Split brains taught us plenty, now super-imaging is imminent, but Michael Gazzaniga, Gary Marcus and Jeremy Freeman show the mystery of mind still eludes us for now
- Book information
- Tales from Both Sides of the Brain: A life in neuroscience by Michael S. Gazzaniga
- Published by: HarperCollins
- Price: $28.99
- Book information
- The Future of the Brain: Essays by the world's leading neuroscientists by Gary Marcus and Jeremy Freeman
- Published by: Princeton University Press
- Price: $24.95/£16.95
"HOW on earth does the brain enable mind?" This line from the preface to Tales from Both Sides of the Brain by neuroscientist Michael Gazzaniga serves as the overarching question for his latest book. And it's also a question that permeates The Future of the Brain, a collection of essays edited by psychologist Gary Marcus and neuroscientist Jeremy Freeman.
His journey begins in the early 1960s as a graduate student at the California Institute of Technology, where he worked with people with split brains. His advisor was Roger Sperry, the neuroscientist who pioneered the study of animals whose brain hemispheres had been surgically separated.
It was also a time when neurosurgeons were beginning to treat severe drug-resistant epilepsy by cutting the corpus callosum, the bundle of nerve fibres that connects the brain's two halves, to stop the spread of epilepsy's electrical storm. Sperry got Gazzaniga studying someone who had undergone this procedure – setting him on course for a life of scientific discovery.
The book is an intimate look at a simpler time, when deep insights could be gleaned by designing deceptively simple yet elegant experiments, such as showing objects to the left or right visual fields of people with split brains and analysing their responses.
Such work led Gazzaniga to his theory that the left brain is an "interpreter", trying to make logical sense of our experiences –even when information is only perceived by the right brain and isn't reaching the left. "Though the left hemisphere had no clue, it would not be satisfied to state it did not know. It would guess, prevaricate, rationalize, look for a cause and effect, but it would always come up with an answer that fit the circumstances," writes Gazzaniga. Above all, he says, it is "the special device... that gives our actions one narrative and the sense that we have but one mind".
Whether you like reading about how such insights happen or care more about the people who have them, Gazzaniga amply delivers. Personally, I enjoyed interludes such as the Caltech party where Richard Feynman offered himself as a subject for split-brain surgery, if Gazzaniga guaranteed he would still be able to do physics. Gazzaniga writes that "Feynman stuck out both left and right hand to shake on the deal!"
Many of the essays point to a future of high-resolution maps or brain atlases, showing genes, connections or brain activity, and taking us well beyond today's fMRI and PET scans. For example, techniques that tag individual neurons with any one of a hundred fluorescent proteins, or make brains optically transparent will transform imaging.
The technologies will generate lots of data, and neuroscientists will need large-scale simulations and brain models to make sense of it. Editors Marcus and Freeman say that we had better get used to seeing the brain as an organ that carries out computations – a notion that is often resisted. They write that "nerve cells exist to compute; the real trick is to figure out what they are computing".
And as we figure that out, will neural interfaces be far behind? The most far-reaching technology imagined in the essays is "neural dust" – specks of silicon coupled to piezoelectric crystals that stimulate and record activity from neurons. These devices would be sprinkled throughout the brain, communicating to a receiver on the skull via ultrasound.
They sound scary. I would have welcomed more on the ethics of such technologies, building on bioethicist Arthur Caplan's argument that mapping the brain must be about more than just gathering information and discussing how to use it. Caplan writes: "Scientists must also debunk hype, allay groundless fears, and anticipate... ways in which efforts may be made to exploit or dupe the public in the name of knowledge derived from brain maps, studies, and scans."
It's a welcome cautionary note, as is a caveat in Block's essay, advocating clarity about the relationship between brain activity and psychological experience. He writes that "massive quantities of data alone cannot produce theoretical breakthroughs in understanding the mind at a psychological level".
Koch and Marcus end with a futuristic essay, looking back from 2064 and hoping for a solution by then to the "hard problem" of how subjective feelings, and consciousness itself, emerge from a physical brain. Maybe in that future a neuroscientist will also write a popular account spanning the momentous 50 years that answered Gazzaniga's question of how on earth the brain enables mind.
This article appeared in print under the headline "From grey matter to you"
Anil Ananthaswamy is a consultant for New Scientist
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