A comparison of saccadic and blink suppression in normal observers

Recent research suggests that blink and saccadic suppression are produced by the same mechanism (Volkmann, 1986; Uchikawa & Sato, 1995; Ridder & Tomlinson, 1993, 1995). These studies demonstrated that blink and saccadic suppression have the same effect on various visual functions. However, none of these studies made a comparison of blink and saccadic suppression in the same individual. The purpose of this study was to compare the effects of blink and saccadic suppression on contrast sensitivity functions in the same subject. The effect of saccadic suppression on the contrast sensitivity function in three normal observers was determined. Employing a two-alternative, forced-choice technique, thresholds were measured for seven spatial frequencies. At each spatial frequency, the threshold was determined immediately following detection of a voluntary saccade. The magnitude of suppression was taken as the log ratio of the contrast sensitivities obtained while foveating the stimulus and those obtained during saccades. The magnitude of saccadic suppression was found to increase as the saccade amplitude increased and to be spatial-frequency dependent. Low spatial frequencies were suppressed more than high spatial frequencies. The blink suppression data have been measured previously (Ridder & Tomlinson, 1993). Saccadic and blink suppression were qualitatively similar. A vertical shift of the data brought the saccadic and blink suppression data into register. These results suggest that blink and saccadic suppression are produced by the same or similar mechanisms.