 just flag that some people will point out there can 0:07:17.320 --> 0:07:21.200 be some sort of dreaming during non rem sleep, but 0:07:21.320 --> 0:07:24.320 this is a very different type of dreaming. When it happens, 0:07:24.360 --> 0:07:28.520 it's just a feeling of something like a simple thought, 0:07:28.640 --> 0:07:32.120 rather than a vivid experience like we typically think of 0:07:32.160 --> 0:07:36.640 with dreams with its whirl of color and activity and 0:07:36.760 --> 0:07:41.240 magnified emotions. Now, just a quick side note, some people 0:07:41.360 --> 0:07:45.240 say I don't dream at night, but in fact you do. 0:07:45.520 --> 0:07:48.360 Everybody does. It's just a matter of waking up at 0:07:48.360 --> 0:07:51.520 the right time. So if I snuck into your house 0:07:51.760 --> 0:07:54.280 and woke you up right when you were having rapid 0:07:54.360 --> 0:07:58.040 eye movement sleep. You'd say, WHOA, I was just dreaming. 0:07:58.400 --> 0:08:02.360 But what often happens is that we enjoy a round 0:08:02.400 --> 0:08:05.440 of dream sleep and then we sink back into a 0:08:05.520 --> 0:08:07.840 deeper sleep, so by the time we wake up, we 0:08:07.880 --> 0:08:12.080 don't remember the dream. So some people get up in 0:08:12.120 --> 0:08:14.760 the morning and they're convinced that they didn't dream at all, 0:08:14.840 --> 0:08:19.080 while in fact they did, they simply don't remember it. Now, 0:08:19.080 --> 0:08:22.280 the question I want to address is why we dream? 0:08:22.720 --> 0:08:26.600 And the first clue comes from a simple observation that 0:08:26.640 --> 0:08:29.400 this is not just a human thing, but something about 0:08:29.440 --> 0:08:34.240 brains in general. You've seen your dog have dreams where 0:08:34.280 --> 0:08:37.280 she kicks her legs around and barks like she's chasing 0:08:37.320 --> 0:08:40.559 a rabbit. But it turns out that all mammals dream, 0:08:40.720 --> 0:08:44.800 and all birds and reptiles they all exhibit rem sleep. 0:08:44.920 --> 0:08:47.840 Even fish have a form of rem sleep. So why 0:08:47.960 --> 0:08:51.920 is this so conserved across the whole animal kingdom. While 0:08:51.960 --> 0:08:55.280 there are various ideas that have been proposed for why 0:08:55.440 --> 0:08:59.800 we dream, some researchers point out that dream sleep seems 0:08:59.800 --> 0:09:05.520 to be important for memory consolidation, which means nailing down 0:09:05.559 --> 0:09:08.760 the memories that you take in during the day. So 0:09:09.080 --> 0:09:11.480 you run around during the day with your eyes open 0:09:11.559 --> 0:09:14.320 and you experience all kinds of new things. 0:09:14.480 --> 0:09:17.200 And the idea is that when you sleep and. 0:09:17.240 --> 0:09:20.800 Dream, you are nailing that down and taking out the 0:09:20.840 --> 0:09:25.520 neural trash in a way that's necessary and useful for 0:09:25.640 --> 0:09:26.920 locking down the memories. 0:09:27.320 --> 0:09:29.559 Another popular idea has been that. 0:09:29.840 --> 0:09:34.160 Dreams help us solve problems because the brain is able 0:09:34.200 --> 0:09:38.040 to process information and make connections that are not possible 0:09:38.120 --> 0:09:41.439 during waking hours. So the idea is that the brain 0:09:41.520 --> 0:09:44.720 is in a more relaxed state during dream sleep. It's 0:09:44.720 --> 0:09:47.560 not as focused on the external world, and this allows 0:09:47.600 --> 0:09:50.520 it to focus on internal thoughts and ideas, which can 0:09:50.600 --> 0:09:54.640 lead to new insights and solutions to problems. And in fact, 0:09:54.679 --> 0:09:57.200 studies have shown that if you are trying to solve 0:09:57.200 --> 0:10:00.480 a problem and you go to sleep, you're more likely 0:10:00.520 --> 0:10:03.000 to solve it when you wake up than if you're 0:10:03.000 --> 0:10:05.600 just thinking about it during the daytime. And if you're 0:10:05.640 --> 0:10:10.080 deprived of dream sleep, you have more difficulty solving problems. 0:10:10.520 --> 0:10:13.640 But of course this might be related to problems of 0:10:13.679 --> 0:10:17.840 sleep in general. Others suggest that rem sleep is involved 0:10:17.960 --> 0:10:21.600 more generally in creativity, and others talk about its role 0:10:21.679 --> 0:10:25.880 in emotional processing. And finally, several thinkers have suggested that 0:10:26.040 --> 0:10:31.000 dreams help us prepare for new situations like fighting or 0:10:31.160 --> 0:10:35.080 escaping from situations, because these are things that we experience 0:10:35.160 --> 0:10:38.560 in real life very rarely, and so the idea is 0:10:38.600 --> 0:10:42.400 that dreams give us practice at these rare situations. 0:10:42.400 --> 0:10:44.040 They keep the wheels greased. 0:10:44.559 --> 0:10:46.120 And I just want to be clear that these are 0:10:46.160 --> 0:10:50.520 all hypotheses for why we dream, and they're not exclusive. 0:10:50.600 --> 0:10:53.800 Dreams might serve multiple roles, so it's not as though 0:10:53.800 --> 0:10:55.720 one of these has to be right at the expense 0:10:55.760 --> 0:10:57.880 of others. But the first thing that I hope is 0:10:57.920 --> 0:11:00.760 clear is that there's a lot of speculation about dreams, 0:11:00.800 --> 0:11:03.800 but we don't really have a single theory that would 0:11:03.880 --> 0:11:07.120 qualify as the answer to why we dream. And certainly 0:11:07.160 --> 0:11:09.320 we don't have a theory that allows us to look 0:11:09.400 --> 0:11:13.760 across the animal kingdom to answer a different question, which 0:11:13.800 --> 0:11:17.400 is why do different animal species, even those who are 0:11:17.400 --> 0:11:23.000 closely related, dream different amounts. For example, if you look 0:11:23.040 --> 0:11:27.160 at the vervet monkey and it's total sleeping time, it 0:11:27.200 --> 0:11:31.240 only spends six percent of that sleep time in rem 0:11:31.440 --> 0:11:35.240 In other words, having dreams, whereas another monkey, the Reesus 0:11:35.240 --> 0:11:39.160 macaque monkey, spends eighteen percent of its time in rem sleep, 0:11:39.280 --> 0:11:43.280 three times as much, even though they're both primate species. 0:11:43.600 --> 0:11:45.520 So it's never been clear to me how any of 0:11:45.559 --> 0:11:48.920 the hypotheses previously proposed would account for any of this. 0:11:49.360 --> 0:11:52.800 But recently, my colleague and I proposed a very new 0:11:53.000 --> 0:11:56.079 kind of theory about dreaming, and it's one that I'm 0:11:56.160 --> 0:12:00.959 very excited about because it gives accurate quantity tative predictions 0:12:01.040 --> 0:12:06.000 across species, something that no other hypothesis even strives to do. 0:12:06.320 --> 0:12:08.400 But before I tell you about that, I need to 0:12:08.480 --> 0:12:11.640 lay some foundation. So let's start with the story of 0:12:11.679 --> 0:12:15.760 a young boy named Ronnie who was born blind. He 0:12:15.880 --> 0:12:18.400 was born in North Carolina, and when he was just 0:12:18.520 --> 0:12:22.800 past year old, his mother abandoned him. She said that 0:12:22.920 --> 0:12:27.439 his blindness was her punishment from God. So he ended 0:12:27.520 --> 0:12:30.840 up being raised in poverty by his grandparents until he 0:12:30.920 --> 0:12:33.080 was five, and then he was sent off to a 0:12:33.160 --> 0:12:36.960 school for the sightless. When he was six years old, 0:12:37.000 --> 0:12:40.320 his mother came by just once and she had another child, 0:12:40.400 --> 0:12:44.040 now a little girl, and his mother said, ron I 0:12:44.080 --> 0:12:46.920 want you to feel her eyes. You know, her eyes 0:12:46.920 --> 0:12:50.520 are so pretty she didn't shame me the way that 0:12:50.559 --> 0:12:53.520 you did. She can see, and that was the last 0:12:53.520 --> 0:12:56.680 time he ever had contact with his mother. So most 0:12:56.720 --> 0:13:00.360 of us can't even imagine a childhood this hard. But 0:13:00.480 --> 0:13:04.000 the silver lining became the fact that Ronnie had a 0:13:04.040 --> 0:13:08.080 gift for music. His instructors spotted this talent and he 0:13:08.160 --> 0:13:12.920 started to formally study classical music with the violin, and 0:13:13.080 --> 0:13:15.520 in no time, this kid was a virtuoso. 0:13:15.640 --> 0:13:16.680 And from there he went. 0:13:16.559 --> 0:13:21.600 On to master guitar and piano and several other string 0:13:21.679 --> 0:13:24.800 and woodwind instruments, and by the time he grew into 0:13:24.880 --> 0:13:28.920 young adulthood, he became one of the most popular performers 0:13:29.080 --> 0:13:31.920 of his day. His name was Ronnie Millsap, and you 0:13:31.960 --> 0:13:33.320 may or may not have heard of him, but in 0:13:33.360 --> 0:13:38.360 the seventies and eighties he dominated pop music and country 0:13:38.400 --> 0:13:43.520 western markets. He released thirty five country music hits at 0:13:43.559 --> 0:13:45.559 the number one slot, and he. 0:13:45.600 --> 0:13:47.439 Earned six Grammy Awards. 0:13:48.240 --> 0:13:51.680 Now you might think it's amazing that Ronnie Millsap could 0:13:51.720 --> 0:13:55.720 be blind and have such an amazing musical career, but 0:13:55.920 --> 0:13:59.240 this is actually not such an uncommon story. Think of 0:13:59.280 --> 0:14:05.440 Andrea about or Ray, Charles Stevie Wonder, or Diane Shore 0:14:05.800 --> 0:14:10.680 or Jose Feliciano or Jeff Healy. All of them are blind. 0:14:11.320 --> 0:14:14.640 For all of them, their brains learned to rely on 0:14:14.679 --> 0:14:18.360 the signals of sound and touch in their environment, and 0:14:18.400 --> 0:14:23.400 they became better at processing those signals then cited people. 0:14:23.680 --> 0:14:27.440 As I write about my book Live Wired, Musical stardom 0:14:27.560 --> 0:14:30.400 is not guaranteed for people who are blind, but brain 0:14:30.520 --> 0:14:36.240 reorganization is guaranteed because if a sense is not getting used, 0:14:36.480 --> 0:14:41.640 like vision, it gets taken over by neighboring senses. There's 0:14:41.680 --> 0:14:46.280 nothing special about the cells, the neurons in the visual 0:14:46.400 --> 0:14:49.080 cortex at the back of your brain. They are simply 0:14:49.600 --> 0:14:54.560 neurons that happened to be involved in processing edges or 0:14:54.600 --> 0:14:57.560 colors for people who have functioning eyes. But if you 0:14:57.600 --> 0:15:01.840 go blind, these exact same neurons can process other types 0:15:01.880 --> 0:15:06.640 of information, So the territory gets redeployed. It gets taken 0:15:06.720 --> 0:15:10.880 over by hearing and by touch, and you get better 0:15:10.960 --> 0:15:15.480 at those other senses. For Ronnie Millsap, his visual cortex 0:15:15.560 --> 0:15:18.479 was not getting used because his eyes were not functioning, 0:15:19.000 --> 0:15:22.240 so these other brain areas took over and he got 0:15:22.280 --> 0:15:27.720 better at those as a result. Perfect musical pitch, for example, 0:15:27.880 --> 0:15:31.880 is much more common in the blind population, and blind 0:15:31.960 --> 0:15:35.920 people are up to ten times better at determining whether 0:15:36.000 --> 0:15:39.520 a musical pitch is subtly wobbling up and down. 0:15:40.000 --> 0:15:42.119 Why, it's just because. 0:15:41.880 --> 0:15:47.040 They have more brain territory devoted to the task of listening. 0:15:47.480 --> 0:15:50.320 There was a recent experiment in which people who were 0:15:50.560 --> 0:15:54.520 sighted or blind had one ear plugged up, and then 0:15:54.560 --> 0:15:57.520 they were asked to point to the locations of sounds 0:15:57.560 --> 0:16:01.280 in the room and pinpointing where a sound is coming 0:16:01.320 --> 0:16:04.960 from normally requires a comparison of the signals at both years, 0:16:05.320 --> 0:16:08.600 So it was expected that everyone would fail miserably at 0:16:08.600 --> 0:16:11.480 this task, and that's what happened with the people who 0:16:11.480 --> 0:16:15.600 could see. But for the blind participants, they were able 0:16:15.640 --> 0:16:20.000 to generally tell where the sounds were positioned. How it's 0:16:20.040 --> 0:16:24.440 because the exact shape of the cartilage of the outer ear, 0:16:24.880 --> 0:16:29.000 even just one ear, it bounces sound around in subtle 0:16:29.000 --> 0:16:33.360 ways that gives clues to location, but only if one 0:16:33.400 --> 0:16:37.640 is highly attuned to pick up on those very subtle signals. 0:16:38.080 --> 0:16:42.920 So people with sight, they have less cortex devoted to sound, 0:16:42.960 --> 0:16:48.200 and so their ability to extract subtle sound information it's underdeveloped, 0:16:48.880 --> 0:16:53.400 But with blind people that skill gets developed. And this 0:16:53.560 --> 0:16:57.640 sort of extreme talent with sound, this is common among 0:16:57.680 --> 0:17:01.480 the blind. Take a young man named Ben Underwood. When 0:17:01.520 --> 0:17:04.800 he was two years old, Ben stopped seeing out of 0:17:04.840 --> 0:17:07.159 his left eye and his mother took him to the 0:17:07.200 --> 0:17:10.480 doctor and they soon discovered that he had retinal cancer 0:17:10.720 --> 0:17:14.080 that was in both eyes. So they tried chemotherapy, they 0:17:14.119 --> 0:17:19.080 tried radiation, but that didn't work, and finally the surgeons 0:17:19.200 --> 0:17:22.200 had to remove both of his eyes. And you can 0:17:22.280 --> 0:17:25.359 imagine the pain that the family went through here. But 0:17:25.440 --> 0:17:28.879 by the time Ben was seven years old, he devised 0:17:28.920 --> 0:17:33.920 a technique that was totally unexpected and unbelievably useful, which 0:17:33.960 --> 0:17:37.639 is that he would click with his mouth and he 0:17:37.680 --> 0:17:41.560 would listen for the returning echoes. And in this way 0:17:41.800 --> 0:17:46.560 he could hear the locations of an open doorway, or 0:17:46.640 --> 0:17:49.959 of a person, or of a parked car, or a 0:17:50.040 --> 0:17:53.960 garbage can and so on. He was echo locating. He 0:17:54.080 --> 0:17:57.600 was bouncing his sound waves off objects in the environment, 0:17:57.840 --> 0:18:17.080 and he was listening to what returned. Now, I saw 0:18:17.119 --> 0:18:20.080 a documentary about Ben a little while ago, and it 0:18:20.240 --> 0:18:23.760 kicked off with the statement that Ben was quote the 0:18:23.840 --> 0:18:27.400 only person in the world who can see with echolocation. Now, 0:18:27.480 --> 0:18:30.160 first of all, we don't really know if he's seeing 0:18:30.240 --> 0:18:32.080 in the same way that you and I might. 0:18:32.040 --> 0:18:32.720 Think of site. 0:18:33.040 --> 0:18:36.320 But much more importantly, Ben was not the only one 0:18:36.400 --> 0:18:41.520 using echolocation. Thousands of blind people do this. In fact, 0:18:41.920 --> 0:18:45.680 the phenomenon has been discussed since at least the nineteen forties, 0:18:45.720 --> 0:18:50.160 when the word echolocation was first coined in an article 0:18:50.240 --> 0:18:54.600 in the journal Science, and this was titled Echolocation by 0:18:54.800 --> 0:19:00.680 Blind Men, bat and Radar. The author wrote, quote, many 0:19:00.720 --> 0:19:04.480 blind persons develop, in the course of time a considerable 0:19:04.560 --> 0:19:10.160 ability to avoid obstacle by means of auditory cues received 0:19:10.520 --> 0:19:14.960 from sounds of their own making. And this included clicking 0:19:15.160 --> 0:19:19.320 or their own footsteps, or cane tapping or finger snapping. 0:19:20.040 --> 0:19:23.520 So the author demonstrated that their ability to echo locate 0:19:23.840 --> 0:19:27.679 was drastically reduced if you put in distracting noises or 0:19:27.720 --> 0:19:32.760 put ear plugs in them. Anyway, the general story is straightforward. 0:19:32.800 --> 0:19:36.399 If a sense is not getting used, it gets taken 0:19:36.440 --> 0:19:40.640 over by neighboring senses. So, for example, if you're blind, 0:19:40.800 --> 0:19:45.120 the territory gets redeployed to hearing and to touch. There's 0:19:45.160 --> 0:19:48.639 nothing special about the neurons and the visual cortex. They 0:19:48.720 --> 0:19:52.240 just happen to be involved in processing vision if you 0:19:52.320 --> 0:19:56.080 have functioning eyes, but if you go blind, these exact 0:19:56.160 --> 0:20:00.199 same neurons can process other types of information. Now, in 0:20:00.280 --> 0:20:05.280 recent decades, there have been thousands of papers demonstrating brain plasticity, 0:20:05.359 --> 0:20:08.600 that is, the brain's ability to reconfigure and adjust its 0:20:08.600 --> 0:20:11.439 own circuitry, And in my book Livewireed, I attempt to 0:20:11.520 --> 0:20:15.880 build up frameworks to surface the big lessons from these papers. 0:20:16.040 --> 0:20:19.840 But to my mind, the biggest surprise about brain plasticity 0:20:20.320 --> 0:20:25.200 is its speed. So some years ago, researchers at McGill 0:20:25.320 --> 0:20:29.200 University took several adults who had recently lost their site, 0:20:29.200 --> 0:20:31.320 and they put them into a brain scanner and the 0:20:31.400 --> 0:20:36.040 participants were asked to listen to sounds. Now, not surprisingly, 0:20:36.160 --> 0:20:40.520 the sounds caused activity in their auditory cortex, but the 0:20:40.600 --> 0:20:44.360 sounds also caused activity in their occipital core. 0:20:44.480 --> 0:20:46.159 Text that's at the back of the brain. 0:20:46.560 --> 0:20:49.040 It's normally what we would think of as visual cortex, 0:20:49.520 --> 0:20:52.600 and that activity would not have been seen there even 0:20:52.640 --> 0:20:55.960 a few weeks earlier when the participants had sight. Now, 0:20:55.960 --> 0:20:59.240 the activity wasn't as strong as that scene in people 0:20:59.280 --> 0:21:02.040 who have been blowing for a long time. But it 0:21:02.080 --> 0:21:06.960 was detectable in the occipital cortex nonetheless, and this demonstrated 0:21:07.000 --> 0:21:11.919 that the brain can implement changes rapidly when vision disappears, 0:21:12.119 --> 0:21:16.000 but how rapidly so. Next, my colleagues at Harvard, led 0:21:16.040 --> 0:21:20.320 by Alvaro pascal Leone, began to wonder about the speed 0:21:20.359 --> 0:21:24.080 at which these major takeovers can happen, and they noted 0:21:24.119 --> 0:21:28.840 that instructors at a school for the blind were required 0:21:28.880 --> 0:21:32.160 to blindfold themselves for seven full days so that they 0:21:32.160 --> 0:21:36.360 could gain a first hand understanding of their students' living experiences. 0:21:36.880 --> 0:21:41.600 So when these cited instructors blindfolded themselves, they became aware 0:21:41.680 --> 0:21:46.639 of enhanced skills with sounds. They could orient to things better, 0:21:46.680 --> 0:21:49.959 and they could judge their distance, and they could identify things. 0:21:50.240 --> 0:21:55.479 Several described identifying people more rapidly and accurately just as 0:21:55.520 --> 0:21:58.199 they started talking, or even just given the cadence of 0:21:58.240 --> 0:22:01.760 their footsteps, And the instructions learned new things like how 0:22:01.800 --> 0:22:05.840 to differentiate cars just by the sounds of their motors. 0:22:06.320 --> 0:22:10.919 So this god pascal Leone and his colleagues, considering what 0:22:11.000 --> 0:22:14.400 would happen if a sighted person were blindfolded in. 0:22:14.400 --> 0:22:16.960 The laboratory for several days. 0:22:17.000 --> 0:22:20.679 So they launched this experiment and what they found was 0:22:20.720 --> 0:22:23.760 nothing short of remarkable. They discovered that when you were 0:22:24.040 --> 0:22:29.439 temporarily blinded, there was neural reorganization, just like we see 0:22:29.720 --> 0:22:32.919 in blind subjects, and it was rapid. In one of 0:22:32.920 --> 0:22:36.679 their studies, people who could see normally were blindfolded for 0:22:36.760 --> 0:22:40.720 five days and they were put through intensive braille training, 0:22:40.920 --> 0:22:43.120 and at the end of the five days, the subjects 0:22:43.160 --> 0:22:47.120 had become quite good at detecting the subtle differences between 0:22:47.200 --> 0:22:51.080 braille characters, much better than a control group of cited 0:22:51.080 --> 0:22:54.240 participants who had the same training without the blindfold. But 0:22:54.320 --> 0:22:57.359 what was especially striking was what happened to their brains 0:22:57.480 --> 0:23:00.719 when you measured them in the scanner. Within fire five days, 0:23:01.040 --> 0:23:06.199 the blindfolded participants had recruited their occipital cortex when they 0:23:06.200 --> 0:23:11.119 were touching objects. So control subjects, not surprisingly used only 0:23:11.480 --> 0:23:14.679 a different part of their brain called the somatisensory cortex, 0:23:15.040 --> 0:23:18.640 and the blindfolded subjects they were also showing these occipital 0:23:18.680 --> 0:23:22.159 responses to sounds and words. 0:23:22.400 --> 0:23:23.240 And by the way, you. 0:23:23.200 --> 0:23:29.320 Could disrupt this new occipital lobe activity by magnetic pulses, 0:23:29.680 --> 0:23:33.200 and then the braille reading advantage of the blindfolded subjects 0:23:33.240 --> 0:23:36.560 went away, so that indicates the recruitment of the brain 0:23:36.640 --> 0:23:39.840 area was not an accidental side effect, but this was 0:23:39.880 --> 0:23:44.639 a critical piece of the improved behavioral performance. And importantly, 0:23:44.720 --> 0:23:48.240 because of the plasticity of the brain, when the blindfold 0:23:48.280 --> 0:23:51.719 got removed, the response of the occipital. 0:23:51.200 --> 0:23:52.720 Cortext to touch or sound. 0:23:53.040 --> 0:23:56.680 That disappeared within a day, and at that point the participants' 0:23:56.720 --> 0:24:01.879 brains returned to looking indistinguishable from every other sighted person 0:24:01.920 --> 0:24:06.159 out there. Now here's the key study that really influenced me. 0:24:06.560 --> 0:24:11.040 These same investigators very carefully mapped out the brain using 0:24:11.160 --> 0:24:16.440 more powerful neuroimaging techniques. So volunteers were blindfolded really tightly, 0:24:16.560 --> 0:24:19.000 and they were put in the scanner and they were 0:24:19.119 --> 0:24:22.680 asked to perform a touching task that required really fine 0:24:22.720 --> 0:24:27.080 discrimination with their fingers. And what these investigators saw was 0:24:27.160 --> 0:24:32.440 activity emerging in the primary visual cortex the occipital lobe 0:24:32.480 --> 0:24:36.359 after an hour. And the shock of these findings was 0:24:36.359 --> 0:24:41.600 their sheer speed. So the reorganization of territory that brains do, 0:24:41.760 --> 0:24:45.679 it's not like the glacial drifting of continental plates, but 0:24:45.840 --> 0:24:50.920 it can be remarkably fast. The brain is always sprung 0:24:51.080 --> 0:24:54.840 tight like a mouse trap to implement rapid change. 0:24:55.280 --> 0:24:58.719 So the key is that the brain's changes. 0:24:58.640 --> 0:25:02.760 Are even fast sure than even the most optimistic neuroscientist 0:25:02.880 --> 0:25:06.160 would have dared to guess at the beginning of this century. 0:25:06.640 --> 0:25:09.840 So let's zoom back out to the bigger picture. So 0:25:10.640 --> 0:25:14.400 for survival you need things like sharp teeth and fast legs. 0:25:14.760 --> 0:25:19.680 You also need neural flexibility. This is what allows brains 0:25:19.720 --> 0:25:24.320 to optimize their performance in a variety of environments. But 0:25:24.400 --> 0:25:29.159