BSR (wave V) and N1 latencies in response to acoustic stimuli with different bandwidths

Shortlatency averaged responses to 0.02--6 kHz broadband (BB) and 2 kHz narrow-band (NB) filtered clicks were recorded from the ear canal and the vertex of five adults with normal audiograms. Response latencies to the signals presented in quiet and with masking noise were compared. For constant spectrum level, the low-frequency limit of the masking noise was systematically increased to 6 kHz. The upperfrequency limit was always 8 kHz. For signals at 40 dB HL, the latencies of wave V and N1 decreased as the lower limit of the noise was raised and nearly equaled the latency for the signals presented in quiet. For signals at 70 dB HL, the latency in quiet was much less than that observed for all noise conditions, i.e., frequencies above 8 kHz would be required to interfere with the signal-dependent synchronous neural activity. Similar effects were measured for both wave V and N1, but the analysis of wave V and N1, but the analysis of wave V--N1 latency intervals suggested a possible signal dependency.