Memory deficits during electrical stimulation of the speech cortex in conscious man

Cerebral zones supporting language and recent memory were mapped by electrical stimulation during neurosurgical treatment of epileptic patients. Stimulation of sites within the left posterior temporo-parietal cortex produced transient dysphasia. Continued stimulation of this cortical region also produced a retrograde type of verbal memory disorder, indicating a failure in the mechanism responsible for retrieval of stored information. In contrast, stimulation of the anterior temporal neocortex did not produce anomia and, instead, resulted in an anterograde memory loss, apparently caused by a defect in the verbal storage mechanism. Comparable stimulation of homologous areas on the right hemisphere did not interfere with object naming or immediate verbal recall.