Wu M, Hou E T, Jen P H
Division of Biological Sciences, University of Missouri-Columbia 65211, USA.
Chin J Physiol. 1996;39(3):167-76.
Under free field stimulation conditions, this study examined the responses of inferior collicular and cortical neurons of the big brown bat, Eptesicus fuscus, to pulsatile amplitude modulated sound pulses by means of temporally patterned pulse trains. When the pulse trains were delivered at different pulse repetition rates between 1 and 100 pps, inferior collicular neurons can follow pulse repetition at a higher rate than can auditory cortical neurons. 85% of 40 inferior collicular neurons studied always discharged impulses to each presented pulse delivered at repetition rates of up to 40 pps and 20% of these neurons could follow the repetition rate throughout the entire range of repetition rates tested. In contrast, only 60% of 56 auditory cortical neurons could follow a repetition rate up to 10 pps. At higher repetition rates, they only discharged impulses to the first pulse of each pulse train. According to variation in number of impulses, filtering properties of responses of inferior collicular and auditory cortical neurons to pulse repetition rate can be described as low-pass, high-pass, or band-pass. Most (63%) inferior collicular neurons behaved like band-pass filters to pulse repetition rate while most auditory cortical neurons behaved like all-pass (52%) or low-pass (37%) filters. Possible mechanisms underlying the different filtering properties between the inferior collicular and auditory cortical neurons are discussed.
