type, zero phase shift, with a 200 ms width, and passband weights determined in the frequency domain (Cook and Miller, 1992). The filter was applied to the waveforms beginning at −200 ms so that the first filtered point was −100 ms. A peak-picking algorithm was used to identify the P1 and N1 ERP components based on changes in the slope (first derivative) of the waveform. The search windows for the P1 and N1 were selected based on the grand average CSD waveforms. The P1 peak was defined as the most positive CSD value from 75–200 ms, and the N1 peak was identified as the most negative CSD value from 125–225 ms. The P1 and N1 peaks were measured at the electrode sites at which they were maximal (P1: P7/P8, P9/P10, PO7/PO8, PO9/PO10; N1: P5/P6, P7/P8, PO7/PO8, PO9/PO10). A schematic of the electrode pairs used in the P1 and N1 analyses, which were also the electrodes from which IHTT was subsequently calculated (described in section 2.7.3), is provided in Fig. 2.
