"Tales from Both Sides of the Brain: A Life in Neuroscience" by Michael Gazzaniga book review

More than a “book about science stuff,” Michael Gazzniga’s Tales from Both Sides of the Brain functions equally well as a clinical neuroscientist’s research log book and an autobiographical account of the man who pioneered these fascinating experiments. Gazzaniga and his team of researchers are best known for their breakthroughs regarding the split brain: patients who lack the ability for one hemisphere of the brain to communicate with the other. Organized like a timeline, Tales walks us through the steps of his major discoveries, all while sharing his unique life experiences along the way.

two hemisphere brain gazzaniga

His research demonstrates that we learn the most when things go wrong. A typical, average functioning brain teaches scientists surprisingly little. But when the brain deviates from this baseline of normality, we learn the correlation between structure and function. How does the brain differ when things don't work the way they should? Just like with Patient HM’s memory deficits, it is through dysfunction that we learn about function. And Gazzaniga's exploration of the split-brain patient is a wonderful example.

In the early and mid 1900s, radical medical therapies seemed to be commonplace. Neurosurgeons tested drastic measures to cure epilepsy that would be immediately discarded by an institutional review board of today. It was known that seizures were related to synchronized electrical activity in parts of the brain. This activity was enhanced when the signal was sent back and forth across the two hemispheres of the brain, like a game of tennis. The conduit pathway that allowed for this to-and-fro activity is the corpus callosum, a thick bundle of white matter fibers that spans the two hemispheres. As these scientists would predict, by severing the connection between the two halves of the brain, you could decrease the intensity or frequency of epileptic events. And for patients with life-threatening seizures unresponsive to medicine, getting this radical surgery was their only real option.

Two hands

The patients, now largely cured of the seizures, experienced an interesting side effect - the surgery resulted in split-brain individuals. Instead of a single brain controlling their body, these patients in many ways behaved as two different brains controlling one body. Each hemisphere learned independently of the other. The left hemisphere had a voice; the right was mute. The two hands, each controlled by a different hemisphere, would even fight each other. The body was seemingly controlled by two different masters.

But, the sneaky and intelligent brains still found a way to communicate to one another. They only talked in a process called cross-cueing: the knowledgeable hemisphere would forcefully shake the whole head when the ignorant hemisphere made a mistake. The ignorant half would feel the head being shaken disapprovingly, and would immediately correct itself.

Science aside, the descriptions of Gazzaniga's experiments are interspersed with anecdotes from his life from outside the laboratory. He talks much of his interest in politics, and the many roles he played in encouraging and organizing events. He talks of his family life, through the multiple cross-country moves for him to following the opportunities presented to him. Although these vignettes and more were unexpected from a science book, I felt that it accomplished the difficult task of humanizing the man behind the science. Gazzaniga proudly declares that he, too, is a human with hobbies and interests outside of his work. Scientists are sometimes afraid to admit this, and every effort should be made to encourage it!

One of my favorite points in the book was his involvement in advising then-president George W. Bush. He sat on a scientific advisory council that navigated the tortuous road of stem cell research in its early days of public awareness. Stem cell research became a deeply politicized topic that had its vocal enemies and advocates - neither of whom actually understood the science. People naturally fear what they don't understand, and Gazzaniga’s involvement with the council reminds me of my unspoken duty as a scientist: share knowledge with the public. The world benefits from a science-literate electorate, and it truly is in our best interest as a scientist to educate.

In studying such a tiny cohort of subjects, Gazzaniga demonstrates the importance of case studies in understanding neurological disorders. The commissurotomy was performed rarely as a treatment for epilepsy; it was only done in the case of the most extreme diagnoses where the patient’s life is frequently at risk and all available drug therapies offered no significant relief of symptoms. In Phineas Gage, the case study was instructive in identifying the frontal lobe as important for high order mental functions such as behavior. For Henry Molaison (Patient HM), his memory deficits following the removal of his temporal lobes taught us a great deal about the hippocampus. Gazzaniga’s commissurotomized split brain patients, likewise, taught us the importance of that huge white matter tract that sends communication between the two halves of our brains.