Split-brain patients respond in a dramatically different manner. When the extra distracters are added to a single visual field, the patients, not surprisingly, take longer to find the target, like everyone else. However, when that same number of added distracters is spread out such that each field gets half of them, the overall reaction time is much faster when compared to everyone else. In other words, each disconnected hemisphere seems to have its own attentional scanning machinery, and each can go to work simultaneously and independently of the other half brain. Luck did these studies on J.W. and also on the Caltech patient L.B.
This was an exciting finding, which was well documented and robust. It was beginning to look like there were many components to the attention system. It looked like some aspects of attention were involved with scanning a visual scene for particular information. Other parts, which were associated with cognitive work, were still connected, presumably through lower brain systems.
Kingstone pushed on these ideas and made them even more interesting. He wondered if each hemisphere was doing its scanning of the arrays using the same kind of strategy. After all, the left hemisphere was the smart, verbal hemisphere, while the right was specialized for grouping visual parts into sensible wholes. Maybe their underlying attentional mechanisms served up their discoveries of the visual world by different means. Alan made the target selection process more difficult. He added even more distracters, such that when using the low-level automatic systems described above, we humans begin to crack. We are smart animals, so we guide our attention through cognitive strategies. In a word, we start using “top-down,” that is, goal-directed and “guided” ways to sort through all the information. Let’s say the task is, Find Louise. One strategy might be, “Look for big hair!” Alan discovered that we can only do that in the left hemisphere.20 The right hemisphere is stuck doing the searches in the standard automatic way. “Look at everyone until you find Louise.” All of this work led us back to an even stronger view about split-brain patients: Not only were the half brains separate, those puppies were also different!
BRAINPRINTS AND THE SWISS CONNECTION
The lab was bubbling with activity. In part this was because it is not in my nature to focus on one topic. When I was growing up seventy years ago, there was no such disease as attention deficit/hyperactivity disorder, so I couldn’t have had it! Now, as I look back, I wonder. My mother always said that I had ants in my pants. Drilling deep on only one topic is a popular way to spend one’s life. But it’s not for me. When working with patients and the ephemeral topics of attention, which requires from hundreds to thousands of boring trials of having patients react to simple lights, my mind became inattentive. I wanted to do different things, more closely connected to basic neuroscience.
We had settled into Pike House, but we were bursting at the seams. If we were going to expand, how? Pike House had an outdoor porch. I asked if the medical school would enclose it for additional office space. I called the contractor who had built my new house, had him give a bid, and the provost quickly agreed to it all. Over the years I had learned that if you present a problem to an administrator, also present the solution. Then it’s only money, and usually administrators can handle small budget items. The job was finished so quickly (that’s how you actually make money in construction) that the college took a shine to my builder, Rusty Estes, and used him frequently thereafter.
Soon, however, we were once again overcrowded. More grants were rolling in, postdocs were flocking, and our new graduate program was filling up with students. The medical school started to get more interested in our enterprise and moved us over to some space in the actual medical school building. The walls were god-awful yellow tiles only matched in ugliness by the well-used linoleum floors. That actually was the first offer. I said I wasn’t leaving our beloved Pike House for that. Okay, said the dean and, after a new paint job and new carpet, over we went. It turned out to be a delightful space and further energized the lab. We could now expand the lab’s pet project: mapping the human brain.
As I already mentioned, my appointment was in psychiatry. For bureaucratic reasons, a Ph.D. could have tenure in a medical school department, and psychiatry filled the bill. My professional associations were with the neurologists and, in particular, the neurosurgeons. When I met David Roberts, who is now the chief of neurosurgery at Dartmouth, he was a resident under the neurosurgeon Donald Wilson, who launched the Dartmouth split-brain series. When Wilson tragically died from throat cancer, Dave took over his lead and is now the world’s authority on split-brain surgery, even though it is rarely done these days.
Dave was also a Princeton man. A few years later, I was visiting Princeton on a short sabbatical. My host, George Miller, who had moved from Rockefeller University, suggested we have Dave down to talk about MRI-guided microscopes for neurosurgery operations. It was the dead of winter, but Princeton had called, so Dave answered. He got on the tiny airplane that flies out of Lebanon, New Hampshire, and showed up to talk to the Psychology Department about his work on the microscope. All I can tell you is that it was one of the best talks I have ever heard (and I have heard a lot of talks). The audience of nonsurgeons was mesmerized. For a neurosurgeon, one of the challenges is that although a brain tumor may be visible on an MRI, there is still the problem of finding it in the 3-D brain during surgery. Dave’s form of brain mapping, using his MRI-guided microscopes to solve this problem, was riveting.
Back at the lab, we had been working on our own brain mapping project. We had started it back at Cornell as a passion of Marc Jouandet’s, a graduate student of mine who joined up with the lab during our Stony Brook days. Marc was an extraordinary talent, driven and smart. He started out building the lab a computer (in a suitcase, which, in those days, deemed it portable) that could help with our studies. He picked up the parts at Tandy Corporation, aka Radio Shack, figured it all out, and bingo, we were into a form, a very early form, of data processing. As it turned out, though, Marc was an anatomist at heart. He came up with the idea of brain mapping, which we enthusiastically called “brainprints,” sort of like fingerprints. We all were going to have our own unique brainprint: another easy-to-say, hard-to-do idea.
Marc always saw the possibilities in both science and life more generally. At one point during my time at Cornell, Charlotte and I planned to take a sabbatical leave so that I could write my first book for general readers, The Social Brain. Most sabbaticals last for a year, a time allotment that did not work for me, due to the needs of my family and running a complex lab. I just couldn’t be away for such a long stretch of time. I hit upon the idea of splitting it up. Travel to a place for a month, then return home, then travel again. I mentioned this in a letter to Marc. Before I knew it, Marc, who had carried out a postdoctoral fellowship at the University of Lausanne, had found the perfect Swiss mountain cabin for us in the village of Caux, just a cog-train ride up the mountain from Montreux—a three-bedroom chalet for $150 a month. We not only booked it; we found ourselves returning to Caux for a month each winter for years.
At Caux, we skied, we worked, we hosted visitors, and we also had the yearly treat of visiting Bill Buckley around the bend in the mountain at Rougemont, where he and his wife wintered each year. During the ten weeks that Bill spent in Rougemont, he managed to write an entire book, maintain his three columns a week, continue to edit National Review, and ski every afternoon after lunch at the Eagle’s Nest.
Bill once complained that Swissair had a rule about flying with dogs, which he found frustrating. There could only be one dog per cabin class and there were only three classes. The Buckleys had three dogs. This meant that they could not sit together for the flight. Pat, his wife, sat in first class with one dog, Bill in business class with the second dog, and the housekeeper in coach with the third dog. For years Bill tried everything he could think of to get this federal rule waived. Nothing worked. Ah, I thought to myself—maybe my brain science connections could come to the rescue of this social inconvenience.
I mentioned something to Bill, and he looked at me with that “yeah, right” face. The matter was dropped.
As the next season approached, I remembered this story and decided to call up Liana Bolis, a neuroscientist and benefactor to the field in dozens of ways. I had written a monograph for her foundation and had attended several superior workshops she had organized, including a trip to China as part of a World Health Organization team to examine neuroscience in China. She was a significant contributor to the Catholic Church in Beijing, which once bound us to listen to a Chinese opera for five hours. More pointedly, she had a significant stake in Swissair. I called her to say I had this special American friend who traveled to Zurich all the time from New York and . . .” She said that she had little to do with the operations of the company but that she would get a manager to call me.
In Swiss fashion, the call came through rather quickly. The manager was very polite and amused by my request. I mean couldn’t they, just once, let the Buckleys both sit in either first or business class? He thanked me for my concern for my friend and after some vague remark we both let the conversation end.
The Buckleys’ flight took off two weeks later. The following night I got a call from Bill. “Mike, last night at JFK, just before the plane took off, the Swissair steward came over to me and asked me to leave my dog in my business class seat, said that he would be fine there and escorted me to an empty first class seat next to Pat! You accomplished what the entire social structure of Gstaad could not and that includes Roger Moore [of James Bond fame].” We all had a good chuckle, but I knew brain scientists had just gone up a notch in his estimation.
At any rate, by the time we arrived at Dartmouth, the brain mapping project had attracted lots of people in the lab, such as our very own neurologist, Mark Tramo. The idea was to take a patient’s MRI scans in cross section and to ultimately have a computer program automatically read the hundreds of scans and generate, from that data, a flat map of the brain, which could be comprehended, visualized, and measured more easily than a real three-dimensional brain. What surprised us was that one of the psychiatrists, Ron Green, skilled in treating serious mental disorders, also took a shine to the project. He started committing hours to the tedious task of tracing the cross sections. At that time, automatic tracing was not available; hand tracing on tissue paper laid over the brain scans by skilled neuroanatomists had to do. It is a beautiful thing to see people who, although they have day jobs, are charged up by an idea and will work endless additional hours on it. This method went on for years until a bright undergraduate from Cornell, William Loftus, came along. He began to figure out how to do it all on a computer. The U.S. Navy’s Office of Naval Research bought us a fancy computer, and Loftus harnessed it for the work.
Techniques are important in science. What’s more important, however, is using them on important questions. Before developing the brainprint, we had determined from MRI scans that the corpus callosums of identical twins were more similar to each other than to unrelated controls. This was one of the first demonstrations that actual brain structures in identical twins were more similar than not.21 With brainprints, we wanted to extend that idea by carefully mapping the surface of the cortex to see if other specific regions of the brain were more similar in twins. We tried, but we were not able to capture it. In the end, our brainprinting process was too laborious, and our subject pool was too thin. That, however, doesn’t mean the question wasn’t addressed by others. Discovering the similarities and differences of twin brains was taken up by the UCLA brain imaging group, and they firmly established how similar twin brains are, both structurally and functionally, using sophisticated and advanced brain imaging techniques that far surpassed ours.22 Still, this experience prepared us for a different “big science” project a few years later. The seeds were laid, but it took about eight years for them to bloom.
ONLY PARTIAL DISCONNECTIONS: THE SEMI-SPLIT MIND
In some sense the overall goal of biological research is to strive to make observations more and more specific. The first success of showing the dramatic effect of a full callosal-splitting surgery, where basically nothing seemed to cross over between the two half brains, soon gave way to the question: What if only specific parts of the callosum are sectioned? Or, what if specific regions remain after surgery? Both of these issues were always on our minds, and opportunities to study such problems popped up unexpectedly.
Classical anatomy of the callosum indicates that the posterior regions of the structure interconnect the visual areas at the back of the brain. As one moves forward, the fibers connecting the parts of the cortex responsible for hearing, touch, and other body sensations and movement become evident. Armed with this knowledge, one would predict that a lesion to the posterior regions of the callosum might cause a problem with the transferring of visual information between the hemispheres. In a way, the idea was that one might see a “modality-specific” split. That is, such a patient might be visually split but not split when tested in other modalities.
Years earlier, I was sitting in my office at NYU when a Brooklyn neurologist called me about a couple of cases. He was following two patients who had had their posterior callosum sectioned as a consequence of a neurosurgical procedure to get at a tumor of the third ventricle, a place in the brain located just below the posterior callosum. He asked if I would like to study the patients. After leaping out of my chair with excitement, all was arranged and led ultimately to a paper that we jointly authored. I love this part of a life in science. A practicing neurologist, though a stranger to me, keeps up with the literature, sees some patients in his office who might be of interest to a basic researcher, discusses it with his patient, who agrees, takes the time to find the researcher (in the days before the Internet), and then, importantly, participates in a research effort. Who says we are not an altruistic species?
These two patients taught us many things. The first case was visually split, just as predicted. His other modalities had been left intact. (He also turned out to be one of the minority of people in whom hemisphere dominance is reversed.23 It was clear from the pattern of his responses that his right hemisphere was dominant for language and speech, while his left was dominant for the usual right hemisphere specialization, such as drawing in three dimensions.) One case, one random call, and we were closer to understanding how the parts of the callosum were organized.
Over the years, other cases were brought to our attention by clinicians, and they too provided more insight into the organization of the corpus callosum. For example, another patient, E.B., had a slightly more extensive posterior split. As expected from the known anatomy, it seemed to prevent tactile and auditory integration. She also had a remarkable ability to integrate motor information in one direction, from the left to the right brain but not from the right to the left brain, again suggesting great specificity of connections.24 After all, where the surgeon actually stops sectioning the callosum is somewhat arbitrary. It makes sense that what information systems get disconnected should vary. These clinical cases, which were presented to us through indirect routes, were enormously interesting. They were made more so because, as a result of the main research program on split-brain patients, we knew what questions to ask.
Still, it was two of our star patients who truly illuminated a few secrets of the callosum. J.W.’s callosum had been surgically split in two stages while we were still at Cornell. His posterior callosum was sectioned first. Ten weeks went by before he underwent his second anterior section. This gave us the unique opportunity to examine him before his surgery, and then after each successive surgery. Preoperatively he was completely normal with respect to our tests. The two half brains were in total communication. John Sidtis, who was another one of my ace postdoctoral fellows, Jeff, and I examined him again after his posterior callosum had been sectioned.
Wilson stopped the surgical section approximately halfway along the callosum, a little farther toward the anterior regions of the callosum than the sections of either of th
e two clinical patients I just described. According to our standard tests, which carefully examined each modality, J.W. seemed completely disconnected. While that was exciting, we knew that the entire anterior half of his callosum was still intact. Since the posterior half section seemed to result in the full split-brain syndrome (as we then understood it), we wondered: What on earth is the anterior portion transferring? What were those 100 million or so neurons in the front of the callosum doing? Sidtis and Holtzman kept pushing.
After we did the routine test of flashing simple pictures to each visual field and determined that J.W. could easily name pictures flashed to the left brain but not pictures flashed to the right brain, we wondered if he could carry out some other kind of cross-integration of information. We set it up by flashing a stimulus to each field. The left hemisphere saw the word sun and the right hemisphere saw a picture of a simple black-and-white line drawing of a traffic light. Our simple question to J.W. was “What did you see?” The conversation went like this (Video 12):
MSG: What did you see?
J.W.: The word sun on the right and a picture of something on the left. I don’t know what it is but I can’t say it. I wanna but I can’t. I don’t know what it is.
MSG: What does it have to do with?
J.W.: I can’t tell you that, either. It was the word sun on the right and a picture of something on the left. . . . I can’t think of what it is. I can see it right in my eyes and I can’t say it.
MSG: Does it have to do with airplanes?
J.W.: No.
MSG: Does it have to do with cars?
J.W.: Yeah (nodding his head). I think so . . . it’s a tool or something . . . I dunno what it is and I can’t say it. It’s terrible.
Tales from Both Sides of the Brain : A Life in Neuroscience (9780062228819) Page 24