Preserved Crossmodal Association Following Bilateral Amygdalotomy in Man

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Abstract
The present study investigated the role of the amygdala in crossmodal association in man. Recent experimental evidence indicates amygdalectomized monkeys show deficits when required to identify, through vision, objects that have been previously examined by touch. We employed a delayed nonmatching to sample task pre- and postoperatively in a patient who underwent bilateral stereotaxic amygdalotomy for intractable aggressivity. Bilateral amygdalotomy did not impair our patient's ability to associate an object from one sensory modality to another, following a short delay. The results suggest that sensory association memory does not depend upon the amygdala in humans. Examination of the neuroanatomic structures affected by the differing surgical procedures in the two species revealed entorhinal and perirhinal cortices were damaged in amygdalectomized monkeys but not in the present case. Because entorhinal cortex is an important structure for the formation of new memory traces, it is possible that damage to the entorhinal and surrounding cortical regions, rather than damage to the amygdala itself, is responsible for the crossmodal association deficit in monkeys.