Blinks Slow Memory-Guided Saccades
Alice S. Powers, Department of Psychology, St. John’s College of Liberal Arts and Sciences, M.A. Basso, Department of Physiology, University of Wisconsin, C. Evinger, Department of Neurobiology and Behavior, Stony Brook
Abstract: The average maximum velocity and duration of memory-guided saccades are less than those of equal amplitude visually-guided saccades. Here we show that the slower velocity of memory saccades compared to visual saccades primarily occurs because a blink accompanies the saccadic eye movement. Using the magnetic induction technique, we measured movements of the eye and the lid in three monkeys during performance of memory- and visually-guided saccades.
Memory-guided saccades accompanied by blinks were significantly slower and of longer duration than memory-guided saccades without blinks. Memory-guided saccades without blinks, however, were only slightly slower than visually-guided saccades. Visually-guided saccades with blinks were much slower than visually-guided saccades without blinks. Blinks occurred more frequently with memory-guided (26.3%) than visually-guided (2.9%) saccades. The higher frequency of blinking with memory-than with visually-guided saccades is consistent with observations that gaze-evoked blinks are less frequent with visual targets.
The blink-evoked eye movements disrupted the trajectory of saccades accompanied by blinks. The superposition of the typically downward and medial blink-evoked eye movements onto the intended saccadic eye movement created a robustly curvilinear trajectory. Nevertheless, the end point accuracy of memory-guided saccades was not significantly different between saccades with and without blinks. Thus, the linkage of blinks and memory-guided saccades affects maximum velocity and trajectory, but not accuracy. The results point to the importance of taking blinking into account when analyzing saccades.
Supported by EY07391 (CE) and EY13692 (MAB).