The purpose of the proposed research is to investigate the neurological basis of the perception of vocal communications in Japanese macaques by use of the ablation-behavior technique. This consists of determining the effects of experimental lesions on the ability of animals to perceive their vocal communication sounds. Because Japanese macaques possess a cortical mechanism for the perception of their vocal communications which is lateralized to the left hemisphere, they provide a model for studying the neurology of human speech perception. The specific experiments consist of 1) determining the degree to which the perception of vocal communications in Japanese macaques is lateralized to the left hemisphere, 2) determining whether the inability of Japanese macaques to categorize their vocalizations following cortical ablation is accompanied by deficits in the ability to discriminate frequency, intensity or temporal aspects of sound, 3) investigating the "species-specific" nature of the perceptual mechanism by determining whether non-Japanese macaques lose the ability to categorize Japanese macaque vocalizations following cortical ablation, and 4) determining the effect of temporal lobe lesions on evoked potentials. Because of their behavioral and neurological similarities with humans, macaques provide an animal model for determining the effects of stroke on communication. Because these animals have a neurological specialization for the perception of their vocal communications which is similar to the human specialization for speech perception, these experiments may enable clinicians to better understand the effects of brain damage in humans on the perception of speech. However, the long-range goals are to further our understanding of how the brain works and to provide an animal model for the development of techniques for repairing damage to the speech areas (such as neural transplants) when such techniques become available.