Saccades (from the French saccade ; “jerk” , “push”  ) - fast, strictly coordinated eye movements that occur simultaneously and in one direction. On the electrooculogram, they look like vertical straight thin lines. Specialists often apply the term "microsaccades" to fast eye movements, the angular amplitude of which does not exceed 1 °. A quick eye movement with an amplitude of more than 1 ° calls "macroaccades." From the point of view of V. A. Filin, this division is purely conditional, since it assumes that these two types of rapid eye movements have a different mechanism of origin. Currently, it is assumed that any rapid eye movements have the same origin and therefore it is advisable to call them in one word - “saccade”.
Automation of saccades is the property of the oculomotor apparatus to make rapid eye movements involuntarily in a certain rhythm. Saccades can be awake in the presence of visual objects (in this case, using the saccades, the point of fixation of the gaze changes, due to which the visual object is examined), in the absence of visual objects, as well as during the paradoxical stage of sleep (Filin V.A., 1987). The nature of the saccade sequence is due to the activity of the central nervous system , the corresponding structures of which are capable of generating a signal by the type of automation, that is, are capable of rhythmogenesis. Each person has his own saccade pattern , which is determined by three parameters: the interval between saccades, their amplitude and orientation. The largest number of saccades follows in 0.2-0.6 seconds, the amplitude of saccades varies in a large angular range from 2 ′ to 15 °, saccades are oriented in almost all directions (right, left, up, down), but usually their number is greater horizontal plane.
Saccades can be carried out arbitrarily. One of the most common methods for studying saccadic eye movements is the “anti-saccadic task”. Under the conditions of this task, the test subject is required to suppress the reflex saccade in the direction of the visual stimulus presented and perform the saccade in the opposite direction.
Saccadic movements are ballistic - having begun, the saccade will be completed regardless of whether the fixation point has changed its position in the time elapsed since the beginning of the saccade. In this regard, saccades are pre-programmed. The system involved in saccade programming is hierarchically organized and includes four levels.
The first level of the saccade system provides direct execution of saccades and includes the external muscles of the eye and nuclei of the III, IV, and VI pairs of cranial nerves (Podvigin et al., 1986).
The second level of the saccade system combines the stem structures of supranuclear control of eye movements. These include the nuclei of the reticular formation of the trunk, the structure of the bridge and some nuclei of the midbrain tires  (Podvigin et al., 1986; Shulgovsky, 1993). Second-level structures control the holistic coordinated movements of both eyes.
The third level of the oculomotor system is represented by structures that control the operation of the saccade stem generator. This level includes the superior dicollis (VD), the basal ganglia , the cerebellum , the corpus callosum , the lateral cranked body , the region of the inner capsule, the pillow complex, and a number of other thalamic nuclei  (Podvigin et al., 1986).
The fourth level of the oculomotor system includes various zones of the cerebral cortex , among which the frontal oculomotor field and posterior dark fields (5, 7 according to Broadman) occupy the most important place. In addition, an additional oculomotor field, dorsolateral prefrontal cortex (field 46), etc. take part in the preparation of saccadic eye movements. This level is necessary for the implementation of arbitrary saccades   (Shulgovsky, 2004).
Saccades in Psychophysiological and Clinical Research
Saccades play an essential role in purposeful behavior, visual perception, and the study of the world around us and are fully developed only among primates (including humans) (Shulgovsky, 1993). The phenomenon of saccadic suppression is associated with them, when the subject does not perceive visual information during the implementation of saccades. In addition, violations of saccadic eye movements objectively reflect neurodegenerative processes during physiological aging, mental and motor disorders    . In the latter case, saccades can be ahead of other motor symptoms and serve as one of the specific markers of the disease  .
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