BIASED POSTURAL VERTICAL IN HUMANS WITH HEMISPHERIC CEREBRAL-LESIONS

This study was aimed at demonstrating the existence of a biased postur al vertical in humans with a recent cerebral lesion. The postural vert ical of patients and controls was analysed comparatively using a self- regulated balancing task, performed in sitting posture. Patients displ ayed a quite constant (19/22) contralesional tilt of the postural vert ical (mean -2.6 degrees), varying with the severity of their spatial n eglect and hemianaethesia. Eight of them showed a pathological contral esional bias (mean -5.5 degrees) as compared to normals. This result i ndicates an asymmetric process of somatic graviceptive information due to some cerebral lesions. When patients were subjected to a transcuta neous electrical stimulation applied onto the contralesional side of t he neck, body verticality was especially improved in those who showed a pathological bias in the postural vertical. This effect could thus b e due to a reduced distortion in the egocentric co-ordinate system for spatial information processing. (C) 1998 Elsevier Science Ireland Ltd . All rights reserved