Involuntary eye movements during fixation

Shortening and prolongation of saccade latencies following microsaccades

“…First, microsaccades are defined as binocular eye movements with almost identical amplitudes and directions in both eyes (Ditchburn and Ginsborg 1953;Krauskopf et al 1960;Lord 1951), pointing at a central rather than a peripheral nervous origin. Second, both microsaccades and large-scale saccades fall on the main sequence (Zuber et al 1965), i.e., the relationship between peak velocity and amplitude in these movements follows a power law.…”

“…Thus, although the neurophysiological origin of microsaccades is still unknown, it is reasonable to assume a common neural circuitry for the generation of microsaccades and saccades (see also Engbert 2005). Beyond that, microsaccades occur involuntarily (Ditchburn and Ginsborg 1953;Ratliff and Riggs 1950), suggesting that subcortical processes might be most relevant in their production.…”

“…Microsaccades' binocularity (Ditchburn and Ginsborg 1953;Krauskopf et al 1960;Lord 1951), involuntary occurrence (Ditchburn and Ginsborg 1953;Ratliff and Riggs 1950), and shared kinematic characteristics with large-scale saccades (Zuber et al 1965) hint at common subcortical mechanisms for the generation of both types of movements (see also discussion). A likely neural correlate of microsaccade generation is the rostral pole of the superior colliculus (SC), a brainstem structure critically involved in the control of saccades and fixations (see Munoz et al 2000, Scudder et al 2002, and Sparks 2002, for reviews).…”

An oculomotor continuum from exploration to fixation

“…The theoretical separation between exploratory gaze shifts and attempted fixation dates back to the discovery of fixational eye movements in the early 1900s (2)(3)(4), and remains central to contemporary discourse in visual, cognitive, and oculomotor research (8). However, mounting evidence in support of a common generator for both exploratory saccades and fixational microsaccades (refs.…”

“…free-viewing | fixational eye movements | miniature eye movements | fixational saccades | natural images C lassic and current vision studies distinguish between visual exploration, characterized by the alternation of saccades and brief fixation periods, and attempted visual fixation, where subjects maintain relative gaze stability despite continuous but minute fixational eye movements (i.e., microsaccades, slow drift, and oculomotor tremor) (1)(2)(3)(4)(5)(6)(7). The theoretical separation between exploratory gaze shifts and attempted fixation dates back to the discovery of fixational eye movements in the early 1900s (2)(3)(4), and remains central to contemporary discourse in visual, cognitive, and oculomotor research (8).…”