The array seen when saccading across a point light source blinking in the dark is displaced in the direction of the saccade. This displacement reflects an abrupt shift of spatiotopic coordinates that precedes the actual eye movement. The extraretinal signal mediating this discrete shift appears to be an oculomotor reference signal, specifying intended eye orientation, that changes discretely before saccades.

Saccadic eye movements create (at least) two related but distinct problems for the visual system: they cause rapid image motion and a displacement of the retinal image. Although it is often assumed that the motion is too fast to be resolved, this is certainly not the case for low-spatial-frequency images. Recent experiments have suggested that the reason we are unaware of the motion during saccades is because motion channels are selectively suppressed, possibly by suppression of the magno-cellular (but not the (...) parvocellular) pathway. This suppression may explain why there is no sensation of motion during saccades, but it leaves open the problem of perceiving a stable world despite continual image displacements. (shrink)