DESCRIPTION (provided by applicant): This project will examine the potential of optical imaging technology for the investigation of functional activity on the surface of the dorsal cochlear nucleus (DCN). This technology has recently come of age as a result of a new generation of optical imaging cameras characterized by ultra high spatial and temporal resolution and the introduction of new, non-toxic voltage sensitive dyes. When these new tools are used in combination, optical imaging provides a powerful approach to mapping brain activity in real time. In the proposed project we will employ a state-of-the-art optical imaging system to study the spatio-temporal dynamics of stimulus-driven and spontaneous activity on the surface of the DCN. First, we will obtain real time image sequences of DCN responses to acoustic stimuli that change in frequency and intensity. The purpose of this experiment is to test the feasibility of optical imaging to examine the spatial and temporal dynamics of information flow within and across the tonotopic array of the DCN. Second, we will use optical imaging to map and quantify increases in spontaneous activity that can be induced in the DCN by intense sound exposure. The goal will be to determine the spatial patterns of this hyperactivity and its temporal behavior. Third, we will image the spatio-temporal patterns of activity that occur on the DCN surface in response to parallel fiber stimulation. The image sequences will be acquired during and after electrical stimulation of parallel fibers at a number of sites across the DCN surface. The goal is to map the path of activation as it flows along the parallel fibers to its target neurons. The significance of these experiments is that they will yield information regarding the dynamics of signal processing and reveal new aspects of DCN circuitry that have been difficult to study electrophysiologically.