Cortical mechanisms of saccadic suppression and visual motion : a transcranial magnetic stimulation study in humans

Anatomically, the visual system of non-human primates shows a complicated pattern of cortico-cortical connectivity. The behavioural relevance of many of these connections is unclear, as is the similarity of connectivity with that in the human brain. We used transcranial magnetic stimulation (TMS) and psychophysics to investigate connectivity among visual areas involved in (1) modulating visual perception during saccadic eye movements and (2) perceiving visual motion. Our first study demonstrated that phosphenes induced by TMS of visual cortex are perceived as more intense shortly after the onset of a saccade. This indicates that the cortical areas responsible for saccade generation are connected to those areas responsible for visual perception. Our second study suggested that, when applied with a very short inter-stimulus interval, TMS over an oculomotor region (FEF) can modulate the effect of TMS applied over a region sensitive to visual motion (V5). This suggests a monosynaptic feedback connection from FEF to V5