Placeholder Image

Subtitles section Play video

  • This machine, which we all have residing in our skulls,

  • reminds me of an aphorism, of a

  • comment of Woody Allen

  • to ask about what is the very best thing to have within your skull.

  • And it's this machine.

  • And it's constructed for change. It's all about change.

  • It confers on us the ability to do things tomorrow that we can't do today,

  • things today that we couldn't do yesterday.

  • And of course it's born stupid.

  • The last time you were in the presence of a baby --

  • this happens to be my granddaughter, Mitra.

  • Isn't she fabulous?

  • (Laughter)

  • But nonetheless when she popped out

  • despite the fact that her brain had actually been progressing

  • in its development for several months before

  • on the basis of her experiences in the womb --

  • nonetheless she had very limited abilities,

  • as does every infant

  • at the time of normal, natural full-term birth.

  • If we were to assay her perceptual abilities, they would be crude.

  • There is no real indication that there is any real thinking going on.

  • In fact there is little evidence that there is any

  • cognitive ability in a very young infant.

  • Infants don't respond to much.

  • There is not really much of an indication in fact that there is a person on board.

  • (Laughter)

  • And they can only in a very primitive way, and in a very limited way

  • control their movements.

  • It would be several months before this infant

  • could do something as simple as reach out and grasp

  • under voluntary control an object and retrieve it,

  • usually to the mouth.

  • And it will be some months beforeward,

  • and we see a long steady progression

  • of the evolution from the first wiggles,

  • to rolling over, and sitting up, and crawling,

  • standing, walking,

  • before we get to that magical point

  • in which we can motate in the world.

  • And yet, when we look forward in the brain

  • we see really remarkable advance.

  • By this age the brain can actually store.

  • It has stored, recorded,

  • can fastly retrieve

  • the meanings of thousands,

  • tens of thousands of objects,

  • actions, and their relationships in the world.

  • And those relationships can in fact be constructed in hundreds of thousands,

  • potentially millions of ways.

  • By this age the brain controls very refined perceptual abilities.

  • And it actually has a growing repertoire of cognitive skills.

  • This brain is very much a thinking machine.

  • And by this age there is absolutely no question

  • that this brain, it has a person on board.

  • And in fact at this age it is substantially controlling its own self-development.

  • And by this age we see a remarkable evolution

  • in its capacity to control movement.

  • Now movement has advanced to the point

  • where it can actually control movement simultaneously,

  • in a complex sequence, in complex ways

  • as would be required for example

  • for playing a complicated game,

  • like soccer.

  • Now this boy can bounce a soccer ball on his head.

  • And where this boy comes from, Sao Paulo, Brazil,

  • about 40 percent of boys of his age have this ability.

  • You could go out into the community in Monterey,

  • and you'd have difficulty finding a boy that has this ability.

  • And if you did he'd probably be from Sao Paulo.

  • (Laughter)

  • That's all another way of saying

  • that our individual skills and abilities

  • are very much shaped by our environments.

  • That environment extends into our contemporary culture,

  • the thing our brain is challenged with.

  • Because what we've done in our personal evolutions

  • is build up a large repertoire of specific skills and abilities

  • that are specific to our own individual histories.

  • And in fact they result in a wonderful

  • differentiation in humankind,

  • in the way that, in fact, no two of us

  • are quite alike.

  • Every one of us has a different set of acquired skills and abilities

  • that all derive out of the plasticity,

  • the adaptability of this really remarkable adaptive machine.

  • In an adult brain of course we've built up

  • a large repertoire of mastered skills and abilities

  • that we can perform more or less automatically from memory,

  • and that define us as acting, moving, thinking creatures.

  • Now we study this,

  • as the nerdy, laboratory, university-based scientists that we are,

  • by engaging the brains

  • of animals like rats, or monkeys,

  • or of this particularly curious creature --

  • one of the more bizarre forms of life on earth --

  • to engage them in learning new skills and abilities.

  • And we try to track the changes that occur

  • as the new skill or ability is acquired.

  • In fact we do this in individuals

  • of any age, in these different species --

  • that is to say from infancies,

  • infancy up to adulthood and old age.

  • So we might engage a rat, for example,

  • to acquire a new skill or ability

  • that might involve the rat using its paw

  • to master particular manual grasp behaviors

  • just like we might examine a child

  • and their ability to acquire the sub-skills,

  • or the general overall skill of accomplishing something

  • like mastering the ability to read.

  • Or you might look in an older individual

  • who has mastered a complex set of abilities

  • that might relate to reading musical notation

  • or performing the mechanical acts of performance

  • that apply to musical performance.

  • From these studies we defined two great epochs

  • of the plastic history of the brain.

  • The first great epoch is commonly called the "Critical Period."

  • And that is the period in which the brain is setting up

  • in its initial form its basic processing machinery.

  • This is actually a period of dramatic change

  • in which it doesn't take learning, per se, to drive

  • the initial differentiation of the machinery of the brain.

  • All it takes for example in the sound domain,

  • is exposure to sound.

  • And the brain actually is at the mercy

  • of the sound environment in which it is reared.

  • So for example I can rear an animal

  • in an environment in which there is meaningless dumb sound,

  • a repertoire of sound that I make up,

  • that I make, just by exposure, artificially important

  • to the animal and its young brain.

  • And what I see is that the animal's brain sets up

  • its initial processing of that sound

  • in a form that's idealized, within the limits of its processing achievements

  • to represent it in an organized and orderly way.

  • The sound doesn't have to be valuable to the animal:

  • I could raise the animal in something that could be hypothetically valuable,

  • like the sounds that simulate

  • the sounds of a native language of a child.

  • And I see the brain actually develop a processor that is specialized --

  • specialized for that complex array, a repertoire of sounds.

  • It actually exaggerates their separateness of representation,

  • in multi-dimensional neuronal representational terms.

  • Or I can expose the animal to a completely meaningless and destructive sound.

  • I can raise an animal under conditions

  • that would be equivalent to raising a baby

  • under a moderately loud ceiling fan,

  • in the presence of continuous noise.

  • And when I do that I actually specialize the brain

  • to be a master processor for that meaningless sound.

  • And I frustrate its ability

  • to represent any meaningful sound as a consequence.

  • Such things in the early history of babies

  • occur in real babies.

  • And they account for, for example

  • the beautiful evolution of a language-specific processor

  • in every normally developing baby.

  • And so they also account for

  • development of defective processing

  • in a substantial population of children

  • who are more limited, as a consequence,

  • in their language abilities at an older age.

  • Now in this early period of plasticity

  • the brain actually changes outside of a learning context.

  • I don't have to be paying attention to what I hear.

  • The input doesn't really have to be meaningful.

  • I don't have to be in a behavioral context.

  • This is required so the brain sets up it's processing

  • so that it can act differentially,

  • so that it can act selectively,

  • so that the creature that wears it, that carries it,

  • can begin to operate on it in a selective way.

  • In the next great epoch of life, which applies for most of life,

  • the brain is actually refining its machinery

  • as it masters a wide repertoire of skills and abilities.

  • And in this epoch,

  • which extends from late in the first year of life to death;

  • it's actually doing this under behavioral control.

  • And that's another way of saying

  • the brain has strategies that define

  • the significance of the input to the brain.

  • And it's focusing on skill after skill,

  • or ability after ability,

  • under specific attentional control.

  • It's a function of whether a goal in a behavior is achieved

  • or whether the individual is rewarded in the behavior.

  • This is actually very powerful.

  • This lifelong capacity for plasticity, for brain change,

  • is powerfully expressed.

  • It is the basis of our real differentiation,

  • one individual from another.

  • You can look down in the brain of an animal

  • that's engaged in a specific skill,

  • and you can witness or document this change on a variety of levels.

  • So here is a very simple experiment.

  • It was actually conducted about five years ago

  • in collaboration with scientists from the University of Provence

  • in Marseilles.

  • It's a very simple experiment where a monkey has been trained

  • in a task that involves it manipulating a tool

  • that's equivalent in its difficulty

  • to a child learning to manipulate or handle a spoon.

  • The monkey actually mastered the task

  • in about 700 practice tries.

  • So in the beginning the monkey could not perform this task at all.

  • It had a success rate of about one in eight tries.

  • Those tries were elaborate.

  • Each attempt was substantially different from the other.

  • But the monkey gradually developed a strategy.

  • And 700 or so tries later

  • the monkey is performing it flawlessly -- never fails.

  • He's successful in his retrieval of food with this tool every time.

  • At this point the task is being performed

  • in a beautifully stereotyped way:

  • very beautifully regulated and highly repeated, trial to trial.

  • We can look down in the brain of the monkey.

  • And we see that it's distorted.

  • We can track these changes, and have tracked these changes

  • in many such behaviors across time.

  • And here we see the distortion

  • reflected in the map of the skin surfaces of the hand of the monkey.

  • Now this is a map, down in the surface of the brain,

  • in which, in a very elaborate experiment we've reconstructed the responses,

  • location by location,

  • in a highly detailed response mapping of the responses of its neurons.

  • We see here a reconstruction of how

  • the hand is represented in the brain.

  • We've actually distorted the map by the exercise.

  • And that is indicated in the pink. We have a couple fingertip surfaces that are larger.

  • These are the surfaces the monkey is using to manipulate the tool.

  • If we look at the selectivity of responses

  • in the cortex of the monkey,

  • we see that the monkey has actually changed the filter characteristics

  • which represents input from the skin

  • of the fingertips that are engaged.

  • In other words there is still a single, simple representation of the fingertips

  • in this most organized of cortical areas

  • of the surface of the skin of the body.

  • Monkey has like you have.

  • And yet now it's represented in substantially finer grain.

  • The monkey is getting more detailed information from these surfaces.

  • And that is an unknown -- unsuspected, maybe, by you --

  • part of acquiring the skill or ability.

  • Now actually we've looked in several different cortical areas

  • in the monkey learning this task.

  • And each one of them changes in ways that are specific

  • to the skill or ability.