Processing of Directional Information in the Gecko Auditory Nerve

摘要

The extreme directionality of lizard ears is created by strong acoustical coupling of the eardrums, with almost perfect transmission from the contralateral ear [1]. To understand the directional cues generated in the auditory periphery, we recorded responses of single units to free-field sound from speakers radially distributed around the gecko. Fibers are strongly directional at both low (200-400 Hz) and high frequencies (1-2 kHz) with an ovoidal directivity that largely follows eardrum directivity. Unlike the linear response of the eardrum, however, the directionality of the auditory fibers is strongly intensity-dependent because of their limited dynamic range. This creates an interesting trade-off between strong directional cues (generated by steep rate-level functions) and wide dynamic ranges and suggests that additional processing by EI neurons is advantageous. We present a simple model for EI processing based on shuffled nerve recordings and show that it increases the directional dynamic range. We also present data from simulated EE processing and coincidence detection. (C) 2018 The Author(s). Published by S. Hirzel Verlag.EAA.