MANUO-OCULAR COORDINATION IN TARGET TRACKING .2. COMPARING THE MODEL WITH HUMAN-BEHAVIOR

Several studies have shown that humans track a moving visual target wi th their eyes better if the movement of this target is directly contro lled by the observers hand. The improvement in performance has been at tributed to coordination control between the arm motor system and the smooth pursuit (SP) system. In such a task, the SP system shows charac teristics that differ from those observed during eye-alone tracking: l atency (between the target-arm and the eye motion onsets) is shorter, maximum SP velocity is higher and the maximum target motion frequency at which the SP can function effectively is also higher. The aim of th is article is to qualitatively evaluate the behavior of a dynamical mo del simulating the oculomotor system and the arm motor system when bot h are involved in tracking visual targets. The evaluation is essential ly based on a comparison of the behavior of the model with the behavio r of human subjects tracking visual targets under different conditions . The model has been introduced and quantitatively evaluated in a comp anion paper. The model is based on an exchange of internal information between the two sensorimotor systems, mediated by sensory signals (vi sion, arm muscle proprioception) and motor signals (arm motor command copy). The exchange is achieved by a specialized structure of the cent ral nervous system, previously identified as a part of the cerebellum. Computer simulation of the model yielded results that fit the behavio r of human subjects observed during previously reported experiments, b oth qualitatively and quantitatively. The parallelism between physiolo gy and human behavior on the one hand, and structure and simulation of the model on the other hand, is discussed.