Saccades to remembered targets: the effects of saccades and illusory stimulus motion

In 10 human subjects, we measured the accuracy of saccades to remembered locations of targets that were flashed on a 20 x 30 deg random dot display, while they tracked a spot of light that stepped between three vertical locations. The background was either stationary or stepping horizontally in synchrony with vertical motion of the spot of light, a condition that induced a strong illusion of diagonal target motion. Memory-guided saccades were less accurate horizontally, but not vertically, when the background moved compared with when it was stationary. The horizontal component of memory-guided saccades correlated better with the position of the background when the target was flashed than with the position of the background at the end of the memory period. We conclude that the visual illusion corrupted the working memory of target-location, but had a lesser effect on the estimate of gaze at the end of the memory period, which seemed to depend more on extraretinal signals.