We are studying neural mechanisms that relate to and account for auditory sensation and behavior. Our basic interest is in how the auditory system is organized to measure and encode cues relevant to certain aspects of sound sensation, especially sound localization and pitch. Organizational principles can be revealed through experiments that relate the responses of single neurons to simple acoustic stimuli (e.g., tones of different frequency; tones or band-limited noises in different locations in space) to their location within auditory nuclei. The products of such experiments are functional maps that reveal how the spatial organization of nuclei and cortical fields under study can account for their known functional (behavioral) results. That is, they show how neurons responsive to given simple stimuli are arrayed within auditory nuclei; and they allow for the production of response-profile maps that reveal the total response within a nucleus or cortical field arising from those given stimuli. It is an objective of this study to produce such maps for the various simple stimuli within divisions of the cochlear nuclear complex and superior olivary complex, within the central nucleus of the inferior colliculus, within divisions of the medial geniculate body, and within primary and secondary auditory cortical fields in the cat. Organizational principles can also be revealed in anatomical-physiological studies of the projections from level to level in the system. These tracer studies reveal how the response properties of neurons at each level arise as a product of highly-ordered, invariably convergent projections into that level. Combined with physiological studies, they also reveal how very different information about sound abstracted by a large number of projecting brainstem auditory nuclei is processed within these higher auditory nuclei and cortical fields. These results shall be related to known psychoacoustic behavior, and should provide basic information about how the auditory nervous system is organized to generate these sensational phenomena.