ABSTRACT
The directional dependence of the transfer function from free field to sites near the tympanic membrane is one cue for sound localization. In cat, this transfer function contains a prominent spectral notch in the frequency range 8-20 kHz. Because the notch frequency varies in an orderly fashion with both azimuth and elevation, knowledge of the notch frequencies in both ears should suffice to localize a broadband sound in the frontal field. The notch is represented in the auditory nerve by a dip in discharge rate among fibers with best frequencies (BFs) equal to the notch frequency and by an inhibitory response in dorsal cochlear nucleus (DCN) principal cells with the same BFs. When a cat moves its pinna, the mapping between sound source location and notch frequency changes; pinna movement is therefore an important auditory event because it can have substantial effects on the apparent spectra of sound sources as well as on their apparent locations. DCN principal cells receive input from the somatosensory system, which produces an inhibitory response when the pinna moves. These findings suggest the hypothesis that the DCN detects and signals, with inhibitory responses, the existence of auditory events with behavioral importance for the cat.
