Responses of bat inferior collicular neurons to recorded echolocation pulse trains

Under free field stimulation conditions, we studied the responses of inferior collicular neurons of the big brown bat, Eptesicus fuscus, to echolocation pulse trains which were recorded during the entire process of hunting. The entire series of recorded echolocation pulse trains was edited in different sequences according to echolocation pulses of different hunting phases. When stimulated with all edited sequences of echolocation pulse trains, the temporal characteristics and the relative position of the echolocation pulses of a specific hunting phase affect the number of impulses of each inferior collicular neuron studied. When stimulated with two different intensities, more than 59% of inferior collicular neurons studied discharged selectively to the echolocation pulses of a specific hunting phase such that the number of impulses discharged to the echolocation pulses of the most and least preferred hunting phases differed by at least 50%. Passible mechanisms for this selective response are discussed.