Suppression of the auditory middle-latency response and evoked gamma-band response in a paired-click paradigm

When two clicks are presented within 500 ms and the clicks are separated by several seconds, a typical finding is a suppression of the amplitude of th e P50 component of the middle-latency auditory-evoked response. In the pres ent study, we investigated whether only the P50 or also the earlier compone nts Po, Na, Pa and Nb, and the exogenous components N100 and P200 exhibit a n amplitude suppression to the second click. In addition, we studied the su ppression behaviour of the auditory-evoked 40-Hz gamma-band response in the time and frequency domain. We found a significant amplitude suppression to the second click for all components of the auditory-evoked potential follo wing Po, which was most pronounced at electrode Cz. When testing the succes sive peaks and troughs of the evoked 40-Hz gamma-band response in the time domain, we found a significant amplitude suppression for peaks and troughs with the same latency and polarity as the middle-latency components followi ng Po, which was most pronounced at electrodes Fz and Cz. Consequently, the amplitude of the 40-Hz evoked gamma-band response in the frequency domain paralleled the findings of the time domain, with a significant amplitude su ppression to the second tone, which was most pronounced at electrodes Fz an d Cz. Results are discussed with reference to the early sensory-gating hypo thesis.