captioning sponsored by rose communications from our studios in new york city, this is charlie rose. >> rose: tonight we continue our journey to the most exciting frontier of science, the brain, last month, we examined how the brain interprets information from the five senses, focusing on the visual system. tonight we'll show you how the brain uses that information to interact with the outside world. our subject is the acting brain. taken together, the parts of the central nervous system devoteed to movement are known as the motor system. the motor system allows to us plan, coordinate every action needed to survive in the physical world. all of the movements we make from the breathing of our heart to the hitting of a tennis ball are controlled by the brain and nervous system. as the legendary biologist charles sharng on the once said "to move things is all that mankind can do and for this task the soul excue tonight is a muscle whether it be a whispering of the syllable or felling of a forest. how does the brain do it? how does the brain translate subjective intentions into physical actions? what happens in the brain when we learn a new skill? why are some of us graceful and others clumsy sfwhoo? why does practice make perfect? much like the visual system, the motor system is astounding in its complexity, it controls over 650 muscles, giving rise to an immense repertoire of movement and actions. coordinating these muscles is a tremendous charge with the motor system carried out mostly without conscious instruction, reflexes, for instance, allow us to respond immediately and unconsciously to changes in our environment. other essential functions such as breathing are also performed automatically and unconsciously. but most of our physical abilities must be learned through practice during infancy and childhood we learn to crawl, walk and use language. by the time we reach adulthood these difficult tasks have become effortless. in, most of what the motor system does is taken for granted until it is interrupted by injury or disease. tonight we'll examine two devastating motor illnesses, stroke and a.l.s., also known as lou gehrig's disease. both of these diseases are tragically common stroke is the leading cause of death in the united states. but for those who survive, the brain'splastyty shows remarkable recovery. despite decades of research, a.l.s. is 1200% fatal. joining me this evening is a remarkable group of scientists who have devoted their careers and their lives to understanding hui the brain controls movement. they are thomas jess is, he studies circuits that forms the basis for the entire motor system. he is a howard hughes medical investigator. daniel wolpert, his research uses mechanical models that mimic human behavior. he heads the wolpert lab at cambridge university in england. john krakauer, he is interested in how the brains learns new skills and how it can regain function even after stroke or injury. he is an associate professor of neurology and neuroscience at columbia university. robert brown, he is a geneticist physician and all around expert on lou gehrig's disease. he teaches and practices at the university of massachusetts. and once again my co-host is dr. eric kandel, he is, as you know, a nobel laureate, a professor at columbia university and also an investigator at the howard hughes medical research center. i'm pleased to have one more time a chance to talk about this extraordinary thing, this brain. we've gone from the... we've gone from the general, to visual now to movement. what are the themes we'll look at tonight? >> well, charlie, you outlined them so beautifully in your introduction. every behavior is mediated through the motor systems, from the simplest to the most complex. all sensory perception, visual perception reaches its completion through the actions of motor systems. in fact, we can think of the motor systems in some ways as being the mirror image of the sensory system. the sensory systems create a ski ma, an internal representation in our brain of the outside world. the motor system uses that internal representation in actions. and like the sensory systems, the motor system is localized to particular regions and it has three important components, a high arkky, if you will, to decide, to make an action, to pick up a glass of water, to mobilize the muscles to actually make that movement and then report back that that movement has been carried out successfully. motor actions vary tremendously from the simplest kind of action to marvelous pirouettes that ballet dancers can do or high jumping pole vaulting extremely skilled performances. some of these are inborn and as you indicate misdemeanor are learned. and the flexibility, the plasticity of the motor system is extraordinary. throughout our lives we can continue to modify our behavior. we play tennis next to one another. i see your tennis game getting better month to month. even at my age. (laughs) >> rose: so it's not getting better at my age, is it? >> even at my age it has a chance of getting better and we only see, as you indicated, that this automatic behavior we take for granted because we do so much of it automatically, we only see that it is important to us when something goes wrong. we can see this, for example, in the sad case of lou gehrig. can we have the video on lou gehrig, please? spectacular baseball player who was hitting about .350 for most of his career. an extraordinary career running over 12 years. never missed a game. game after game throughout the season. all of a sudden he began to find a weakening in his stroke. he still saw the ball as clearly as he ever did, but he couldn't get his bat around him powerfully. and you can see the dramatic decline in his batting average going from .350 to .150 in the period of a year and a half. and ultimately, for the first time in over a thousand games, he had to be benched. that was because he developed a.l.s., a disease we're going to consider today. >> rose: just make this point about science. science builds on what you have learned before. here is sir charles sherrington, this book "the integrative action of the nervous system, published in 1960. this is also based on some lectures he did at yale. it's a remarkable story of how science works. jup >> you're absolutely right. there are occasional people-- we call them giants-- who not only make extraordinary contributions sherrington worked out the simplest reflex pathways in the final cord, stimulated the motor cortex, saw how it moved particular limbs but alsoed that insight to see how the whole brain works. the sbi graveive action of the nervous system means sensory information is come in, it's processed to give rise to a variety of movements. this not only applies to motor systems, it applies to every aspect of nervous system function. there is xi station of appropriate movements, inhibition of inappropriate movements. this is a brilliant peres yent set of insight wes owe to sherrington. we're still living in a sherringtonian world today. >> rose: we talk about and touch on all these things we have been talking about. eric and i have assembled a group of people i think you will find extraordinary in terms of their insight and how they can demonstrate what we are talking about. because we're talking about motor functions, what you can see. you will also discover as you listen to them that there is a remarkable thing that is coming out of this, insight into how the brain functions in its highest level. so we begin with understanding the significance of the motor system. >> well, i think we have to ask a very fundamental question, perhaps the most fundamental question we can ever ask and i think it's remiss that eric hasn't asked it. why do animals have brains? it's a fundamental question because there are many species who don't have brains. that so that's a fundamental question we should be taught on our first day of school. and if you think about it, it's obvious. we have one for one reason and one reason only, and that's to produce adaptable and complex movement. there's no other reason to have evolved a brain. so the only way we can affect the outside world is through contractions of muscles. so think about communications, speech, gestures, sign language, they're all mediated by contracting muscles. so we need to remember that things like sensory processing, perceptual system, memory and cognitive processs are all important but they can only be important to drive action or suppress future actions. there's no point laying down memories of childhood or perceiving the color of a rose if it doesn't lead you to do something different with your motor system later in life. so if you think from an evolutionary point of view, there's no point having the thinking processs if they can't be expressed through action. so i'm a really movement chauvinist. i though understand the brain we have to understand movement, which is the final output. >> rose: to understand the brain we have to understand movement. >> we can't look at memory or perception in isolation from action. and we can say if you don't believe in this argue. there's many species who live very happy lives in our planet, do very well socially but they don't need to move. so the tree is a nice example. it doesn't require complex movement, it hasn't evolved a brain. but the clinching for those who don't believe this is this animal here. this is the humble sea squirt. it's a rudimentary animal, it has a brain, a spinal cord and it swims in its juvenile life. and at some point it implants itself on a rock and never leaves the rock again. and the first thing in implanting on that rock is to digest its own brain and nervous system for food. once it doesn't need to move, it doesn't need that brain anymore. so i think it's really the brain is there for movement. >> rose: and is this the reason we've never had a robot that can be as graceful as a six-year-old walking down a road? >> that's a very good question. so we can ask how well are we going understanding how the brain controls movement and the answer is i think we've done pretty well but we've got a long way to go. and you can begin by asking how well can you build machine which is can do the things humans do. how well can we build machines that decide what chess piece to move where. if we pit gary kasparov against i.b.m. blue, occasionally blue will win. and if it played any one here it will win every time. (laughter) but we need to think about now build magazine which has got the manual dexterity of a five-year-old. pit a five-year-old's dexterity to manipulate a chess piece against the best robot, there's no competition. the five-year-old wins easily. and so we can say why is that the first problem of deciding what to move so easy and the control problem so hard. one reason is the five-year-old child will tell you. you need to solve what piece can move where. look at all possible movements a president end of the game and choose what makes you win. the algorithm is very simple. the problem is moves. but with fast computers and approximations we get close to the answer. when it comes to being dexterous it's very unyear problems you have to solve to be dexterous and there are real problems in sensing the world and acting upon chit have a lot of complexity. but i'd love to show you a video. >> rose: please do. >> i'd like to show you a video of what's cutting edge in robotics and cutting edge in human performance just to give you a feel of how close we're getting. so if we could roll the video of the robot. what this video shows is the end of a three-year project by my colleagues in germany teaching a robot to pick up a glass and pick up a jug of water and pour water into a glass. as you can see, it does the task but it's not doing it anywhere as fluidly or speedily as a human would do it. you would regard this as poor performance. that is very challenging task. and if if you want it to do something different, there's another three year project. there's no generalization from one task to another. so this is a fundamentally very difficult problem. let's care in now to what we regard, perhaps, as the cutting edge human performance. so you see a small child, a nine-year-old, winning the world record for cup stacking. now, cup stacking is a popular support. it involves taking cups and stacking them and unstacking them in a particular sequence as fast as you can. >> rose: this is great! (laughs) >> we've got a very long way to go before we get anywhere near to building these machines or understanding how that child learns to do that task. >> rose: let's look further at the anatomy. talk about how about how it works. >> well, the mysteries that daniel has just outlined for you have been puzzling neuroscientists for over 100 years or so and charles sherrington was really the first of the modern generations of neural scientists who tried to understand the mechanisms that really linked the way into the way out. so in the brain, in the nervous system, there are many ways in. the individual senses that we've talked about and previous discussions. sense of vision, a sense of touch, the sense of smell. but sherrington and people of his time realized that despite all of the many ways in, there's only way out, and that's the motor system. and sherrington was the first to articulate this idea that the motor system is the final common pathway of all of the sensory world that impinges on the brain and the way that that information is processed to produce coordinated movement. and so in the 19th century, there had been a series of experiments trying to understand and deconstruct what movement really is. even the simplist of movements to move one's hand or to move one's thumb rishz several components or several processing events. the first is actually to plan the movement. one has to be able to control the nature of the movement before there's any sign of muscle contraction. the second is the execution of movement and the thirdd is to achieve some reporting of the consequences of that movement. and sherrington and his colleagues really outlined the idea that these different functions, planning, execution, and reporting, are assigned to different regions of the brain. and the first experiments that changed the way we think about the field were some electrical stimulation experiments. so with the crude tools available, people start to stimulate different regions of the surface of the brain and look for the consequences in terms of movement. so some areas where you're stimulated gave no overt signs of mooucht. but there are other areas, hot spots, if you like, which we now know is the motor cortex and the premotor cortex and they're shown here in this colored region where very low intensity stimulation would illicit movement. and more than that, that was a precise register or map between the place in which the stimulating probe was located and the type of movement. and so it turns out in the remarkable way that somehow the brain achieves a map of the body surface and so stimulation in one place will produce the movement of the thumb. stimulation of an adjacent reason will produce a movement of the wrist and elbow and shoulder and yet another region will produce movements of the leg. so in this way people began to realize that there was this precise register between the surface of the brain and the mull groups, the 600 or so you mentioned that have to be activated in precise pattern to produce a coordinated movement. >> rose: this is really a beautiful example, perhaps the best example we have in the brain of functional localization. that different aspects of behavior, different aspects of sensory perception are localized. the detailed map of the movements of the body on the surface of the brain. >> sherrington began to reason that if the cortex is the site of initiation or planning of movement yet the muscles are out in the periphery, there has to be an anatomical conduit or link between the site of stimulation and the site of muscle contraction and what sherrington in a systematic way did is to show that the information that is being initiated in these cortical regions has always of that information regardless of the type of movement, has to be funneled down the central nervous system, essentially to the spinal cord. and sherrington began to examine the nature of an organization of circuits that existed within the spinal cord. and very soon he realized and articulated within that within the spinal court... so this is now a cross section, a cut slab through the spinal cord, that the key intermediary between all of this cortical information and the actual contraction of the muscle was this group of neurons shown here which are spinal motor neurons. so of the tens of thousands of neurons, classes of neurons that existed in the brain, only one of those classes, the motor neuron, actually sends a process out of the central nervous system, out of the brain and spinal, to communicate with the periphery. so all of these dexterous tasks that daniel showed you are really dependent on the activity of motor neurons. and if we have 600 muscle groups we now know that in order to accommodate the combination of muscle activity, we need 600 motor neuron subtypes. so in a nutshell, the problem that the brain has to solve is how to initiate movement exactly when you want to move, how to control exactly which part of the body you want to move. and all of that information has to be funneled down into the spinal court and activate just the right set of motor neurons in the right combination to produce coordinated movement. >> rose: is there a dramatic difference between a reflex action and a conscious action? >> yes. so this is the other great insight that sherrington had and it comes to the third component of movement. there's no point in moving or acting if the brain and the central nervous system and the body doesn't get some reporting of the consequences of action. so sherrington spent much of his life not only working on the way the cortex interacts with the spinal cord but the way this information is fed back through recording of the state of muscle contraction. so any coordinated movement, the cup stacking that we saw, requires the fact that the brain received online information about the efficacy with which those motor tasks are performed. and that feedback information comes in through sets of sensory neurons that are acting as if you like a strain gauge, monitoring the intensity and the timing of mull contraction. and feeding that in the simplest reflex circuit back directly to form a single synaptic connection with the motor neuron. so this is an involuntary stretch reflex circuit, if you like. so perhaps we could first of all demonstrate this mono synaptic reflex in action. >> rose: all right. (laughs) >> so i'm going to try to fool tom's nervous system. in particular his low spinal cord, into thinking that this knee has been flexed and what you will see is that independently of any of tom's efforts of the contrary, the nervous system will respond by attempting to extend the knee back out and i will fool it by using a reflex hammer and using a very standard reflex. tom you just want to relax? what you can see is that a short percussion here, he kicks the leg back up. this involves three elements. it involves the final cord perceiving the fact there's been a stretch. this has a sensory feedback essentially in the spine cord, there's an integration of that sensory information in the spinal cord to the motor output which allows essentially a motor signal let's correct the problem let's extend the knee. (laughter) this would new york his sleep. so here is the spinal cord, here are the muscles, the knee, this pathway we've activated the sensory input into the spinal cord thenedly one synapse we've transformed sensory input to motor out