Prepulse effects as a function of cortical projection system

A putative gating mechanism reduces startle blink, midline scalp potentials beginning with P50, and perceived loudness of startling stimuli. Tactile p restimuli were paired with auditory startle stimuli to determine if: (1) P5 0 inhibition is due to an extrinsic mechanism, (2) pairing differentially a ffects potentials reflecting modality specific and nonspecific system activ ity, and (3) crossmodal pairing modifies perceptual magnitudes of both pair members. Stimuli were presented alone and in pairs separated by 60 or 360 ms. Event-related potentials (ERPs) were recorded from midline and lateral sites: E:MC was recorded from several facial and scalp muscles. Pairing red uced blink, and midline F50, N100 and P200 amplitudes; reductions were grea ter at the longer interval. P30 was largely unaffected by pairing. Pairing also differentially affected lateral N100 components reflecting later activ ity in specific and nonspecific systems. Results show that prestimulus inhi bition of ERPs is not due to intrinsic refractoriness and that pairing diff erentially affects ERPs associated with modality specific and nonspecific p rojection systems. (C) 2001 Elsevier Science B.V. All rights reserved.