WEBVTT - From the Vault: Split Brain, Part 1 0:00:05.720 --> 0:00:07.960 Hey, welcome to Stuff to Blow Your Mind. My name 0:00:08.000 --> 0:00:11.039 is Robert Lamb and I'm Joe McCormick, and it's Saturday. 0:00:11.160 --> 0:00:13.680 Time for a vault episode, a classic episode of Stuff 0:00:13.680 --> 0:00:16.239 to Blow Your Mind. This is a part one of 0:00:16.239 --> 0:00:20.160 our exploration of the split brain experiments. This episode was 0:00:20.200 --> 0:00:25.320 originally published January. If you have not listened to these episodes, 0:00:25.360 --> 0:00:27.960 you've probably listened to episodes where we refer back to him, 0:00:28.440 --> 0:00:30.600 or even older episodes where we kind of laid the 0:00:30.640 --> 0:00:33.960 ground work for actually doing this exploration, because this is 0:00:34.000 --> 0:00:37.680 an important topic. You know, how does our brain work, 0:00:37.720 --> 0:00:41.120 What happens and what is revealed when there is a 0:00:41.159 --> 0:00:46.240 division in the brain when hemispheres are separated from each other. 0:00:46.400 --> 0:00:50.680 There's some groundbreaking experiments that we cover in these episodes. Yeah, 0:00:50.760 --> 0:00:53.199 this pair of episodes is one of my favorites, and 0:00:53.240 --> 0:00:55.920 we hope you enjoy it. The powers of Hide seem 0:00:55.960 --> 0:00:58.880 to have grown with the sickliness of Jackal, and certainly 0:00:58.920 --> 0:01:01.160 the hate that now divide did them was equal on 0:01:01.200 --> 0:01:04.959 each side. With Jekyll, it was a thing of vital instinct. 0:01:05.280 --> 0:01:08.080 He had now seen the full deformity of that creature 0:01:08.120 --> 0:01:11.200 that shared with him some of the phenomena of consciousness, 0:01:11.560 --> 0:01:14.440 and was co heir with him to death and beyond 0:01:14.520 --> 0:01:17.679 these links of community, which in themselves made the most 0:01:17.680 --> 0:01:21.080 poignant part of his distress. He thought of hide for 0:01:21.200 --> 0:01:24.720 all his energy of life, as of something not only 0:01:24.800 --> 0:01:28.960 hellish but inorganic. This was the shocking thing that the 0:01:29.000 --> 0:01:31.800 slime of the pit seemed to utter, cries and voices, 0:01:32.120 --> 0:01:35.800 that the amorphous dust gesticulated and sinned, that what was 0:01:35.880 --> 0:01:40.800 dead and had no shape should usurp the offices of life. 0:01:43.680 --> 0:01:46.560 Welcome to stuff to blow your mind from how Stuff 0:01:46.560 --> 0:01:55.000 works Dot Carl, Hey, you welcome to stuff to blow 0:01:55.040 --> 0:01:57.240 your mind. My name is Robert Lamb, and I'm Joe 0:01:57.320 --> 0:02:01.200 McCormick and Robert. Why are you reading Robert Lewis even Sanadas? Oh? 0:02:01.360 --> 0:02:03.720 Because that's from the strange case of Dr Jackal and 0:02:03.800 --> 0:02:07.320 Mr Hyde from eighteen eighty six, and it concerns the 0:02:07.440 --> 0:02:12.000 idea of there being two entities within the human skull, 0:02:12.120 --> 0:02:15.959 two entities within the mind, indeed, two minds within the brain. 0:02:16.400 --> 0:02:18.240 And I think this is an interesting place to start 0:02:18.280 --> 0:02:22.240 because while it presents a very erroneous vision of the 0:02:22.320 --> 0:02:27.560 lateralization of human brain function, it also uh it gets 0:02:27.560 --> 0:02:29.519 some of the same like hair standing up on the 0:02:29.560 --> 0:02:31.960 back of the neck that the actual research we're going 0:02:32.000 --> 0:02:33.880 to be talking about today does, at least for me. 0:02:34.080 --> 0:02:36.560 Oh yeah, I mean, Robert Louis Stevenson was a fabulous 0:02:36.560 --> 0:02:38.560 writer and he's he's one of those authors that you 0:02:38.600 --> 0:02:40.880 can read today and it holds up so well. Did 0:02:40.880 --> 0:02:43.400 they ever make a good Jekyl and Hyde movie. It's 0:02:43.400 --> 0:02:45.240 been a very long time since I've saw it, but 0:02:45.320 --> 0:02:47.280 there was an adaptation and may have been a TV 0:02:47.360 --> 0:02:50.840 adaptation with Michael Caine Michael Kine. Yeah, and I remember 0:02:51.360 --> 0:02:54.440 really loving that and being quite disturbed by it as 0:02:54.440 --> 0:02:56.720 a child. Now, I was thinking there had to be 0:02:56.919 --> 0:03:00.440 a Jekyl and Hyde with Tim Curry as Jacky and Hide. 0:03:00.480 --> 0:03:02.680 But I think maybe I'm confusing that with the Muppet 0:03:02.680 --> 0:03:05.320 Treasure Island where he's uh, you're thinking of the Muppet 0:03:05.360 --> 0:03:09.480 Jackal and high. He's long, John self man, that scene 0:03:09.480 --> 0:03:14.320 where he tramples Kermit to death is brutal. Well, yeah, 0:03:14.360 --> 0:03:15.880 so so we are. We are beginning with kind of 0:03:15.960 --> 0:03:18.480 an erroneous model. But but I think helpful and because 0:03:19.040 --> 0:03:21.480 it is often easy to think of the brain as 0:03:21.600 --> 0:03:24.840 the thing itself, right, we fall into this center our 0:03:25.000 --> 0:03:27.400 mode of of of of you know, the thinking of 0:03:27.440 --> 0:03:30.600 the brain body relationship as being a rider and its horse, 0:03:30.639 --> 0:03:32.959 when instead it is more this idea of a centaur. 0:03:33.200 --> 0:03:37.360 This this this one single entity, um, you know, and honestly, 0:03:37.400 --> 0:03:41.240 we see this reflected in so many real and fictional scenarios. Uh. 0:03:41.520 --> 0:03:44.560 Take for instance, the late physicist Stephen Hawking a brilliant 0:03:44.560 --> 0:03:47.920 brain within a body that was gradually paralyzed by motor 0:03:48.000 --> 0:03:51.280 neuron disease. Or just look to our dreams in which 0:03:51.280 --> 0:03:53.440 the inner world of the brain runs wild while the 0:03:53.440 --> 0:03:56.720 body goes on lockdown. Uh, you know, think of our imaginings, 0:03:56.760 --> 0:03:59.800 our inner thoughts versus our outer smile and then they're 0:03:59.840 --> 0:04:04.240 all those disembodied brains and science fiction right from Crying 0:04:04.400 --> 0:04:07.160 and his robot body and teenaging Ninja Turtles to the 0:04:07.160 --> 0:04:10.280 Brain that Wouldn't Die Cane and RoboCop to one of 0:04:10.280 --> 0:04:11.800 the best I know that's one of one of your 0:04:11.840 --> 0:04:15.040 favorites as well, greatest of all time Lovecraft, the Whisper 0:04:15.040 --> 0:04:17.920 and Darkness, and so many Doctor Who characters, is especially 0:04:18.200 --> 0:04:20.880 the Daleks brain guy from MST three K. We just 0:04:20.960 --> 0:04:23.360 keep keep coming up with these these visions of the 0:04:23.720 --> 0:04:27.839 brain as they just sort of the central human thought experience. 0:04:27.920 --> 0:04:29.560 You know, I never thought of this until now, but 0:04:29.600 --> 0:04:32.520 actually the brain guy from Mystery Science Theater is kind 0:04:32.520 --> 0:04:36.040 of a great illustration of Daniel Dennett's short story thought experiment, 0:04:36.080 --> 0:04:38.760 where am I I wonder if there was any connection there, 0:04:39.480 --> 0:04:40.880 so I gonna have to have to have to reach 0:04:40.920 --> 0:04:43.360 out to the MST guys on that. You know, there 0:04:43.360 --> 0:04:46.240 are those like plot lines where his brain gets separated 0:04:46.279 --> 0:04:51.000 from him as somewhere else. Um, of course, we know 0:04:51.080 --> 0:04:53.680 that things are not this simple. No brain is an island. 0:04:53.720 --> 0:04:56.440 It's affected by a host of outside influences, including all 0:04:56.480 --> 0:04:59.640 sorts of environmental nervous stimuli. And we're learning more and 0:04:59.640 --> 0:05:03.400 more about the role of our microbiome and various parasites 0:05:03.920 --> 0:05:07.240 in human cognition. But even if we're to to distrib 0:05:07.240 --> 0:05:09.719 away all of that, even we're actually to become a 0:05:09.839 --> 0:05:13.640 brain and a tank, you know, Kane's brain in RoboCop 0:05:13.680 --> 0:05:16.040 two or or any of these sci fi visions take 0:05:16.040 --> 0:05:18.760 out all that external stuff just the brain, we still 0:05:18.839 --> 0:05:21.560 have to contend with the fact that the brain, like 0:05:21.600 --> 0:05:24.880 a government, is composed of different houses. The brain consists 0:05:24.920 --> 0:05:30.080 of two cerebral hemispheres connected by the corpus colossum. Uh, 0:05:30.200 --> 0:05:33.719 each each hemisphere with many different modules, all of these 0:05:33.760 --> 0:05:37.600 acting in concert with each other, all of it interconnected. Yeah. 0:05:37.680 --> 0:05:40.560 One comparison I've seen in some of the neuroscience research 0:05:40.640 --> 0:05:43.119 we're looking at today is that the brain is often 0:05:43.160 --> 0:05:46.920 described as a computer, you know, or by the metaphor 0:05:47.000 --> 0:05:48.839 of a computer. You know. It's not that it is 0:05:48.880 --> 0:05:51.839 a computer, but that Yeah, there's the analogy that the 0:05:51.839 --> 0:05:54.240 brain is like a computer in the different parts of 0:05:54.240 --> 0:05:57.120 the brain, or maybe sort of like different programs that 0:05:57.279 --> 0:06:00.800 run on that computer. But at least to one researcher 0:06:00.920 --> 0:06:03.240 we were reading, I said, maybe it's more accurate to 0:06:03.400 --> 0:06:06.920 think of the brain not as a computer running different software, 0:06:06.960 --> 0:06:10.960 but as a vast network of computers that are each 0:06:11.120 --> 0:06:15.200 capable of operating independently, but most of the time operate 0:06:15.320 --> 0:06:18.279 in in tandem. It's right. This is an example where 0:06:18.680 --> 0:06:21.120 if you don't really have much of an understanding of 0:06:21.120 --> 0:06:24.240 how computer works, the the the idea of thinking of 0:06:24.279 --> 0:06:29.240 the human mind as a computer as technology is more harmful. 0:06:29.360 --> 0:06:32.040 But if you have, if you have a better understanding 0:06:32.080 --> 0:06:34.039 of how computer actually works, it could perhaps be a 0:06:34.080 --> 0:06:38.920 more helpful metaphor Cuttle cat cuttle fish to the second 0:06:39.000 --> 0:06:44.799 oil Age Kingdom with or darkness. I don't dispute the eurostata, 0:06:45.040 --> 0:06:50.400 but if he's down here, we know not blood but darkness, 0:06:50.440 --> 0:06:56.479 the earth's black riches. No I could taste it on 0:06:56.560 --> 0:07:01.320 my lips. Today, I want to talk to you about 0:07:01.400 --> 0:07:12.800 the science of transgenesis terms genesist show. Now. I wanted 0:07:12.840 --> 0:07:14.520 to to I thoink it would be helpful to just 0:07:14.560 --> 0:07:18.560 go ahead and consider one particular question right up top now. 0:07:18.840 --> 0:07:22.640 And we've certainly received questions like this following episodes in 0:07:22.720 --> 0:07:26.760 which brain hemispheres are discussed, such as our discussions on 0:07:27.040 --> 0:07:30.200 the bicameral mind hypothesis or the alphabet in the Goddess. 0:07:30.720 --> 0:07:34.160 Because there's this kind of pop understanding, right that each 0:07:34.200 --> 0:07:37.600 side of our brain controlled certain aspects of being, and 0:07:37.600 --> 0:07:40.720 that certain individuals have certain leanings that you know you 0:07:40.760 --> 0:07:43.160 have right brain people, left brain people, and that when 0:07:43.200 --> 0:07:47.000 that we can reconnect with our less favored hemisphere. Now, 0:07:47.200 --> 0:07:50.640 there certainly are some pieces of evidence that we're gonna 0:07:50.640 --> 0:07:54.520 look at in this episode that certain functions of human 0:07:54.560 --> 0:07:58.040 life are strongly lateralized in one half of the brain 0:07:58.120 --> 0:08:00.960 or the other, but they're not necessarily these functions or 0:08:00.960 --> 0:08:05.200 personality traits that are understood in popular consciousness, like logic 0:08:05.320 --> 0:08:08.520 and creativity, right like taking or that you're gonna take 0:08:08.560 --> 0:08:10.240 some sort of a quiz online and find out if 0:08:10.240 --> 0:08:13.080 you're a right or lefty in terms of your brain. Now, 0:08:13.080 --> 0:08:16.160 a lot of these ideas apparently were popularized by nineteen 0:08:16.240 --> 0:08:19.040 seventy nine book titled Drawing on the Right Side of 0:08:19.080 --> 0:08:22.680 the Brain by Betty Edwards uh and and the downstream 0:08:22.960 --> 0:08:25.920 myth that kind of you know, took over a popular 0:08:25.960 --> 0:08:27.800 culture for a little bit. There is that, yeah, you 0:08:27.880 --> 0:08:30.920 had left side logic, right side creativity, And even in 0:08:31.000 --> 0:08:34.079 people who know better people, we still talk like this. 0:08:34.280 --> 0:08:37.120 I've noticed that I use this metaphor even though I 0:08:37.160 --> 0:08:40.000 know it's wrong. Like I will sometimes think of people 0:08:40.000 --> 0:08:42.840 as being very right brained or very left brained, even 0:08:42.880 --> 0:08:45.280 though that I know that that I've read before about 0:08:45.280 --> 0:08:48.000 how that's not correct. Well, likewise, if I hear it 0:08:48.120 --> 0:08:51.200 mentioned sanny yoga class, I'm going to be less inclined. 0:08:51.240 --> 0:08:52.679 I'm not going to be the jerk in the yoga 0:08:52.720 --> 0:08:55.120 class that like perks up and says, actually there's some 0:08:55.200 --> 0:08:58.480 interesting you know, I'm gonna set back and enjoy the 0:08:58.520 --> 0:09:01.440 class because because it's one of those things that can 0:09:01.559 --> 0:09:04.880 can feel true, right. But the idea goes back further 0:09:05.160 --> 0:09:07.320 than this particular book. I mean, it goes back to 0:09:07.400 --> 0:09:09.760 some of the earlier discoveries that we're going to discuss 0:09:09.800 --> 0:09:14.120 here about hemispheric division. Um. You know, the ideas of 0:09:14.520 --> 0:09:20.040 neurologist Paul Broca who lived eighteen four through eighty French 0:09:20.200 --> 0:09:25.440 neurologist or Carl Vernica who lived who live eighteen forty 0:09:25.480 --> 0:09:28.720 eight through nineteen o five, a German. They studied patients 0:09:28.720 --> 0:09:32.600 who had communication troubles due to brain injury um, such 0:09:32.600 --> 0:09:35.720 as you know, left temporal lobe injuries, and they figured 0:09:35.760 --> 0:09:39.440 that this was the language center. Thus language was left 0:09:39.559 --> 0:09:42.240 hemisphere focus. And this is one thing that actually has 0:09:42.280 --> 0:09:45.480 been more born out by good research in in the 0:09:45.520 --> 0:09:48.560 history of neuroscience, is that one thing it's very clear 0:09:48.640 --> 0:09:51.400 the left hemisphere of the brain does, is it is 0:09:51.559 --> 0:09:54.679 dominant in language function. Yes, it's not that the right 0:09:54.720 --> 0:09:57.160 brain can't do any language, but it can't do a 0:09:57.200 --> 0:09:59.480 whole lot of language certainly can't do what the left 0:09:59.480 --> 0:10:03.280 hemisphere do. Right. Uh, now, we we kicked off the 0:10:03.320 --> 0:10:07.280 episode with reading from Robert Louis Stevenson against Scottish author. 0:10:07.360 --> 0:10:12.320 He lived eighteen fifty eight. And according to neuroscientist Elizabeth Waters, 0:10:12.320 --> 0:10:15.000 who's put together some you know, wonderful ted talks and 0:10:15.040 --> 0:10:18.840 ted ed videos about this, uh this, this, uh this topic, 0:10:19.160 --> 0:10:22.080 she points out that Robert Lewis Stevenson, in his book 0:10:22.160 --> 0:10:24.600 Strange Case of Dr Checkl and Mr Hyde, presented the 0:10:24.600 --> 0:10:28.600 notion of a logical left hemisphere that is in combat 0:10:28.679 --> 0:10:31.000 in you know, in in in in this uh this 0:10:31.120 --> 0:10:35.120 struggle with an emotional right hemisphere, and uh it's It's 0:10:35.120 --> 0:10:38.800 also worth noting that Robert Lewis Stevenson was also inspired 0:10:38.840 --> 0:10:42.920 by two popular French cases of individuals who exhibited dual personalities, 0:10:43.280 --> 0:10:46.920 uh their name. They were credited as being uh Felida 0:10:47.280 --> 0:10:50.679 X and Sergeant Fay. And these were apparently cases that 0:10:50.720 --> 0:10:53.319 were really you know, well covered in French and British 0:10:53.360 --> 0:10:55.200 press at the time. You know, it's kind of popular 0:10:55.280 --> 0:10:59.560 science influencing, uh, popular science fiction. Do you have any 0:10:59.600 --> 0:11:02.440 sense of whether what was presented to the public about 0:11:02.480 --> 0:11:05.720 these cases was largely accurate or was mis leading? I don't, 0:11:05.720 --> 0:11:06.880 but I'd love to go back and look at it, 0:11:06.880 --> 0:11:08.400 because if you know, this is a case where you 0:11:08.440 --> 0:11:11.560 can the science influences the science fiction, and the science 0:11:11.600 --> 0:11:15.840 fiction influences, uh to a certain extent, how the public 0:11:15.880 --> 0:11:19.880 thinks about a given topic. Now, other another influence on 0:11:20.000 --> 0:11:22.440 Robert Louis Stevenson. Apparently he had a just a terribly 0:11:22.559 --> 0:11:25.920 high fever uh at one point during which he claimed 0:11:25.960 --> 0:11:30.440 to have experienced a split into which he experienced quote 0:11:30.480 --> 0:11:35.640 myself and quote that other fellow. Yeah, so this apparently 0:11:35.640 --> 0:11:37.680 had a big influence on him. An according to biograph 0:11:37.760 --> 0:11:41.160 for Claire Harmon, author of Myself and the Other Fellow, 0:11:41.520 --> 0:11:44.560 duality and the idea of the double self turn up 0:11:44.600 --> 0:11:48.120 again and again in Robert Louis Stevenson's work. Well, maybe 0:11:48.160 --> 0:11:50.040 I'm over interpreting here, and this could be just kind 0:11:50.080 --> 0:11:53.200 of a mundane parallel, but I mean I see stuff 0:11:53.240 --> 0:11:55.800 like that even in Treasure Island, you know, his adventure 0:11:56.120 --> 0:11:59.160 where long John Silver is at the same time a 0:11:58.840 --> 0:12:02.000 a pay sand and sort of good father figure and 0:12:02.080 --> 0:12:05.079 also an evil pirate. Yeah. Yeah, this is the the 0:12:05.240 --> 0:12:06.800 argument here, is, yeah, that this is the type of 0:12:06.840 --> 0:12:09.600 duality that that he was obsessed with, and and so 0:12:09.679 --> 0:12:11.280 much of it, so many of his works, I mean, 0:12:11.400 --> 0:12:14.400 essentially had a fever induced psychedelic experience and then this 0:12:14.480 --> 0:12:17.040 lining up with various elements of his of his life. 0:12:17.360 --> 0:12:20.240 I mean, that is the meat he chewed upon. But 0:12:20.320 --> 0:12:23.600 of course, this popular understanding of the left right division, 0:12:23.640 --> 0:12:26.760 you know that like the side ruled by passion and 0:12:26.800 --> 0:12:29.120 the right brain and the side ruled by logic and 0:12:29.160 --> 0:12:32.240 reason and the left brain. That's not exactly right, right, 0:12:32.440 --> 0:12:35.520 you know, as we'll explore, doctors actually looked to patients 0:12:35.520 --> 0:12:39.079 with missing brain hemispheres or separated hemispheres, and as appealing 0:12:39.120 --> 0:12:42.240 as this notion, maybe it didn't really hold up. I mean, 0:12:42.280 --> 0:12:45.760 they were all still logical and creative beings. You didn't 0:12:45.800 --> 0:12:49.080 just end up with us, you know, a Spock or 0:12:49.120 --> 0:12:51.000 whatever the opposite of Spock would be in the Star 0:12:51.040 --> 0:12:53.920 Trip universe. To be clear, though, Yeah, the brain is 0:12:54.000 --> 0:12:58.040 divided into two hemispheres and internal regions like the striatum, 0:12:58.160 --> 0:13:02.640 the hypothalamus, the thalamus, and the brainstem. They're also organized 0:13:02.640 --> 0:13:06.040 with left and right sides as well, despite appearing to 0:13:06.080 --> 0:13:08.000 be continuous when you when you sort of look at 0:13:08.040 --> 0:13:10.520 illustrations of them. Yeah, and for the rest of the 0:13:10.600 --> 0:13:12.320 this episode, in fact, this is gonna be the first 0:13:12.320 --> 0:13:14.440 of two episodes we're going to be looking at ways 0:13:14.520 --> 0:13:18.440 that despite this uh, this like emotional versus logical split 0:13:18.559 --> 0:13:22.199 being wrong, there are very interesting ways that the brain 0:13:22.280 --> 0:13:26.040 hemispheres are different and do different things. In fact, well, 0:13:26.160 --> 0:13:28.360 we can start with the mundane ones I guess right, 0:13:28.440 --> 0:13:32.640 like mundane motor control differences. Exactly, we can look to 0:13:32.760 --> 0:13:36.240 the two arms and legs. For instance, the right hemisphere 0:13:36.240 --> 0:13:38.880 of the brain controls the left arm and leg, the 0:13:39.000 --> 0:13:41.800 left hemisphere controls the right armand leg. Now I have 0:13:41.920 --> 0:13:45.920 read that in a way like both hemispheres can in 0:13:46.000 --> 0:13:49.840 some way to some degree control both arms. But that 0:13:50.080 --> 0:13:52.520 when he gets done to like fine motor control of 0:13:52.600 --> 0:13:56.200 like controlling the actions of the hand especially, that's where 0:13:56.200 --> 0:13:59.079 he gets really lateralized and like it's really going to 0:13:59.160 --> 0:14:02.280 be your right rain that's controlling what your left hand 0:14:02.480 --> 0:14:06.840 does with its fingers. Now, a more complex example is 0:14:06.960 --> 0:14:10.440 in but one that's extremely important is each eye has 0:14:10.520 --> 0:14:13.960 a left and right visual field, with the left visual 0:14:14.000 --> 0:14:16.600 field sent to the right hemisphere and the right field 0:14:16.640 --> 0:14:19.240 sent to the left hemisphere. Now, this can also be 0:14:19.280 --> 0:14:21.960 misunderstood because I've seen it represented in the press in 0:14:22.040 --> 0:14:25.360 places that where like the left eye goes to the 0:14:25.440 --> 0:14:28.200 right hemisphere and the right eye goes to the left hemisphere. 0:14:28.240 --> 0:14:31.440 And that's not quite right either, because both hemispheres can 0:14:31.440 --> 0:14:33.880 get some information from both eyes. But it has to 0:14:33.880 --> 0:14:37.560 do with the side of the visual field that you're 0:14:37.560 --> 0:14:40.920 talking a right, So like stuff that you perceive over 0:14:41.080 --> 0:14:44.400 to the left part of what you're looking at that 0:14:44.440 --> 0:14:47.720 goes to the right hemisphere, and stuff you perceive over 0:14:47.760 --> 0:14:50.320 in the right area of what you're looking at to 0:14:50.440 --> 0:14:52.640 the right of your center of vision that goes to 0:14:52.680 --> 0:14:55.600 the left hemisphere. And then our visual experience of reality 0:14:55.600 --> 0:14:58.960 it comes together from these two feeds. Movement and vision 0:14:59.280 --> 0:15:04.320 depend in on this uni hemispheric relationship. Now, why do 0:15:04.360 --> 0:15:06.640 our brains work this way? Yeah? Why the crossover? Why 0:15:06.640 --> 0:15:08.400 don't you just go straight up parallel? It's one of 0:15:08.440 --> 0:15:11.480 those things about the humanivice. It seems needlessly complicated, right um, 0:15:12.280 --> 0:15:14.960 And the thing is we're not entirely sure. One theory 0:15:15.080 --> 0:15:18.080 that has been discussed is that animals developed more as 0:15:18.240 --> 0:15:21.040 as animals developed more advanced nervous systems, there was an 0:15:21.040 --> 0:15:24.320 advantage in escaping to the right if something came at 0:15:24.360 --> 0:15:27.240 you from the left. So these are examples where we 0:15:27.280 --> 0:15:30.600 can actually look to specific hemispheres and say here, here 0:15:30.640 --> 0:15:33.320 here's where they're most active. But we can't easily extend 0:15:33.320 --> 0:15:35.920 this idea to other aspects of cognition, and certainly not 0:15:35.960 --> 0:15:39.440 to the overall human experience or things like pure logical 0:15:39.440 --> 0:15:42.520 thinking or creativity. No, not that. But there are some 0:15:42.600 --> 0:15:47.280 cognitive functions that do appear to be pretty strongly lateralized 0:15:47.280 --> 0:15:49.800 in one way or another, and one of them, obviously 0:15:49.880 --> 0:15:53.000 is language. We mentioned this, Yeah, that's localized to the left, 0:15:53.360 --> 0:15:57.000 especially complex language and the power of speech. There's some 0:15:57.080 --> 0:15:59.640 research indicating that like the right brain might be able 0:15:59.680 --> 0:16:03.760 to have a sort of simple lexicon or understand very 0:16:03.840 --> 0:16:07.400 simple bits of language, but if you want to generate 0:16:07.600 --> 0:16:11.840 a sentence like speak one out loud, or understand complex 0:16:11.880 --> 0:16:15.080 instructions in language, this is usually going to be dominated 0:16:15.080 --> 0:16:17.760 by processes in the left hemisphere. And we should also 0:16:17.800 --> 0:16:20.520 say that everything we say about hemisphere is in this 0:16:20.560 --> 0:16:24.040 episode is going to be for most cases. There there 0:16:24.080 --> 0:16:26.720 cases where this is reversed, where people have like the 0:16:26.920 --> 0:16:29.760 switching of which hemisphere is dominant, but we're talking about 0:16:29.800 --> 0:16:33.640 the majority of cases here right now. Meanwhile, attention, we 0:16:33.680 --> 0:16:36.400 see that more localized to the right hemisphere. Yeah, and 0:16:36.440 --> 0:16:39.960 this would be especially things like visual and spatial reasoning, 0:16:40.160 --> 0:16:43.160 like the right hemisphere is going to be very important 0:16:43.200 --> 0:16:46.200 if you need to imagine a map in order to 0:16:46.360 --> 0:16:52.280 give directions. So brain activity unbalancing, where one one side 0:16:52.360 --> 0:16:55.640 is more active in a given task than another. This 0:16:55.640 --> 0:16:58.640 this occurs based on which system is being employed in 0:16:58.680 --> 0:17:02.560 a given task, rather than anything about an individual or 0:17:02.600 --> 0:17:05.199 their background of This is all, of course, assuming a 0:17:05.200 --> 0:17:08.919 healthy brain. Obviously, if one side of your brain is missing, 0:17:09.000 --> 0:17:12.480 there's going to be more activity beside it's there. Now, 0:17:12.840 --> 0:17:16.439 no evidence suggests that individual individuals have truly dominant sides 0:17:16.480 --> 0:17:18.359 of the brain when it comes to their you know, 0:17:18.400 --> 0:17:21.919 their personality makeup, right, You're not like creative right brained 0:17:22.000 --> 0:17:25.480 or logical left brain right And likewise that the logic 0:17:25.560 --> 0:17:30.000 and creativity split idea. Uh you know again, you'll have 0:17:30.040 --> 0:17:33.560 individuals that are certainly more logical perhaps or more creative. 0:17:33.920 --> 0:17:37.080 But as as neuroscigned, as Elizabeth Waters has pointed out 0:17:37.280 --> 0:17:41.000 among many others, logic and creativity are not these two 0:17:41.080 --> 0:17:45.000 distinct notions. You know, they're deeply interlinks. Yeah, Like being 0:17:45.119 --> 0:17:49.040 good at logic is in many cases being a certain 0:17:49.080 --> 0:17:53.320 type of creative. Yeah, I mean, what you might dismiss 0:17:53.400 --> 0:17:56.439 is just a really logical exercise, like safe solving a 0:17:56.480 --> 0:18:00.080 complex math problem that may well require that will require 0:18:00.119 --> 0:18:03.720 some creative thinking. Likewise, a creative endeavor like say, writing 0:18:03.760 --> 0:18:07.600 a poem, finishing a novel, coming up with a cool joke, whatever, 0:18:07.960 --> 0:18:10.320 you know, those are gonna going to be activities that 0:18:10.440 --> 0:18:12.960 also involve logic. In fact, some of what we're going 0:18:13.000 --> 0:18:15.080 to discuss in this pair of episodes in in the 0:18:15.080 --> 0:18:17.840 neuroscience research turns this whole thing on its head in 0:18:17.840 --> 0:18:20.800 a way, because the left part of the brain that's 0:18:20.800 --> 0:18:25.119 more dominant in exercises involving speech and language often tends 0:18:25.160 --> 0:18:28.880 to be the more creative one in explaining behaviors. Right 0:18:28.920 --> 0:18:31.760 it's the one that tends to interpret and come up 0:18:31.800 --> 0:18:35.240 with explanations for things, as will as well talk about 0:18:35.320 --> 0:18:38.560 later on, which is a creative exercise, whereas the right 0:18:38.600 --> 0:18:41.040 brain tends to more often be the part of the 0:18:41.080 --> 0:18:47.720 brain that records experiences accurately without creating explanations for them exactly. 0:18:48.200 --> 0:18:50.600 And but but certainly, if I'm gonna, you know, drive 0:18:50.640 --> 0:18:53.440 home anything, we want to point out that that the 0:18:53.760 --> 0:18:58.840 creativity logic anything that employs these these two loose idea, 0:18:58.880 --> 0:19:02.520 you know, buckets of of of cognition. You know, these 0:19:02.560 --> 0:19:04.959 are going to be products of whole brain cognition like 0:19:05.040 --> 0:19:08.040 our our the brain is all these areas of the 0:19:08.040 --> 0:19:11.840 brain are working together, uh to create this effect. Now, 0:19:11.960 --> 0:19:15.199 ultimately in this episode we're going to be asking what 0:19:15.400 --> 0:19:19.960 happens when you cut those two hemispheres of the brain apart. Yes, 0:19:20.520 --> 0:19:22.240 but I guess we'll have to get to that after 0:19:22.320 --> 0:19:28.160 a break. Than alright, we're back now. Before we get 0:19:28.200 --> 0:19:30.720 to the idea of severing the brain hemispheres, we should 0:19:30.720 --> 0:19:34.280 probably talk about a little more about Broca and Vernica. Yeah, 0:19:34.320 --> 0:19:37.280 these are just two really key individuals to this whole 0:19:37.280 --> 0:19:40.320 discussion and even just the idea of understanding the human brain. 0:19:40.840 --> 0:19:45.359 Um So Paul Broca will start with him again eighteen 0:19:45.400 --> 0:19:49.320 eighty He was a French surgeon, neurologist and anthropologists. And 0:19:49.440 --> 0:19:51.800 he is also for anyone who hasn't read the book 0:19:51.880 --> 0:19:54.199 but has seen the title, he is the namesake for 0:19:54.240 --> 0:19:58.520 Carl Sagan's book Broke His Brain. Sagan describes at one 0:19:58.560 --> 0:20:01.840 point point holding a jar are containing the noted scientist's 0:20:01.880 --> 0:20:06.639 brain weight like imagining doing this literally doing literally doing it? Okay, 0:20:06.680 --> 0:20:09.280 holding holding the jar that contains his brain, and then 0:20:09.359 --> 0:20:11.840 thinking about like what you know, talking He talks a 0:20:11.840 --> 0:20:15.399 bit about Broca and and and you know, his his work, 0:20:15.480 --> 0:20:19.600 his personality, but also just sort of meditates on what 0:20:19.640 --> 0:20:22.879 you're doing when you when you hold this brain in 0:20:22.920 --> 0:20:26.440 your hands. I want to imagine that, having not read 0:20:26.480 --> 0:20:29.240 this book, it is in fact just like a caper story, 0:20:29.400 --> 0:20:32.360 with Broker's brain as the MacGuffin, and it gets traded 0:20:32.359 --> 0:20:34.800 around and their car chases, Sagan's trying to get it 0:20:34.840 --> 0:20:37.840 back from the KGB spies. Uh no, not quite, but 0:20:37.920 --> 0:20:41.760 Dante Skull shows up as well. Oh nice, so broken. 0:20:41.800 --> 0:20:45.440 Though he made important contributions to our understanding of cancer, 0:20:45.600 --> 0:20:49.800 the treatment of aneurysms and aphasia and his Sagan pointed out, 0:20:49.960 --> 0:20:52.200 Broca was also quite concerned with the medical care of 0:20:52.240 --> 0:20:54.240 the poor. He was you know, he was. He was 0:20:54.280 --> 0:20:57.520 a free thinker. He was a strong darwin supporter, and 0:20:57.840 --> 0:21:00.439 above just about everything, he was the founder of modern 0:21:00.480 --> 0:21:05.119 brain surgery. And Broco was influential in identifying regions of 0:21:05.160 --> 0:21:09.160 the brain as being especially responsible for certain cognitive functions. Right. Yeah, 0:21:09.160 --> 0:21:13.159 he investigated the rheinan cephalon the smell brain. But his 0:21:13.400 --> 0:21:16.800 name actually goes to a small region in the left 0:21:16.840 --> 0:21:21.840 frontal lobe of the cerebral cortex what we call Broca's area. UH. 0:21:21.880 --> 0:21:25.800 This is left hemisphere, third frontal convolution. To be specific, 0:21:26.200 --> 0:21:29.800 this is the area where articulate speech is largely localized 0:21:29.800 --> 0:21:33.040 and controlled. And his Segan pointed out given the importance 0:21:33.080 --> 0:21:36.760 of language and articulate speech and human evolution, this portion 0:21:36.800 --> 0:21:40.280 of the human brain may be considered, in Sagan's words, 0:21:40.320 --> 0:21:43.520 the seat of our humanity and some respects. And it's 0:21:43.520 --> 0:21:46.600 also something anatomists have looked for in the remains of 0:21:46.600 --> 0:21:52.359 our hominid ancestors, such as Homo habilists. Columbia University anthropologist 0:21:52.440 --> 0:21:56.320 Ralph Holloway Sagan sided us you know, studied and claimed 0:21:56.320 --> 0:21:59.200 to have found evidence for its development of a Broca's 0:21:59.280 --> 0:22:02.119 area some two million years ago, and this would have 0:22:02.119 --> 0:22:05.399 been around the time early tool use was beginning. UH. 0:22:05.680 --> 0:22:10.439 Also South African paleol anthropologist Philip Tobias also made this claim, 0:22:10.720 --> 0:22:14.800 though according to Suzanne Kemer, associate professor of Linguistics at 0:22:14.840 --> 0:22:18.360 Rice University, quote, these claims have been controversial. Many see 0:22:18.440 --> 0:22:22.240 no regular impressions that could be ascribed to brain structure here, 0:22:22.680 --> 0:22:25.760 and I can imagine it's probably difficult to just look 0:22:25.800 --> 0:22:29.240