Handedness change after dominant side amputation: Evaluation from a hand laterality judgment task.

Amputation of the dominant hand forces patients to use their non-dominant hand exclusively. Whether this chronic forced use of the non-dominant hand would affect the handedness preference remains an open question. In this study, the handedness preference in amputees was evaluated using a hand laterality judgment task by comparing recognition speeds of their lost hand and remaining hand. A handedness index was defined as lateralization between response times to the left hand and the right hand. Healthy controls responded faster to the pictures of dominant hand than that of non-dominant hand, while amputees did not show this handedness advantage. The handedness index was significantly correlated to the response time, accuracy, amputation age and the time post amputation. Amputees with poorer performance experienced severer handedness change and new amputees were more likely to suffer handedness change. Our results suggest that handedness is changed after dominant side amputation and the handedness change might not be induced by chronic use of the intact hand.