Gateway to the Mind

the Bell Telephone system brings you another of its series of programs on science man's effort to understand nature's laws [Music] The Sound Stage with its gadgets and equipment will serve as a sort of Workshop in the telling of our science story human senses how they work and what they mean to man and to help us along we'll have the assistance of various members of the crew who work here thanks for the tour Bill quite a place this Sound Stage yeah they're ready on the Aristotle set doctor well thanks let's go oh doc I always thought this Aristotle was a real old guy guy with a long beard you know real ancient well Bill although Aristotle lived about 2500 years ago he wasn't always an ancient when he was a young man like many other people of his time he was interested in trying to learn about the human senses but here he is getting a shave and surrounded as always by some of his students certainly there is nothing more distressing to the human senses than a dull razor Master continue udus what are your thoughts concerning the human senses as meat and wine are nourishment to the body the senses provide nutriment to the soul all knowledge must come through the senses all that we perceive and all of the awareness of our daily existence then we may summarize thus these senses bring us touching seeing hearing tasting smelling and all that we know of the world comes to us through these five senses so Aristotle was the first guy to figure it out huh not the first maybe but Aristotle wrote some very interesting things about the census well worth reading today yeah but everything comes to us through our senses yes indeed bill now you think about it with without the information your senses bring you you'd be like a man locked in a dark cave now in one big respect Aristotle was wrong we have many more than five senses and for another thing we don't hear with just our ears alone we don't smell just with our noses we don't taste just with our tongues hey wait a minute doc after 20 years behind this camera you're not going to tell me I don't see with my eyes are you no in a strict sense you don't Hal your eyes like your other sense organs simply receive Impressions from the outside send them on to the brain and that gets into my department doctor good it's always interesting to see what you animators come up with well trying to draw a character that represents a sense pretty tough assignment huh you bet but we have to show how they work so we finally came up with our old friend Mercury Messenger to the gods but a kind of a a wiry electrical Mercury very quick responsive number one supplies us with a big percentage of our information reacts to the air vibrations we call sound one of the two chemical senses another chemist taste specialist reacts only to Salty Sweet Bitter and sour responds to changes in surface or or skin conditions so there they are the familiar five not like Messengers really more like dispatchers dispatching information through the network of the sensory nervous system let's see how touch does it okay now let's take the tip of the finger that's where the sensory endings of touch are most plentiful when the skin touches something our friend here dispatches a sort of signal to headquarters well in very simple terms that's about what happens but how that signal gets to headquarters in the brain that's the first part of our big story within our bodies is a marvelous network of nerves nerves that carry the signals and carry them to the brain carry the signals but how Doc by electricity see the nerves of this network are made up of the long thin fibers of living nerve cells n cells that can make their own electricity Luigi galvani experimenting with what was then known as animal electricity accidentally touched the big muscle in the leg of a frog with two pieces of metal that were in contact with each other the electrical stimulus caused the Frog's leg to jump that was almost 200 years ago the arguments that grew out of galvani's experiment led to vault's discovery of the principle of the electric battery doc don't tell tell me I got an electric battery somewhere inside of me no not batteries but nerve cells hundreds of millions of them each capable of making electric charges Bill turn on this machine will you this is an actual recording of the electrical impulses going from a living eye to a living brain HK heartline of the Rockefeller Institute for medical research who made this recording is studying patterns of impulses in the optic nerve fibers and how these patterns serve as information for the brain these impulses race through our sensory system whenever sense receptors trigger electrical discharges into the nerve fibers each nerve cell passes the impulse Along by discharging its electricity to fire the next cell in the chain the impulses jump along it speeds up to 100 m an hour or more these living cells are self-charging they recover and are ready to fire again in a tiny fraction of a second dot then this nerve Network can carry all the different signals from all the different senses yes that's a funny thing the senses are all different the signals are all alike yeah but then how could the brain know which sense is sending the message B you just ask the big question that brings us up to the brain it's the areas in the brain the specific areas where the signals end up that tell us whether we are touching seeing hearing tasting or smelling ever since Johannes Mueller a German physiologist of the 19th century recognized this scientists have been trying to understand how the brain transforms information it receives into action s sensation and thought after all it's not the easiest thing in the world to look in on the actions and workings of a living brain maybe that's where the animator has an advantage he can invent one that's an interesting idea look here's just a few of the hundreds of sketches that we waited through trying to make our drawings agree with your facts couldn't find a place for those 12 billion nerve cells had you no we soon realized that the best we could hope to do was map a part of it into a kind of a electronic headquarters this is our try and it shows up pretty well on this enlarged drawing most of the nerve impulses enter here from the spinal cords uh-huh and they pass through here to this relay Center at the base of the brain yes that would be what is called the thalamus and the impulses go on upward to their destination yes their destination in the gray outer layer of the brain called the cortex we've drawn electronic tubes to indicate the areas where the messages come in oh here's a better View now you see if the impulses came from the eye they'd come down through here in the same way we've set up tubes for the ear nose tongue touch and all the rest and these electrical impulses come alive as pictures on what we call the master receiver and I suppose the smaller screen represents the memory section right impressions are recorded and stored there for later reference now here on the master dispatching board we transform sensory information into into conscious action walking talking and so on all right let's see this electrical headquarters of yours in operation well L was in charge of the making it work department so Lou's the one who really has to make these drawings move huh well I do the thinking and he does the work thanks Dad well doctor we've animated a little sequence here about a character we call Joe commuter here he is undisturbed by any outside uh stimulus like that 7:15 specially takes five mornings a week who's the little man he's new around here isn't he well he represents the thinking part of Joe's brain he checks things against memory and past experience and decides Joe's actions on the probabilities of the future Joe Joseph next on the agenda [Music] breakfast good morning dear and so the day begins [Music] what a beautiful day it's nice to live in the country I think I'll walk to the station well what do you know wild strawberries I used to taste wonderful when I was a kid hold it hold it right there now let's back up and break that action down into slow motion and see what happened the first thing Joe has to decide is whether these really are strawberries that's where the eye comes in [Music] H they look familiar let's [Music] check strawberry huh of [Music] course well what about the other senses not much action here strawberries aren't very [Music] noisy meanwhile touch is checking up on everything coming and contact with the [Music] skin and so headquarters is informed the berry is picked wait a minute how about checking with the lab sense of smell ahuh and that worried look is natural after all how do you describe the smell of a strawberry stimulus dispatched analyzed okay by headquarters go ahead eat it taste it another chemist gets into the ACT taste this time how is it should be [Music] sweet sour sour well a lot happened in those few moments and Lou what was it that triggered all those little sensory characters into action well the light from the strawberry carried the stimulus to the eye B buzzing stimulated the ear and the chemical reaction on the nose and tongue stimulated the sensory endings of smell and taste stimulus that's the key word stimulus is that film ready all set doctor fine let's take a look at it it's the key word because all forms of life respond to a stimulus it's one of the things that all living creat creatures have in common turn it on [Music] Bill just as human beings with their complicated sense organs and nervous systems respond to the stimulus of touch so do the simplest one- cell animals which can be seen only with a microscope this is an amoeba these various single cell animals have of course no specialized sensory cells or nervous systems but they lead A busy life in their microscopic world the first important groups of multi-celled animals have a simple nerve Network connecting individual sensory cells and are particularly sensitive to [Music] touch jellyfish have notches around the perimeter of their bodies in which there are sense organs sensitive to light and to food this inquisitive looking animal uses his tentacles for touch but also has an eye the base of each of them these more complex animals have the sensory cells grouped together into sensory organs connected by a nervous system with a primitive brain in the insect world you may find many surprises the hearing organs of the grasshopper or on the side of his abdomen and he tastes food even before he eats it with small appendages outside his mouth most insects have organs for both touch and smell on their antenna in some insects sight is more important the dragonfly has unique compound eyes that practically cover his head fish can taste all over their bodies like other animals their sense organs developed according to their particular needs the chameleon can look in two directions at once because each eye works independently of the other the alligator has an extra eyelid to protect protect his eyes when he opens them underwater some snakes like the pit viper have a special Sense on their faces that detects the heat of warm-blooded prey at a distance among the birds of prey the faul and especially has a Keen Eye the cat whose senses are all quite welldeveloped is highly sensitive to the stimulus of touch on the tips of his whiskers in each instance the pattern of each animal's sensory development is reflected in the development of its unique brain structure compared to those of many animals man's senses are much less acute he can't see like a falcon smell everything a dog smells but man lives by his wits as well as his senses man and only man possesses a brain that gives him the capacity of imagination and thought far beyond the limited mental activity needed for daily survival an only man has developed a singular ability to speak to reason and to plan far into the [Music] future George I know that this is your office but what exactly happens here here my job is to control the strength of the electrical currents coming from the microphones and bring them into balance on this console it's called mixing and then it's recorded on film not anymore Magnetic Tape now in other words these sounds are first converted into electrical impulses and then they're balanced and Amplified in this console and then recorded that's correct that's a lot like the ear works vibrations electricity sound so it is but George's ear is a much more complicated instrument than the equipment he operates how does the inside of the human hearing apparatus look to an animator Jean well I'll tell you Doctor let's find out by following the sound of Chopsticks right into George's ear the outer ear is shaped somewhat like a funnel ending at the eardrum the surface of the eardrum is pushed back and forth by the vibrations of the sound waves the movement of the eardrum sets the oses in action three little bones commonly known as the hammer Anvil and sturup this film shows the human eardrum which is only about A4 of an inch across these are the ticles that work within the human ear the tiny stup works with a rocking motion creating pressure on the fluid of the inner ear the ccka driving back and forth this little lever mechanism increases the pressure about 10 times and now we discover what really happens to Chopsticks here's a simplified view of the ccka it's lined with a thin Bassel membrane which contains 24,000 hairlike cells in this illustration they somewhat resemble the keyboard of a piano the sound waves now transformed into fluid pressure waves disturb the hairlike cells along the basil keyboard according to the pitch of the notes each pitch vibrates a particular group of tiny hair cells triggering electrical impulses that proceed along the auditory nerve and form a brain pattern which to us means [Music] music now those nerve impulses we heard a while ago they're the same for uh well seeing or hearing well to answer your question Bill come and help me will you here again is Dr harlin's recording of optic nerve impulses Dr Lloyd bider Florida State University has made these recordings of impulses originating in the taste buds recordings have also been made for smell for impulses from the olfactory nerve they're all the same yes the impulses for all the senses are the same there's another interesting thing a little further on this role here as the stimulus from outside increases the number of impulses goes up accordingly [Music] these things were first demonstrated in the 1920s by Ed Adrian of the University of Cambridge it's the same with all of our senses taste for instance this time the chemicals of food or drink excite the hairlike cells of the taste buds which line the crevices of our tongues the remarkable thing is the Taste is not just one sense it's actually Four sweet salt sour and bitter seems to me I taste more different ways than just four that's because when you're tasting things you're also smelling things the range of smell seems to be boundless seem to be about as many different smells as there are things to smell and of course taste plus smell equals flavor Jean come on we have to go over the West TRX sure you know a fell told me that if you hold your nose you can't tell whether you've got a little piece of apple or onion on your tongue yeah how about that that's right when we taste something the chances are we also smell it hey Doc this pop tastes cold am I smelling that oh yes that's another thing in our mouths we have temperature senses which react to ice cream hot coffee hot and cold things certainly we find that the sense of smell is most useful to man perhaps primitive man like the animals made much greater use of it for most animals smell is still the most trustworthy sense turn on the machine will you the delicate thawn uses his sensitive nose as well as his ears to warn of approaching danger many stories are told about the moth's extraordinary sense of smell with receptors located on its most remarkable antenna ants too have receptors for smell on their antenna now we know about the rabbit big ears always cocked and a busy nose always alert and speaking of a busy nose bill in the case of the dog do you know what he was smelling a bone molecules you mean to say we smell molecules whatever we smell is in the form of tiny molecules that being volatile take off into the air we smell smell them as odors Aromas for example they bring us the first sweet scent of new spring blossoms rich and long remembered experiences come to us through the air as Tiny molecules and wafted free on the clear morning Breeze they can smell mighty good we helped the molecules get to the right place by sniffing they lined up in a chemical laboratory for that's what the upper chamber of the nose actually is when the molecules reach this chamber they chemically stimulate the millions of cell filaments on the AL Factory patch and from here as in the case of the other senses messages races electrical impulses to the brain where we experience the sense of smell [Music] [Music] Doc before you get to the science of how we see I'd like to introduce you to the big eye well it's true the human eye has often been compared to the workings of a camera you step right this way doc now suppose we start with a lens you can see inside the sunbox the light coming through the lens is focused on the film now this is the iris and we can Reg at the way it opens and closes to admit various degrees of light now suppose we look at the side now the film moves down here where the light coming through the lens strikes it so this is where the negative is exposed yes that's right well hell your camera is a fine machine for taking moving pictures now let's look at something much more remarkable [Music] this is a closeup of a normal human eye the periodic blinking of our lid keeps the outer eye surface moist up under the lid and at Each corner of the eye are tiny glands manufacturing tears which wash away dirt particles and contain an antibiotic to combat germs the iris opens and closes automatically to control the amount of light admitted through the pupil to the inner eye ever wonder what what a doctor sees when he looks inside your eye well here it is the retina the only place in a living man where some of his nervous system can be seen this part of the eye compares to the film in the camera it's on this delicate screen that all objects of our vision are transformed into Myriad electrical impulses this is the blind spot where the nerve fibers of the retina come together to form the optic nerve which bundles them out to the brain there are no light receptors at this point so it is literally a blind spot now in this diagrammatic side view light reflected from an object strikes the transparent surface of the eye the cornea the iris opens or closes to the correct aperture the light passes through the lens which brings it into focus on the retina this curved screen contains over 125 million tiny light sensitive cells each capable of dispatching an individual message to the brain in this photo micrograph of the crosssection of the retina we can actually see some of these cells this depression is the fobia here we have our sharpest Vision concentrated in an area the size of a pin head this is the visual center of the eye looking at something means catching its image on the fobia we have two kinds of light sensitive cells cones and rods the cones in bright light light transmit our color vision in dim light they cease to work and the rods take over rods transmit our vision only in black and white this is why as daylight deepens into dust colors dim and Fade Away here's a diagrammatical closeup of the rods and cones each rod and Cone is sensitive to light because of a pigment contained in its tip when this colored substance is struck by light it's chemically changed this excites the nerve sending messages to the brain which enable us to see this then is the human eye an organ which inspires poets as well as scientists for it is the eye that gives us the colorful everchanging world of vision in order to examine the last of Aristotle's five senses the sense of touch let's drop in on this gentleman to whom we have already been introduced return again to that road map of his sensory system and out to that suburb we visited before and it's a Well populated place because in one tiny area we find not only the sense of touch but at least four other [Music] senses these are true senses just like Aristotle's major five for each has its own signal system and nerve endings that can be individually identified for example these are the free nerve endings of pain there are millions upon millions of these tiny filaments throughout our bodies Well jean why don't you try one of your real life dramas to show how this team of Senses operates okay let's take the situation of a lady testing a hot iron bill here has consented to act the exacting role of housewife I'm one of those martys to science you hear about okay let's run through the whole act oh Bravo and here's the way it works now in slow motion when the tip of the finger touches that hot surface a number of things happen and happen fast hundreds of pain endings charge into action touch sends out information on Surface conditions heat and cold report the temperature changes on the skin pressure reacts to the sensation of finger against iron so these sensory messages race up the finger and the arm and reach the spinal cord where there's something like um oh an automatic switchboard where pain triggers an immediate reflex action as well as continuing to the brain now the reflex signal races back and activates the muscles of the arm and the finger is jerked away from the iron and it's only when the other sensory messages report in on the master receiver and the pain impulse finally reaches the thalamus that our little man knows the finger has been hurt [Music] well isn't it true doctor that some people are more sensitive to pain than others oh yes yes that's very true people differ greatly in this doctor when you sit down thank you really enormous variations in what we call the threshold of pain some people are born with no sense of pain at all no toothache that bad was really very serious to touch a hot iron cut yourself badly and feel no pain imagine a child who would have to be watched every second because he would never know when he'd hurt himself what about the other senses doc sense of humor sense of Balance common sense Horse Sense well these are everyday expressions Common places figures of speech except the sense of balance and that's a very real sense without the sense of balance you couldn't stand up certainly you couldn't walk and behind this sense of balance is a most interesting mechanism deep within the inner ear we have the semicircular canals which are filled with liquid associated with the lining of these curved channels are minute hair cells now it's generally believed that when we move our heads the liquid disturbs these hair cells which send signals to the brain we also have sense receptors in our muscles and tendons to tell the brain of any change in muscle tension when Bill stands on one foot he can feel this automatic interplay of the different muscles of his leg and of course his eyes tell him what he does coordinating all of this information from ears muscles and eyes at assembly points the nervous system sends back reflex motor impulses to the right muscles telling them to tighten or relax to keep the body in balance this automatic feedback between the incoming signals and the outgoing compensating actions is what enables the cat to land on its feet or an acrobat to spin through the air to a precise Landing now in slow motion we can see what happens when a cat is dropped from an upside down position his eyes and equilibrium organs in his ears cause him to write his head this puts an uneven tension on the neck muscles and their tension receptors excite reflexes which bring the body back into alignment with the head like the falling cat we too are constantly getting sensory reports which themselves induce the next motion this series of reflexes involving what is known as feedback results in controlled and accurate motion hey Doc what do they got to say about tickling well seriously some physiologists say that tickling should be considered a real sense I'd like to see you make a character out of that one you know the more we talk about the sensus the more characters we seem to be getting it's getting to be like a regular three- ring uh circus yeah tada [Music] [Music] the [Music] [Music] [Music] the a the the [Music] seems to stop and and go back again but it doesn't it goes all the way around it's an optical illusion but even though you you tell me my eyes still won't believe it well let's attach a bar to the framework and see what'll [Music] happen the trapezoid still appears to move back and forth but the bar goes around no I'm really mixed up well let's move up to an overhead view and see what happens plainly it does go all the way around and the bar moves with it reason we are fooled from this angle is that the trapezoid and its windows are not rectangular in shape but we expect them to be because we have learned by experience that windows are rectangular and even though we know it's turning all the way around our brain still interprets the visual image in terms of past experience yellow scarf hung on a short wire from one end of the trapezoid moves around in a ghostlike circle while again in spite of what we know the window seems to stop move back and forth [Music] [Laughter] [Music] I'll never trust another trapezoid now let's go to Princeton University where the trapezoid experiment and others relating to perception and past experience were done it's here in the demonstration laboratory that these windows were constructed why do the the two heads seem to change size answer the windows are distorted and this appears to be a normal room man and a boy watch now the man and boy are greatly distorted in size the answer is obvious if we look at the room from another angle where we see that the room is is distorted the people are normal Professor Hadley cantrol Princeton psychologist can tell us the significance of what we have seen the demonstrations you have just seen were devised by the scientist adelbert Ames while they are amusing Illusions they are much more than that for they demonstrate some rather profound psychological principles involved in all of man's experience they show that our exper erence is much more than a simple reaction to something outside and that we have to learn through our own past Behavior the significance of the Impressions our sense organs bring to us and again this leads us to understand that the world we know is created in large measure from our past sensory experience an interesting experiment that shows how the brain reacts to sensory simulation can be shown here on the oscilloscope and this instrument can be used to detect the impulses that reach the brain from the sensory organs now this brain is resting and the pattern of response is smooth but if the eyes are suddenly stimulated by a flashlight we see a violent variation in the pattern now let's observe what happens when a sudden loud noise is heard so outside stimulation activates the brain the screen's ready doctor thank you we wonder how human beings would react in situations where there was a near absence of things happening what happened to him well in a way nothing looks to me like he's been in an accident no this is an experiment that took place at McGill University students volunteered to participate in this study of human behavior under extreme and prolonged monotony their hands and arms were softly covered to muffle a sense of touch all harsh lights subdued by a mask comfortable beds quiet and yet it was impossible for most of these students to take it for more than 24 to 48 hours the psychologist doeb and his associates who conducted these experiments found that deprived of ordinary everyday sensory experience es the subjects began to lose touch with reality those who stuck it out began to see things hear things distortions set in hallucinations some began to see dots of light lines simple geometric patterns then the patterns became distorted another described hallucinations of little yellow men with black caps with their mouths [Music] open one said he saw the recurring vision of eyeglasses passing in A procession like an animated movie cartoon as the time went on these Visions became more disturbing unreal often frightful deprived of normal sensory bombardment the brain May cease to function in the usual way for instance studies in France and at Harvard University have shown that hallucinations are fairly common among long distance truck drivers after long monotonous hours on the road [Applause] the cockpit of a jet aircraft groaning along in the stratosphere can duplicate very closely the hypnotic monotony experienced by the students at McGill lack of change little stimulation to the senses illusion Distortion hallucinations May set in what happens to men in an Antarctic white out when they lose all sense of distance and all objects seem to float in midair what is the strange exhilaration known as Rapture of the deep that can cause divers to discard their breathing apparatus these are problems that scientists in and out of the arm services are studying this centrifuge machine for example helps to determine how the human senses function under abnormal conditions moreover we are living in an age when man is extending his senses into far-reaching Realms that he once only imagined to the sources of meteors and cosmic rays in England a radio telescope like a huge electronic ear can catch faint radio waves broadcast from the distant galaxies and nebula of outer space [Music] electronic senses circling the earth send information to man's waiting brain all these magnificent tools are nothing in themselves they are really only extensions of man's basic senses so that he can see further hear better feel more delicately the simple truth is no matter how much man May extend his senses the more he must depend upon the ones he has and so inevitably we return to our basic theme We Exist through our senses we are bound to reality through our senses we learn we survive we grow through our senses in Laboratories hospitals universities young men and women many of them still studying for their degrees are investigating exploring dedicating their minds and imaginations to the adventures of research studying the science of our senses the mechanism of taste and smell and the Brain itself the center to which the senses report is being studied in every country of the Civilized world the final wonder is that the experience brought to our brains by the senses is recorded there for the rest of our lives Dr Wilder Penfield director of the Montreal Neurological Institute will tell us one of the truly great physiological discoveries of the 20th century thank you Dr Baxter during my life as a brain surgeon it has been necessary to operate on Good many men and women good many hundreds and to expose the brain under local anesthesia with the patient conscious in those operations it is a useful practical procedure to stimulate the cortex electrically these are not experiments in that process we have stumbled quite accidentally on the fact that there is recorded in the nerve cells of the human brain a complete record of the stream of Consciousness all those things of which a man was aware in any moment of time are are recorded there and all the sights and sounds which you ignored and the thoughts which he ignored are absent from that record the operations are carried out under local anesthesia so that the patient is conscious and can talk he does not feel anything when the electrode touches the brain with its gentle electrical current it is as though the electrode touched a wire recorder or a or a strip of film and he relives a period of time when I talked to them afterwards about how it seemed to them they say it is much more real than any remembering it is as though they were reexperiencing it I believe you're about to hear the actual words of patients in response to this stimulus which they were quite unaware of while they were in the operating room you will hear them as I heard them I have a sudden feeling as though I lived through all this before now I see them they're laughing my friends and I'm with them in a house in South Africa they're my old friends I hear children's voices I hear them down along the river I'm sitting in a railroad station in a small town small town in Kentucky it's winter and the wind is blowing outside and I'm Waiting for a Train I see the whole thing a guy coming through the my friends and I'm with them in a house in South Africa they're my old friends I hear Jordan's voices I hear them down along the river I'm sitting in a railroad station in a small town small town in Kentucky it's when and the wind is blowing outside and I'm Waiting for a Train I see the whole thing a guy coming through the fence at a baseball game I was watching these two teams play when this fell came through the fence I hear a song I haven't heard it since I was in high school there it is again [Music] the brain of man contains a record of his past a living Storehouse of remembered moments of all his days what we do what we feel are registered there our multiple Sensations the whole awareness of the wonderful world in which we live [Applause] [Music] so is recorded the total spectrum of Human Experience a tapestry woven from the memories of past Sensations ever growing and unique in each of us this has been a story of the human senses and how their signals relate to the brain of man all his knowledge knowledge indispensable in understanding his world how man chooses to use this knowledge in shaping his world will determine the future of mankind [Music] [Music] y [Music] [Music] the Bell Telephone system takes pride in bringing you this program and its series of shows on science we acknowledge our gratitude to the distinguished Board of advisers covering the broad range of modern Science Biology and genetics medicine bacteriology and botany chemistry geoh physics physics anthropology electronics and Acoustics mathematics engineering for the program you have just seen our thanks to the special advisers who have suggested and check the scientific material the Bell Telephone system is indebted to all these men and to many institutions for the generous support they've given this Venture in public education through entertainment [Music]