Effects of sequential lesions of suprasylvian gyri and visual cortex on pattern discrimination in the cat

Abstract

Listen

Translate article

Eight cats were trained preoperatively on a pattern discrimination between horizontal and vertical striped stimuli which had no differences in total luminous flux or total amount of contour, and in which consistent local luminous flux cues were eliminated. The cats then received in different orders a 4-part sequence consisting of lesions of: (a) visual cortex; (b) middle suprasylvian gyri; (c) posterior suprasylvian gyri; or (d) a control retention period in which no lesion was administered. Following each manipulation in the sequence cats were tested on the pattern discrimination and retrained to criterion if necessary. The following results were obtained: (1) Discrimination performance following the retention period was equal to or greater than criterion for normal cats and cats with either or both suprasylvian lesions. Thus, for these cats retention was perfect. In contrast, cats with lesions of visual cortex showed a clear deficit in the ability to retain the discrimination over the retention interval. (2) Initial suprasylvian lesions in normal cats produced little if any deficit in performance. (3) In cats having previously undergone removal of visual cortex and retrained to criterion, suprasylvian lesions produced a substantial disruption of the discrimination. (4) Cats lacking both visual cortex and suprasylvian gyri were significantly more impaired than cats lacking visual cortex alone, both in their average postoperative performance level and in the maximum level attained after extensive retraining. Results 3 and 4 suggest that although the suprasylvian gyri have relatively little essential role in pattern discrimination by normal cats, this region may be involved in the residual pattern discrimination ability of cats lacking visual cortex. (5) Finally, despite their extreme impairment, cats with complete lesions of visual cortex and suprasylvian gyri were able to perform the pattern discrimination at levels significantly above those expected by chance.