N1m recovery from decline after exposure to noise with strong spectral contrasts.

Comb-filtered noise (CFN, derived from white noise by suppressing regularly spaced frequency regions) was presented for 3 s followed by two types of test stimuli. One test stimulus (SB) was comprised of spectra centered in the stop-band regions of the CFN and the other test stimulus (PB) of spectra centered in the band pass regions of the CFN. Magnetoencephalographically recorded N1m responses evoked by SB stimuli were decreased relative to the N1m response evoked by PB stimuli. This effect was maximal when the interval between the CFN and test stimuli was short (0.5 s) but was detected at intervals up to 2 s. The results suggest lateral inhibition in the auditory cortex and point to a decay of inhibition lasting on the order of seconds.