THE BILATERAL REACH TO GRASP MOVEMENT

This study investigated the kinematic organization of bilateral reach to grasp movements. In Experiment 1 non-homologous bilateral movements were performed. One limb reached to grasp an object using whole hand prehension; the contralateral limb simultaneously reached to grasp an object using precision grip. Corresponding unilateral movements were a ssessed. Movement duration for each limb in the bilateral condition wa s similar. However, with earlier temporal settings for peak wrist acce leration and velocity, the limb performing precision grip showed a lon ger approach (deceleration) phase to the object. Unilateral precision grip movements showed a longer movement duration and deceleration phas e than unilateral whole hand prehension movements. In Experiment 2 hom ologous bilateral movements were assessed. Both limbs performed either a reach and whole hand prehension or a reach and precision grip. Agai n the precision grip movements showed longer movement and deceleration times. Experiment 3 consisted of bilateral non-homologous pointing mo vements and a pointing movement with one limb while reaching to grasp with the contralateral limb. It was found that the earlier temporal se ttings of peak acceleration and velocity with the precision grip limb of the non-homologous bilateral task (Expt. 1) were largely due to the performance of distal grasping actions. It is concluded that a kinema tic parameterization which is independent to each limb is evident for bilateral tasks which require functionally independent actions.