When motion takes form : an electrophysiological approach to visual motion perception in humans

When and where is visual motion processed in the human brain? This question is highly relevant considering the importance of motion for our perception of the dynamical world surrounding us. In the present work we studied motion processing, firstly through its main characteristic: direction, and secondly using form from motion stimuli (FfM), consisting in a form emerging from motion. Our purpose was to investigate the temporal dynamics of involved brain mechanisms and to localize underlying cortical substrates. To do so we studied healthy subjects as well as neurological patients, using electrophysiological approaches : electroencephalography (surface EEG) and intracranial recordings. Our main finding indicates that motion direction is already processed at 80-110ms in the temporo-occipital cortex, and then at 170-220ms in the parieto-occipital and the temporo-occipital cortex. Perception of FfM requires further processing occurring around 220-360ms, located in lateral occipital cortex but also in parieto-temporo-occipital cortex. These results show that motion is processed rapidly to supply information for other processing of the visual system.