Absence of gaze direction effects on EEG measures of sensorimotor function

OBJECTIVE: Gaze direction is known to modulate the activation patterns of sensorimotor areas as seen at the single cell level and in functional magnetic resonance imaging (fMRI). To determine whether such gaze direction effects can be observed in scalp-recorded electroencephalogram (EEG) measures of sensorimotor function we investigated somatosensory evoked potentials (SEPs) and steady state movement related cortical potentials (MRPs). METHODS: In two separate experiments, SEPs were elicited by electrical stimulation of the median nerve (experiment 1) and steady state MRPs were induced by 2 Hz tapping paced by an auditory cue (experiment 2), while subjects directed their gaze 15 degrees to the left or to the right. RESULTS: Gaze direction failed to produce any appreciable differences in the waveforms of the SEPs or MRPs. In particular, there was no effect on peak amplitude, peak latency and peak scalp topography measures of SEP and MRP components, or on spatial or temporal parameters of dipole models of the underlying cortical generators. Additional frequency domain analyses did not reveal reliable gaze-related changes in induced power at electrode sites overlying somatosensory and motor areas, or in coherence between pairs of parietal, central and frontal electrodes, across a broad range of frequencies. CONCLUSIONS: EEG measures of sensorimotor function, obtained in a non-visual motor task, are insensitive to modulatory effects of gaze direction in sensorimotor areas that are observable with fMRI.