Spectrotemporal characteristics of echolocation pulses and frequency tuning by inferior collicular neuron of Rhinolophus pusillus

摘要

We studied the echolocation calls and acoustic response properties in the inferior colliculus of the least horseshoe bat Rhinolophus pusillus. Bats emitted CF/FM (constant frequency/frequency modulated) pulses with 2-3 harmonics. The peak frequency, pulse duration, interpulse interval of the calls were 105.3 ± 1.7 kHz, 39.5 ± 9.6 ms, 73.9 ± 16.0 ms, respectively. In the 159 recorded neurons, the percentage of E (echolocation) neurons whose best frequencies (BFs) were corresponding to the first and second harmonics of the signals were 32.7％ (52/159) among which CF1 neurons were 11.3％(18/159), FM1 were 20.1％(32/159) and FM2 were 1.3％(2/159), respectively. BFs were correlated with the recording depths and the E neurons were distributed between 349-1 855 (1 027.5 ± 351.6) μm the minimum threshold (MT), latencies were 6-74 (43.1 ± 14.5) dB SPL, 10.0-26.0 (14.6 ± 3.8) ms respectively. The types of 53 recorded frequency tuning curves (FTCs) including 51 single peaked neurons and 2 double peaked neurons were all V-shaped and most of which were narrow types (70.6%, 36/51; Q_10-dB10-dB of CF1, FM1 and FM2 neurons were 18.3 ± 11.2, 8.7 ± 4.7 and 6.9 ± 0.3, respectively. NE (non-echolocation) neurons were either wide or narrow types and the Q_10-dB was 6.6 ± 5.1 which was lower than E neurons. The BFs of the two neurons with double peaks were corresponding to the frequency range of low frequency area and high frequency area including E neurons’ [ Acta Zoologica Sinica 52(3): 528 –535, 2006].