Oculomanual Coordination in Tracking of Pseudorandom Target Motion Stimuli

Oculomanual coordination was investigated in 9 healthy subjects during tracking of pseudorandom motion stimuli. Each subject was required to track visual stimuli under eye-hand (EH) and eye-alone (EA) conditions. Subjects were exposed to 3 types of mixed sinusoidal stimulus with varying frequency or amplitude of the highest frequency component, or various degrees of irregularity. Progressive degradation in tracking performance was nonlinearly induced by an increase in either (a) the highest frequency component or (b) its amplitude, but not by stimulus irregularity. No significant difference was found in eye velocity gain and phase under the EH and EA conditions. Eye and hand responses were found to be highly correlated in gain and phase when compared across frequencies and motion stimuli. The results suggest that frequency and amplitude are dominant factors controlling the breakdown of oculomanual performance in response to pseudorandom stimuli. Frequency responses of smooth pursuit eye movements are not affected by the hand motion in pursuit of unpredictable stimuli. Eye and hand motor systems appear to share common nonlinear drive mechanisms when pursuing pseudorandom target motion stimuli.