Brain Function in Psychiatric Disorders Reconsidered

To the Editor.—  In a conceptually important study, Gur et al¹ measured with the xenon Xe 133 inhalation technique the blood flow in the grey matter of the superficial cortex. Their subjects were schizophrenic patients who were taking medication and control subjects at rest and during verbal and spatial tasks that were designed to explore hemispheric asymmetries in processing. The authors concluded that patients and control subjects did not differ at rest, but differences emerged with cognitive activation such that in patients the verbal task induced symmetric increases in blood flow and the spatial task induced greater left hemispheric increases, whereas in control subjects changes were compatible with hemispheric specializations. When sex differences were examined, schizophrenic women showed minimal changes that were greatest when performing the verbal task and not the spatial task as in other groups.Some of these results are open to question because group differences all