Tales from Both Sides of the Brain : A Life in Neuroscience (9780062228819)

by Gazzaniga, Michael S.

  Over the next few years, we hammered away at it with the patients we studied (Video 10), and the “interpreter” revealed itself in many classic experiments. The one described above was a typical example of the speaking left hemisphere piping up with some kind of story to explain the actions that were initiated by the right hemisphere without the knowledge of the left hemisphere. At other times the left hemisphere would explain away emotional feelings caused by the right hemisphere’s experiences. As I have mentioned earlier, emotional states appear to transfer between the hemispheres subcortically, and this transfer is not affected by severing the corpus callosum. Thus, even though all of the perceptions and experiences leading up to that emotional state may be isolated to the right hemisphere, both hemispheres will feel the emotion. Though the left hemisphere will have no clue why or where the emotion came from, it will always try to explain it away. For example, I showed a scary fire safety video about a guy getting pushed into a fire to the right hemisphere of V.P. When asked what she saw, she said: “I don’t really know what I saw. I think just a white flash.” But when asked if it made her feel any emotion, she said: “I don’t really know why, but I’m kind of scared. I feel jumpy, I think maybe I don’t like this room, or maybe it’s you, you’re getting me nervous.” She then turned to one of the research assistants and said, “I know I like Dr. Gazzaniga, but right now I’m scared of him for some reason.” The left hemisphere felt the negative valence of the emotion but had no knowledge of what the cause was. The interesting thing is that lack of knowledge does not stop it from coming up with a “makes sense” explanation that fits the circumstances: I was standing there and she was upset. Her interpreter put the two together into a cause-and-effect conclusion. I must have scared her.

  The interpreter can affect many cognitive processes, including memory. For instance, Elizabeth Phelps, then a postdoctoral fellow and now a distinguished cognitive neuroscientist at NYU, and I showed a series of photographs to split-brain patients. The photographs told the story of a man getting up in the morning and getting ready for work. Later, we showed them another series of photographs and asked which ones they recognized. These photographs included the same pictures, some new ones that were unrelated to the story line, and some that were closely related to the story line. While the right and left hemispheres both accurately identified the previously seen photographs, the left hemisphere also falsely recognized the new pictures that were related to the story.

  The left hemisphere has a tendency to grasp the gist of a situation, make an inference that fits in well with the general schema of the event, and toss out anything that does not. This elaboration has a deleterious effect on accuracy but usually makes it easier to process new information. The right hemisphere does not do this. It is totally truthful and only identifies the original pictures.

  The interpreter also will explain away input from the body as illustrated in the following classic experiment (which most likely would not pass muster today with a human subjects committee). Stanley Schachter and Jerry Singer told volunteers for an experiment that they were getting a vitamin injection to see if it had any effect on the visual system. What they really received was an injection of epinephrine and what the researchers really wondered was if the appraisal of their physical reaction would depend on the surroundings. Some of the subjects were told that the vitamin injection would cause side effects such as palpitations, tremors, and flushing, and some were told that there were no side effects. After the injection of epinephrine (which does have the side effect of palpitations, tremors, and flushing), a confederate of the researcher came into the room with the volunteer and behaved in either a euphoric or an angry manner. The volunteers who were told about the “side effects” of the injection attributed their symptoms to the drug. Those who were not informed, however, attributed their autonomic arousal to the environment. Those who were with the euphoric confederate reported being elated, and those with the angry confederate reported being angry. Three different, reasonable “cause-and-effect” explanations for the same physical symptoms came spewing out of their left hemisphere interpreters. Only one was correct, however: the injection of epinephrine.

  So when it comes to the interpreter, facts are cool, but not necessary. The left brain uses whatever is at hand and ad libs the rest. The first makes-sense explanation will do. It looks for cause and effect and creates order out of the chaos of inputs that have been presented to it by all the other processes spewing out information. This is what our brain does all day long: It takes input from various areas of our brain and from the environment and synthesizes it into a story that makes sense.

  THE RIGHT HEMISPHERE LEARNS TO SPEAK

  Case P.S. was also the first to reveal another major reality in split-brain research—his right hemisphere actually began to speak simple utterances. Soon after his surgery, he behaved like many split-brain patients. The left hemisphere could understand language and could speak. The right hemisphere could also understand simple language but could not speak. That was the standard situation. P.S., however, was beginning to behave differently. He startled us by uttering single words out of his right hemisphere.26

  We knew it was right hemisphere speech because of a simple test. We would flash a picture of an object to each hemisphere and ask P.S. to name what he saw. About two years after his surgery, he began to name objects no matter which hemisphere saw them. To test to see if information was somehow transferring between the two hemispheres, we changed the question. We didn’t ask “What did you see?” but “Are the pictures the same or different?” He couldn’t do it. It was weird. If the pictures flashed separately to the right and left hemispheres had been, say, of an apple and duck, he could say “apple” and “duck,” but these separated hemispheres couldn’t compare what they saw and indicate if the pictures were the same or different. Of course, if both pictures had been presented to one hemisphere or the other, to say “same” or “different” was trivially easy.

  We pushed hard on this. The ability of a right hemisphere to change and be able to speak was there, no doubt about it. Over the following years, this ability began to appear in other patients as well. We would later find that both Case V.P. and J.W. learned to speak out of the right hemisphere. In one test we showed how exotic it could become (Figure 22) .

  FIGURE 22. Case P.S. began to make one-word utterances out of the disconnected right hemisphere, so we presented him with what we called the “triple story” test. We presented five word pairs in a sequence that would tell the following story: “Mary Ann May Come Visit Into The Town Ship Today.” This is what our normal subjects recited when we presented them with the test. Each of P.S.’s hemispheres, however, discerned a different story line. The left brain saw “Ann Come Into Town Today” and the right brain saw “Mary May Visit The Ship.” The dialogue above is how Paul’s two hemispheres reported the experience. The left brain responded, and then the right brain suggested a different arrangement of words, leading to the summary response at the end, combining both outputs.

  (Courtesy of the author)

  Overall, our excitement was unbounded. Every working scientist, scholar, or detective of anything, for that matter, knows the rush that occurs with discovery. Another secret of the natural world revealed, and you were there, front-row seats and all. It was an exciting time, and more changes were on the horizon. I had decided to take a job at Cornell University Medical College and was moving back to New York City.

  CHAPTER 5

  BRAIN IMAGING CONFIRMS SPLIT-BRAIN SURGERIES

  The scientist, by the very nature of his commitment, creates more and more questions, never fewer. Indeed the measure of our intellectual maturity, one philosopher suggests, is our capacity to feel less and less satisfied with our answers to better problems.

  —G. W. ALLPORT

  I JOINED THE FACULTY OF CORNELL UNIVERSITY MEDICAL COLLEGE at a time when doctors didn’t advertise their services and money wasn’t the 24/7 topic of hospital employees. Medical schools we
re exciting places to be and the doctors worked hundred-hour weeks without blinking an eye. It was the tempo and the intensity of a first-rate medical school that captured my energies. I loved it and I knew I was going to learn a lot.

  The first big thing was that I had traded graduate students for medical residents, who were completely different animals. Graduate students are trained in the experimental methods of science, on how to do experiments. Residents are a bit older and wiser. They are making more decisions in a day than most of us make in a year. They interact with people dying, rejoicing, crying, laughing, the whole gamut of life’s emotions. In a word, they are seasoned in a way graduate students are not. My job was to help bring these two kinds of experiences and skills together to study human cognition. I was to now mentor both Ph.D.s and M.D.s

  Fred Plum, the legendary chairman of the Department of Neurology at Cornell, was the catalyst. Somehow he had gotten it in his head that his residents needed to be trained in neuropsychology, and somehow he got hold of me when I was at Stony Brook. The first idea was to come into town on Thursdays and do special neuropsychology rounds with the residents. That was a bold idea since I didn’t know much about the vast variety of neurologic syndromes. I had read about them all and had experience with aphasics, but actually examining all kinds of patients? How was I going to be professorial about that, and on rounds no less?

  Working the rounds at Cornell quickly became one of the great experiences of my life. Plum’s residents, all of them, were outstanding and some of the kindest and most fun-loving people I have ever known. They quickly figured out I was the rookie at rounds. In a way, they gracefully became the teachers and I became the student. I found myself loving the neurology wards.

  Soon enough, I began to get the hang of it and started to suggest experiments that might reveal something new about a classic syndrome. Busy residents don’t mess around. If an idea crystallized, they wanted to do the experiment right then. “Here,” they would say, “let’s take the patient down the hall to the storage room. We can set up a projector on the table in there.” Or, “There is a patient on Six East with a global amnesia. Get the portable EEG machine. We can document her seizures and then give IV Valium to bring her around.” They did all of this on top of their regular grueling workload.

  It wasn’t long before Plum decided his plan for adding neuropsychology to his neurology program was working. He offered me a full-time job as a professor. I loved the idea, and it came at a moment when my personal life was changing as well. The offer came at a time when Linda and I had decided to go different ways. She would stay in Stony Brook with our four daughters—a huge source of joy in my life—during the week, and I would come out and spend the weekends with them. That was very tough stuff, but to everyone’s credit, it worked out for everyone involved.

  LEARNING FROM PATIENTS AND ACCESSING THE UNCONSCIOUS

  I convinced LeDoux to join me in my new lab at Cornell, and together we tried to figure out what our next projects might be. One of these grew out of rounds. One of the residents was Bruce Volpe, a superb physcian and a human with a preternatural energy. He started to show us patients with lesions in their right parietal cortex with what seemed to me the most bizarre syndrome. You’d ask such a patient to look right at your nose. Then you’d raise your left hand, showing either one or two fingers, and ask the patient what they saw. They’d easily give the right answer. Do the same thing with the right hand. Again the patient gave the right answer. Now came the critical observation. Raise both hands, such that the left was showing one or two fingers and the right was as well.

  A truly remarkable thing happened. These patients all denied the information being provided by your right hand. It was as if your right hand no longer existed. The phenomenon is called “double simultaneous extinction.” It goes on all the time in the neurologic clinic and is a disorder of attention. After one gets over the astonishing reality of the syndrome, the question arises: What the heck happens to that information about the right hand that you know got into the brain? After all, when only the examiner’s single, right hand was elevated, the patient easily named the number of fingers that were raised. When the information was suppressed by having both hands raised, was that information no longer accessible to the patient’s conscious cognitive system? Or was it accessible, but the patient unable either to talk about it or to be aware that the information was being used to help him or her make a decision? Maybe this anomaly would provide an avenue into the unconscious. Volpe and LeDoux went to work.

  While Volpe rounded up a group of patients with similar lesions who manifested this phenomenon, LeDoux designed the experiment and helped Bruce learn some of the tricks of the psychological trade. The critical experiment was simple. We planned to flash pictures into each visual field simultaneously and ask the patients if the pictures were the “same” or “different.” Thus the patient was simply required to make one spoken response. Yet, to get it right, information from both visual fields would somehow have to be combined in the brain and, following that process, go to the speech centers for a response. The first step was to see if the patients could do the task successfully. The answer was clear. The patients, who would deny the presentation of information in their left visual field, nonetheless could use it to make the correct “same” or “different” judgment. As you can imagine, when the patients were asked what had been presented on the “same” trials, they simply said two apples or whatever the stimuli had been. When asked what was presented on the “different” trials, however, they could never name the picture shown to the “extinguished” field.1 Bingo, the experiment worked. This experiment turned out to open up a small cottage industry of research. Put simply, we had demonstrated that information that could not be consciously accessed could nonetheless influence how a seemingly conscious decision was made. We were able to peek into the vast unconscious, the networks that most likely govern most of what we do. We were terribly proud of ourselves, and soon enough, others took up the idea and extended it in many clever ways.

  THE JOYS OF MENTORING AND FRIENDSHIP

  I don’t believe in “training” graduate students. I believe in exposing them to possibilities, under the assumption that if they need to know something in greater detail, they will learn it on their own. That is how I learned whatever it is that I know. When people talk about training, they generally mean taking an amorphous mind and shaping it into something. It is the sort of thing that goes on at universities that are not yet in possession of high-quality students. It is not the sort of thing that should go on at serious centers of discovery. Mentoring, on the other hand, is productive, necessary, and enjoyable.

  Mentoring now takes place years beyond graduate school. The intricacies of modern knowledge are so vast that the graduate school experience has become only a small part of the total development of a young scientist. Over the years, especially when I was at Cornell, my experience in mentoring was mostly with students at the postdoctoral level. Students generally came to me with backgrounds in psychophysics* or cognitive psychology,† wanting to study patients with neurologic problems. Patients with focal lesions usually caused by strokes (or what was called “broken brains”) provide an excellent means to study the workings of the mind.

  One afternoon, Leon Festinger and I were lunching at Dardanelles in the Village. At the time, his interests were turning away from psychophysics and moving into archaeology and human origins. He asked me if I might be interested in taking on one of his students, Jeffrey Holtzman. To sweeten the deal, he said he would throw in his expensive computer-based eye-tracking device (Figure 23). The device was way too useful (and expensive) to end up in storage somewhere. The eye tracker allowed the experimenter to present visual information to a subject and very precisely stabilize where it fell on the retina. This means, for example, that if a stimulus was presented in the left visual field, something we did daily with our split-brain patients, the eye tracker would track the eye if it moved and automatically reposition the s
timulus being presented. As Leon casually pointed out, the system was useless without Jeff to run it. Being a sucker for high-tech gizmos, I told him to send Jeff up for an interview.

  FIGURE 23. Jeff Holtzman with his eye tracker.

  (Courtesy of the author)

  One never really expects a new acquaintance to become a truly close friend. At the ripe old age of thirty-nine, I felt as though I had already met all of my lifelong friends, and that everyone I was to meet from that point forward would fit into the second-rung category of “acquaintances.” As if to illuminate the foolishness of that point of view, in walked Jeff, and, within a week, we were inseparable. I relished that friendship for six years, and then Jeff died of an awful disease. His death was like suffering a brain lesion—part of me was gone and forever unrecoverable.

  The year he graduated from the New School, Jeff married Ann Loeb, a dazzling young lawyer. Her first boss was Rudolph Giuliani. Ann became an authority on the First Amendment, and she read the copy for every issue of Forbes and the Daily News before it was put to bed. She also tried to read Jeff’s scientific papers. It was Greek to her, but she did it anyway. Her sense of humor surpassed even his, which is saying something. It served her well in surviving the high-stakes world of New York City law . . . and being married to Jeff. They howled together, and just when he thought he had gotten her on something, she upped the ante.

  Being with Jeff was like being on Saturday Night Live all day long. We would start to giggle at precisely the same moment when listening to a lecture, and we would have to avoid eye contact, looking straight ahead and concentrating fully to prevent a major disruption from occurring. Occasionally, I would giggle when he didn’t, or vice versa. What’s going on? I would think. Is Jeff even listening? Has he fallen asleep? Usually not, and wonderful arguments would follow over drinks at the Rockefeller University bar. We had them almost every night for six years. His sassy wit was nonstop and his impudence was an art form. One night as we left the bar, he said to me, “I think about Charlotte when I go to bed. Who do you think about?” Charlotte is my wife. How can you ever forget someone like that (Figure 24)? I tried to top him but I never quite made it.