COMPRESSION OF VISUAL SPACE BEFORE SACCADES

Saccadic eye movements, in which the eye moves rapidly between two res ting positions, shift the position of our retinal images, If our perce ption of the world is to remain stable, the visual directions associat ed with retinal sites, and others they report to, must be updated to c ompensate for changes in the point of gaze, It has long been suspected that this compensation is achieved by a uniform shift of coordinates driven by an extraretinal position signal(1-3), although some consider this to be unnecessary(4-6). Considerable effort has been devoted to a search for such a signal and to measuring its time course and accura cy, Here, by using multiple as well as single targets under normal vie wing conditions, we show that changes in apparent visual direction ant icipate saccades and are not of the same size, or even in the same dir ection, for all parts of the visual field, We also show that there is a compression of visual space sufficient to reduce the spacing and eve n the apparent number of pattern elements,The results are in part cons istent with electrophysiological findings of anticipatory shifts in th e receptive fields of neurons in parietal cortex(7) and superior colli culi(8).