A frontal cortical potential associated with saccades in humans.

We describe a frontal EEG potential which begins 25-35 ms before intentional saccadic eye movement. It consists of a 15-20 muvolt monophasic positive waveform with peak during or just after movement, and returns to EEG baseline 150-200 ms after its onset. The waveform is largest at a midline position just anterior to FZ (10-20 system), is independent of visual input such as fixation guides, and is not related to saccade direction or amplitude. The potential is difficult to observe in some subjects and is independent of the "pre-saccadic spike potential". It may be related to the discharge of single cortical neurons that signal the initiation of saccadic movements, but not their exact metrics; a possible generator is the supplementary eye fields of the dorsomedial prefrontal cortex.