Modulation of the P1 component during the interference period. Grand average waveforms (block 1 and block 2 combined) of P1 posterior electrode of interest (EOIs, n = 20) during the interference period showed significant differences across tasks. P1 peak amplitudes for IS interruptors were greater than peak amplitudes for DS distractors, but not baseline stimuli. DS peak amplitudes were significantly smaller than baseline peak amplitudes [B > DS: P1 suppression]. The topographic ERP difference map shows suppression (B-DS) during the P1 time frame of 75–105 ms (peak latency mean for DS and B ±1 SD) based on the grand average across all participants and electrodes. Of the posterior electrodes, the following electrodes were identified as participants' P1 intervening stimuli EOIs: Iz, O1, O2, P8, P9, P10, PO3, PO4, PO7, PO8. This grand average was created using the unique EOI for each participant. Positive amplitudes are plotted as up going. Error bars represent SE. *, significant differences (P < 0.05, FDR corrected).