Summary This research will examine the synaptic and circuit-level properties of neurons of the mouse cochlear nucleus in vitro, based on recent work that defined cell types through transcriptomic profiles. Major cell types will be recorded from using patch clamp techniques monitoring the properties of their axonal projections, synaptic input from auditory nerve, and intrinsic properties and then correlate these with the cells individual transcriptomic profile using Patch-seq. This will provide new functional insight into the diversity within major classes of cells in cochlear nucleus. Next, we will use mouse cre lines to drive expression of optogenetic tools in order to resolve functional differences in the connectivity and inhibitory synapses of different classes of interneuron. Last, we will optogenetically activate specific populations of principal cell while recording from single principal cells in order to examine homotypic synaptic connections among principal cells. These results will provide unprecedented insight into the capacity of neurons in the cochlear nucleus to perform computations on incoming sensory signals. Moreover the results will provide a foundation for future studies examining how these computations are distorted with hearing impairment.