A Leg to Stand On
by Oliver Sacks
Summit Books, 222 pp., $14.95
Neurologists lead philosophically confounded professional lives—by necessity rather than choice. No other profession is so implacably condemned to dwell in that restless and prismatic space that lies between body and mind. If to the philosopher the mind–body problem is a playground for fancy analytic footwork, for the neurologist, it is a dilemma that compels the same kind of awesome respect that the mariner feels for the sea. For there is a compelling contradiction in any enterprise that, on the one hand, must diagnose highly subjective, introspective states, and, on the other, must locate the “causes” of these states and narratives in the objective world of brain tracts, nuclei, tissue bundles, Brodmann areas, and the rest. When Descartes located the soul in the pineal gland (the only unpaired structure in the brain) and argued that it must be so, because the soul too is unitary, he was only playing a hyperbolic version of the neurologist’s game.
The idea that psychological “dispositions”or “functions” have “seats” in the brain is a very ancient one. Its shrill explicitness in the phrenology of Franz Gall and Johann Spurzheim in the midnineteenth century was by no means its dying cry. It is an appealingly simple idea, localization, and it seemed to explain, in a deceptively superficial way, the findings from brain lesions, from stimulating the exposed brain directly with weak electrical current, and most recently, from the study of “unit receptors” in the cortex that fire, say, only when the eye is stimulated by contours, by lines in horizontal or vertical position, or by similar minutiae of stimulation. In consequence, “bits” of sensation or behavior have got matched up with bits of brain, and maps of the correspondences are drawn and redrawn for the textbooks showing “where” different functions “reside.”
It is a curious logical exercise, such neural cartography, particularly since we have also known for a long time that there are in the mantle of the human cortex alone a staggering 5 X 109 available connections between individual nerve cells, as well as reverbatory or Lorente de No circuits that proliferate connections between larger units than single cells. To say, for example, that stimulating a particular spot along the front of the fissure of Rolando is responsible for the contraction of the index finger is no more or less sensible than to say that the ticket printer in the Conrail ticket office is responsible for the grimy ride from Grand Central to New Haven. No wonder, then, that neurology is a discipline that suffers perennially the ravages of misplaced concreteness. Were it not so, we would never have experienced the ghastly trephinings of sick patients by medieval brain surgeons or, for that matter, the prefrontal lobotomies performed in our own century by their inheritors, one of whom (I hope to the perduring embarrassment of the committee) was awarded the Nobel Prize for Medicine in 1949.
But it is not only the “tissue side” of neurology that has suffered from the …