Sensitivity of offset and onset cortical auditory evoked potentials to signals in noise.

Objective: The purpose of this study was to determine the effects of SNR and signal level on the offset response of the cortical auditory evoked potential (CAEP). Successful listening often depends on how well the auditory system can extract target signals from competing background noise. Both signal onsets and offsets are encoded neurally and contribute to successful listening in noise. Neural onset responses to signals in noise demonstrate a strong sensitivity to signal-to-noise ratio (SNR) rather than signal level; however, the sensitivity of neural offset responses to these cues is not known.
Methods: We analyzed the offset response from two previously published datasets for which only the onset response was reported. For both datasets, CAEPs were recorded from young normal-hearing adults in response to a 1000-Hz tone. For the first dataset, tones were presented at seven different signal levels without background noise, while the second dataset varied both signal level and SNR.
Results: Offset responses demonstrated sensitivity to absolute signal level in quiet, SNR, and to absolute signal level in noise.
Conclusions: Offset sensitivity to signal level when presented in noise contrasts with previously published onset results.
Significance: This sensitivity suggests a potential clinical measure of cortical encoding of signal level in noise.