The Marvel and Mystery of the Brain

By Diane Ackerman. Scribner. 300 pp. $25

On the one hand, there is the mind: a web of faculties aware of itself and the universe, capable of learning a new piano sonata or recalling a spring snowstorm 40 years ago. On the other hand, the brain: a three-pound blob. For thousands of years, few people saw a connection between the two. In 1652, the English philosopher Henry More flatly stated that the brain "shows no more capacity for thought than a cake of suet or a bowl of curds." Today, of course, it's clear that the brain is far more than goop. Electricity and neurotransmitters shuttle among its billions of neurons, producing our passions, reasoning and consciousness. Yet most of us still have trouble feeling a link between the details of the brain -- its oligodendrites, its nodes of Ranvier, its alpha-2A noradrenergic receptors -- and our own existence.

In recent years this chasm has attracted a corps of bridge-builders. They have packed shelves with books that try to link neuroscience to every aspect of our lives. The latest addition is An Alchemy of Mind, by Diane Ackerman. In some ways Ackerman's book is not much different from the rest. She surveys the same well-traveled territories, with chapters on topics such as consciousness, language and the mental differences between the sexes. If you keep up with brain research news in The Washington Post, there won't be many scientific surprises for you here. But Ackerman is unusual in that she writes not as a scientist or a science journalist. Instead, she's a poet (albeit a poet with a remarkable appetite for journals with names like Cerebrum). And it's as a poet that she shows her greatest strengths in writing on the brain, as well as her greatest weaknesses.

Ackerman knows that poetry and fiction are full of profound insights into the workings of the mind. She knows how to pluck a passage out of Proust, Shakespeare or Virginia Woolf to illustrate a point. In some cases she chooses instead to lyrically recall an experience of her own (such as her personal experience with the blending of sensation known as synesthesia). But she also knows that literature can illuminate that mind in a different way. The mark of a great author is the ability to bootstrap language to higher levels of meaning with the help of symbols, metaphors and figures of speech. And the brain, at its most basic level of information-processing, depends on a similar sort of poetic bootstrapping. It doesn't passively reproduce the sensations that enter its neurons as into a pinhole camera. Instead, it grabs a limited number of details and then builds around them an elaborate hypothesis about the world. "We are all unwitting poets," Ackerman says.

Ackerman spends much of An Alchemy of Mind turning her metaphor-making neurons back on themselves to find captivating ways to describe how the brain works. Heaven knows neuroscience could use an infusion of poetry. When scientists (and science writers) try to describe the brain to the public, they are too easily satisfied with feeble metaphors. Receptors are locks, for example, and neurotransmitters are keys. Yet keys and locks are rigid, as Ackerman points out, while receptors and neurotransmitters are yielding and floppy. Someone needs to find a new metaphor, and she offers some that are both evocative and meaningful, as when she refers to short-term memory as a "mental scratch pad." But too often she offers mud instead of light.

"Most children don't remember much before the age of two or three," she informs us, "because the cortex develops slowly and the brain hasn't activated its thinking cap yet." Thinking cap? What exactly does that mean? You can scour an entire neurology textbook and still not be able to answer that question. Describing how music is encoded in memory, Ackerman writes about neurons producing proteins "which then return to the synapse where the music was being processed and glue that music to the site." A miniature jukebox now dangles from a nerve, making us none the wiser.

A bad metaphor can do more than just befuddle. It can give a reader precisely the wrong idea about how nature works. Those who hope to learn the basics about the brain in An Alchemy of Mind will sometimes be misled by pretty-sounding language. Ackerman informs us, for example, that our ancestors were faced with the paradox of getting a big human brain out of a mother's narrow birth canal. "The solution we found was to give birth earlier," she declares, as if our ancestors convened a meeting where they voted to redesign their genome. Still, Ackerman deserves credit for taking on what is an important mission -- a mission that is, at least for the moment, doomed to failure.

She's right when she says that "no image English offers -- say, of dominoes, ricochets, echoes, or ripples -- can capture how in the brain everything affects everything else all at once, or how our everythingness always lingers in mind as we engage the everythingness of everyone else." Despite the shortcomings of our ideas and our language, we must keep searching for new ways to express the workings of the brain. It is in those images, more and more, that we see ourselves. *

Carl Zimmer's books include "Soul Made Flesh: The Discovery of the Brain -- and How It Changed the World" and "Evolution: The Triumph of an Idea."