Middle-component AERs during backward masking.

This study examined the middle-component averaged electroencephalic response (AER) to tonal stimuli presented in a backward-masking paradigm. Ss were 4 normal-hearing young adults. Tone-Only (TO), Masker-Only (MO), and Tone-Masker (TM) responses were collected. The visual impression was that the TO response was not significantly different from the extracted response to the tone (T) from the TM response. This result obtained when the tone in the TM condition was presented either slightly above (+5 db) or slightly below (-5 db) perceptual threshold. Backward masking was discussed in terms of two contrasting views of the auditory system: the classical auditory nervous system alone and a parallel system combining the classical auditory and the reticular sensory systems. Speculations were made for each system regarding the type of AER expected for a stimulus submerged in backward masking. The mechanism responsible for backward masking was seen as a preperceptual device that allows discrete samples of the auditory environment to be processed. This mechanism was discussed in terms of its possible relation to forward masking and to loudness enhancement.