Impairments in route negotiation through a maze after dorsolateral frontal, inferior parietal or premotor lesions in cynomolgus monkeys.

Ten cynomolgus monkeys were trained to follow a fixed route through a whole-body maze consisting of 3 X 3 matrix of 9 compartments, all with interconnecting doors. Two monkeys learned to use proprioceptive guidance such that they tended to produce the same sequence of movements even if they entered the maze by a different door. They were not impaired by bilateral lesions to inferior parietal cortex (Area 7a/PG). The rest used non-proprioceptive guidance relying on external cues in the environment, probably outside the maze. These were impaired by bilateral lesions of either dorsolateral frontal or posterior parietal cortex. At least 3 different strategies may be used for route negotiation. Postoperative comparisons of the frontal and parietal groups on the effects of rearranging the external cues and on learning a new route through the maze suggested that the groups were differentially impaired in the use of different strategies. In a subsequent study, bilateral lesions to premotor cortex (Area 6) resulted in an impaired ability to follow a route using either proprioceptive or external cues.