The long-term objective of this research is to understand fundamental neural coding mechanisms and neural circuits in auditory cortex that subserve cortical representations of biologically important sounds. We will use the common marmoset (Callithrix jacchus) as our experimental model to investigate these questions. Marmosets have a hearing range similar to that of humans and are an ideal model system for studying audition and deficits and diseases in hearing. With the recent progress in creating transgenic marmosets, this model system is poised to become a major non-human primate model for hearing research. Our laboratory has pioneered major neural recording techniques in awake and behaving marmosets. In this application, we will focus on elucidating neural coding mechanisms underlying spatial and harmonic processing in non-primary auditory cortex. Aim 1 will characterize functional properties of parabelt areas of auditory cortex. Aim 2 will study cortical organization of spatial information. Aim 3 will study topographic organization of harmonic processing in marmoset auditory cortex. Findings from the proposed study will shed lights on neural mechanisms responsible for hearing and have implications for understanding how the auditory system operates in normal or diseased conditions.