CONTRASTING EFFECTS OF LATERAL STRIATE AND SUPERIOR COLLICULUS LESIONS ON VISUAL-DISCRIMINATION PERFORMANCE IN RHESUS-MONKEYS

Tested 3 rhesus monkeys with lesions of lateral striate cortex (LSC), 4 monkeys with superior colliculus (SC) lesions, and 3 unoperated monkeys for retention of a preoperatively acquired pattern discrimination. The 3 groups of monkeys were then tested in 2-choice, color discrimination tests, 1 involving varying degrees of stimulus-response (S) separation and the other, administered several months later, involving various directions of S separation. Ss were also tested in a series of 2-choice pattern discriminations, following each of which they were tested for relearning when the patterns were masked with bars or circles. LSC lesioned Ss were moderately retarded in retention of the pattern discrimination, whereas those with SC lesions were not. SC lesioned Ss, but not those with LSC lesions, were impaired in both S separation tests, which demonstrates that their deficit was not transient or solely due to a difficulty in shifting the gaze in 1 direction. The LSC Ss, unlike those with SC lesions, were deficient in relearning discriminations between masked patterns. Findings suggest that SC and LSC may be involved in 2 different aspects of attention, respectively: shifting attention (and orientation) from 1 spatial locus to another and maintaining attention on fixated stimuli. (40 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1979 American Psychological Association.