Saccadic Masking - Mechanism For Saccadic Masking

Mechanism For Saccadic Masking

A saccade is a fast eye motion, and because it is a motion that is optimised for speed, there is inevitable blurring of the image on the retina, as the retina is sweeping the visual field.

Blurred retinal images are not of much use, and the eye has a mechanism that 'cuts off' the processing of retinal images when it becomes blurred. Humans become effectively blind during a saccade. This phenomenon is called saccadic masking or saccadic suppression.

There are two major types of saccadic suppression (or masking), the first is flash suppression (the inability to see a flash of light during a saccade - see Dodge 1900) and the second is saccadic suppression of image displacement which is characterized by the inability to perceive whether a target has moved or not during a saccade (Bridgeman, G., Hendry, D., & Stark, L., 1975).

Because saccadic suppression starts before the actual onset of the saccade, it cannot be triggered by retinal motion and must be centrally activated by the brain. Supporting this idea, a significant reduction of the cortical signals retinotopically encoding stimuli briefly presented immediately before the execution of a saccade has been found as early as in primary visual cortex (Vallines, I., & Greenlee, M.W., 2006).