CEREBRAL-DOMINANCE AND ASYNCHRONY BETWEEN BIMANUAL 2-DIMENSIONAL MOVEMENTS

The asynchrony of bimanual movements was investigated. Right- and left -handers traced simple geometrical patterns (ellipses) continuously wi th both hands. All combinations of the direction of rotation in each h and were executed at different rhythms. Geometrically, performances we re largely independent of manual dominance. However, by comparing the passage times at homologous positions. the authors found that the domi nant hand led the nondominant one by about 25 ms. The asynchrony was a ffected by neither movement type nor rhythm. The variability of the as ynchrony varied along the trajectory, with well-defined maxima and min ima. The variability profiles for movements that engaged homologous mu scles differed markedly from those that engaged nonhomologous muscles. The authors discuss the hypothesis that bimanual periodic movements a re timed by a lateralized functional module and asynchrony is due to t he necessity of transmitting time-keeping information to the other hem isphere.