Imagine yourself, armed with a pad of paper and a pencil in each hand, sitting looking at a dot right smack in the middle of a TV screen. Simple visual geometric shapes will be flashed, and all you have to do is draw them simultaneously. Easy, right? It is easy only if both of the pictures flashed are the same thing. So if two circles are flashed, no problem. If a circle and square are flashed, however, it’s a big problem for you and me and Alan Alda. We start, then stop, then draw something out of whack. None of it is done simultaneously: Instead each hand works in an alternative style. In short, with this little task, the human and his great big brain seem totally flummoxed.
Now J.W. is asked to do the same thing. The two circles, no problem. The square and the circle: again, no problem and done instantly (Video 14). It was as if two people were present, one guiding each hand with absolutely no interference from the other. No statistics are needed to see this effect, though thorough experimental description is always required to pick apart the spatial and temporal aspects of the seemingly unfathomable skill, and this was done as well.3
ANOTHER RIGHT HEMISPHERE SPEAKS UP
While literally dozens of experiments were going on, most of them showing how poorly the two separated half brains intercommunicated both sensory and motor information, another development was also occurring right before our eyes. It looked like J.W.’s right hemisphere was beginning to speak. Although it had been quiet for years, like a late-developing child, suddenly one-word utterances were coming forth. When this happens, it begins to feel like the person is no longer split. Each side describes and reacts to its own sensory sphere, and together they look whole to the outside world. After all, within a half brain hundreds to thousands of modules interact to produce that half brain’s mind. Maybe mind left and mind right, though separate, look unified not only to the outside observer but also to the inside observer.
Kathy Baynes decided to figure out what was going on with J.W. She knew all the patients, having started with us in New York and traveled with us to Dartmouth and now to Davis. She is one of the people who truly make universities and research centers work. She is collaborative to the core and generous with her huge intellectual skills to projects that are not even central to her passion, the study and nature of human language. The bait on the hook for her was language, of course, and J.W. seemed to be undergoing some language changes. Was this brain plasticity at work? Was it a clever way to cross-cue? Was sensory information transferring over to the smarty-pants left hemisphere? The first thing to do was to carefully define J.W.’s changing behavior.
As you know by now, one of the cardinal tests for splitness is to flash pictures of objects, words, anything to the left and right visual fields. If a patient is speaking only out of the left hemisphere, only stimuli in the right visual field should be named. If the patient starts naming left visual field stimuli that are only streaming to the nonverbal right hemisphere, something is going on. What was it?
J.W. had undergone his surgery at twenty-six. By now his left hemisphere had been separated from his right hemisphere for fifteen years. For most of that time, the left hemisphere had been doing all the talking. If asked questions, it answered them while the seemingly patient right hemisphere came along for the ride. When J.W.’s right hemisphere spoke up, we were all stunned. Was the right hemisphere going to be like Sleeping Beauty and dazzle us with stories of forbearance? Was it going to show differences in intellect, capacity, personality, and indeed, be a different kind of agent?
In the last chapter, I mentioned a BBC special on conjoined twins,4 which is a remarkable story of love, normality, and gumption under the most unlikely of circumstances. The twins, Abby and Brittany, are conjoined at the chest and torso, and have a single pair of arms and legs. Although Abby controls one arm and leg and Brittany the other arm and leg, they are athletically coordinated. Scientifically, they are two people locked into one body. They each have different desires, different likes and dislikes, and different personalities. It is as odd as it sounds, and yet their life seems natural to them. The circumstances are their normal circumstances: The person adjusts, normalizes. The trick is to get others to allow them to be normal. This is where their parents (who have raised them brilliantly) and their friends excelled. Brittany and Abby have conversations with each other all day long. They have their differences, but they are also incredibly able to cooperate and cue the other on matters that will assist in the management of their commonly shared body. In short, there is independence yet cooperation.
Now imagine yourself standing directly behind another person and then being tightly taped together. It is a good taping job, such that when one head moves left, the other is perfectly yoked to it and winds up looking to the left as well. When a hand moves, the taped hand of the partner moves along with it. Again, there is no question there are two separate and equal minds guiding what amounts to one body. How long would it take to learn to talk to the other, so goals are shared? How long would it take for strategies to be formed so that the motor commands to one hand from its brain would serve as a cue to the yoked hand? For example, when left hand A wants to move to the left, left hand B somehow needs to be cued that it should relax and go with the flow: Hand A would start to move, and hand B would sense this through proprioception* and learn to go with it. How long would all of this take? In J.W.’s case, approximately fifteen years.
With J.W., it didn’t happen all at once. One could say it took practice, practice, practice. Approximately seven years after his surgery, J.W. was able to do a curious thing. His left hemisphere speech apparatus could name which of two numeric stimuli had been presented to his right hemisphere. Oddly, his left hemisphere didn’t know and couldn’t access the information for internal use. Let’s say I had flashed the number 2 to his right brain. I then flashed the number 2 directly to the left hemisphere. Could the left hemisphere say “same” or “different”? It could not, and on such tests the left hemisphere performed at chance. Yet, if I had asked the left hemisphere to simply speak, it would respond correctly and say “2.”5 Weird!
Somehow the right hemisphere was setting up the speech apparatus, but in a special way. At this point, both hemispheres had to know what the possible answers were in each test. Additionally in this experiment, there could be only two possibilities, “1” or “2.” Again, somehow the right hemisphere could set the speech apparatus to one of two possible reactions. It seemed it must do it down low in the overall speech apparatus mechanism, since the left brain cognitive mechanism seemed ignorant of the information. We ran a further test to show that the only thing at play was the capacity to set the speech system with one or two possibilities for response. As long as the two possibilities were known, this interhemispheric parlor trick worked. Instead of asking J.W. to say “1” or “2,” I then asked him to say “indescribable” or “indestructible.” Again, both hemispheres knew what the two choices were. Asked to compare the words as same or different, both hemispheres failed, but when the word was flashed to the right brain, the left brain correctly managed the spoken response.
After another seven years, J.W. had begun upping his game. Now he was naming about 25 percent of the pictures flashed to his supposedly mute right hemisphere. We started out using pictures of familiar family and friends, as well as pictures taken from a standard set of pictures of neutral objects and animals. We presented the stimuli in both the quick-flash method and in our eye tracker, which allowed for the picture to remain in full view for up to five seconds. The results were clear. J.W. was naming the stimuli about 67 percent of the time and it didn’t matter if they were flashed or remained on for viewing. The right hemisphere had definitely changed. Its control of the speech apparatus was now good (Figure 39).
FIGURE 39. Here we tested J.W.’s capacity to develop speech in his right hemisphere, by presenting him with images to name. To ensure he wasn’t cheating, we used an image-stabilizing eye tracker. Here he is viewing the display screen through the stabilizing device with one eye. His oth
er eye is covered with a patch and his head and chin are secured by a bite board for maximum control.
(Courtesy of the author)
Even more surprising was J.W.’s seeming ability to describe what we called “complex scenes” flashed to his right hemisphere. While he never could name the scene completely accurately, he did pick individual elements in a picture. For example, he initially identified one scene correctly, but then incorrectly described it after being prompted for further information. The scene depicted a woman wearing a black dress and washing clothes in an old-fashioned washer. Behind her was a clothesline with laundry hanging from it. Here is what J.W. said (the experimenter’s comments are in parentheses):
It was a person . . . Would it be someone hanging out their laundry? One person. Must have been a woman. (Did you see any laundry?) I think so. I think she was reaching up and that’s what she was doing. . . .
Take another example, which was a scene depicting a woman standing behind another woman who was sitting at a table and crying. There was a stove and sink in the background. In response to this scene, J.W. said:
The first thing I thought of was a woman baking. I don’t know why. . . . (Was she sitting or standing or . . .) Standing up by a table or something.
J.W.’s response does not capture the meaning of the scene, but it does convey some of its visual attributes.
Another example shows how J.W. could capture both visually and semantically similar information about the stimulus. The scene depicted a racetrack with two racing cars driving around it and another car that had crashed and overturned. There was a grandstand off to the left behind the track.
Looked like something moving like a vehicle or something or somebody running or something like that. (Did it look like one thing or . . .) At least one. It was centered on one. Maybe there was something in the background. (If you had to guess what it was, what would you guess?) Either somebody running, or, a curved picture. Looked like coming around a corner almost . . . someone running. Maybe it was a track. It was hard to tell.
The level of performance looks like a possible response from a less capable mental system. After all, language is not what the right hemisphere normally does. Is this a fumbling infantlike language system in a grown-up body/brain? It did appear that J.W.’s naming performance became worse as the visual stimuli became more complex. J.W.’s performance level was indeed like other patients who had also developed speech after their callosal section. In all cases, utterances from the right brain seemed to be only single-word responses. Producing multi-word descriptions was seemingly not possible for J.W. Yet it sounded like he was making them.
We came to see that this kind of capacity has a collaborative strategy between the two hemispheres. We knew that there was no interhemispheric transfer of information mediated by pathways in the brain. We also knew J.W. had no syntactic ability in his right hemisphere. While his language was extensive, his right hemisphere couldn’t tell the difference between “a blind Venetian” and “a venetian blind.” Word order had no impact on him, as Kathy had determined in test after test.6
So how was he doing it? We finally figured out that the collaboration could consist of the left hemisphere generating complex descriptions based on one- or two-word “clues” generated by the right hemisphere.7 It’s like the old couple again. One is droning on, and the other pops in with a single word to get the narrative back on track. The droner notes it, continues with the pitch, makes adjustments, pauses, only to get another single word from the partner, and on and on.
After intense study in Davis, J.W. unfolded in slow motion, making it easier to see his progress. When speech developed in P.S. and V.P., it happened quickly, within one year, and it seemed different. J.W.’s progression was slower and also reminiscent of the original Caltech series of patients.
LEFT BRAIN/RIGHT BRAIN DIFFERENCES FROM CELLS TO PROCESS
One of the great values of working in an interdisciplinary center is that experiments and questions come to mind that otherwise might not. Leo had trained a young neuroanatomist, Jeffrey Hutsler, and I had the good fortune of being able to hire him. He was exceptionally bright, a tinkerer who got things to work in the lab and, paradoxically, was hilariously funny yet also a bit of a loner. Getting things to work in a cellular and chemical neuroanatomy lab is a lonely job. It takes lots of time and patience and sheer hard work. It was only because Jeff and I happened to be in the same place at the same time that we were able to go after one of the underlying questions of human brain function: Is there something special about the human cortical areas that enables language?
The question of “nature versus nurture” pops up often in the field of brain science. Do things come wired up with little possibility of change? Or is a framework laid down by genetics but modifiable? In the lab next to Jeff’s, we were watching with our own eyes the stirrings of language and speech from J.W.’s formerly mute right hemisphere. Had the underlying wiring changed or had it already been there and begun reemerging in a way we didn’t yet understand?
There was another part to the puzzle. The split-brain patients had all been carefully studied by Hillyard and his colleague Marta Kutas. Marta was soon to become the world’s expert on a particular brain wave she had unearthed, called the N400, fondly referred to as the “semantic incongruity” wave.8 Participants in her tests would listen to a sentence like “I take my coffee with cream and . . .” and then an ending would be flashed that was either congruous, “sugar,” or incongruous, “cement.” When this was done on normal subjects, the brain answered back with the N400 brain wave response when the word was incongruous, but not when it was congruous. Marta had in essence found a brain biomarker for syntax.
People who study electrical brain waves also want to know where the waves are coming from. There is a long and complicated story about the “generators” of brain waves. In normal subjects, the N400 wave was present over both cerebral hemispheres, even though only the left hemisphere was believed to be involved in language comprehension. What would happen with split-brain patients? Kutas and Hillyard studied five patients overall, and the result generated even more intrigue.
In many previous studies, the five split-brain patients studied had all shown evidence of language in their right hemispheres. Thus it was of little surprise that each half brain could detect a semantic anomaly and could indicate it by pointing with the appropriate hand to the word that made no sense. What was so surprising was that only two of those same five patients produced an N400 wave when an incongruous word was shown to the right hemisphere. At the time of these tests, these were the two split-brain patients who had shown evidence of right hemisphere speech.9 Had Marta found some kind of marker associated with only a fully realizable language and speech complex? Were the neural processes that enabled this brain wave already there or had the right hemisphere learned to speak? Maybe language alone didn’t do the trick. Maybe the wave appeared only when the hemisphere could comprehend that, indeed, the incongruity was semantic!
It was time to go under the hood. Could Hutsler find out some basics on normal postmortem brains? Is the language cortex special and if so, where is it? We started by simply comparing the cortical areas in the dominant left hemisphere that were classically defined in the neurology books as being associated with speech with the corresponding area in the right hemisphere. Of course, to do this, we needed to study postmortem brains. Enter two dynamos from the Veterans Administration hospital in Martinez, just south of Davis: Robert Knight and Robert Rafal. By objective standards, these were two of the best behavioral neurologists in the country. They were also a lot of fun. Unlike many of my colleagues, they also loved to teach.
Karl Lashley was not quite on the mark when he told Roger Sperry that if you have to teach, teach neuroanatomy because it never changes. Lashley was right that the major lobes, fiber tracts, and major nuclei are normally situated where they are supposed to be. That is, the basic infrastructure of the busy brain city is all there: all the stores, r
oads, and alleys. Where he got it wrong was in the details of the connections. Neurons do change and vary where they do their business . . . all over the place. But first, Hutsler wanted to know if the cellular organization of the left language cortex was different from the cortex found in the normally language-absent right hemisphere. He found many differences in the underlying cortical organization of the left and right hemispheres that, overall, suggested the cortical neurons were making many more connections to other neurons on the left side. He did not find there were more neurons, per se.
BUILDING AN INTELLECTUAL COMMUNITY
The UC Davis community was hopping with activity. One way we enlivened the tomato patch was to bring in visitors. Our new center building was up, and I had adorned the walls with the paintings by Henry Isaacs, a gifted landscape artist from Vermont and a dear friend. The new hires added their own huge energy, and the Davis faculty supported the enterprise completely. Still, it never hurts to add dessert. I cooked up an idea to have a visiting-professor program.
The first requirement of a visiting professor is to invite a truly outstanding intellect: someone who has the knack for real interaction and who works and thinks at a very high level. Someone with such capacities is welcomed by all factions because everyone realizes they will learn something. I went after Endel Tulving, the distinguished Canadian expert on human memory. I had heard he might consider spending some time out of Toronto because, even though he was retired, the University of Toronto had mishandled his pension and had left him shortchanged. I had met him only once before, at a New York meeting, and we immediately took a shine to each other. I was soon to learn he was a native Estonian. He had escaped from the horrors of the Red Army when he was seventeen and migrated through Germany, where he finished his high school education and then moved to Canada. It was in Germany that he decided he wanted to be a psychologist.
Tales from Both Sides of the Brain : A Life in Neuroscience (9780062228819) Page 27
