Mirror images and unilateral spatial neglect

Responding correctly to a mirror image requires the creation of a rather pe culiar form of dual representation. Mirror agnosia and mirror ataxia, i.e. a deficit in reaching an object reflected in a mirror, have been reported t o be associated with parietal lobe lesions. This prospective study was cond ucted to investigate the capacity of subjects with neglect to identify the mirror image nature of visual information. Four consecutive brain-damaged p atients with neglect, selected on the basis of specific criteria, and four control subjects performed grasping and object displacement tests under two response conditions (normal mirror and inverted mirror). Video recordings of the tests were analyzed to assess performance using the following criter ia: (i) direction of the arm movement during the initial phase of movement, (ii) number of corrections of the hand position before grasping. The contr ol subjects successfully grasped the objects in both experimental condition s. The patients (1) neglected the contralesional space, grasping objects co rrectly in the ipsilesional space (normal mirror condition) and (2) neglect ed the ipsilesional space, grasping a correctly objects in the contralesion al space (inverted mirror). Controls used real object-centered correction c lues to modify the position and direction of their hand movement. The patie nts only produced horizontal displacements of the upper limb in the 'health y' and neglected space. These results suggest that patients with neglect do not use the same clues and do not modify their procedures as they cannot r ecalibrate their spatial representations. These differences concerned non-m irror-image clues and directional and positional as well as attentional vec tors. Theoretical and rehabilitative implications are discussed. (C) 2001 E lsevier Science Ltd. All rights reserved.