Responses of inferior collicular neurons to frequency- modulated sweeps in the Kunming mouse (In English)

摘要

Very few studies have been performed on the inferior colliculus (IC) by using frequency modulated (FM) stimulus though its acoustical response properties have been investigated by using pure tone in the Kunming mouse ( Mus musculus , Km). In the present paper, the responses of IC neurons to FM stimulus in the free-field conditions were examined. The main results were as follow: 1) according to the difference in the MT for pure tone and FM stimuli, the 99 IC neurons recorded were classified into three types; type Ⅰ neurons (57/99, 57.58%) were characterized by the lower MTs for the FM stimuli than for pure tone stimuli, while type Ⅲ neurons (30/99, 30.30%) were characterized by the lower MTs for the pure tone stimuli; a small fraction of neurons (type Ⅱ,12/99, 12.12%) exhibited no change of the MT when both types of stimuli were presented; 2) comparison of type A with type C neurons, we found that the former had lower characteristics frequencies (CFs) and Q_20dB ( P 20dB, P < 0.05); 3) 36 IC neurons (36/99, 36.36%) were direction selective and among them 61.11% (22/36) were up-selective and 38.89% (14/36) were down-selective neurons; up-selective neurons had a wider distribution across type Ⅰ, Ⅱ, and Ⅲ neurons than down-selective neurons; 4)the CFs of type Ⅰ and direction selective neurons had densest distribution over the range of 10 kHz–20 kHz (77.19% and 83.33%, respectively); 5) among the 24 recorded neurons responding to 3 different modulation rates, most of them (15/24, 62.50%) were more sensitive to rapid FM stimuli; the proportion of the direction selective neurons decreased with the increasing modulation rates (45.83% vs 41.77% vs 33.33%). Our data suggest that IC neurons of Km mouse could process FM stimuli effectively. FM sounds may play a significant role in acoustic communication in the Km mouse[ Acta Zoologica Sinica 53(4): 659–667, 2007].