Visuo-spatial performance following posterior parietal and lateral frontal lesions in stumptail macaques.

Three groups of four monkeys were trained to negotiate a small hand ("stylus") maze, and to use a "pointer" to guide response in a two-choice position discrimination task. One group was given bilateral lesions of posterior parietal cortex, and the second bilateral lesions of lateral frontal cortex. Postoperative impairment on the maze was evident in three of the four parietal animals, and both operated groups showed impairment on the pointer task. Since maze performance was positively associated with speed of stylus recovery in a control version of the task but was not correlated with pointer task performance, it is suggested that the parietal deficit resulted primarily from a sensory-motor dyscoordination rather than a spatial perceptual disorder. The latter could however be the cause of parietal impairment on the pointer task. Error analysis suggests an interpretation of the frontal deficit on the pointer task in terms of perseveration on position.