Frequency-related differences in the speed of human auditory processing

Three experiments were performed, two comparing the peak latencies of auditory evoked potentials (AEPs) elicited by 250 Hz and 4000 Hz tone pips and a third comparing simple reaction times (RTs) to the same stimuli. In the AEP experiments, the latencies of brainstem, middle and long-latency components were delayed following 250 Hz tone pips in comparison with the latencies of the same components evoked by loudness-matched 4000 Hz tones. Frequency-related latency differences increased with component latency, ranging from less than 1.0 ms for wave V of the brainstem AEP, to more than 20.0 ms for the cortical N1 component. Interpeak latency differences were also significantly lengthened following the 250 Hz tone pips. In the behavioral study, RTs were 14.6 ms slower following 250 than 4000 Hz tone pips. The results suggest that the time required for the sensory analysis of auditory signals varies inversely with their frequency.