Human presaccadic spike potentials. Of central or peripheral origin?

Electroencephalographic (EEG) activity associated with voluntary and spontaneous saccades were analyzed in 12 normal subjects to determine the influence of volition upon the presaccadic spike potentials (SPs). In addition, two different electrode configurations, of a temporal and a parietal derivation, and two different filter bandwidths were simultaneously analyzed to clarify issues regarding the structure, function, and origin of SPs. An off-line averaging of the pre- and postsaccadic EEG epochs showed distinct spike potentials associated with spontaneous saccades in both the temporal and the parietal locations. Subsequent statistical analyses indicated that the amplitude of the SPs associated with spontaneous saccades was not significantly different from the respective amplitude of SPs preceding voluntary saccades. Independent effects of filter bandwidth and electrode derivation are suggestive of a complex late presaccadic EEG activity.