SPATIAL COORDINATION IN A BIMANUAL TASK-RELATED TO REGULAR SWITCHING OF MOVEMENT VECTORS

The spatial aspect of cooperation between the two upper extremities wa s investigated using a bimanual task involving drawing simultaneous zi g-zag lines on a vertical surface. In 62 trials by 31 strongly right-h anded subjects three performance types were identified; Type I involve d alternation of dominance in sideways and vertical movement component s, in Type II a constant vertical movement was superimposed upon sidew ays movement, and Type III showed no consistent pattern across the two hands. These performance types differed significantly on the measure oi: spatial coordination, with Type I having the best, and Type III th e poorest. These results suggest that on this bimanual task better spa tial symmetry in limb movement is achieved when both hands employ simi lar within-hand strategies, involving switching between vectors for al l muscle groups.