Role of the corpus callosum in bimanual coordination: a comparison of patients with congenital and acquired callosal damage.

The objective of the study was to investigate temporal control in patients with congenital as compared to acquired pathology of the corpus callosum during two different bimanual paradigms: (i) a drawer-opening task during which one hand opened a drawer while the other hand reached and grasped a small object, and (ii) rhythmical circling movements that were executed according to the in-phase or antiphase mode. Synchronization values revealed that patients with acquired callosal dysfunction generally showed optimal behaviour during the goal-directed and familiar drawer-opening task but demonstrated strong tendencies towards desynchronization during circling movements, which became most apparent for antiphase coordination. Whereas one patient with callosal agenesis showed a similar performance, the other acallosal patients performed both activities successfully. These observations indicate that patients with congenital absence of the corpus callosum can make use of compensatory mechanisms for allowing temporal synchronization during bimanual movements whereas patients with acquired callosal dysfunction are severely hampered when the task places significant demands on the control processes. The data also underline that the ability of callosal patients to precisely time events in coordinated actions depend on the task constraints.