Zoological Studies

Vol. 46 No. 5, 2007

Echolocation Calls and Neurophysiological Correlations with Auditory Response Properties in the Inferior Colliculus of Pipistrellus abramus (Microchiroptera: Vespertilionidae)

Feng Luo1,2,5, Jie Ma4, An-An Li2, Fei-Jian Wu2, Qi-Cai Chen2, and Shu-Yi Zhang3,*

1Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, China
2College of Life Sciences, Central China Normal University, Wuhan 430079, China
3School of Life Science, East China Normal University, Shanghai 200062, China
4Department of Physiological Science, University of California at Los Angeles, Los Angeles, CA 90095-1606, USA
5Graduate School of the Chinese Academy of Sciences, Beijing 100049, China

Feng Luo, Jie Ma, An-An Li, Fei-Jian Wu, Qi-Cai Chen, and Shu-Yi Zhang (2007) The present study examines the echolocation calls and auditory responses of single neurons in the inferior colliculus (IC) of Pipistrellus abramus (Microchiroptera: Vespertilionidae). The data showed that there was a neurophysiological correlation of the auditory response properties with echolocation calls in IC neurons. The echolocation calls of P. abramus were broad-band swept from 86.6 to 43.2 kHz. The ending frequencies of the first harmonics which centered around 40 (average, 43.2; range, 37.0-47.0) kHz, were relatively more stable than the initial high frequencies. The average peak frequency was 52.1 (range, 43.3-57.6) kHz of which the majority (81%, 154 of 190 calls) ranged from 50.1 to 60 kHz. We recorded the responses of 75 single IC neurons to pure tones. Most IC neurons had the best frequency (BF) at between 30 and 50 kHz (centered around 40 kHz) (73%, 54 of 75) and between 50.1 and 60 kHz (19%, 14 of 75), respectively corresponding to the ending frequencies of the first harmonics and peak frequencies. The minimum threshold (MT) distribution was wider, and the average MT was significantly higher for neurons with a BF of 30-50 kHz than for neurons with a BF of 50.1-60 kHz (62 11 vs. 49 8 dB SPL, p < 0.001, t-test). The latency distribution was also slightly wider for neurons with a BF of 30-50 kHz (71% between 6.1 and 8.0 ms) than for neurons with a BF of 50.1-60 kHz (79% between 4.0 and 6.0 ms). Our study of echolocation calls and auditory response properties of IC neurons suggests that the IC of P. abramus can effectively process emitted pulses and echoes during hunting.

Key words: Echolocation calls, Auditory response properties, Inferior colliculus, Pipistrellus abramus.

*Correspondence: Qi-Cai Chen and Shu-Yi Zhang contributed equally to this work. Tel: 86-21-62233755. E-mail:syzhang@bio.ecnu.edu.cn