Comparative characteristics of predictive eye-hand tracking.

Eye and arm-hand movements were recorded in human subjects under three conditions. In the first a spot of light moved 30 deg back and forth sinusoidally at different frequencies. Limits of ocular pursuit were about 60 deg/sec at a frequency of about 1 Hz. In the second condition the arm and hand pointed a lever at the spot of light and pursued the moving visual target together with the eyes. The maximum velocity and frequency of ocular pursuit increased by about 20-30% with the addition of arm-hand movements. The arm and hand could move the lever faster than the eyes could pursue, but phase relations with regard to position between arm-hand movements and the visual target deteriorated at about 2 Hz when the eyes were unable to pursue the target. In the third condition the arm and hand drove the lever in self-paced movements, and the eyes pursued a target at the end of the lever. Maximum eye velocity increased slightly in two of three subjects in this condition, but no eye movements were made above 2.2 Hz. In contrast, self-paced arm and hand movements were made at frequencies up to 5 Hz and velocities of 400 deg/sec. The data are consistent with previous studies that indicate that the limits of ocular pursuit can be extended when eye movements are coupled to efferent signals and/or proprioceptive input from the skeletal motor system. The data also support previous findings of a dual-mode control system for the skeletal musculature during repetitive movements (Freund 1986).(ABSTRACT TRUNCATED AT 250 WORDS)