Head and trunk orientation modulate visual neglect.

Five patients with left visual neglect after right hemisphere lesions were examined with a line bisection and a reading task under five different conditions: head and trunk straight ahead, head or trunk oriented 20 degrees to the left and head or trunk oriented 20 degrees to the right. Fixation was always straight ahead. Five patients with right hemisphere lesions but without neglect and five normal subjects served as controls. In all neglect patients, turning the head or trunk to the left reduced line bisection and reading errors significantly as compared with the other three conditions and with the control groups. The modulation of neglect behaviour by trunk as well as head position supports the hypothesis of a disturbed egocentric coordinate system leading to neglect.