Effects of eye position on estimates of eye displacement for spatial updating.

Neurons in the parietal cortex represent spatial memory of visual stimuli in an eye-centered coordinate frame. To preserve spatial stability across eye movements, spatial memory must be updated during each eye movement. Because eye movement signals in the parietal cortex are known to be modulated by eye position in the orbit, estimates of eye displacement on the basis of these signals could also be influenced by eye position. The present study examined the possible effect of eye position on the accuracy of memory-guided saccades in monkeys following saccades or smooth pursuit during the memory period. The results showed that eye position has a modest effect on saccade localization, suggesting that eye position signal plays a modulatory role in updating visuospatial working memory.