Blinks slow memory-guided saccades

1Stony Brook University.
Journal of Neurophysiology (Impact Factor: 2.89). 11/2012; 109(3). DOI: 10.1152/jn.00746.2012
Source: PubMed


Memory-guided saccades are slower than visually-guided saccades. The usual explanation for this slowing is that the absence of a visual drive reduces the discharge of neurons in the superior colliculus. We tested a related hypothesis, that the slowing of memory-guided saccades was due also to the more frequent occurrence of gaze-evoked blinks with memory-guided saccades compared to visually-guided saccades. We recorded gaze-evoked blinks in three monkeys while they performed visually-guided and memory-guided saccades and compared the kinematics of the different saccade types with and without blinks. Gaze-evoked blinks were more common during memory-guided saccades than during visually-guided saccades, and the well-established relationship between peak and average velocity for saccades was disrupted by blinking. The occurrence of gaze-evoked blinks was associated with a greater slowing of memory-guided saccades compared to visually-guided saccades. Likewise, when blinks were absent, the peak velocity of visually-guided saccades was only slightly higher than that of memory-guided saccades. Our results reveal interactions between circuits generating saccades and blink-evoked eye movements. The interaction leads to increased curvature of saccade trajectories and a corresponding decrease in saccade velocity. Consistent with this interpretation, the amount of saccade curvature and slowing increased with gaze-evoked blink amplitude. Thus, although the absence of vision decreases the velocity of memory-guided saccades relative to visually-guided saccades somewhat, the co-occurrence of gaze-evoked blinks produces the majority of slowing for memory-guided saccades.

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