Corticofugal modulation of frequency tuning of inferior collicular neuronsin big brown bat, Eptesicus fuscus

In order to explore the possible mechanism of corticofugal modulation of ex citatory frequency tuning curves (EFTCs) of midbrain neurons, we examined t he change of sharpness, frequency-intensity response area, minimum threshol d of both EFTCs and inhibitory frequency tuning curves (IFTCs) of inferior collicular neurons during corticofugal modulation using two-tone inhibition paradigm and micro electrical stimulation technique. Our data showed that corticofugal inhibition increased sharpness, minimum threshold, and decreas ed the frequency-intensity response area of EFTCs, at the same time it decr eased the sharpness, minimum threshold but increased the frequency-intensit y response area of IFTCs. The opposite results were observed for EFTCs and IFTCs of corticofugally facilitated inferior collicular neurons, During cor ticofugal Inhibition, the percent change of frequency-intensity response ar ea of EFTCs had significant correlation with the percent change of that of IFTCs, These data suggest that cortical neurons are likely to improve frequ ency information processing of inferior collicular neurons by modulation of IFTCs.