A Study of Visual Memory: Verbal and Nonverbal Mechanisms in Patients with Unilateral Temporal Lobectomy

Abstract

Patients with unilateral left or right temporal lobectomy were evaluated on several visual tasks demanding perception and memory for verbal and nonverbal information. Recognition thresholds for words and random patterns projected tachistoscopically to the central visual field did not reveal a perceptual disorder for either temporal group. Also, the left and right temporal patients commanded an intact immediate memory span for a long string of verbal or nonverbal material. However, when the test memoranda exceeded this memory span, dissociable deficits appeared; the left temporal patients did poorly with verbal items, the right, with nonverbal information. The findings support the verbal-nonverbal distinction for mnemonic processes assigned to the left and right temporal lobes in man. Although immediate registration and short-term storage of information are unimpaired by temporal lobe injury, temporal lesions constrict the hold mechanism, and the amount of information that can be retained for a long period of time.