Unit responses in ventral cochlear nucleus reflect cochlear coding of rapid frequency sweeps.
This study examines the encoding of rapid frequency sweeps in single units of the ventral cochlear nucleus (VCN). Sweeps were designed to explore the role of cochlear mechanics in shaping the temporal responses across cells in the VCN. The time course of frequency change for rapidly rising frequency sweeps theoretically produced simultaneous displacement maxima by cancelling travel time along the cochlear partition. Rising sweeps with longer time courses only partially canceled travel time, while falling sweeps had time courses of frequency change equal to or greater than travel time. Falling sweeps thus augmented normal travel time. Latency of unit firing to sweeps across unit characteristic frequency (CF) reflected cochlear delay-line mechanics. The latency-CF functions agreed with predictions from travel-time estimates for rising-frequency sweeps, but responses to falling sweeps were less predictable.