Effect of inhibitory spectral integration on acoustic intensity sensitivity of neurons in the inferior colliculus of the big brown bat Eptesicus fuscus (In English)

摘要

By means of a particular two-tone paradigm under free field stimuli conditions, the current in vivo study was undertaken to explore whether the nonlinear integration between different frequency channels might modulate the sensitivity of sound intensity in inferior collicular (IC) neurons. We recorded neural spike activities simultaneously from 2 sites in the IC of 12 tranquilized and anesthetized big brown bat Eptescus fuscus with a pair of 3 M KCl glass electrodes. The following major findings were made. 1) Of 110 sampled neurons, the responses of 85.5% paired neurons (94/110) were inhibited whereas the others (14.5%, 16/110) were facilitated by addition of paired sound . 2) Percent inhibition in firing rate at 10 dB above MT decreased with increasing either best frequencies (BFs) or recording depth significantly. 3) Inhibition efficiency was large at lower stimulus intensity but decreased significantly with increasing stimulus intensity. 4) Neurons with a masker sound within their frequency tuning curves (FTCs, MSin) received more inhibition and more dynamic range (DR) reduction than those with a masker sound out of their FTCs (MSout). 5) There were three types of DR variation. DR of 61.6% (45/73) neurons decreased, 10.9% (8/73) increased, and 27.5% (20/73) unchanged or changed within 10%. Our data further support the hypothesis that the inhibitory spectral integration of different frequency channels in the IC might involve an active neural modulation of intensity coding [ Acta Zoologica Sinica 50 (3): 380 - 388, 2004].