Amygdalectomy impairs crossmodal association in monkeys.

Monkeys trained on both visual and tactual versions of an object memory task (delayed nonmatching-to-sample) received bilateral ablations of either the amygdaloid complex or the hippocampal formation of the brain. Although both groups performed well on the two intramodal versions (visual-to-visual and tactual-to-tactual), the amygdalectomized monkeys were severely impaired relative to the hippocampectomized monkeys on a crossmodal version (tactual-to-visual). The findings suggest that the amygdala is critical for certain forms of crossmodal association and that the loss of such associations underlies many of the bizarre behaviors that make up the Klüver-Bucy syndrome.