Figure 3.

Butterfly plots showing grand average (n = 8) superimposed channels with fixation-related potentials (FRPs, upper panels) and corresponding electrooculogram (EOG, lower panels) for fixations on button. The signals were low-pass filtered at 7 Hz and baseline corrected (high-pass filtering was not used). Note the similarity between the waveforms for left and right button positions (in the left and in the right, respectively) within most of the fixation interval. Zero millisecond corresponds to the beginning of fixation. The baseline interval (200–300 ms) is shown by dark gray bars. The light gray bars show 400–500 ms interval from which the EEG amplitudes were averaged to obtain estimates of the trend over the fixation used in the subsequent analysis (Figures 4, 5). Dwell time threshold was 500 ms (marked with the vertical lines in the right edges of the light gray bars).