FIGURE 10. Norman Geschwind played an early role in establishing the idea of having neural disconnection syndromes in neurology. He is generally credited as the father of behavioral neurology in America. Being in his company was always a pleasure.
(Courtesy of the author)
Geschwind sent a copy of his prepublication manuscript to Sperry for comment sometime during the early months of 1962, right when we were testing W.J. but before we had published our findings. In the manuscript, he credited Sperry’s animal work for his and Kaplan’s idea of examining their patient for disconnection effects. Sperry had given a colloquium at Harvard during the fall of 1961 describing some of that work. The broad outlines were already known by then, and it was entirely routine for a researcher to talk about their “latest” findings. At that time, I was working feverishly back in Pasadena testing W.J. preoperatively. Sperry was not pleased to receive the manuscript a few months later. Both research groups were working entirely independently and he didn’t want any potential confusion on that point. After all the years of his and Myers’s foundational animal work and our early and, as yet, unpublished work on W.J., he didn’t want anyone thinking that his human work stemmed from Geschwind’s findings.
Roger Sperry was a fierce competitor—an athlete who had lettered in three varsity sports in college. During the early part of my training, Sperry got into a huge feud with his own mentor, Paul Weiss, then the most eminent neurobiologist there was. In a heated, specially arranged addendum to a Weiss summary in something called the Neuroscience Research Program, Sperry let him have it. In an autobiographical essay about her illustrious career, another of Weiss’s students, Bernice Grafstein, recounted it like this:
I was greatly relieved, therefore, that my failure to progress with the problem of motor system regeneration, when I eventually summarized my results for Weiss toward the end of 1964, did not seem to trouble him particularly. He seemed not at all perturbed that my findings might be less consistent with his ideas than with ideas of specific reconnection that were identified with Roger Sperry. In fact, in his summary report of a workshop session at the Neurosciences Research Program at about that time, Weiss claimed to embrace the idea of specificity in regeneration, with reservations only about the necessity of uncovering the detailed mechanisms involved [although he still insisted that these might include functionally coded activity patterns that could serve as “messages for selective reception].15
Sperry, on the other hand, was adamant about disengaging his views from any associated with Weiss. In a statement that he insisted on appending to the same report, Sperry reasserted his own primacy in the development of the idea of “selective, chemotatic (sic) growth of specific fiber pathways and connections governed by an orderly pattern of specific - chemical affinities that arise out of . . . embryonic differentiation” (Sperry, 1965). He believed that throughout their long association Weiss had assimilated his (Sperry’s) contributions without adequate acknowledgment, and that there had been “a buildup in the literature of a complex web of ambiguity, forced terminology, and confusion of issues that [was] almost impossible to untangle for anyone not intimately acquainted with the underlying history.” He was not content that Weiss should just confirm that specificity was operating in the growth and termination of regenerating axons; he believed that he had been deprived of the opportunity that Weiss had promised him to publicly “get things out in the open, face the issues and clarify points of controversy.”
Clearly throughout his career you were either on Sperry’s team or the other guy’s team. Geschwind was a new rival. It was also true that if someone graduated from Sperry’s team and became a competitor, the frequency of critical remarks about that person went up. During my stint at Caltech it happened every time. One day when he was criticizing somebody who had left the lab, I realized that after I earned my degree and left the lab this would probably also happen to me. At the time, however, we were on the same team and I shrugged the thought aside, with assumption that it was just part of life in science.
Geschwind’s complete findings, ultimately published in the journal Neurology in October 1962, served an important role in activating the interest of neurologists in the callosum. It reconnected the clinical literature with a rich earlier history about the importance of the callosum, previously worked out by the German neurologist Hugo Liepmann and the French neurologist Joseph Dejerine around the turn of the twentieth century.
Years later, Geschwind and I were guests at an International Neurology Meeting in Kyoto. It was a very formal event at a large conference hall. The auditorium was lined with translators madly trying to deal with the multiple languages being used. Norman was on the dais with a group of famous neurologists from around the world. The emperor of Japan was also on the dais with his wife, listening to what must have seemed like gibberish. Each speaker always rose and bowed toward the emperor before going to the podium to speak. Not Norman. When he was called up to speak, he went directly to the podium, said his piece, returned directly to his chair, and sat down.
After the session I asked Norman about it. His failure to conform was noticeable, to say the least. Norman said, “Hell no, I am not going to bow to the emperor of Japan after what he did to our troops.” He was indeed an honorable man and a competitor. Over the years, I became a friend of Geschwind’s and friends with the entire Boston VA’s neuropsychology group. If we ever spoke about the issue of precedence, I don’t remember it, and we had dozens of opportunities to do so. Norman was a scholar and a conversationalist like few others. It was always a joy to be in his company. He wrote a paper in 1965 for the journal Brain that to this day is a classic review of the neurologic “disconnexion” syndromes (as it was spelled in the British publication).16 Indeed, the paper launched the field of behavioral neurology in America.
While Geschwind’s unsolicited manuscript was passed around Caltech, it didn’t have much of an impact on our thinking. Sperry said that whenever someone makes a discovery in science, someone else always says, “Yeah, but so-and-so thought of it before you.”
In many ways, Sperry was more socially conscious than most. He was always thinking about how his actions might impact the social fabric of scientists. Bogen, in his autobiography, tells of another story that captures this quality. He was discussing an exception to Sperry’s leisurely way of getting a manuscript out for publication:
Roger did not always delay. One day when I was visiting the lab I asked him about the Gordon paper on lateralized olfaction in split-brain patients. He said, “We have to send this olfactory paper in immediately.” “Why?” I asked. “Because I have just refereed for Neuropsychologia a paper with a similar experiment in rats. People know that with human subjects, we can do in a few weeks what would take many months in rats. If we delay, people might think that I got the idea when refereeing the rat paper.” Roger seemed to think of everything. I idolized him and hung on his every word, of which there were not very many. I thought him the experimental physiologist of our time.17
At that time, I was way too callow to comprehend the complexities of sharing credit for an intellectual idea or that it’s a constant battle to take the scientist out of science. Unfortunately, it is now commonplace to have authors suggest to journal editors a list of preferred and a list of nonpreferred reviewers. This recent trend has arisen because many people have realized that pettiness has held back many scientific developments. New ideas need a chance to be expressed. This practice, however, under the rationale that it would be a “conflict of interest,” also disallows people from critically interacting. Should someone really be disqualified to review a paper because they have a different interpretation of the underlying data? That is anathema to the very nature of science.
At the time, I just kept doing experiments, and after a while the whole manuscript exchange episode passed. After all, we had already realized that the disconnection story and the loss of some capacities was not the most profound implication of the split-brain studies. We had
begun to understand that we could test each half brain separately, independent of the influence of the other half. Unlike classic neurology, where you study the absence of mental capacity caused by lesions in particular areas, we could study the presence of mental capacities. It was a whole new ball game.
ESTABLISHING THE BASICS
Though the trembling excitement of the discovery would soon pass, we knew we had a research gold mine on our hands that could explain some of the brain’s mysteries. The slow, careful exploration of what we had to do to confirm and extend the basic findings needed to begin. Right off the bat, we ran into a complicated problem. Our original paper in PNAS had been mostly about limiting visual information to one hemisphere or the other. This was relatively easy to do. The next phase called for limiting touch information to one side of the brain. This was not easy at all.
The visual system in humans and similar mammals is neatly laid out in our body plans. Stare ahead and look at one spot. Both of your eyes are pouring visual information into your brain. Does it enter in an orderly manner? Yes, it does. Each eye sends its information up the optic nerve and half of the information stays on the same side of the brain and half of it crosses over and goes to the opposite hemisphere (Figure 11). So, if you are still fixating on that point, everything to the left of the fixated point in either eye is projected solely to your right hemisphere. Thus each eye is contributing to that experience. It follows, then, that visual information to the right of the fixated point is being solely projected to the left hemisphere. This is true for all of us, including our split-brain patients.
FIGURE 11. Schematic of how information is projected into the brain by the visual system.
(Adapted from various sources of Sperry and Gazzaniga)
This makes it easy to test each hemisphere separately when using visual stimuli. One simply has to present whatever it is you are interested in knowing more about to the right or left visual field. Once again, information from the right visual field goes to the left hemisphere and information from the left visual field goes to the right hemisphere. Got it? Then you are ready to start thinking about these experiments.
Working out the strategy for testing how a separated hemisphere would deal with touch—or, more formally, somatosensory information—is more challenging. How the brain receives information from the body is quite different. This was beautifully laid out by Jerzy Rose and Vernon Mountcastle in a chapter of the 1959 Handbook of Physiology,18 which I read at the time. They were the world’s authorities and their clarity was inspirational.
Here is how it works. The left half of your body sends most, but not all, of the information about touch to the right hemisphere. If you are holding an object in the left hand, the touch information related to the object’s overall shape, called stereognostic information, goes to your right brain. More basic sensations associated with the mere presence or absence of having been touched, however, go to both hemispheres. Rose and Mountcastle made this abundantly clear by also describing the anatomy that supports this reality. The reverse is true for the right half of the body. Information from the right hand about an object’s shape goes directly to the left hemisphere, while the less definitive presence or absence of information goes to both hemispheres.
Clearly, from the perspective of getting completely lateralized information into only one hemisphere, the visual system was the way to go: simple, clean, and highly lateralized. The somatosensory system, however, was presenting a challenge. Some forms of the information from the world of touch went to the opposite half brain while others went to both half brains. How were we going to make sense of this? It turned out to be intriguing, thanks in large part to the work that had gone on before us.
To solve this puzzle, we first blindfolded the split-brain patient and placed an object in the right hand. Then we asked, “What do you have in your hand?” The object was always named correctly: no fuss, no muss. The shape information had gone to the left hemisphere. Then we placed the object in the left hand and asked the same question. This time the shape information went to the right, nonspeaking hemisphere. The patients were usually not able to name it. Interestingly, however, they would manipulate the object appropriately. This suggested that their right hemisphere “knew” what the object was but because it had no speech center, it couldn’t name the object. Nor could the shape knowledge of the object be communicated to the left speaking hemisphere. The fact that the object was manipulated correctly also indicated that both hemispheres had stored information about the nature of objects, sort of a double memory system leading to redundancy in our brain organization. All of this from one bedside test:19 Fantastic!
One sunny afternoon I was testing W.J in his home in Downey. I can still remember how much delight he showed on the following test. I had prepared a set of small wooden blocks that had small tacks protruding from them. I was looking to see if he could tell the difference between a block with one tack and a block with several tacks. I blindfolded him and started presenting the blocks, first to the right hand, which found it easy to do, and then to the left hand. The task was simply to match the blocks. I would first give one of them to him, then take it away and put it in with a group of blocks. He would then pat around on the tabletop and try to find it again among the other blocks. It turned out each hand could do this simple “match to sample” task.
What was most interesting, however, was what his left hand (under control of the right brain) would do when presented with the block with one tack. He would pick it up by the tack and twirl it. It seemed as if his right brain was showing off his dexterity with the hand it controlled, even though it could not relay information about what the object actually was. He also was chuckling to himself while he was doing this. It seemed as if his right hemisphere was an independent personality enjoying the moment. It was one of my first realizations in these early days that there were “two minds” present at all times. I remember asking W.J., “Why are you laughing?” He replied, “I don’t know. Something in my left hand I guess.”
What was puzzling, however, was the fact that sometimes W.J. did name an object held in the left hand correctly. How was that happening? How could that work? It took months before I finally figured out what now appears to be an obvious answer. As Sperry use to say, “Nothing is simpler than yesterday’s solutions.”
The key was to remember those neural pathways and the double representation that Rose and Mountcastle had written about: Some of the fibers from the somatosensory system do not cross over to the opposite half brain. They climb up ipsilaterally, that is, to the half brain along the same side as the point of stimulation. It was unclear, however, what these fibers were doing. Finally, I hit upon the experiment that revealed the answer.
I limited the number of objects to be identified to two, a plastic triangle or a plastic ball. All W.J. had to do while blindfolded was say which one I had placed in his left hand. After a few trials, W.J began guessing correctly on every test trial. How was he doing it?
Imagine you are given such a task but are required to wear a thick leather garden glove. The instant recognition of the nature of the object would be gone due to the muffled information you would be getting through the glove and you would have no immediate stereognostic information. How could you figure it out? You would quickly learn to find an edge on the object and press hard on it. Presence or absence of information is the kind of minimal signal those ipsilateral pathways can transmit. In a split-brain patient, without any shape information coming in from the right hemisphere, the left (speaking) brain would quickly learn “I feel an edge” or “I don’t feel an edge” and then conclude: If an edge, it must be a triangle; if I don’t feel anything, then it must be a ball.
That was exactly what W.J. was doing. He would manipulate the object until his thumb could press down hard on an edge. That became the cue that initiated the whole cascade of events I just described. This was one of the first realizations that split-brain patients use external self-cueing to reintegrate some
of their disconnected information. By self-cueing I mean a behavior that is induced by one hemisphere and perceived (through one or more of the senses) by the other hemisphere. This in turn allows that other hemisphere to initiate an appropriate response. It is startling when you first see it.
This seemingly simple observation points up a deep problem for those of us trying to figure out how the brain works. As will become more apparent later on, many researchers consider the brain to be made up of dozens if not thousands of modules. A module is a local, specialized, neuron network that can perform unique functions and can adapt to or evolve to external demands. Modules work independently, yet in some kind of coordinated way, to produce unitary behavior. Think of a city with hundreds of different independent businesses. Taken together, however, they perform all that needs to get done for a city to operate and appear to be a unified whole. How all the modules are coordinated is the question. Over the years, it has become apparent to me that one way the modules come to produce unity is by cueing each other, usually outside the realm of conscious awareness. The self-cueing seen in a disconnected speaking hemisphere is omnipresent, and we have observed many different strategies. In this case, primitive touch cues are picked up and then that information is intertwined with the limited decision set of two possible items to render a correct answer. This is but one strategy. But I’ve gotten ahead of myself.
Tales from Both Sides of the Brain : A Life in Neuroscience (9780062228819) Page 6
