Gray Matters

Read Time:
3m 38sec

SECOND ­NATURE: Brain Science
and Human ­Knowledge.

By Gerald M. Edelman. Yale Univ. Press.
203 pp. $24

In Second Nature, Nobel ­Prize–­winning neuroscientist Gerald Edelman proposes what he calls ­“brain-­based epistemology,” which aims at solving the mystery of how we acquire knowledge by grounding it in an understanding of how the brain ­works.

Edelman’s title is, in part, meant “to call attention to the fact that our thoughts often float free of our realistic descriptions of nature,” even as he sets out to explore how the mind and the body interact. He favors the idea that the brain and mind are unified, but has little patience with the claim that the brain is a computer. Fortunately for the general reader, his explanations of brain function are accessible, buttressed by concrete examples and ­metaphors.

Edelman suggests that thanks to the recent development of instruments capable of measuring brain structure within millimeters and brain activity within milliseconds, perceptions, thoughts, memories, willed acts, and other mind matters traditionally considered private and impenetrable to scientific scrutiny now can be correlated with brain activity. Our consciousness (a ­“first-­person affair” displaying intentionality, reflecting beliefs and desires, etc.), our creativity, even our value systems, have a basis in brain ­function.

The author describes three unifying insights that correlate mind matters with brain activity. First, even distant neurons will establish meaningful connections (circuits) if their firing patterns are synchronized: “Neurons that fire together wire together.” Second, experience can either streng­then or weaken synapses (neuronal connections). Edelman uses the analogy of a police officer stationed at a synapse who either facilitates or reduces the traffic from one neuron to another. The result of these first two phenomena is that some neural circuits end up being favored over ­others.

Finally, there is reentry, the continued signaling from one brain region to another and back again along massively parallel nerve fibers. Since reentry isn’t an easy concept to grasp, Edelman again resorts to analogy, with particular adeptness: “Consider a hypothetical string quartet made up of willful musicians. Each plays his or her own tune with different rhythm. Now connect the bodies of all the players with very fine threads (many of them to all body parts). As each player moves, he or she will unconsciously send waves of movement to the others. In a short time, the rhythm and to some extent the melodies will become more coherent. The dynamics will continue, leading to new coherent output. Something like this also occurs in jazz improvisation, of course without the threads!” Reentry allows for distant nerve cells to influence one another: “Memory, imaging, and thought itself all depend on the brain ‘speaking to itself.

Edelman concedes that neurological explanations for consciousness and other aspects of mind are not currently available, but he is confident that they will be soon. Meanwhile, he is comfortable going out on a limb: “All of our mental life . . . is based on the structure and dynamics of our brain.” Despite this cheeky optimism about the explanatory powers of neuroscience, Edelman acknowledges the pitfalls in attempting to explain all aspects of mind in neurological terms. Indeed, ­culture—­not ­biology—­is the primary determinant of the brain’s evolution, and has been since the emergence of ­language, he notes.

In light of Edelman’s enthusiasm for a ­brain-­based epistemology, I was surprised to learn that he considers Sigmund Freud “the key expositor of the effects of unconscious processes on behavior.” Such adulation ignores how slightly Freud’s conception of the unconscious, with its emphasis on sexuality and aggression, resembles the cognitive unconscious studied by neuroscientists. More important, as Edelman concedes, Freud’s grasp of biology was poor, and he perhaps made too much of certain brain activities, such as dreams. Dreams may simply result from the state of consciousness that occurs during rapid eye movement ­sleep.

Despite these minor quibbles, Second Nature is well worth reading. It serves as a bridge between the traditionally separate camps of “hard” science and the humanities. Readers without at least some familiarity with brain science will likely find the going difficult at certain points. Nonetheless, Edelman has achieved his goal of producing a provocative exploration of “how we come to know the world and ourselves.”

—Richard Restak

More From This Issue