Reducing rightward bias of subjective straight ahead in neglect patients by changes in body orientation.
Résumé
BACKGROUND: The subjective straight ahead (SSA), a measure of the representation of body orientation, has been shown to be shifted to the lesion side in neglect patients, and to be influenced by stimulation of sensory systems involved in postural control. METHOD: This study investigates the influence of changing body orientation in the sagittal plane on the SSA in 21 patients with a right hemispheric lesion, of whom 12 had neglect, in comparison with six healthy control subjects. In order to quantify both horizontal components of SSA error (ie, yaw rotation and lateral shift), the study used a method requiring the alignment of a luminous rod with SSA. RESULTS: Neglect patients showed a significant rightward shift in the sitting position, which was greatly reduced in the supine position. No shift occurred in patients without neglect or in controls. Yaw rotation did not reach significance in any group. CONCLUSION: The data showed that the body centred frame of reference, mostly translated in neglect, is strongly improved in the supine position. Changing body orientation seems to be a convenient tool to correct the representation of body midline.