Visual-spatial functions persist following temporal and posterior parietal cortex lesions in rat

Adult rats were prepared with either posterior parietal, temporal, or sham neocortical lesions. Gross kinetic functions and equilibrium were assessed on alternate days for 12 days following surgery by placing the animal on an elevated rod (3.5 cm diameter) oriented 20° to horizontal and rating locomotor functions. Although all groups improved with experience and time postsurgery, rats with posterior parietal lesions exhibited a greater kinetic disturbance throughout the testing period. After a 3-week recovery period, the animals were trained on a visual-spatial task in which a visual stimulus located at the choice point cued whether the escape platform was located in the left or right arm of a T-maze. Animals were trained at a rate of 20 trials per day until a criterion of 18 correct responses in a series of 20 trials was observed. This task differed from that used in a similar previous study in this laboratory (1) in that stimulus saliency was increased and rats were punished for errors by confinement to the incorrect alley for 15 s when errors were made. All rats learned the task, and although there were subtle differences in the rate of acquisition between the groups, there were no gross differences on any of several measures of learning and performance. It is concluded that, under appropriate conditions, rats with injuries in these posterior association regions can learn and perform a task requiring the execution of different spatial responses on the basis of visual landmark cues that are spatially discontiguous from the escape site.