Abstract
The smooth pursuit system moves the eyes in space accurately to track slowly moving objects of interest while compensating for visual inputs from the moving background. In daily life, smooth-pursuit is performed by coordination of eye and head movements (i.e. gaze-pursuit). To examine the effects of visual background and contribution of head movement in head-free pursuit, in this study we examined smooth gaze pursuit in a young Japanese monkey that was trained to pursue a target moving on the vertical screen at 0.5Hz (±20°). Eye and head movements were recorded by the search coil method. Body movements were restrained and care was taken to minimize the weights of head holder during head-free pursuit. Eye-, head- and gaze- (eye+head) gains (re target velocity) were calculated in head restrained and free conditions with or without a random dot visual background. In head-free pursuit, vertical gaze velocity gains with and without a background were 0.75-0.90 and 0.86-0.97, respectively. Head velocity gains were 0.24-0.44 and were similar with or without a background. Upward gaze velocity was significant lower than downward. Eye velocity gains ranged from 0.41 to 0.65. Upward eye velocity gains were significantly lower than downward in both head-free and restrained conditions. Eye velocity in head-free pursuit led target velocity by the mean of 14°, whereas head velocity lagged target velocity by the mean of 34°. No asymmetry was observed in leftward and rightward pursuit with a background. [Jpn J Physiol 54 Suppl:S181 (2004)]
