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From Motricity to Mentality

Brian Hayes

I of the Vortex: From Neurons to Self. Rodolfo Llinás. x + 302 pp. The MIT Press, 2001. $27.95.

Chuck Knoblauch, until lately the second baseman for the New York Yankees, has been suffering from a strange affliction: He has forgotten how to throw to first base. The throws that give him the most trouble are the easiest ones, in situations where he has plenty of time to think about what he's doing. By his own report, the thinking is the root of the problem. Before the ordeal began, his arm knew how to throw, and his head didn't need to bother about it; now, his head won't stop meddling, and the ball often goes astray.

Knoblauch's plight reminds us that the relations between mind and body are not always those of master and servant. None of us knows—at the level of consciousness—how to walk, or breathe, or throw a baseball. If we had to take charge of these movements, issuing commands to all the hundreds of muscles in just the right sequence, who would not collapse in a quivering mass?

Rodolfo Llinás, a distinguished neurophysiologist at the New York University School of Medicine, believes that such "automatic" motor acts, which we can perform but not explain, teach lessons to be taken very seriously. He calls the movements fixed—action patterns (FAPs), and he argues that they are where thinking and consciousness began. Active movement—what Llinás calls motricity—is the very source and main stem of mental life. "That which we call thinking is the evolutionary internalization of movement."

Only organisms that move have brains, Llinás points out. A tree has no need of a central nervous system because it's not going anywhere, but an animal on the prowl needs to see where it's headed and needs to predict—perhaps even envision—its future place in the world. The poster—child organism for this close connection between motricity and mentality is the sea squirt. This marine creature starts life as a motile larva, equipped with a rudimentary brainlike ganglion of about 300 neurons. But after a day or two of cavorting in the shallows, the larva finds a hospitable site on the bottom and puts down roots. As a sessile organism, it has no further use for a brain, and so it eats it! (Llinás resists the urge to give the punchline that always follows when this story is told to an academic audience: "It's a lot like getting tenure.")

The notion that the "I" of consciousness evolved from a central facility for planning and predicting movement is one of the major themes that Llinás wants to convey in this book. A second theme is the importance of rhythms and patterns of synchronization in brain function. If you look only at the wiring diagram of the nervous system—the geometric or topological network of connections between neurons—you can fail to notice the striking temporal organization of neural activity. But the temporal patterns actually predate the spatial ones: Rhythmic excitations are seen even in early embryonic muscle and nerve tissue, before the brain itself has begun to coalesce. In the mature brain, dispersed populations of cells organize themselves into vast phase—locked choirs that hum steady notes or chirp in unison when given the right stimuli. These consistent and carefully maintained rhythms surely mean something. "Temporal coherence is believed to be the neurological mechanism that underlies perceptual unity, the binding together or conjunction of independently derived sensory components."

Llinás draws particular attention to a 40—hertz neural duet sung by the thalamus and the cerebral cortex, two areas of the brain with dense interconnections. This is a signal he has explored in his own laboratory, in difficult experiments that call for simultaneously recording the activities of dozens of neurons. His findings have led him to believe that the 40—hertz signal is a central, organizing drumbeat. It is "a candidate for the generation of unitary perceptual entities" and "a main mechanism of brain function." Furthermore: "Subjectivity or self is generated by the dialogue between the thalamus and the cortex."

Do these conclusions deliver what Llinás promises in his subtitle—a pathway "from neurons to self"? At best I would say he gives us a series of stepping stones, and at a few places along the trail the reader is asked to make a fairly acrobatic leap from one stone to the next. Many of the ideas presented here strike me as highly plausible hypotheses, and they may very well turn out to be true; but as yet they are supported only by rather scant evidence. When Llinás claims that his schema is "the only way to explain" an observation, I am not always persuaded that every other possibility has been ruled out.

But a fully mechanistic and pedestrian explanation of the brain is surely too much to ask. As Llinás remarks, "'I' has always been the magnificent mystery."—Brian Hayes

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