The overall objective of this research is to characterize the response features of single units of auditory cortex and the cochlear nuclei that are associated with the identification and discrimination of speech sounds. Using the unanesthetized, nonhuman primate trained in and performing a behavioral task, we will evaluate rate and temporal features of unit responses to synthesized speech sounds and selected components of these sounds. Specifically, we will determine the extent to which spatial and temporal encoding described in the eighth nerve of the anesthetized cat is found in the awake primate at brainstem and cortical levels, and the extent to which selected sounds, which behavioral data indicate are processed selectively in one cortical hemisphere or the other, demonstrate hemispheric lateralization in single-cell response characteristics. We will compare neural activity and behavioral discrimination of speech-like sounds over conditions of degradation of the distinguishing spectral cues for these sounds. The relationship of change in neural representation to change in behavioral performance will be determined.
