Scalp distribution components of brain activity evoked by visual motion stimuli

We analyzed the scalp distribution of electrical brain activity elicited by visual motion stimuli in 14 healthy adults. Stimuli were square-wave gratings of high or low contrast moving with a velocity of 4.9 deg/s on a computer monitor. Adaptation to motion was varied by changing the so-called duty cycle of stimulus presentation (i.e., the relation of motion to total presentation time) in order to enhance motion-related activity. Data obtained with motion stimuli were compared with checkerboard pattern reversal evoked activity. Spatial principal components analysis revealed four latent topographical components that accounted for 92.05% of the variance. Two components showed occipital extreme values surrounded by steep potential gradients while another two components displayed lateralized activity. Analysis of the contribution of these spatial components to the observed potential fields revealed significant differences between activity evoked by pattern reversal and that evoked by motion. The topographical patterns of cortical activation changed rapidly within 240 ms after motion onset. Our results confirm the sequential and parallel activation of different neuronal generators selectively sensitive to physical stimulus parameters of motion stimuli. The converging evidence of specialized quality-specific streams of sensory processing stemming from single-unit recordings in monkeys and imaging methods is supplemented by our electrophysiological results reflecting the activation of different brain areas.