Central control of eye movements.

Abstract

Eye-movement research continues to provide an excellent tool for understanding the central control of motor function, both in health and disease. This article reviews recent findings in relation to saccadic eye movements, particularly antisaccades and microsaccades, with particular emphasis on the control of inaction, something which has recently become topical. Microsaccades are under the control of the cerebral cortex, particularly the frontal and parietal eye fields. Their frequency and direction alters following presentation of visual stimuli. Spontaneous alterations in their frequency are correlated with alterations in the frequency of the gamma-band activity in the visual cortex as well as, interestingly, the heartbeat. Studies of saccades in Parkinson's disease have demonstrated abnormalities of prosaccade suppression which have variously been shown to correlate with freezing of gait, postural instability, minimal cognitive change and stimulation of the subthalamic nuclei. In stroke patients, abnormal patterns of saccade activity are associated with poor performance on reaching studies when using the weak arm. Eye-movement studies continue to provide new insights into the control of movement in general but have been particularly useful in investigating the process of suppressing unwanted movement.