Coordination of Eye-Head Movements in Alert Monkeys: Behavior of Eye-Related Neurons in the Brain Stem
Usually, fixation of a target appearing in the visual field is accomplished by coordinated eye and head movements. A series of studies has shown that this spatially coordinated behavior is a reflex that utilizes the sensory feedback generated by head movement (Bizzi, 1974; Bizzi, Kalil, & Tagliasco, 1971). This reflex interacts with centrally initiated motor programs for moving the head and eyes. To maintain target fixation during head turns, activation of vestibular receptors initiates signals that lead to diminished saccade size and generates compensatory eye movements (Dichgans, Bizzi, Morasso, & Tagliasco, 1973; Morasso, Bizzi, & Dichgans, 1973). During these combined eye-head movements, the sum of the eye position within the orbit and of the head position is equal to the required total gaze shift. When the head is held fixed, total gaze shift is accomplished by the eye saccade. This orderly sequence of movements is presented in Figure 6-1.
KeywordsHead Movement Vestibular Stimulation Experimental Brain Research Pontine Reticular Formation Saccade Size
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