Abnormal motor asymmetry only during bimanual movement in schizophrenic patients compared with healthy subjects

In schizophrenia, research on motor asymmetry has focused on the direction and the degree of handedness using unimanual motor tests and tasks. However, typically both hands collaborate in the production of most manual movements. This study explored motor asymmetry exhibited during unimanual and bimanual tasks in schizophrenic and healthy subjects using a new experimental motor battery. Specifically, the authors investigated the motor indices of laterality during finger-tapping and hand-turning tasks in four unimanual and four bimanual conditions in 84 schizophrenic and 31 healthy subjects, all right-handed. The schizophrenic patients showed reduced motor asymmetries only during bimanual tapping compared with healthy subjects due to reduction in right-hand performance. These results stress the importance of considering bimanual conditions in the assessment of motor asymmetries, and suggest that it is necessary to use bimanual tasks to test hypotheses about abnormal motor lateralization in schizophrenia.