VELOCITY PROFILE OF HUMAN HORIZONTAL SACCADES

To assess saccadic trajectories, we evaluated the velocity profile using the 'skewness ratio' (the proportion of acceleration time to total saccadic duration) as a parameter. Horizontal cross-center saccades against target movements of 10-degrees, 20-degrees and 30-degrees were measured in 6 normal subjects using the magnetic search coil method. As the amplitude increased the period of the deceleration phase became prolonged: 10-degrees saccades were almost symmetrical and 30-degrees saccades were skewed to a ratio of about 0.3. A close relationship between duration and skewness ratio was found, and the skewness ratios of temporal saccades were smaller than nasal ones. This skewness ratio would be a useful parameter for assessing the velocity profile of human saccades.