Visuospatial functions in the rat following injuries to striate, peristriate, and parietal neocortical sites

Abstract

The influence of lesions located generally within four regions of the rat#’s posterior neocortex upon the acquisition and retention of two-choice visual discriminations was assessed using a Thompson-Bryant apparatus. The ability to distinguish visual patterns was tested by utilizing stimuli composed of 45° versus 135° alternating black and white stripes (both total and local luminance cues were controlled). “Brightness” discrimination was assessed by using black and white card discriminanda. Posterior parietal injuries resulted in a dysfunction on each of the four tasks, but rats with this injury eventually attained criterion for each of the habits. Smaller, more anteromedial parietal lesions failed to disturb pattern discrimination and were not studied in the other paradigms. The only deficit observed in rats with medial peristriate injuries was a slight retardation in acquisition of the pattern discrimination. Since the effects of lateral peristriate and striate injuries upon pattern vision have been well described previously, the effects of these lesions on the retention and acquisition of the black-white discrimination were studied. Lateral peristriate lesions, but not striate lesions, were associated with a retention loss of the brightness problem. This loss was detected even with a recovery interval of 60 days. Both striate and lateral peristriate lesions retarded black-white discrimination acquisition. Discussion focuses on the probable natures of the visual dysfunctions associated with these injuries.