Pratique du Shadowing: 2. Foundations: This Is Your Brain - Apprendre l'anglais à l'oral avec la vidéo
Création de la leçon...
1
Dr. John L.
2
We're going to begin the class proper, Introduction to Psychology, with a discussion about the brain.
3
And in particular, I want to lead off the class with an idea that the Nobel Prize the prize -winning biologist,
4
Francis Crick, described as the astonishing hypothesis.
5
And the astonishing hypothesis is summarized like this.
6
As he writes, the astonishing hypothesis is that you, your joys and your sorrows, your memories and your ambitions, your sense of personal identity
7
and free will are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules.
8
As Lewis Carroll's Alice might you might have phrased it, you're nothing but a pack of neurons.
9
It is fair to describe this as astonishing.
10
It is an odd and unnatural view.
11
And I don't actually expect people to believe it at first.
12
It's an open question whether you'll believe it when this class comes to an end.
13
But I'd be surprised if many of you believe it now.
14
Most people don't.
15
Most people, in fact, hold a different view history.
16
Most people are dualists.
17
Now, dualism is a very different doctrine.
18
It's a doctrine that can be found in every religion and in most philosophical systems throughout history.
19
It was very explicit in Plato, for instance.
20
But the most articulate and well -known defender of dualism is the philosopher René Descartes.
21
And Rene Descartes explicitly asked a question,
22
are humans merely physical machines, merely physical things?
23
And he answered no. He agreed that animals are machines.
24
In fact, he called them beast machines and said animals, non -human animals, are merely robots.
25
But people are different.
26
There's a duality of people.
27
Like animals, we possess physical material bodies.
28
But unlike animals, what we are is not physical.
29
We are immaterial souls that possess physical bodies, that have physical bodies, that reside in physical bodies,
30
that connect to physical bodies.
31
So, this is known as dualism because the claim is, for humans at least, there are two separate things.
32
There's our material bodies and there's our immaterial minds.
33
Now, Descartes made two arguments for dualism.
34
One argument involved observations about human action.
35
So, Descartes lived in a fairly sophisticated time and his time did have robots.
36
These were not electrical robots, of course.
37
They were robots powered by hydraulics.
38
So, Descartes would walk around the French royal gardens.
39
And the French royal gardens were set up like a seventeenth -century Disneyland.
40
They had these characters that would operate according to water flow.
41
And so if you stepped on a certain panel, a swordsman would jump out with a sword.
42
If you stepped somewhere else, a bathing beauty would cover herself up behind some bushes.
43
And Descartes said, boy, these machines respond in certain ways to certain actions.
44
So, machines can do certain things.
45
In fact, he says our bodies work that way too.
46
If you tap somebody on the knee your leg will jump out.
47
Well, maybe that's all we are.
48
But Descartes said that can't be because there are things that humans do that no machine could ever do.
49
Humans are not limited to reflexive action.
50
Rather, humans are capable of coordinated, creative, spontaneous things.
51
We can use language, for instance.
52
And sometimes my use of language can be reflexive.
53
Somebody says, how are you?
54
And I say, I am fine, how are you?
55
But sometimes I could say what I choose to be.
56
How are you?
57
Pretty damn good.
58
I could just choose.
59
And machines, Descartes argued, are incapable of that sort of choice.
60
Hence, we are not mere machines.
61
The second argument is of course quite famous.
62
And this he came to using the method of doubt.
63
So, he started asking himself the question, what can I be sure of?
64
And he said, well, I believe there's a God, but honestly, I can't be sure there's a God.
65
I believe I live in a rich country, but maybe I've been fooled.
66
He even said, I believe I have had friends and family, but maybe I am being tricked.
67
Maybe an evil demon, for instance, has tricked me, has deluded me into thinking I have experiences that aren't real.
68
And of course the modern version of this is the matrix.
69
The idea that the matrix is explicitly built upon Cartesian Descartes' worries about an evil demon.
70
Maybe everything you're now they're now experiencing is not real but rather is a product of some other perhaps malevolent creature.
71
Descartes similarly could doubt he has a body.
72
In fact, he noticed that mad men sometimes believe they have extra limbs
73
or they believe they're of different sizes and shapes than they really are.
74
And Descartes said, how do I know I'm not crazy?
75
I mean, crazy people don't think they're crazy, so the fact I don't think I'm crazy doesn't mean I'm not crazy.
76
He says, how do I know, Descartes said, I'm not dreaming right now.
77
But there is one thing, Descartes concluded, that he cannot doubt.
78
And the answer is he cannot doubt that he is himself thinking.
79
That would be self -refuting.
80
And so Descartes used the method of doubt to say, there's something really different about having a body.
81
That's always uncertain from having a mind.
82
And he used this argument as a way to support dualism, them as a way to support the idea that bodies and minds are separate.
83
And so he concluded, I knew that I was a substance, a whole essence or nature of which is to think and
84
that for its existence there is no need of any place nor does it depend on any material thing.
85
That is to say the soul by which I am, what I am, is entirely distinct from body.
86
Now, I said before that this is common sense
87
and I want to illustrate the common sense nature of this in a few ways.
88
One thing is our dualism is a mesh in our language.
89
So, we have a certain mode of talking about things that we own or things that are close to us, my arm, my heart, my child, my car.
90
But we also extend that to my body and my brain.
91
We talk about owning our brains as if we're somehow separate from them.
92
Our dualism shows up in intuitions about personal identity.
93
And what this means is that
94
common sense tells us that somebody can be the same person even if their body undergoes radical and profound changes.
95
The best examples of this are fictional.
96
So we have no problem understanding a movie where where somebody goes to sleep as a teenager
97
and wakes up as Jennifer Garner, as an older person.
98
Now, nobody says, oh, that's a documentary.
99
I believe that thoroughly true.
100
But at the same time nobody, no adult, no teenager, no child ever leaves and says, I'm totally conceptually confused.
101
Rather, we follow, we follow, we follow the story.
102
We can also follow stories which involve more profound transformations as
103
when a man dies and is reborn into the body of a child.
104
Now, you might have different views around, people around this room will have different views as to whether reincarnation really exists.
105
But we can imagine it.
106
We can imagine a person dying and then re -emerging in another body.
107
This is not Hollywood invention.
108
One of the great short stories of the last century begins with a sentence by Franz Kafka.
109
As Gregor Samsa awoke one morning from uneasy dreams, he found himself transformed in his bed into a gigantic insect.
110
And again, Kafka invites us to imagine waking up into a body of a cockroach and we can.
111
This is also not modern.
112
Hundreds of years before the birth of Christ Homer described the
113
fate of the companions of Odysseus who were transformed by a witch into pigs.
114
Actually that's not quite right.
115
Anyway, she didn't turn the men into pigs.
116
She did something worse.
117
She stuck them in the bodies of pigs.
118
They had the head and voice and bristles and body of swine
119
but their minds remained unchanged as before so they were penned there weeping.
120
And we are invited to imagine the fate of, again, finding ourselves in the bodies of other creatures.
121
And if you could imagine this, this is because you are imagining what you are as separate from the body that you reside in.
122
We allow for the notion that many people can occupy one body.
123
This is a mainstay of some slapstick humor, including the classic movie, All of Me, Steve Martin, Lily Tomlin, highly recommended.
124
But many people think this sort of thing really happens.
125
One analysis of multiple personality disorder.
126
is that you have many people inside a single body fighting it out for control.
127
Now, we will discuss multiple personalities sort of towards the end of the semester
128
and it turns out things are a good deal more complicated than this.
129
But still, my point isn't about how it really is but how we think about it.
130
Common sense tells us you could have more than one person inside a single body.
131
This shows up in a different context involving exorcisms, where many belief systems allow for the idea that people's behavior,
132
particularly their evil or irrational behavior, could be because something else has taken over their bodies.
133
Finally, most people around the world,
134
all religions, and most people in most countries at most times believe that people can survive the destruction of their bodies.
135
Now, cultures differ according to the fate of the body.
136
Some cultures have the body going to, sorry, the fate of the soul.
137
Some cultures have you going to heaven or descending to hell.
138
Others have you occupy another body.
139
Still others have you occupy an amorphous spirit world.
140
But what they share is the idea
141
that what you are is separable from this physical thing you carry around
142
and the and the physical thing that you carry around can be destroyed while you live on.
143
These views are particularly common in the United States.
144
In one survey done in Chicago a few years ago, people were asked their religion and then were asked what would happen to them when they died.
145
Most people in the sample were Christian and about 96 % of Christians said, when I die I'm going to go to heaven.
146
Some of the sample was Jewish.
147
Now, Judaism is actually a religion with a less than clear story about the afterlife.
148
Still, most of the subjects who identified themselves as Jewish said when they die they will go to heaven.
149
Some of the sample denied having any religion at all, said they have no religion at all.
150
Still, when these people were asked what would happen when they would die, most of them answered, I'm going to go to heaven.
151
So, dualism is a mesh.
152
A lot rests on it.
153
But as Crick points out, the scientific consensus now is that dualism is wrong.
154
There is no you separable or separate from your body.
155
In particular, there is no you separable from your brain.
156
To put it the way cognitive scientists and psychologists and neuroscientists like to put it, the mind is what the brain does.
157
The mind reflects the workings of the brain just like computation reflects the working of a computer.
158
Now, why would you hold such an outrageous view?
159
Why would you reject dualism in favor of this alternative?
160
Well, a few reasons.
161
One reason is dualism has always had its problems.
162
For one thing, I think it's a profoundly unscientific doctrine.
163
We want to know as curious people how children learn language, what we find attractive or unattractive,
164
what's the basis for mental illness.
165
And dualism simply says it's all non -physical as part of the ether and hence fails to explain it.
166
More specifically, dualists like Descartes struggle to explain how a physical body connects to an immaterial immaterial soul.
167
What's the conduit?
168
How could this connection be made?
169
After all, Descartes knew full well that there is such a connection.
170
Your body obeys your commands.
171
If you bang your toe, stub your toe, you feel pain.
172
If you drink alcohol, it affects your reasoning.
173
But he could only wave his hands as to how this physical thing in the world could connect to an immaterial mind.
174
Descartes, when he was alive, was reasonable enough concluding that physical objects cannot do certain things.
175
He was reasonable enough in concluding, for instance, as he did, that there's no way a merely physical object could ever play a game of chess because,
176
and that, such a capacity is beyond the capacity of the physical world and hence which you have to apply, you have to extend explanation to an immaterial soul.
177
But now we know we have what scientists call an existence proof.
178
We know physical objects can do complicated and interesting things.
179
We know, for instance, machines can play chess.
180
We know machines can manipulate symbols.
181
We know machines have limited capacities to engage in mathematical and logical reasoning to recognize things,
182
to do various forms of computations.
183
And this makes it at least possible that we are such machines.
184
So, one, you can no longer say, look, physical things just can't do that because we know physical things can do a lot.
185
And this opens up the possibility that humans are physical things, in particular, that humans are brains.
186
Finally, There's strong evidence that the brain is involved in mental life.
187
Somebody who held a dualist view that said that what we do
188
and what we decide and what we think
189
and what we want are all… have nothing to do with the physical world would be embarrassed by the fact
190
that the brain seems to correspond in intricate and elaborate ways to our mental life.
191
Now, this has been known for a for a long time.
192
Philosophers and psychologists knew for a long time that getting smacked in the head could change your mental faculties,
193
that diseases like syphilis could make you deranged, that chemicals like caffeine and alcohol can affect how you think.
194
But what's new is we can now in different ways see the direct effects of mental life.
195
Somebody with a severe and and profound loss of mental faculties,
196
the deficit will be shown correspondingly in her brain.
197
Studies using imaging techniques like CAT scans,
198
PET, and fMRI illustrate that different parts of the brain are active during different parts of mental life.
199
For instance, the difference between seeing words,
200
hearing words, reading words, and generating words can correspond to different aspects of what part of your brain is active.
201
To some extent, if we put you in an fMRI scanner and observe what you're doing in real time, by looking at the activity patterns in your brain,
202
we can tell whether you're thinking about music or thinking about sex.
203
To some extent, we can tell whether you're solving a moral dilemma versus something else.
204
And this is no surprise if what what we are is the workings of our physical brains.
205
But it is extremely difficult to explain if one is a dualist.
206
Now, so what you have is the scientific consensus is
207
that all of mental life including consciousness and emotions and choice and morality are the products of brain activities.
208
So, you would expect that when you rip open the skull and look If you look at the brain, you'd see something glorious.
209
You'd see like, I don't know, a big shiny thing with glass tubes and blinding lights and sparks and wonderful colors.
210
And actually though, the brain is just disgusting.
211
It looks like an old meatloaf.
212
It's gray when you take it out of the head.
213
It's called gray matter.
214
But that's just because it's out of the head inside the head it's bright red because it's pulsing with blood.
215
It doesn't even taste good.
216
Well, has anybody here ever eaten, brain?
217
I mean, it's good with cream sauce, but everything's good with cream sauce.
218
So, the question is, how can something like this give rise to us?
219
And, I mean, you have to have some sympathy for Descartes.
220
There's another argument Descartes could have made that's a lot less subtle than the ones he did make
221
which is that thing responsible for free will and love and consciousness?
222
Ridiculous.
223
What I want to do and what the goal of neuroscience is is to make it less ridiculous, to try to explain how the brain works,
224
how the brain can give rise to thought.
225
And what I want to do today is take a first stab at this question
226
but it's something we'll continue to discuss throughout the course as we talk about different aspects of mental life.
227
What I want to do though now is provide a big picture.
228
So, I want to do is start off small with the smallest interesting part of the brain
229
and then get bigger and bigger and bigger here, talk about how the small part of the brain, the neurons, the basic building blocks of thought,
230
combine to other mental structures and then to different sub -parts of the brain and finally to the whole thing.
231
So, one of the discoveries of psychology is that the basic unit of the brain appears to be the neuron.
232
The neuron is a specific sort of cell.
233
And the neuron has three major major parts as you can see illustrated here.
234
Neurons actually look quite different from one another but this is a typical one.
235
There are the dendrites, these little tentacles here.
236
And the dendrites get signals from other neurons.
237
Now, these signals can be either excitatory, which is that they raise the likelihood the neuron will fire,
238
or inhibitory, in that they lower the likelihood that the neuron will fire.
239
The cell body sums it up.
240
And you could view it arithmetically.
241
The excitatory signals are pluses, the inhibitory ones are minuses, and then if you get a certain number,
242
plus sixty or something, the neuron will fire.
243
And it fires along the axon, the thing to the right.
244
The axon is much longer than the dendrites and in fact some axons are many feet long.
245
There's an axon leading from your spinal cord to your big toe, for instance.
246
It is so shocking, the lights go out.
247
Surrounded, surrounding, to complete a mechanical metaphor that would have led Descartes to despair,
248
thank you colleague, surrounding the axon is a myelin sheath which is actually just insulation.
249
It helps the firing work quicker.
250
So, here are some facts about neurons.
251
There are a lot of them, about a thousand billion of them, and each neuron can be connected to around thousands,
252
perhaps tens of thousands, other neurons.
253
So, it's an extraordinarily complicated computing device.
254
Neurons come in three flavors.
255
There are sensory neurons which take information from the world.
256
So, as you see me, for instance, there are neurons firing from your retina sending sending signals to your brain.
257
There are motor neurons.
258
If you decide to raise your hand, those are motor neurons telling the muscles what to do.
259
And there are interneurons which connect the two.
260
And basically the interneurons do the thinking.
261
They make the connection between sensation and action.
262
It used to be believed, and it's the sort of thing I would've, when I taught this course many years ago I would lecture on, that neurons do not once you lose them,
263
they, you never get them back.
264
This is actually not true.
265
There are parts of the brain in which neurons can regrow.
266
One interesting thing about neurons is a neuron is like a gun.
267
It either fires or it doesn't.
268
It's all or nothing.
269
If you squeeze the trigger of a gun really hard and really fast, it doesn't fire any faster or harder than if you just squeezed used it gently.
270
Now, this seems to be strange.
271
Why?
272
How could neurons be all or nothing when sensation is very graded?
273
If somebody next to you pushed on your hand the degree of pushing, you'd be able to notice it.
274
It's not either pushing or not pushing.
275
You can—degrees of pushing, degrees of heat, degrees of brightness.
276
And the answer is although neurons are all or nothing, there are ways to code code intensity.
277
So, one simple way to code intensity is the number of neurons firing.
278
The more neurons, the more intense.
279
Another way to increase intensity is the frequency of firing.
280
So, I'll just use those two.
281
The first one is the number of neurons firing.
282
The second one is the frequency of firing in that something is more intense if it's bang, bang, bang, bang, bang, bang, bang, then bang, bang, bang, bang.
283
And these are two ways through which neurons encode intensity.
284
Now, neurons are connected and they talk to one another.
285
And it used to be thought they were tied to one another like a computer, like you take wires and you connect wires to each other.
286
You wrap them around and connect them.
287
It turns out this isn't the case.
288
It turns out that neurons relate to one another chemically in a kind of interesting way.
289
Between any neurons, between the axon of one neuron and the dendrite of another, there's a tiny gap.
290
The gap could be about one ten -thousandth of a millimeter wide, this infinitesimal gap.
291
And this gap is known as a synapse.
292
And what happens is when a neuron fires, an axon sends chemicals shooting through the gap.
293
These chemicals are known as neurotransmitters and they affect the dendrites.
294
So, neurons communicate to one another chemically.
295
These, again, the chemicals could excite the other neuron, excitatory, bring up the chances it will fire,
296
or inhibit the other neuron, inhibitory.
297
Now, neurotransmitters become interesting because a lot of psychopharmacology,
298
both of the medical sort and the recreational sort, consists of fiddling with neurotransmitters.
299
And so you could see this through some examples.
300
There are two sorts of ways you could fiddle with neurotransmitters and correspondingly two sorts of drugs.
301
There are agonists
302
and what an agonist does is increases the effect of neurotransmitters either by making more neurotransmitters
303
or stopping the cleanup of neurotransmitters or in some cases by faking a neurotransmitter, by mimicking its effects.
304
Then there are antagonists that slow down the amount of neurotransmitters either
305
because they destroy neurotransmitters or they make it hard to create
306
or in some cases they go to the dendrite of the neuron
307
and they kind of put a paste over it so that the neurotransmitters can't connect.
308
And it's through these clever ways that neurons can affect your mental life.
309
So, for instance, there is a drug known as is called curare.
310
And curare is an antagonist.
311
It's a very particular sort of antagonist.
312
It blocks motor neurons from affecting muscle fibers.
313
What this does then is it paralyzes you because your motor neurons, you send the command to your arm to stand, to lift up, it doesn't work.
314
You send the command to your leg to move, it doesn't work the motor neurons are deactivated
315
and then because the way you breathe is through motor neurons you then die.
316
There's alcohol.
317
Alcohol is inhibitory.
318
Now, this may be puzzling to people.
319
It's mildly paradoxical because you may be thinking alcohol is not inhibitory.
320
On the contrary, when I drink a lot of alcohol I lose my inhibitions
321
and become a I become a more fun person.
322
I become more aggressive and more sexually vibrant and simply more beautiful.
323
And so in what way is alcohol inhibitory?
324
Well, the answer is it inhibits the inhibitory parts of your brain.
325
So you have parts of your brain that are basically telling you now, largely in the frontal lobes, Okay, keep your pants on.
326
Don't hit anybody.
327
Don't use bad words.
328
Alcohol relaxes, shuts down those parts of the brain.
329
If you take enough alcohol, it then goes down to inhibit the excitatory parts of your brain and then you fall on the floor and pass out.
330
Amphetamines increase the amount of arousal.
331
In particular, they increase the amount of norepinephrine, a neurotransmitter that's responsible for just general arousal.
332
And so, amphetamines include drugs like Speed and Coke.
333
There are… Prozac works on serotonin.
334
When we discuss clinical psychology and depression,
335
we'll learn the extent to which neurotransmitter disorders are implicated in certain disorders like depression.
336
And one problem is that for depression is that there's too little of a neurotransmitter known as serotonin.
337
Prozac makes serotonin more prevalent and so in some extent might help alleviate depression.
338
Parkinson's disease is a disease involving destruction of motor control and loss of motor control, difficulty moving.
339
and one factor in Parkinson's is too little of a neurotransmitter known as dopamine.
340
The drug L -dopa increases the supply of dopamine and so does something to alleviate, at least temporarily, the symptoms of Parkinson's.
341
So, you have neurons and they're clustered together and they fire and they communicate to one another.
342
So, how does this all work to give rise to creatures who could do interesting things like talk and think?
343
Well, again, it used to be believed that the brain is wired up like a computer, like a PC or a Mac or something like that.
344
But we know this can't be true.
345
It can't be true because there's two ways in which the brain is better than a computer.
346
For one thing, the brain is highly resistant to damage.
347
If you have a laptop and I I persuade you to open it up.
348
for me and I take the pliers and kind of snip just about anywhere, your laptop will be destroyed.
349
But the brain is actually more resilient.
350
You can take a lot of brain damage and still preserve some mental functioning.
351
To some interesting sense, there's some sort of damage resistance built into the brain
352
that allows different parts of the brain to take over if some parts are damaged.
353
A second consideration is the The brain is extremely fast.
354
Your computer works on wires and electricity but your brain uses tissue and tissue is extremely slow.
355
The paradox then is how do you create such a fast computer with such slow stuff?
356
And you can't, if the brain was wired up like a personal computer, it would take you four hours to recognize a face.
357
But in fact, we could do things extremely quickly.
358
So, the question then is, how is the brain wired up?
359
And the answer is, unlike many, unlike commercially generated computers, the brain works through parallel processing,
360
massively parallel distributed processing.
361
There's a whole lot of research, and this is research some of which takes place outside psychology departments
362
and in engineering departments and science departments trying to figure out how a computer can do the same things brains can do.
363
And one way people do this is they take a hint from nature
364
and they try to construct massively distributive networks to do aspects of reasoning.
365
So, there's a very simple computational network that is interesting
366
because it kind of looks to some extent like the the way neurons look and this is often known as neural networks.
367
And people who study this often claim to be studying neural
368
network modeling to try to build smart machines by modeling them after brains.
369
And in the last twenty years or so this has been a huge
370
and vibrant area of study where people are trying to wire up machines
371
that can do brain -like things from components
372
that look a lot like neurons and are are wired up together as neurons are.
373
One consideration in all of this is that this is a very young field and nobody knows how to do it yet.
374
There is no machine yet that can recognize faces or understand sentences at the level of a two -year -old human.
375
There is no machine yet that can do just about anything people can do in an interesting way.
376
And this is in part
377
because the human brain is wired up in an extraordinarily more complicated complicated way than any sort of simple neural network.
378
This is a sort of schematic diagram, you're not responsible for this, of parts of the visual cortex.
379
And the thing to realize about this is it's extraordinarily simplified.
380
So, the brain is a complicated system.
381
Now, so we've talked a little bit about the basic building blocks of the brain, neurons.
382
We've then talked about how neurons can communicate to one another then turned to how neurons are wired up together.
383
Now let's talk a little bit about different parts of the brain.
384
Now, there are some things you don't actually need your brain to do.
385
The study of what you don't need your brain to do
386
has often drawn upon this weird methodology where this was actually done in France a lot where they would decapitate people.
387
And when after they decapitated psychologists would rush to the body of the headless person
388
and sort of test out reflexes and stuff like that.
389
It's kind of gruesome.
390
But we know there are some things you don't need your brain for.
391
You don't need your brain for newborn sucking, limb flexation and withdrawal from pain.
392
Your limb will pull back even if your head is gone.
393
Erection of the penis can be done without a brain.
394
Vomiting, also done without a brain.
395
Here, I need a volunteer.
396
Very simple.
397
This will not involve any of the excellent, any of the above.
398
Could you stand up?
399
Just, okay.
400
This is a new shirt so I want to stay away.
401
No, this is, if you hold out your hand and one hand flat, excellent, excellent.
402
That's the textbook, fifth edition.
403
Perfect.
404
What you'll notice is, thank you very much, What you'll notice is this hit and this hand went back up.
405
This is something automatic, instinctive and does not require your brain.
406
So, your brain isn't needed for everything.
407
What does your brain do?
408
Well, some things that your brain does involve very low level internal structures.
409
And these are called subcortical structures because they're below the cortex.
410
They're underneath the cortex.
411
So, for instance, what we have here is a diagram of the brain.
412
The way to read this diagram is it's as if it were my brain.
413
I'm facing this way.
414
My head gets cut in half, down here.
415
And then you can see the brain.
416
So, this is the front over here.
417
That's the back.
418
Some key parts are illustrated here.
419
The medulla, for instance, is responsible for heart rate and and respiration.
420
It's very deep within the brain and if it gets damaged you could, you're likely to die.
421
The cerebellum is responsible for body balance and muscular coordination.
422
And to give you again a feeling for the complexity of these systems, the cerebellum contains approximately thirty billion neurons.
423
The hypothalamus is responsible here for feeding,
424
hunger, thirst, and to some extent sleep deep and here is the same brain parts in close -up.
425
Now, all of these parts of the brain are essential
426
and many of them are implicated in interesting psychological processes but where the action is is the cortex.
427
Isn't this beautiful?
428
The cortex is the outer layer and the outer layer is all crumpled up.
429
You ever wonder why your brain looks wrinkled?
430
That's because it's all crumpled.
431
If you took out somebody's cortex and flattened it out, it would be about two feet square, sort of like a nice, like a rug.
432
And the cortex is where all the neat stuff takes place.
433
Fish don't have any of it.
434
So, no offense to fish, but I think that fish don't have much of a mental life.
435
Reptiles and birds have a of it and primates have a lot and humans have a real lot.
436
Eighty percent of the volume of our brain about is cortex.
437
And the cortex can be broken up into different parts or lobes.
438
There is the, and again this is facing in profile forward, there is the frontal lobe, easy to remember, this part in front,
439
the parietal lobe, the occipital lobe, and the temporal lobe.
440
And one theme we're going to return to is this is half the brain.
441
It's, this is in fact the left half of the brain.
442
On the other half, the right half, everything's duplicated with some slight and subtle differences.
443
What's really weird, one really weird finding about these lobes is that they They include topological maps.
444
They include maps of your body.
445
Here's a cartoon which actually illustrates a classic experiment
446
by some physiologists who for some reason had a dog's brain opened up and started shocking different parts of the brain.
447
You could do brain surgery while fully conscious because the brain itself has no sensed organs to it.
448
And it turns out that the dog, when he's at part of its brain, its leg would kick up.
449
And it took Dr. Penfield at McGill University to do the same thing with people.
450
So, they were doing some brain surgery.
451
He had a little electrical thing just on.
452
I don't know how he got to do this.
453
He started zapping it and boom, the person's parts of her body would move.
454
More than that, when he zapped other parts of the brain, people would claim to see colors.
455
And he zapped other parts of the brain, right, people would claim to hear sounds.
456
And other parts of the brain people would claim to experience touch.
457
And through his research and other research it was found that there are maps in the brain of the body.
458
There is a map in the motor part of the brain, the motor cortex of the sort up on the left
459
and the sensory cortex of the sort that you could see on the right body.
460
And if you…and you could tell what's what by opening up the brain
461
and shocking different parts and those parts would correspond to the parts of the body shown in the diagram there.
462
Now, two things to notice about these maps.
463
The first is they're topographical and what this means is that
464
if two parts of the…two parts are close together on the body they'll be close together on the brain brain.
465
So, your tongue is closer to your jaw than it is to your hip in the body.
466
So, too, in both the motor cortex and the somatosensory cortex.
467
Also, you'll notice
468
that the size of the body part represented in the brain
469
does not correspond to the size of the body part in the real world.
470
Rather, what determines the size in the brain
471
is the extent to which either they have motor command over it or sensory control.
472
So, there's a whole lot of sensory organs, for instance, focused along your tongue and that's why that's so big and an enormous amount on your face.
473
But your shoulder doesn't even make it on there because although your shoulder might be bigger than your tongue, there's not much going on.
474
In fact, if you draw a diagram of a person what their body is corresponding to the amount of somatosensory cortex,
475
you get something like that.
476
That's your sensory body.
477
Eww.
478
Now, so you have these maps in your head.
479
But the thing to realize is, and these maps are part of your cortex, but the things to realize is that's an important part of what goes on in your brain
480
but less than one quarter of the cortex contains these maps or projection areas.
481
The rest is involved in language and reasoning and moral thought and so on.
482
And in fact the proportion as you go from rat, cat, monkey, humans, less and less of it is devoted to projection areas and more and more to other things.
483
So, how do we figure out what the other parts of the brain do?
484
Well, there's all sorts of methods.
485
Typically these are recent imaging methods like cat scan and pet scan and fMRI which,
486
as I said before, show parts of your brain at work.
487
If you want to know which part of your brain is responsible for or language,
488
you could put somebody into a scanner and have them exposed to language
489
or do a linguistic task or talk or something and then see what parts of their brain are active.
490
Another way to explore what the brain does is to consider what happens to people
491
when very bad things happen to their brain.
492
And these bad things could could happen through lesions, through tumors, through strokes, through injury.
493
For the most part, neuropsychologists don't like helmet laws.
494
Neuropsychologists love when motorcyclists drive without helmets because through their horrible accidents we gain great insights into how the brain works.
495
And the logic is if you find somebody crudely,
496
if you find somebody with damage to this part of the brain right here and that person person can't recognize faces,
497
for instance, there's some reason to believe that this part of the brain is related to face recognition.
498
And so through the study of brain damage
499
and the study of…we can gain some understanding of what different parts of the brain do.
500
And so people study brain damages, brain damage that implicates motor control such as apraxia.
501
And what's interesting about apraxia is it's not paralysis.
502
Somebody with apraxia can move, do simple movements just fine, but they can't coordinate their movements.
503
They can't do something like wave goodbye or light a cigarette.
504
There's agnosia.
505
And agnosia is a disorder which isn't blindness because a person could still see perfectly well.
506
Their eyes are intact.
507
But rather what happens in agnosia is they lose the ability to recognize certain things.
508
Sometimes this is described as psychic blindness.
509
And so they may get visual agnosia and lose the ability to recognize objects.
510
They may get prosopagnosia and lose the ability to recognize faces.
511
There are disorders of sensory neglect, some famous disorders.
512
Again, it's not paralysis, it's not blindness, but due to certain parts of your, damaged parts of your brain, you might lose, for instance,
513
the idea that there's a left side of your body or a left side of the world.
514
And these cases are
515
so interesting I want to devote some chunk to a class in the next few weeks to discussing them.
516
There are disorders of language like aphasia.
517
The classic case was discovered by Paul Broca in 1861, a patient who had damaged a part brain and can only say one word,
518
tan, and the person can say, tan, tan, tan, tan, and everything else was gone.
519
There's other disorders of language such as receptive aphasia where the person could speak very fluently
520
but the words don't make any sense and he can't understand anybody else.
521
Other disorders that we'll discuss later on include food -acquired psychopathy.
522
where damage to parts of your brain, particularly related to the frontal lobes, rob you of the ability to tell right from wrong.
523
The final, I want to end, we're talking about neurons, connections between neurons, how neurons are wired up, the parts of the brain, what the different parts do.
524
I want to end by talking about the two halves of the brain and ask the question, how many minds do you have?
525
Now, if you look at the brain, if you took the brain out and and held it up.
526
It would look pretty symmetrical, but it actually is not.
527
There are actual differences between the right hemisphere and the left hemisphere.
528
How many people here are right -handed?
529
How many people here are left -handed?
530
How many people here are sort of complicated, ambidextrous, don't know, bit of the right, bit of the left people?
531
Okay.
532
Those of you who are right -handed, which comprises about nine out of ten people, have language in your left hemisphere.
533
And in fact, we're going to be talking about right -handed people for the most part, making generalizations in what I'll talk about now.
534
Those of you who are left -handed are more complicated.
535
Some of you have language in your right hemisphere, some in your left hemisphere, some God knows where.
536
It's complicated.
537
Now, the idea is that some things are duplicated.
538
So, if you were to lose half your brain the other half can actually do a lot
539
but some things are more prevalent and more powerful in one part of the brain than the other.
540
And I want to show you a brief film clip from Scientific American that illustrates the differences between the hemispheres.
541
But before doing that I want to provide some introductory facts.
542
Some functions are lateralized.
543
So, typically language in the on the left.
544
Again, this is a right -handed centric thing but if you're right -handed language on the left, math and music on the right.
545
There's a crossover and this is important when we think about the studies
546
that will follow but the crossover is
547
that everything you see in the left visual field goes to the right side of your brain.
548
Everything in the right visual field goes to the left side of the brain and similarly there's a crossover in action.
549
So, your right hemisphere controls the left side of the body your left hemisphere controls the right side of the body.
550
Now, finally, the two halves are connected.
551
They're connected by this huge web called the corpus callosum.
552
And I'm just going to skip this because the movie illustration will go through some of this.
553
This illustrates certain themes
554
that are discussed in detail wrote in the great book concerning lateralization of different parts of different mental capacities,
555
some in the left hemisphere, some in the right hemisphere.
556
But it also serves as a useful methodological development,
557
which is a nice illustration as to how looking at people who are incredibly unusual,
558
such as this man who had his brain bisected, so his left hemisphere and his right hemisphere don't communicate with one another, how looking at such people,
559
such extreme cases can provide us with some understanding of how we normally do things.
560
And this again is a theme we'll return to throughout the course.
561
This is generally the general introduction of the brain that I wanted to provide, giving the framework for what I'll be talking about later on throughout the course
562
so that I might later on make reference neurons or neurotransmitters
563
or the cortex or the left hemisphere and you'll sort of have the background to understand what I'm talking about.
564
But I want to end this first real class with a bit of humility as to what psychologists know and don't know.
565
So, the idea behind a lot of psychology, particularly a lot of neuroscience and cognitive psychology, is to treat the mind as an as an information processor, as an elaborate computer.
566
And so, we study different problems like recognizing faces or language or motor control or logic.
567
The strategy then often is to figure out how, what sort of program can solve these problems
568
and then we go on to ask how could this program be instantiated in a physical brain.
569
So we would have solved, we study people much as we'd study a computer from an alien planet or something.
570
And I think people, this strategy is one I'm very enthusiastic about.
571
But there still remains what's sometimes called the hard problem.
572
consciousness and this involves subjective experience.
573
What's it like?
574
So, my computer can play chess.
575
My computer can recognize numbers.
576
It can do math and maybe it does it kind of the same way
577
that I do it but my computer doesn't have feelings in the same sense.
578
This is, these are two classic illustrations.
579
This is from a very old Star Trek episode, it illustrates angst.
580
I think a starship is about to go into the sun or something.
581
And that's my older kid, Max, who's happy.
582
And so the question is, how does a thing like that give rise to consciousness and subjective experience?
583
And this is a deep puzzle.
584
And although some psychologists and philosophers think they've solved it, most of us are a lot more skeptical.
585
Most of us think we have so far far to go before we can answer questions like Huxley's question.
586
Huxley points out how it is that anything
587
so remarkable as a state of consciousness comes about as a
588
result of irritating nervous tissue is just as unaccountable as the appearance of the Dijin, of the genie, when Aladdin rubs his lap.
589
It seems like magic that a fleshy lump of gray, disgusting meat can give rise to these feelings.
590
The second bit of humility, while I'll end the class on, is I am presenting here and I'll be presenting throughout this semester what you can call a mechanistic conception of mental life.
591
I'm not going to be talking about how beautiful it is and how wonderful it is and how mysterious it is.
592
Rather, we're going to be trying to explain it.
593
We're going to be trying to explain fundamental aspects of ourselves including questions like how do we make decisions, why do we love our children,
594
what happens when we fall in love, and so on.
595
Now, you might find this sort of project in the end to be repellent.
596
You might worry about how this, well this meshes with humanist values.
597
For instance, when we deal with one another in a legal and a moral setting, we think in terms of free will and responsibility.
598
If we're driving you cut me off, you chose to do that.
599
It reflects badly on you.
600
If you save a life at risk to your own you deserve praise.
601
You did something wonderful.
602
It might be hard to mesh this with a conception in which all actions are the result of neurochemical physical processes.
603
It might also be hard to mesh notions such as the purported intrinsic value of people.
604
And finally, it might be hard to
605
mesh the mechanistic notion of the mind with the idea that that people have spiritual value.
606
Faced with this tension, there are three possibilities.
607
You might choose to reject the scientific conception of the mind.
608
Many people do.
609
You may choose to embrace dualism, reject the idea that the brain is responsible for mental life, and reject the promise of a scientific psychology.
610
Alternatively, you might choose to embrace a scientific worldview and reject all these humanist values.
611
And there are some philosophers and psychologists who do just
612
who claim that free will and responsibility and spiritual value and intrinsic value are all illusions.
613
They're pre -scientific notions that get washed away in modern science.
614
Or you could try to reconcile them.
615
You could try to figure out how to mesh your scientific
616
view of the mind with these humanist values you might want to preserve.
617
And this is an issue which you're going to return to throughout the course.
618
Okay, I'll see you on Wednesday.
📺 Même chaîne
C11
The Renovations of Notre-Dame | The Age of Cathedrals with R. Howard Bloch
University StudentsWorking Adults
C16
2. Socratic Citizenship: Plato's Apology
IELTS PrepTOEFL PrepCambridge Exam Prep
C15
Contract Law 1 Intro Hamer v Sidway (just say no)
Cambridge Exam PrepBusiness EnglishUniversity Students
C11. Introduction: What is Political Philosophy?
University StudentsWorking Adults
✨ Vidéo recommandée
C155
66 phrases
What science can’t answer, according to physicist Jim Al-Khalili | Big Think
IELTS PrepTOEFL PrepUniversity Students
C1400 phrases
Intro to Neuroscience, Overview and goals
University StudentsWorking Adults
B22
14 phrases
Would You Upload Your Mind?
IELTS PrepTOEFL PrepUniversity Students
C11
318 phrases
What neuroscience reveals about free will and psychopaths | Sam Harris, Roger Penrose, Sophie Scott
IELTS PrepTOEFL PrepUniversity Students
C16
51 phrases
1 6 What Illusions Teach Us
University StudentsWorking Adults
C11
598 phrases
Husserl: Phenomenology and the Life World
University StudentsWorking Adults
C11
258 phrases
Once You Unlock The Third Eye, Reality Is Yours
Business EnglishUniversity StudentsWorking Adults
C11
53 phrases
The Science of Early Childhood Development
University StudentsWorking Adults
C17
26 phrases
a dream about being a person...
University StudentsWorking Adults
C11
146 phrases
The Most Complex Language in the World
IELTS PrepTOEFL PrepUniversity Students
C13
118 phrases
How Language Shapes the Way We Think • Professor Lera Boroditsky • Duocon 2022
IELTS PrepTOEFL PrepUniversity Students
C13
159 phrases
Episode 1: "What is social ontology?" - Prof Brian Epstein
University StudentsWorking Adults
Vocabulaire et conseils d’expression pour cette leçon
Cette vidéo contient 618 phrases et 7892 mots à répéter en shadowing. La partie parlée dure 53:06. Le locuteur parle à un rythme régulier d’environ 149 mots par minute, confortable pour le shadowing. 82 % des mots font partie des 3 000 mots les plus courants en anglais ; le reste mérite d’être vu avant de commencer.
Vocabulaire clé de cette vidéo
15 mots de la vidéo à retenir, avec leur prononciation et leur sens :
| Mot | Prononciation | Sens |
|---|---|---|
| cortex nom | /ˈkɔɹtɛks/ | cortex |
| bang nom | /ˈbæŋ/ | coup, détonation |
| hemisphere nom | /ˈhɛmɪsfɪə/ | hémisphère |
| wire nom | /ˈwaɪɚ/ | fil |
| complicated adjectif | /ˈkɑm.plɪˌkeɪ.tɪd/ | compliqué, alambiqué |
| disorder nom | /dɪsˈɔɹdɚ/ | désordre |
| illustrate verbe | /ˈɪl.əˌstɹeɪt/ | illustrer |
| extent nom | /ɪkˈstɛnt/ | mesure |
| psychology nom | /saɪˈkɑ.lə.d͡ʒi/ | psychologie |
| connect verbe | /kəˈnɛkt/ | accoupler, connecter |
| involve verbe | /ɪnˈvɑlv/ | impliquer, involver |
| psychologist nom | /ˌsaɪˈkɑl.ə.d͡ʒɪst/ | psychologue |
| mesh nom | /mɛʃ/ | maillage |
| sensory adjectif | /ˈsɛn.sə.ɹi/ | sensoriel |
| consciousness nom | /ˈkɑnʃəsnəs/ | conscience |
Les verbes à particule que vous entendrez
| Mot | Sens |
|---|---|
| figure out verbe | cerner |
| turn out verbe | se finir, se terminer |
| open up verbe | ouvrir |
| point out verbe | pointer |
| take over verbe | reprendre |
| bring up verbe | élever |
| go out verbe | sortir |
| go through verbe | traverser |
Prononciation à surveiller
Le locuteur utilise 109 contractions et formes réduites, comme don't, I'm, can't. Prononcez-les sous leur forme courte, telles que vous les entendez.
- Les sons « th »: hypothesis /haɪˈpɒθɪsɪs/, mathematics /mæθ(.ə)ˈmæt.ɪks/, thirty /ˈθɝti/
- Les sons « sh » et « zh »: mesh /mɛʃ/, consciousness /ˈkɑnʃəsnəs/, notion /ˈnoʊʃən/, shock /ʃɔk/, tissue /ˈtɪʃ.(j)u/
- Mots longs — placez bien l’accent: complicated /ˈkɑm.plɪˌkeɪ.tɪd/, psychology /saɪˈkɑ.lə.d͡ʒi/, psychologist /ˌsaɪˈkɑl.ə.d͡ʒɪst/, communicate /kəˈmjuːnɪkeɪt/, intensity /ɪnˈtɛnsɪti/
Comment s’entraîner avec cette vidéo
- Écoutez la vidéo en entier une fois sans parler et notez les mots que vous ne connaissez pas.
- Répétez phrase par phrase à vitesse normale, en reprenant chacune jusqu’à ce que votre rythme corresponde à celui du locuteur.
- Enregistrez-vous et comparez avec l’original, en faisant attention à des mots comme cortex, bang, hemisphere.
La grammaire de cette vidéo
Les structures que le locuteur utilise le plus, avec les mots exacts de la vidéo :
| Structure | Dans la vidéo |
|---|---|
| Phrases conditionnelles if + proposition, will/would + verbe — une condition et son résultat | If you look at the brain, you'd see |
| « Used to » used to + verbe — une habitude ou un état passé qui n’est plus vrai | used to be |
| Voix passive be + participe passé — l’accent est mis sur ce qui arrive, pas sur qui le fait | is summarized · can be found · is known |
| Present perfect have/has + participe passé — une action passée qui compte encore maintenant | I've been fooled · has tricked · has taken |
Qu'est-ce que la technique du Shadowing ?
Le Shadowing est une technique d'apprentissage des langues fondée sur la science, développée à l'origine pour la formation des interprètes professionnels. Le principe est simple mais puissant : vous écoutez de l'anglais natif et le répétez immédiatement à voix haute — comme une ombre suivant le locuteur avec un décalage de 1 à 2 secondes. Les recherches montrent une amélioration significative de la précision de la prononciation, de l'intonation, du rythme, des liaisons, de la compréhension orale et de la fluidité.