Gazzaniga is known to anyone even remotely connected to cognitive neuroscience, which is why you probably are reading this review. Most would know him for his work on people with split brains, namely divisions along the corpus callosum that allow the two halves of the brain, left and right, to operate independently. This allows for lateralization of function to be examined in laboratory settings. Gazzaniga is neurological royalty.

This means there is no surprise in a weighty book based on his life, and the trajectory of his work.

His work begins and ends as a narrative, starting with his moving to Caltech in pursuit of proximity to a girlfriend, such humble origins perhaps of his genius; within the narrative are insights into Gazzaniga that we do not see on YouTube. And his split-brain interests began there, in psychobiologist Sperry’s lab.  The regulations at the time were few, if you wanted to put half a rabbit’s brain to sleep, you just went ahead and did it, no IRB review needed. And while he was torturing rabbits with electrodes and eeg’s and unilateral chemical ablation, Linus Pauling, on his way to a second Nobel Prize, would drop by, while suing William F Buckley Jr, a lifelong friend of Gazzaniga’s. This is what working at Caltech looked like.

However, Gazzaniga first introduces us to his dad, an influence in his life, proving that there has to be this kind of normality in his early life, as distinct from Nobel Prize winners popping in and kibitzing. But this is not boring: how do you beat the fact, even in his mundane family, that his maternal grandfather was the first plastic surgeon in Los Angeles and treated Mary Pickford, Charlie Chaplin, Tom Mix and Marion Davies? Hollywood royalty in his family tree, but dead in a motor vehicle accident before he knew him.  Luck can be bad or good, and for Gazzaniga he understood that luck is a big part of a life in science, and so the discovery of patient W.J. who he could test, following a commissurotomy demonstrated to him that he was the luckiest man on earth….that, and Groucho Marx sauntering across stage during a debate under his auspices.

And so the book focuses on the 6 seminal patients, the study of which directed his thinking over the next 50 years.

The observation that both hemispheres could see and act on the same stimulus in their respective areas of observation but only the left hemisphere could talk about it would lead to a Nobel prize being awarded 20 years later for the research that emerged.

Bogen, the neurosurgeon who began the first commissurotomy series, remarked again, as Gazzaniga did above, that had there been a review committee, as there is now, the surgeries and hence the research would never have happened.

Tim Noakes, now retired from his work at Cape Town University, is currently facing the same issues, and being pilloried for his experiments in the Banting diet with the argument now presented that innovation is frowned upon, even pilloried, in the new risk averse age, and that hence these giant leaps, universally, are unlikely now. We have always done things a certain way is a mantra that would have derailed Gazzaniga and Bogen back then.

In their time, a chief of service gave permission and that was enough. Sigh.

Even so, Gazzaniga notes something many people I speak to forget: getting a hold on how the brain works is almost paralysing in its difficulty, so much so that had he known that, he wouldn’t have tackled the job.  His, and even Sperry’s naivety in the field meant there were no preconceived ideas in the way of their innovation, even in the creation of new terminology to illuminate on how split-brains worked.

He of course had to borrow from Morgan and Sperry and others in terms of signposts along the way, and terminology as noted above, and absorb the competitive challenges from Geschwind and Edith Kaplan from Boston. (I recall Edith had a very interesting handbag which had real clocks ticking in the transparent sides, which made me want to follow her around and determine if she was on New England time!).

Now in terms of following Gazzaniga around, perhaps there are people reading this who do not quite understand what Gazzaniga’s work implies. Here then is a summary.

Primitive man would have been only dimly aware that he or she had emotions. As Damasio has shown, these are physical states, and we still are in that shape: however, we now have feelings, a perception of the underlying emotional state which informs us as to the nature of what we perceive as emotions that are on the go in the non-conscious physical entity of our nervous system. So in the primitive brain, there was no left-right discrimination as we know it: rather, there was redundancy, with the right side of the brain mirrored on both sides of the brain, so damage from some outside source would take out a function in one hemisphere, but the contralateral side would take over seamlessly, as it was doing anyway. This meant that we were born then, and now in fact, with visual working memory, so we could track and learn from birth, and hold things in a bus memory while we worked out what was going on. So each baby born now still is born with the visual working memory hard-wired in. As laterality of function evolved, namely the emergence of right handedness and speech specialized largely to the left hemisphere, the two hemispheres began to look markedly different in right handers mostly, but function in both left and ride handers tended to now be lateralized. Vestiges of both bilateral redundancy and modern lateralization still exist, for instance in stroke damage causing left visual field neglect. For the immediate time after the stroke in the right hemisphere, the person loses complete awareness of the left side of the world, but retains the right side largely, thanks to the tiny bit of redundancy of that function in the left hemisphere. However, over time, this laterality wanes a bit, and the loss of the left side of the world, of which the patient is initially unaware, reduces to perhaps some loss of visual field, a scotoma perhaps.

In this way, we developed a method of internalized speech, initially out loud, but then made private, as our thoughts. This advantage in wresting control of the forces of evolution had good and bad effects, as we see in modern threats in the environment that we have caused, but provided us with a verbal counterpart to the visual working memory, a kind of simulator of outcomes. Babies now were still born with visual working memory, but now develop a verbal working memory counterpart ‘de novo’ which gradually develops across the formative years, maturing enough so that school age children can think silently and choose behaviours in the here and now that have the best outcomes in the future.  The advantages of this simulator of outcomes allows us to dominate the world, and the consequences of this combination of working memories in the visual and verbal modalities allows for human creativity.

This is now what Gazzaniga has shown in his split brain studies, apart from a myriad of other demonstrations of cognitive science that are described in this book.

Gazzaniga notes that new ideas need a chance to be expressed, as Noake’s above is pleading, and that often mainstream science, entrenched in a single world view, will delay the advancement of the field, hence the comment that science advances one funeral at a time. He notes here that one often might best choose your own peer reviewers for a journal article to prevent being stifled.  Many big findings are initially not recognized by science, and so his first paper was rejected by the NEJM.

The matching redundancy of the brain halves is still easy to demonstrate for lower functions such as touch, where we can identify, with a split brain, that we are holding an object and manipulate and find it even when blindfold with either hand, BUT we cannot name the object if it is in the left hand, as the left hand cannot draw on the hemispheric capacity to name the object and tell the tester what it is in our hand. The same is true of the sense of touch which goes to both hemispheres. For the higher, more recently evolved capacities related to speech for instance, and for the lower evolved senses such as vision, these are lateralized in terms of function, speech less so than vision, where each eye is served by the contralateral side.

And this is all true, but then how does a patient finally work out what is in the left hand? Cues such as the angle of an edge or similar physical feature can let the verbal side work out what the object might be, and so all is NOT that clear as I noted it above: these subtleties dominated Gazzaniga’s lab work from the early days of his index patient W.J.

Modules of the brain, thus, although separate, can integrate by cuing each other and thus produce a unified whole.

Perhaps the most intense finding at the time was that cuing demonstrated that the brain had no central motoric command centre, no CEO: the ipsilateral hand could be controlled by the hemisphere on that side, not just the other, by this cuing effect. This could only be true, as shown in deeply divided brains, not just the corpus callosum, if there was no central system for the control of the limbs, less so for the hands.  One hemisphere could direct the movement, but when the hand touched, the other limb would rapidly now swing into action as it now had access to information not possible say on visual cue alone.

This is how the brain compensates after injury, by using ipsilateral cuing via the contralateral systems activities, as we learn to inform the uninformed system how to do these tasks anew.

What could be a more interesting finding? Simply that there is considerable variation in humans and this remains a mystery for researchers such as he.

Let’s imagine how this works: flashing numbers from 1-9 to one hemisphere, the left, resulted in immediate correct naming. The same was true of the right hemisphere, which actually couldn’t speak out those numbers on its own. What was happening was that the right hemisphere was quick to identify 1, but slower progressively to identify 9. So the right hemisphere was providing simple cues, eg a stiffening of the neck to move the head once, twice etc., and the left then was able to blurt out the number of moves it counted. Forcing the patient to immediately identify the number without the time allowed to cue, removed the cue and restored the inability of the right hemisphere to name the number correctly.

And so Gazzaniga tells the story of how his science evolved, and how his and the world’s understanding of the the brain evolved, with Sperry earning a Nobel prize, and Gazzaniga advancing to become one of the most respected cognitive neuroscientists in the world, and as many academics are, a skilled writer.

He documents his work in really entertaining terms, passing on a wealth of information in the process, teaching as he goes by default. This is a work that fascinates me, but will do the same for those less schooled, even entirely unschooled in the field of neuroscience in general, or in split brain studies in particular.

Definitely should be a best seller in the field, and out of it in the general public.

 

© 2015 Roy Sugarman

 

Roy Sugarman, PhD, Director: Applied Neuroscience, Performance Innovation Team, EXOSÔ USA.