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

by Gazzaniga, Michael S.

  Gary Lynch and Rick Granger had sent in a manuscript for the inaugural issue (Figure 34) that was full of math.6 As Charlotte and I began to put it into the proper form for electronic delivery to MIT, we learned the hard way that PageMaker was not designed to do mathematical notations easily. It took us five days of fiddling around to get the manuscript into shape. Even though our manuscripts with simple text and figures were a snap, overall our first issue took way too much time. Something had to be done, so I decided to visit MIT Press and sort it out. MIT, I thought, one of the greatest scientific institutions on earth, would surely know how to make this new electronic printing easy.

  FIGURE 34. The cover of the first issue of the Journal of Cognitive Neuroscience was a painting by the neuroscientist Alex Meredith, who coauthored a paper included in the issue. Each subsequent issue featured a fresh cover.

  (Courtesy of the author)

  It turned out we were ahead of the curve. MIT hadn’t yet geared up for the new era of computer-based publishing. They still did it the old-fashioned way, using typesetters and human proofreaders. To our surprise, nobody in academic publishing had switched over. We managed to get two or three issues to them, leaving blank spaces in the text where the formulas were placed. To our glee, MIT simply told us to collect the manuscripts, and they would take it from there. They have been stellar ever since, and, of course, it’s all done electronically now.

  Successful journals take a lot of loving care to get going. Establishing a flow of high-quality articles is one trick. In the days of print, each issue was an event and each had to be balanced and attractive. We gave each issue a different, artistic cover, where we would trumpet artists and photographers. When putting together an issue, Charlotte and I would pour ourselves a cognac and climb into bed with our inbox of accepted articles. We picked the papers for the upcoming release that we thought made for interesting reading as a group, rather than in the order in which they were accepted for publication. It worked. To this day, the journal is a major success and one of the top-ranking journals in psychology and bioscience. This is in no small part due to the fact that Charlotte remains the managing editor.

  MORE FUNDING, MORE RESEARCH, MORE KNOWLEDGE

  Meanwhile, many visiting researchers were making a mess of the scientific literature on split-brain patients.7 The researchers seemed not to understand how cross-cueing tricks, used by the split-brain patients to function in the world, could make it look as if their brains were not split. Many concluded, based on this misunderstanding, that there were noncallosal pathways deep in the brain exchanging information. The idea was that split-brain patients might not be so dramatically split after all. If these studies and conclusions were correct, the results of split-brain studies looked very different. Indeed, the very notion that the mind could be divided at its joints was up for grabs.

  The proper testing of split-brain patients, while seemingly straightforward, is exhausting. Skilled experimenters have learned through experience and are well aware of all the strategies and tricks patients unconsciously and unintentionally use to cue themselves. They are cross-cueing all the time, and as a result, any experiment is at continual risk of not working properly. Even very sophisticated scientists can fall victim to appearances. We had several such episodes over the years. As a result, from time to time, erroneous messages were being reported and trumpeted in the scientific literature.

  One very senior visitor to the lab was my old friend Donald MacKay. He visited while we were still in New York City. He and his physicist wife, Valerie, were dead set on showing that there were not two different agents in one disconnected brain. They had asked to test patients J.W. and V.P., and, of course, we obliged. They were both spectacular scientists and friends. They were not, however, attuned to the tricks of the split brain. The MacKays’ task was to try to get one hemisphere to bet against the other. If it worked, they thought it would demonstrate the presence of two mental systems, each with its own “free will.” They would accept the idea that there were indeed two mental systems, each with its own evaluative system, and that they were wrong. If it didn’t work, they thought that would suggest there were not two minds, but merely two executive systems managing nonessential processing separately or something like that. They set up a clever test, but it was doomed to be nonconclusive because the split-brain patients could cue and control a situation in ways that undercut the experimental design.

  In the MacKays’ experiment the first order of business was to communicate to J.W. the idea of how to be a guesser. So in full view of both hemispheres, Valerie wrote a number from 0 to 9 on a piece of paper. J.W. could see it, but Donald, who was going to play the role of guesser, could not. The game would then be that Donald would guess a number, and J.W.’s left hand would be required to answer what he knew by pointing to one of three options printed on a card: “go up,” “go down,” or “OK.” If J.W. had seen Valerie write, say, a “3,” and Donald had guessed “7,” the correct answer for the left hand would have been to point to the option “go down.” This all proved very easy to learn and is a good example of what we had come to appreciate after years of split-brain testing. Always train the patient on the general strategy of the test before starting to examine how one or the other hemisphere might respond when asked to work alone. In short, the game of “twenty questions” was easy, and J.W. picked up this version of it very quickly. To wind up this phase of the test, Donald and J.W. switched tasks. J.W. was to be the guesser and to guess which number Donald had been privately shown by Valerie. Again J.W. learned to do this quickly and, of course, his responses were guesses since he had no way of knowing the number that Valerie had shown Donald.

  Now it was time to test the right hemisphere alone. MacKay started off his experiment by asking J.W. to say what he saw when a number from 0 to 9 was flashed to the left visual field, and an alphabet letter was flashed to the right visual field. Of course, in standard split-brain style, J.W. could only name the alphabet letter that had been flashed to the left speaking hemisphere via the right visual field. Then MacKay asked the left hand to respond to his numerical guesses by pointing to the card with the three options on it “go up,” “go down,” or “OK.” Again, J.W.’s right hemisphere picked it up fast. From the experimenter’s point of view this is a tense time and becomes exhausting. After all, one is witnessing a nontalking half brain perceiving a number and choosing a response on its own terms and outside the realm of awareness of the chatty left hemisphere. One is seeing a module working independently, as if it were its own mind, yet still in the same skull as the left talking half brain. All of our intuitions are that this cannot be, and yet it is, right in front of our own eyes.

  MacKay was now building up to his key test. Could things be set up such that J.W.’s left hemisphere became the “guesser,” while the right was the keeper of the secret number? Here again, the secret number was projected to the silent right hemisphere. Instead of MacKay being the guesser, however, J.W. was told to let his mouth do the guessing, which meant, of course, his left hemisphere. Once again J.W. proved able to play this game of “twenty questions” with himself. This struck us as very eerie, before we realized that everyone probably does the same thing. Your conscious mind makes a guess, which your unconscious mind listens to. It then becomes active, which in turn makes you think of other associations, which finds you zeroing in on what an answer to a question might be.

  The final step now arrived. MacKay set two boxes of tokens in front of J.W., one for the left hand and one for the right hand. MacKay then proposed to J.W. that the right brain (left hand) should be paid a token by the left brain (right hand) for every piece of information the left brain needed to solve the problem. Thus, after the secret number had been flashed to the right brain, the left brain needed some information as to whether a guess it (the left brain) had made was correct. Thus it would now cost the left brain a token every time it ventured a guess, to be paid to the right brain.

  To keep things in balance, the l
eft brain received added tokens, too, if it guessed the answer quickly. If the right brain made a mistake in its answers, it was penalized by the experimenter, who took three tokens out of its box (the left hand’s box) and gave the tokens to the left brain (the right hand’s box). That was to keep the right hemisphere honest and not mislead the left hemisphere, thereby requiring it to spend more tokens to eventually get the right answer! The game went on like this, and it all seemed to sort of work, but still nothing new was really being learned.

  MacKay then threw some red meat into the game. Why, he asked J.W.’s right brain, don’t you charge the left brain three tokens instead of one token for a piece of information? The right brain immediately agreed, which in due course depleted the left brain’s token box, and the game was over. Why didn’t the left brain (right hand) refuse the request for three tokens or embark on a bargaining session with the right brain (left hand)? Because nothing close to that happened, the MacKays felt they had preliminary evidence that each hemisphere did not have its own evaluative system and that, therefore, there was but one mind in the skull. They thought that somehow, information was being integrated across the midline through some unspecified subcortical system.

  I disagreed. There were so many possible alternative explanations. The simple truth was that the reward values to the game, which they had assumed were being lateralized to one hemisphere, were likely shared by both hemispheres. It was already known that cross-cueing of emotional valence was a reality. The MacKays carefully noted my disagreement with their interpretation of the experiment when their subsequent article in Nature appeared a few months later.8 Still, the paper attracted attention and others started examining other kinds of studies, which basically were testing for some kind of transfer between the hemispheres. The next visitor to the lab was a young neuropsychologist from Montreal’s McGill University, the talented, dashing, yet enigmatic, and ultimately tragic Justine Sergent.

  It is commonly observed between a dog and his master, between an old married couple, and between the horse Clever Hans and his trainer that a subtle cueing is going on all the time, most of it outside the realm of consciousness. It doesn’t take too much for a trainer to cue his dog to stop at a particular point in space, which raises problems for validating the idea that bomb-seeking dogs are really doing the finding rather than following the master’s hypothesis. In psychology, the well-known Clever Hans account, the horse that could do arithmetic, was all about the master unconsciously cueing the horse when to stop stomping his foot.

  Couples and old friends can usually conclude a sentence begun by the other, having had so much practice together in social exchanges. In fact, couples can anticipate most everything, including each other’s thoughts. With that in mind, how do you think two half brains coordinate to coexist together after months and years of minute-by-minute practice? My bet is they work it out quickly through having intimately shared expectations about the world they live in. While it may be difficult to predict the reactions of someone you just met, it is usually not too hard to predict those of spouses, children, fathers, mothers, and so on. It follows that it should not be too hard to predict behaviors of the half brain living next to your other half brain, watching the same world and feeling the same emotions, the same rewards and punishments of life. It is because of this that studying split-brain patients is difficult: What seems like central integration of information usually is not.

  Still, the MacKays had floated an idea, and others thought that their ideas needed to be tested out. Having worked with these patients day in and day out for years, neither my lab nor I shared in that opinion. If correct, it would not only be news for split brain research but also surprise other researchers that higher-level processes could take place in subcortical structures. Sergent also wanted to pursue the idea that some kind of higher-order information exchange between the hemispheres was still intact following callosal section. She too did her work on one of our New York runs up to New England.

  The long and short of her experiment was simple enough. First, see if each hemisphere could judge if consonants and vowels were different and keep a record of how fast they could do it. Easy, each hemisphere could, and vowels triggered a faster response than consonants. Then flash a consonant to one hemisphere and a vowel to the other, or a consonant to both hemispheres or a vowel to both hemispheres. In all cases, only one manual response from one hand was allowed—press one key if it was a vowel, and the other key if it was a consonant. Now, seemingly, with only one response allowed, the hemispheres had to exchange information, especially on the trials where one hemisphere was getting a consonant and the other a vowel. Since in this case each hemisphere had a different goal, how was the hand going to react? Because there was no incorrect answer on this test, the clues to underlying mechanisms could be gleaned only from the reaction times.

  J.W. did not hesitate doing the task. If reaction times had not been measured, one would have simply observed that another visuo-motor task was being carried out easily. With the reaction times noted, however, another story was possible. J.W. responded most quickly when vowels were presented to both hemispheres. He was slower to respond when a vowel went to one hemisphere and a consonant to the other. Finally, he was slowest when each hemisphere was presented with a consonant. This pattern of findings led Sergent to the conclusion that there must be higher-order information crossing between the hemispheres. In her assessment, if the two hemispheres were not interacting at all, all reaction times should be the same. Jeff and I disagreed. We told her that the most logical explanation was that there was a cross-cueing strategy going on, one completely separate mental system cooperating with another mental system hopelessly intertwined, since both had to use the same body to express themselves. In that unique kind of situation, strategies for action would be in order. The strategy appeared to be this: Respond fast if it’s a vowel. That explains why two vowels are the fastest, as each hemisphere knows this rule. It also easily explains why two consonants were the slowest. In that case, each brain was waiting to see if the other was going to opt for a fast response. When that didn’t occur, each side could independently conclude that both sides must have seen a consonant. In the conflict conditions, while one side may have wanted to respond quickly, the other through various subcortical strategies was trying to go more slowly.

  Jeff and I were convinced we were right, but at the time, Sergent had her own views. Within a month, she had the study published in Nature!9 We sent her other data that we had collected on patient V.P. that supported our view—she saw it differently. So, we decided to disagree about it and let it go. Over the next few years, however, the view was trumpeted by Sergent and others, including several studies from the Sperry lab. While Sergent acknowledged a few years later that the study she did on J.W. was flawed, she had gone on to test some of the West Coast split-brain subjects and felt overall that her ideas were confirmed. So, seemingly out of nowhere, it was now commonplace to see the argument that higher-order information did transfer between the hemispheres but specific details of perceptual information did not. What was going on? It was time to do a thorough study, and this was a new graduate student moment for Sandra Seymour at Dartmouth. It wound up taking a few years to complete the work, but it was a beautiful and complete study.

  Seymour reviewed all of the published data on all of the split-brain patients in the United States. She determined that only two patients were providing support for the so called “reunified” view of the split brain: Cases L.B. and N.G. from the California series. Case L.B. was problematic for many reasons, one of which was that it was not clear if his callosum was completely sectioned. MRI results were mixed. On cross field comparisons of perceptual information, he scored more like normal than did the split-brain patients. As a result, and before trying to understand the puzzling results from L.B. and N.G., Seymour decided to rerun the East Coast patients, J.W., V.P., and D.R., on all the tests run by Sergent. It was Sergent’s work that represented some of the strongest
claims that subcortical pathways were responsible for the interhemispheric integration of higher-level abstract information.10 In fact, she argued that it is the very abstract nature of the information that made interhemispheric comparison possible. Sergent reasoned that the subcortical pathways were less efficient at, or incapable of, transfer or cross-comparison of stimulus identity. In short, she reported that performance might be compromised when simple physical identity was emphasized, whereas performance improved when the same stimuli were being compared for meaning. I still don’t fully understand how Sergent came to that way of thinking.

  At any rate, Seymour retested the East Coast patients using the exact tests Sergent had used on the two key Caltech patients. She also tested Sergent’s proposal that abstract representations, but not sensory information, could transfer in the split brain. On this test she required the patient to compare numerical values represented by a digit in one visual field and a group of dots that added up (or not) to the digit value in the other visual field. This task could be performed only if the abstract idea—that is, the notion of, say, “seven”—were shared between the hemispheres.

  In the end, we simply could not replicate the results reported by Sergent for the West Coast patients L.B., N.G., and, to some extent, A.A. So, what was going on? Indeed, several other researchers were beginning to report interhemispheric interactions testing the Caltech patients. This was even more puzzling since, as already pointed out, their surgery involved more interhemispheric disconnections than did that of the East Coast patients. Put simply, the East Coast patients appeared more disconnected, not less, even though their secondary commissure, the anterior commissure, was intact. How could this all be?