Do we have brain to spare?

Abstract

The human brain would seem to have enough redundancy and plasticity so that the loss of a modest number of neurons or connections might have little consequence. But because the brain—unlike the liver, with its array of nearly identical portal lobules—has exquisitely specialized substructures involved in sensory, motor, and integrative functions, impairment following structural loss may depend not only on how much brain is lost, but where. Modest focal neuronal losses in eloquent areas of the brain may produce dramatic deficits; more extensive diffuse losses of neurons in so-called “silent” areas may be less obvious or go unnoticed. Hebb was moved to write his classic Organization of Behavior …