Presaccadic spike potential to horizontal eye movements.

Presaccadic spike potentials prior to 20 degrees horizontal eye movements were recorded from 4 electrode sites around the eye with Pz as reference. The technique of back-averaging from the onset of the saccade was used and separate wave forms were obtained for abducting and adducting movements. The spike onset began between 12.0 and 4.4 msec before the beginning of the saccade with a significantly earlier onset with adduction (right eye P less than 0.001, left eye P less than 0.025). The peak occurred between the onset of eye movement and 7.8 msec after the beginning of the movement; the peak also occurred significantly earlier with adduction (right eye P less than 0.01, left eye P less than 0.01). The amplitude of the onset to peak measured from 32.2 to 47.0 microV with greater amplitudes on adduction compared to abduction although the differences were not statistically significant. Several of the traces also showed a later smaller component, after the main onset-to-peak complex, that has not been previously reported.