Temporal Masking Assessed With Cortical Auditory Evoked Potentials

The purpose of this experiment was to determine the effects of sequential sounds on cortical auditory evoked potentials and to investigate temporal masking. The study tested the hypotheses that forward masking reduces the amplitude of the/ba/-evoked response for short intervals between masker offset and signal onset (Δ t ) but not for Δ t 's, and that it prolongs the latency of the response even for long Δ t 's. In addition, it was expected that this latency shift recovers to baseline as an inverse function of Δ t .

Cortical auditory evoked potentials evoked by the consonant-vowel/ba/ were measured in 32 young normal-hearing adults. This signal was either presented alone or in the presence of a preceding speech-shaped noise masker. When the masker was present, the Δ t 's were 3, 10, 32, or 100 msec. The masker was presented at 70 dB SPL, and the signal at 70 dB pSPL. The dependent variables were the N1-P2 amplitude and the N1 latency.

The presence of the masker increased the N1 latency of the/ba/-evoked response but this prolongation was not dependent upon Δ t . Similarly, the presence of the masker reduced the N1-P2 amplitude of the/ba/-evoked response but this reduction was not dependent upon Δ t .

The pattern of results did not support the hypotheses. Rather, they suggested that, for cortical auditory evoked potentials evoked by configurations of sequential sounds, a leading sound can affect the response to a lagging sound in a manner that is distinct from conventional forward-masking effects, where recovery functions are the norm.