VISUAL MEMORY AND VISUAL SPATIAL FUNCTIONS IN THE RAT FOLLOWING PARIETAL AND TEMPORAL CORTEX INJURIES

Adult rats were prepared with either posterior parietal, temporal, or sham neocortical lesions, and after assessing gross locomotor functions, trained in cognitive visual tasks. Training was conducted in a modified circular water maze wherein the water was made opaque with a white nontoxic powder paint. The order of the tasks was counterbalanced within groups. One task was a visual matching-to-sample problem with an intertrial interval of 20 s. The second task was a visual spatial conditional problem in which visual stimuli (white or gray cards) cued spatial choices in a T maze that was inserted into the tank. After completing these tasks, the animals were trained on a simple visual pattern discrimination and a simple position habit. Both lesion groups demonstrated significant deficits on both cognitive tasks. Since gross visual perceptual, spatial, and motor abilities were found to be unaffected by the lesions, it is suggested that a generalized retardation in cognitive functions follows injuries in these sites. Also, qualitative evidence supported the conclusion that posterior parietal cortex plays an important role in integrating visuospatial stimuli with motor responses.