The temporal structure of signals plays important roles in communication. The proposed projects aim to provide new insight into how midbrain neurons respond selectively to particular temporal features of communication sounds, specifically pulse rate and duration. Experiments will investigate the role of NMDA-type receptors in amplifying responses and augmenting temporal selectivity. Other experiments will be the first to explore the role of projections from the nucleus of the lateral lemniscus to the inferior colliculus in generating temporal selectivity. Focal pharmacological manipulations will be combined with whole-cell intracellular recordings. We also propose to use new computational methodology to delineate the time course of excitatory and inhibitory conductances. This novel and powerful methodological approach has only recently been applied to the in vivo study of central auditory systems (Rose et al., 2013), and holds great promise for enabling auditory system researchers, as well as the neuroscience community at large, to gain unprecedented insight into the mechanisms that underlie computations in the brain. This approach will also be used to investigate the roles of dynamic properties of inhibition, and thereby evaluate a new model of interval selectivity. The last set of experiments will investigate whether IC neurons of the various temporal selectivity classes respond selectively to particular natural calls of leopard frogs. These new experiments are expected to further our understanding of the network and cellular properties that underlie the temporal selectivity of midbrain neurons.
Deficiencies in the neural processing of temporal information figure prominently in disorders of speech recognition. For example, impaired recognition of speech appears to stem, in part, from age-related deficits in temporal interval discrimination. The neural bases of these deficits are still unclear; it is therefore, important to understand how auditory systems encode and process the temporal structure of acoustic signals.