Event-related potentials (ERP) and statistical comparison of scalp maps during the preparatory period.

<p>From A–C, ERP comparison between each pair of tasks at the electrode FCz during the preparatory period. Color traces indicate the ERP for each type of task (red for antisaccade, green for prosaccade and yellow for no-go). During the instructive period (while S1 was present), a progressive negative potential was developing. During the gap period, this negative potential increased abruptly. The black horizontal line denotes the baseline value. This negativity was greater during prosaccadic than no-go (A), during antisaccadic than prosaccadic (B) and during antisaccadic than no-go (C) tasks. The offset of S1 (open triangle) and the onset of S2 (filled triangle) are indicated. Please note the visual evoked potentials (N1) triggered by the offset of S1 (black arrows). Calibration and voltage polarity for A–C is indicated in A. D–F show in the first two columns the topographical voltage distribution and in the third the statistical comparison between the same pairs of tasks shown in A–C, during the last 500 ms of the instructive (top row) and gap (bottom row) periods. Scalp distribution of voltage negativity was mainly located fronto-centrally. During the instructive period, significant differences in negativity were exclusively found between antisaccadic versus prosaccadic and no-go tasks. During the gap period, significant differences were found between the three tasks. Red points indicate electrodes with statistical differences (p<0.05).