IBN-9728599 Fuzessery The world of sounds produces an auditory 'scene' which is an analogue of the way we see a visual scene with our eyes. In a complex auditory scene, different acoustic signals from different spatial origins produce different 'streams' of sounds competing for the brain's attention. Further, it has been assumed that particular circuits of nerve cells act as dedicated 'feature detectors' to extract characteristic aspects of important signals such as communication songs or language. This project combines anatomy with physiology to study these issues in the unusual model auditory system of the pallid bat. This animal uses regular hearing to detect its prey moving on the ground in the dark, but it also uses ultrasonic hearing for echolocation during flight, for navigation. Some of the anatomical pathways in the brain show clear segregation of two pathways, one for the 'passive' listening for prey, and one for the 'active' listening for the bat's own echolocation vocalizations. However, in the auditory cortex, some single nerve cells (neurons) respond to both the low- and the high-frequency signals. Functional mapping of the cortex, and studies of the responses of single cells to competing inputs in this unusual system will provide clear evidence of how well cortical organization can serve more than one functions, and to see whether single nerve cells can shift their function depending on the behavioral context of the incoming signal. Results of this work will clarify some very fundamental principles in sensory processing by the brain in general, beyond simply hearing, and could have potential importance for developing remote sensors and hearing aids.
