Matching and imitation of hand and finger posturesin patients with damage in the left or right hemispheres

Abstract

To disentangle perceptual, conceptual and motor aspects of imitation of gestures,reproduction of meaningless postures of either the hand or the fingers was examined in twoconditions. In the matching test a target gesture had to be identified among an array of fourgestures performed by different persons and seen under different angles of views. For imitation,the same gestures had to be imitated. Thirty five patients with LBD, 21 patients with RBD, and17 healthy controls were examined. LBD patients had more difficulties with imitation than withmatching while RBD patients had more difficulties with matching than with imitation. Regardlessof whether imitation or matching was tested, LBD patients made more errors with hand than withfinger postures whereas RBD patients made more errors with finger than with hand postures. Thisconstellation of results is compatible with the assumption that errors are caused by faultyvisuoperceptual processing in RBD, and by defective conceptual mediation in LBD. Defectivemotor execution does not appear to be a significant source of imitation errors in either group.