Electrophysiologic studies of the auditory cortex in the awake monkey

An overview of some recent developments in the study of central auditory processes is presented. We describe findings from single cell physiologic studies that contribute to our understanding of central auditory function, the development of behavioral techniques permitting precise evaluation of hearing in animals, and the power and potential of integrative neurophysiologic-behavioral investigations in defining and analyzing central neural mechanisms that underlie normal perception and imperception. The influence of changes in intermodality attention on evoked activity of 25 cells of the auditory cortex is described and compared to effects of other attentional changes. A small but consistent increase in excitatory cell evoked discharge rate and a reduction in initial latency of response are shown to be correlated with a shift from a visual to an auditory task. In general, behavioral states ranging from sleep-waking to attention to a specific acoustic cue are shown to influence responsiveness of the auditory system and variability of response. Procedures are described for effective control of attentional factors and reduction of electrophysiologic variability. The contributions of these data and procedures to studies of the encoding of complex auditory signals and studies of neural mechanisms underlying such disorders as noise induced hearing loss are discussed.