Role of the posterior parietal association cortex in the processing of spatial event information.

Humans and monkeys with damage to the parietal association cortex (PC) exhibit deficits on visual-spatial tasks that are often dependent upon the attentional requirements of the task at hand. In order to test whether there is a correspondence between humans and rats in terms of the function of PC in the processing of spatial information, separate groups of rats were trained in two list-learning tasks, a win-stay task and a win-shift task, on an eight-arm radial maze. It is assumed that these two tasks vary in degree of required attention effort, because the win-shift rule is considerably easier for the rat to learn than the win-stay rule. One group of animals in each condition was given preoperative training before receiving bilateral aspiration lesions of PC. Another group in each condition received PC lesions prior to training. The results indicated that animals with PC lesions are unable to acquire either the win-stay or the win-shift rule. However, of the animals with preoperative training, only the win-stay trained animals were deleteriously affected by the brain lesion. The win-shift animals showed no postoperative decline in performance. Because rats with PC lesions are only impaired on the more demanding spatial task, these results are consistent with the human clinical observations.