Frequency overrepresentation found in the inferior colliculus of Japanese house bats, Pipistrellus abramus.

Abstract

In this study, we examined the best frequencies of the inferior collicular neurons of Japanese house bats, Pipistrellus abramus. The bats emit long (>10 ms) and shallow FM pulses (quasi‐CF) during their search phase, narrowing the frequency range at around 40 kHz. If the narrowed frequency range is important for detecting a small frequency change or frequency modulation, the bats may need a finer frequency resolution than other frequency ranges. So, the neurons responsive to the frequency range at around 40 kHz must be over‐represented somewhere in the auditory system, typically in the inferior colliculus. In order to examine this hypothesis, the tonotopic organization of the inferior colliculus of P. abramus was measured electrophysiologically by metal microelectrodes. Results show that the frequency range corresponding to their quasi‐CF frequency, at around 40 kHz, appears to be over‐represented in the inferior colliculus. [Research supported by an ONR grant.]