The long-term objective of this research is to understand fundamental neural coding mechanisms in auditory cortex that subserve cortical representations of biologically relevant sounds. We will use the common marmoset (Callithrix jacchus) as our experimental model to address these questions. This model system provides several important advantages over other species, namely, a hearing range similar to that of humans, a rich vocal repertoire, an auditory cortex that lies largely on the lateral surface of the cerebral cortex and a high reproductive rate while in captivity. In this application, we will focus on elucidating neural mechanisms underlying cortical representations of harmonicity and spatial location. Aim 1 will study neural representations of harmonic structures in auditory cortex across the entire hearing frequency range of marmosets in both primary and non-primary auditory cortex. Aim 2 will use intracellular recording and inactivation techniques to investigate cellular mechanisms underlying cortical representations of pitch and harmonicity. Aim 3 will investigate neural representations of spatial location in marmoset auditory cortex using novel stimulation paradigms. Findings from the proposed study will shed light on neural mechanisms responsible for hearing and have implications for understanding how the auditory cortex operates in normal or diseased conditions.