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Neuroscience: Halving it all

Douwe Draaisma enjoys the autobiography of Michael Gazzaniga, who has studied split brains for half a century.

Tales from Both Sides of the Brain: A Life in Neuroscience

Ecco: 2015. 9780062228802 | ISBN: 978-0-0622-2880-2

From the 1940s onwards, scores of people with intractable epilepsy were treated by surgically severing their corpus callosum, the nerve bundle that connects the left and right sides of the brain. In these 'split-brain' patients, each hemisphere operates independently. Michael Gazzaniga — known as the father of cognitive neuroscience — spent more than 50 years investigating these “splits”, as he calls them affectionately in his compelling autobiography, Tales From Both Sides of the Brain.

Michael Gazzaniga pioneered research into how the brain's hemispheres can operate independently. Credit: Rick Friedman/Corbis

As a psychology student at Dartmouth College in Hanover, New Hampshire, Gazzaniga became interested in the way brain enables mind. In the summer of 1960, he positioned himself at just the right place: Roger Sperry's lab at the California Institute of Technology (Caltech) in Pasadena. Sperry had begun a research programme on split brains, based on studies with cats and monkeys. Gazzaniga and fellow pioneer Joseph Bogen extended this to people who had had the operation. Over the decades, as Gazzaniga relates, the programme branched out to explore perception, language, facial recognition, reasoning and many other cognitive processes. It produced a wealth of information on hemispheric specialization.

As the book unfolds, it becomes clear that split brains present a nested set of conundrums. The first is that roughly 200 million neural fibres have been cut, but nothing — apparently — happens. Memory, personality, cognition; everything is still intact.

To demonstrate that both hemispheres are operating separately requires shrewd experimental procedures, which Gazzaniga pioneered in the early 1960s. These revealed the second conundrum, that the left brain can see and feel things that the right brain does not, and vice versa, yet the patient experiences a single, unitary mind. Even downright discrepancies — the right brain seeing a picture of a naked person, leaving the left brain wondering about the blush — are explained away by the mind using cleverly improvised stories.

These stories point to yet a third conundrum. Why are humans, whether with an intact or a severed callosum, so left-sided? Split-brain experiments have pointed to the existence of a 'narrator' or 'interpreter', a faculty housed in the language hemisphere (almost always the left) that explains why we behave as we do.

Unlike Bogen, who proposed some now-discredited theories on 'left-brained' white city dwellers and 'right-brained' Hopi Indians in the 1970s, Gazzaniga always kept a sober perspective on hemispheric differences. Much of his later work served to debunk the popular idea of a rational, cold-hearted left brain ranged against an emotional, intuitive right brain.

In his autobiography, Gazzaniga often seems to be a man of two minds himself. His style is colloquial and unassuming (Caltech “was chock full of mighty smart cookies and most of them could run circles around me”). He is a self-confessed big-picture man, leaving mathematics and technicalities to others. He acknowledges that the course of a career, including his own, is often steered by luck and coincidence, rather than strategy. There is also a shocking nostalgia for the days before ethical committees on animal research, when cats were gathered “from the alley”.

This cheerfully detached tone, however, is absent when Gazzaniga deals with credit and priority. His experiment with Bogen's epilepsy patient W. J. in 1962 was the first to reveal that each hemisphere remains unaware of stimuli processed by the other. Bogen had suggested pre- and post-surgery experiments. “Thus begins a line of research that, twenty years later, almost to the day, will be awarded the Nobel Prize,” notes Gazzaniga. That 1981 prize (in Physiology or Medicine) was awarded to Sperry for his split-brain research — not to Sperry, Gazzaniga and Bogen. By then, Gazzaniga's relationship with Sperry had become tense, and Sperry refused to let him conduct further tests on Caltech patients.

Gazzaniga writes about Sperry with much admiration and little affection. He portrays him as a fierce competitor. Gazzaniga explains that at the pioneering stage of research, ideas become inextricably mixed, and that in science — as in families — people may come away from the same event with different memories. He clearly feels that the Nobel prize should have had more than one recipient.

Gazzaniga was at the heart of a pivotal research programme and struck up friendships with neuroscience and psychology luminaries, such as David Premack, George Miller, Leon Festinger, Endel Tulving and Steven Pinker (who wrote the book's introduction). Thus, his natural appetite to tell juicy behind-the-scenes stories is more than welcome. Historians in particular have always appreciated eighteenth-century philosopher Bernard Mandeville's dictum that private vices can be turned to public benefit.

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Correspondence to Douwe Draaisma.

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Draaisma, D. Neuroscience: Halving it all. Nature 518, 298–299 (2015).

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