Your mind, your brain

There are limits to what brain scans can tell us.

Can brain imaging technology help us define the human mind? In a new book, Yale biophysicist Robert Shulman—himself an early adopter of that technology—suggests that some scientists who think so are getting ahead of the research.

Put a rat in a brain scanner, twang its left lower whisker, and the same spot in its cortex lights up every time. Functional magnetic resonance imaging (fMRI) experiments like this can illuminate the workings of the brain. A variant of the MRIs used in hospitals, fMRI tracks how blood flow waxes and wanes in the brain; more blood flow in a particular spot means those neurons are firing more. Researchers have successfully used the technique to map the brain’s sensory centers. Now they’re hunting for the seats of memory, decision-making, attention, and other complex mental processes.

But in Brain Imaging: What It Can (and Cannot) Tell Us about Consciousness, Shulman argues that attempts to localize such complex processes haven’t worked. When a person remembers some particular thing, from multiplication tables to a loved one’s face, we can observe “the brain activity necessary for that act,” he explains in an e-mail. “But trying to locate a mental process like memory does not succeed and cannot,” because the brain activities that support remembering depend heavily on context—the “who, what, when, and how” of each specific act of remembering.

In other words, highly complex processes aren’t located in discrete modules: there probably isn’t a love center or a memory center. Shulman believes that the “module” hypothesis can distort how neuroscientists interpret their results. He points out that the same brain regions can light up during tasks requiring working memory and tasks requiring attention. It was when he discovered this in one of his own early experiments that he started to question his earlier premises.

All these arguments challenge the current direction of cognitive neuroscience, a field that looks for the biology undergirding mental activity. Says Shulman, “I differ very much philosophically from modern thought.”

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