The proposed study is a combined electrophysiological and computational modeling study of the dorsal cochear nucleus (DCN). The principal aim of these proposed efforts is to further our understanding of the DCN's neuronal circuitry and role in audition. The DCN is a peripheral, laminated, auditory nucleus, and while its role in audition is not certain, evidence suggests that it may be involved in signal-in-noise tasks. A conceptual model of the DCN's neuronal organization that includes specific functional interactions among various physiologically defined unit types has been developed. This model is derived on data obtained in both single- and multi-unit recording experiments in unanesthetized, decerebrate cats. This conceptual model of DCN neural circuitry will be critically evaluated by simultaneously recording the activities from pairs of physiologically defined DCN units under various stimulus conditions, and comparing the results of multi- unit analysis (cross-correlation) with model predictions. The experimental study will provide data on the modes of stimulus- dependent neural correlation that exist, and on the extent to which these modes operate in the nucleus. These behaviors will be correlated with parameters such as ratio of the units' best frequencies, and unit separation. In conjunction with the experimental component of the work, we seek a tighter coupling of existing theroretical methods to DCN neurophysiology, and explicit formulations of our conceptual DCN models. These formulations, which are realized in computationally-efficient computer simulations, provide the quantitative context required to test hypotheses. The confluence of data provided by this research promises to result in a significantly greater understanding of the neuronal circuitry of the DCN.