Inhibition plays an important role in creating the temporal response properties of duration-tuned neurons (DTNs) in the mammalian inferior colliculus (IC). Neurophysiological and computational studies indicate that duration selectivity in the IC is created through the convergence of excitatory and inhibitory synaptic inputs offset in time. We used paired tone stimulation and extracellular recording to measure the frequency tuning of the inhibition acting on DTNs in the IC of the big brown bat (Eptesicus fuscus). We stimulated DTNs with pairs of tones differing in duration, onset time, and frequency. The onset time of a short, best duration (BD), probe tone set to the best excitatory frequency (BEF) was varied relative to the onset of a longer duration, non-excitatory (NE) tone whose frequency was varied. When the NE tone frequency was near or within the cell's excitatory bandwidth (eBW), BD tone evoked spikes were suppressed by an onset-evoked inhibition. The offset and duration of the suppression decreased as the NE tone frequency departed from the BEF. We measured the inhibitory frequency response area, best inhibitory frequency (BIF), and inhibitory bandwidth (iBW) of each cell. We found that the BIF closely matched the BEF, but the iBW was broader and usually overlapped the eBW measured from the same cell. These data suggest that temporal selectivity of midbrain DTNs is created and preserved by having cells receive an onset-evoked, constant-latency, broadband inhibition that largely overlaps the cell's excitatory receptive field. We conclude by discussing possible neural sources of the inhibition.
- auditory physiology
- big brown bat (Eptesicus fuscus)
- excitatory/inhibitory frequency response area
- synaptic tuning
- temporal processing
- Copyright © 2016, Journal of Neurophysiology