Forward masking of auditory nerve and brainstem responses using high-pass noise maskers.

The effects of varying the low-frequency cutoff of a high-pass noise used as a forward masker for a broadband click (40 dB HL) are compared for wave V of the auditory brainstem response and N1 from the ear canal. Derived responses were also obtained using a waveform subtraction technique. N1 amplitude and wave V latency were most sensitive to the changes in the masker low-frequency cutoff. Results suggest that N1 is biased toward the high frequencies, most likely because of its requirements for high neural synchrony, and is not necessarily related to the maximum area of excitation. Wave V, on the other hand, seems to be less dependent upon highly synchronous events and is more closely related to activity in the mid-to-lower frequencies. Complex behavior of wave V was observed as a function of delta T which suggests that temporal as well as spatial factors can interact in their contributions to wave V.