Compound stimulus differentiation behavior in the rhesus monkey following periarcuate ablations

Anatomical and physiological investigations in cat and monkeys have demonstrated the existence of association areas where evoked and unit responses associated with more than one sensory modality can be recorded. Although it is often assumed that these areas of association cortex form the anatomical substratum for complex cognitive and integrative behavior in higher mammals, there is little experimental evidence in non-human primates to support this viewpoint. This experiment investigated the effects of periarcuate ablations on the ability of the rhesus monkey to perform a compound stimulus (light and tone) versus component stimuli (light or tone) differentiation. Ablation of this well-known polysensory area in the frontal lobe led to large and persistent impairments in performance on this task, while the ability to perform intramodal and intermodal differentiations was spared. Ablations of comparable size in other parts of the frontal lobe had no affect on the performance of these tasks. It was concluded that one function of the periarcuate region may be to synthesize multiple sources of sensory input occurring simultaneously into meaningful elements.