Biology 202
2000 Third Web Report
On Serendip

It seems like the Dr. Jekyll-Mr. Hyde phenomenon is not limited to mental institutions after all-there are possibly multiple personalities residing in people all around you: the guy across the table at the café, the woman at work who never shuts up, the loveable weirdo you call your sister, and even that cryptic person that stares back at you from every smooth, shiny surface.

We can all attest to feeling internally divided at some point in our lives. It's not that hard to pinpoint such an experience; most instances of indecision are good examples, and so are displays of "uncharacteristic" behavior under the influence of drugs, and times of internal rationalization for things we do that "feel bad." Have you ever heard of an athlete prepping himself for a critical moment in a game, or of a student telling herself to calm down before an exam? Who is prepping the athlete, and who is being prepped by him? Likewise, who is calming the student, and who is being calmed by her? It really isn't that foreign a notion that there really may be a 'jostling crowd of "I"s' within us, and the workings of the nervous system seem to provide a rather convincing manifestation of this notion of multiple "I"s:

"...brains have been divided, to reduce epileptic seizures... careful testing has demonstrated dual independent decision making

imagine half your brain removed, kept alive with blood processing equipment for any length of time; each half now independent with an eye and an ear; each half obtaining a different point of view and a diverging set of experiences -each half would still be you -each half would no longer know what the other was thinking (besides ouch!) this is essentially logically identical to the situation that exists between you and me right now -as exists between everyone -as exists between you and different yous, in different sources of time

it's SPLIT BRAIN reality!!"

-from YOU, by Mike Wilber (1)

The split brain syndrome was first discovered in the laboratory by Roger Sperry and Ronald Meyers in the late 1950's. Initially, experimentation was done with cats and later with monkeys. The first human patient underwent split brain surgery in 1961. (2) Split brain surgery involves the severing of the corpus callosum, a broad, thick mass of nerve connecting the cerebral hemispheres (3). Split brain surgery was done to alleviate intractable epilepsy: in some forms of epilepsy, a seizure will start in one hemisphere, triggering a massive discharge of neurons through the corpus callosum and into the second hemisphere. To prevent this, a callosotomy can be performed: the resulting inability of one side of the brain to stimulate the other would therefore greatly reduce the likelihood of severe epileptic seizures. (4)

The isolation of the two cerebral hemispheres from each other led not only to reduction of the severity of epileptic seizures, but also to some very remarkable observations: "To the casual observer, the early split brain patients appeared perfectly normal. They could talk and read and had no problems recognizing the world about them. The seizures gone, they seemed happy, alert and healthy." (3) But then Michael S. Gazzaniga made a startling discovery: if the patient held up an object in his left hand, he couldn't name it, but he had no trouble naming the object if he held it with his right hand. (3)

According to Sperry, it seemed that the brain was "two separate realms of conscious awareness; two sensing, perceiving, thinking and remembering systems." (3) The two hemispheres that appear at first glance to be mirror images of one another, upon closer examination have been found to be highly specialized regions that serve differing functions. (5) As Ned Herrmann writes, for most people, "the left hemisphere was shown to be logical, analytic, quantitative, and verbal, whereas the right hemisphere was revealed to be conceptual, holistic, intuitive, imaginative and non-verbal. Thus a classic dichotomy was born." (6) Now we can probably think of the brain as a laterally specialized structure.

These two different hemispheres communicate via the corpus callosum. According to Michael Gazzaniga, "The two hemispheres can develop their own specialized functions, yet still take advantage of each other's benefits through the callosum." (7) Thus when the callosum is severed, the communication is broken, and so we have two separate, previously conversing, components of the brain operating in parallel. As mentioned earlier, for the most part, everyday cognition and behavior appears to be intact. It is only when specific tests are administered that the symptoms of disconnection emerge.

To understand split brain experiments, it must first be established that the cerebral hemispheres have contralateral control of our bodies: "In general, the right hemisphere interprets information and controls actions of the left side of the body. The left hemisphere controls actions of the right side of the body. If the connection between the hemispheres is severed, sensory information cannot pass to the correct region of the brain in order for the corresponding response to be made." (8)

Given this, we can now look into standard split brain experiments: "In a standard split brain experiment, a split-brain patient is seated in front of a screen that hides his or her hands from view. Behind the screen there are a couple of objects which the subject cannot see, in this case a deck of cards and a key. The patient focuses their eyes on the center of the screen, and the word "key" is flashed very briefly in the left field of vision. Information from the left field of vision is received by the nonverbal right hemisphere of the brain, and the person is not able to tell the experimenter what they saw. The patient is then asked to use their left hand to reach behind the screen and pick out the object which corresponds with the word that was flashed. Since the right hemisphere controls movement of the contralateral half of the body, the left hand will be able to correctly identify the object, even though the patient is unaware they even saw a word flashed. Further, as long as the object is in the patient's left hand behind the screen and hidden from view, they cannot relay to the observer what the object is." (9)

It had seemed initially that a person's brain might be a "marriage of genius and idiocy" because the split brain patients could name objects presented to the left hemisphere but not the right hemisphere. But further experiments revealed that "the right cerebral hemisphere wasn't an imbecile after all...it was as nimble in abstract geometric logic as the dominant left cerebral hemisphere was with words...Before the corpus callosum had been cut, if the right hemisphere needed a word, all it had to do was put in a call to the left side. But now it was on its own. It would have to learn to hang on to information coming in from the external world. Indeed, it could do that, too. Within six months, the right cerebral hemisphere was well on its way to literacy. " (2) Indeed, there appears to be evidence for right hemisphere language: split brain patients can use their right hemisphere to make simple grammatical distinctions, but this ability is limited: performance is poor when word order is important or when words must be broken down to constituent parts. (10)

Not only did some patients exhibit minimal evidence of right hemisphere language sometime after the split brain surgery, but also, one patient, Paul, could carry out verbal commands presented to his "mute" right hemisphere, and could even write answers to questions asked of his right hemisphere. Thus, "instead of wondering whether or not Paul's right hemisphere was sufficiently powerful to be dubbed conscious, we are now in a position to ask Paul's right side about its views on matters of friendship, love, hate and aspirations. 'Who are you?' He writes: 'Paul.' 'Where are you?' He writes: 'Vermont.' 'What do you want to be?' He writes: 'Automobile racer.' When the left hemisphere was asked the same question, he wrote (with his right hand), 'Draftsman.''' (11)

A little eerie, isn't it? Now let's think about what this means: who wants to be the racer, and who wants to be the draftsman? Where is Paul? In his right hemisphere, or his left? The question itself is misleading-it assumes he must be in one or the other-but it doesn't mean that we should ignore it entirely, as it does get us to think about how to approach the problem of where Paul is.

As John Rennie of the Scientific American put it, "...research seemed to say that two different people lived inside everyone's head, and that idea took root in popular culture...Gazzaniga's update on that work shows that the true character of those divorced hemispheres is rather more complex." (12) Despite the many cocktail conversations about whether person X is right or left brained and the many objections from educators that were concerned that society doesn't value right brained people as much as it does left brained people, our brains, our selves, probably cannot be understood in such simplistic, right versus left terms. As Gazzaniga himself stated in an interview with Alan Alda, "The right brain takes in a part of the sensory world. It takes half of it. But it relays that information to the left, and the left takes in its own half, and the two get combined, if you're doing a problem-solving task, in the left hemisphere. But just as well, the right brain is taking information from the left...the basic sensory input is the same in both hemispheres; the motor output is the same...There are devices that work on the sensory input that seem to be lateralized... But you have to be very careful about what you're talking about." (13) Though the left hemisphere does seem to be the problem-solving, rational system in the brain, and according to Gazzaniga, "the right hemisphere can't think well at all" (13), we cannot automatically seat consciousness in the left hemisphere. For most of us, the brain works as a whole, and this whole is probably more than a simple summation of its parts. Left hemisphere "I" and right hemisphere "I" need not add up to the whole person "I".

But for some of us, and I am thinking especially of split brain patients as I write this, the brain cannot function as a whole, and it seems that the "I" we could perhaps otherwise assign to our whole brain (and even this may be a wrongful assignment) comes to be thought of as divided into two parts. Putting the discussion in terms of the context of our class, the split brain experiments seem to reveal not one, but two I-function boxes, operating in parallel, with a somewhat more dominant left side box in most of us. But relative dominance of two (most likely inadequate) contenders is no measure for winning the "I" title.

It doesn't seem to make sense to say that draftsman Paul out-Paul's racer Paul, does it? Neither can we conclusively say that what the "real" Paul wants to be is some combination of the two aspirations, because if there are two boxes, there certainly may be more. Besides, who's to say that just because we can't find one place to lock "I" into and it made an appearance in two places, that there must either be two "I"s to begin with, or that the original "I" must have gotten divided into two sub-"I"s? It is also possible, is it not, that the same "I" we saw living in the left side of town also has a home on the right, and that it doesn't necessarily dress or act the same way in its two homes? If that is a viable notion, then so too is the possibility that "I" also has a workplace, a favorite vacation site, a weekend hangout, and many, many other places it could be seen at if tracked down sneakily enough. Theoretically, "I" could really be anywhere, and it could even be in many places at the same time, and yes, "I" itself might not be entirely self-aware or consistent either. Must we deal with our failure to localize "I" in its entirety by cutting it up into bits, and pinning the shreds to the several places we've seen it? Must we make "I" immobile, unchanging, limited to our boxes or sub-boxes?

This brings us back to the "Where is Paul?" question. It is the same question that bothered me and many of my classmates when asked who performed the reflex actions in an otherwise paralyzed individual. It is the same question that arises when you wake up with a hangover and your friends are teasing you about how crazy you were last night dancing on the table (lampshade on your head, no less) and you don't even believe you could have done it. It is the same question that poses itself when you wonder how your friend's sweet, baby hugging boyfriend could have hit her with so much rage.

I hadn't realized it when I started writing this, but it is also the same question that I was trying to answer when I wrote my previous paper on subliminal perception (14), trying to figure out how people could know things "they" were unaware of knowing. And it is perhaps the same question I started off trying to answer when I wrote my first paper about early understandings of the nervous system (15), in which to a large extent I explored how people began their attempts to localize this notion of "I". In doing that, and in thinking through the duration of this course, it has become increasingly clear that from hundreds of years ago, neither physiologists, nor philosophers, nor saints nor sadhus have been able to put their finger on where "I" really is. And perhaps they never will. Perhaps "I" is wider than the sky, and no line, no boundary, no dissection into parts and sub-parts, will ever draw its limits.

As John Rennie aptly puts it, "In some sense our heads are home to many potential minds, not just two. The question I've sometimes pondered is where those other people are before the injuries bring them to light. Are they created by the truncated circuitry? Or are they always there, murmuring voices in the chorus of our consciousness? And yet this is probably a misleading way to understand minds and brains-whole, split or splintered. Our brains work as they do because they are not naturally rent apart. Unlike the people in medical histories, we the uninjured enjoy the choice of finding the best or worst of those other voices within us. The orators, artists, beasts and angels of our nature await their chance." (12)

It is tempting to limit "I" to the confines of a cerebral hemisphere or an isolated gland, to limit its expression to a given mode or mechanism. But our "I"s keep popping up in other places, in other ways, bewildering us, taunting us to pin it down, to design more precise probes, better targeted experiments. And we do. As the game of hide and seek progresses to subsequent rounds, we don't even know if we're getting close, but we can only hope that we are getting closer. It seems possible that we are on a curve that is approaching the asymptote of "I", but we might never actually hit it. But as long as we can get closer still, I hope we never give up.

WWW Sources

2)History of Split Brain Experiments , a very concise historical account.

3) split-brain.html , an easy to read yet informative take on the split brain syndrome.

4) CALLOSOTOMY , a lecture slide from the University of Alberta.

5) Hemisphere Specialization, a Macalester website on lateral cerebral specialization.

6) Is it true that creativity resides in the right hemisphere of the brain?, An expert's view, from the the Ask the Experts section of the Scientific American website

7) Michael Gazzaniga on the Corpus Callosum, a magazine article by Gazzinaga.

8) Information Highways, more from Macalester, about somatosensory and motor pathways.

9) Standard Split Brain experiment, still more from Macalester.

10) Split Brain: Later-RH Language, another lecture slide from the University of Alberta.

11) Split Brain Consciousness , one last Macalester page!

12) All for One, an Editorial from the Scientific American, July 1998

13) Alan Alda Interviews Scientists, an interview with Michael Gazzaniga.

14) What You Don't Know You Know, my second web paper.

15) We've Come A Long Way, my first web paper.

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