TOPOGRAPHY OF VISUALLY EVOKED BRAIN ACTIVITY DURING EYE-MOVEMENTS - LAMBDA-WAVES, SACCADIC SUPPRESSION, AND DISCRIMINATION PERFORMANCE

Eye movement-related brain activity was studied in 14 subjects by reco rding EEG topographically in 16 channels over the occipital brain area s. Potential fields obtained with or without the simultaneous presenta tion of a visual stimulus during the time course of horizontal saccade s were compared. Without visual stimulation, eye movements were follow ed at a mean latency of about 65 ms by a lateralized occipital dominan t component whose topography was determined by the direction of the sa ccade but whose latency was independent of the time course of the eye movements. This component was reminiscent of lambda waves, however, it could also be elicited in complete darkness. When stimuli were presen ted during saccades, component latencies increased significantly, and there were also topographic changes in the evoked potential fields. Ne gative centroids were located more anteriorly and positive ones more p osteriorly on the scalp when compared to brain activity recorded with stable eye positions and visual stimulation. All subjects reported no suppression of visual stimuli when presented during saccades occurred. This was confirmed by testing the discrimination performance of an in dependent group of 27 subjects. Our data show that the execution of sa ccades elicits electrophysiological patterns of activation in the visu al cortex even without visual input. The increase of component latency observed during saccades as well as topographical differences suggest that visual information is processed by different neuronal elements d uring saccadic eye movements. (C) 1997 Elsevier Science B.V.