Corticofugal regulation of excitatory and inhibitory frequency tuning curves FTCs.of neurons in the central nucleus of bat inferior colliculus ICc. was studied by electrical stimulation of the primary auditory cortex AC stimulation. under free field stimulation conditions using a two-tone inhibition paradigm. AC stimulation narrowed the excitatory FTCs and asymmetrically expanded the lateral inhibitory FTCs of corticofugally inhibited ICc neurons. The opposite results were observed for excitatory and inhibitory FTCs of corticofugally facilitated ICc neurons. These data support previous reports that corticofugal systems work together with widespread lateral inhibition to regulate subcortical frequency processing.