Moving topography of human presaccadic spike potentials in visually triggered saccade and optokinetic nystagmus.

The spatio-temporal nature of presaccadic spike potentials (SP) associated with the visually evoked saccade and with the fast phase of optokinetic nystagmus was investigated by means of moving electroencephalographic topography. In both cases, SPs were recognized about 15-25 msec before the quick eye movements (peak time 3-7 msec). The amplitude of SPs was +5 to +7 microV for the visually guided saccade and +3.5 to +4.5 microV for optokinetic nystagmus. The location of the SPs was the mid-parieto-occipital region on the scalp, but their topographical character was that of a brainstem potential. In the case of the visually guided saccade, before the appearance of SP, an antecedent potential in the form of a slow positive charge appeared in the parietal region. From their spatio-temporal characteristics, the SPs investigated in this study were interpreted as mass potentials of the brainstem nuclei which generate eye movements.