Auditory space-time receptive field dynamics revealed by spherical white-noise analysis

Numerous studies have investigated the spatial sensitivity of cat auditory cortical neurons, but possible dynamic properties of the spatial receptive fields have been largely ignored. Given the considerable amount of evidence that implicates the pri-mary auditory field in the neural pathways responsible for the perception of sound source location, a logical extension to earlier observations of spectrotemporal receptive fields, which characterize the dynamics of frequency tuning, is a description that uses sound source direction, rather than sound frequency, to examine the evolution of spatial tuning over time. The object of this study was to describe auditory space-time receptive field dynamics using a new method based on cross-correlational techniques and white-noise analysis in spherical auditory space. This resulted in a characterization of auditory receptive fields in two spherical dimensions of space (azimuth and elevation) plus a third dimension of time. Further analysis has revealed that spatial receptive fields of neurons in auditory cortex, like those in the visual system, are not static but can exhibit marked temporal dynamics. This might result, for exam-ple, in a neuron becoming selective for the direction and speed of moving auditory sound sources. Our results show that;14% of AI neurons evidence significant space-time interaction (inseparability). Key words: auditory cortex; receptive field; white-noise anal-ysis; reverse-correlation; sound localization; motion sensitivity The acoustic environment contains both static and dynamic sound sources that must be localized for communication and survival. It is well known that auditory cortex, including the primary auditory (AI) field, plays a significant role in sound localization (Jenkins an