Contributions from eye movement potentials to stimulus preceding negativity during anticipation of auditory stimulation

Cognitive anticipation of a stimulus has been associated with an ERP called " stimulus preceding negativity'' (SPN). A new auditory delay task without stimulus- related motor activity demonstrated a prefrontal SPN, present during attentive anticipation of sounds with closed eyes, but absent during distraction of attention and during attention with fixed gaze. ERP maxima found near the eyes required examination of eye movement interference, wherefore six monopolar EOG electrodes were included. Similarities between ERPs and potentials evoked by voluntary eye movements with respect to spatial distribution and polarities of amplitudes around the eyes and over the frontal cortex suggested that, in the closed-eyes condition, small involuntary downward eye movements occurred during attentive anticipation of sounds. Analyses of single trials corroborated this interpretation. On this basis it is suggested that the SPN was caused by such eye movements.