Left of what? The role of egocentric coordinates in neglect

OBJECTIVES—Egocentric coordinate systems centredon the trunk, head, and gaze have been investigated in a patient whodisplays severe extrapersonal neglect and in five control subjects.
METHODS—The subjects were tested with a blindtactile exploration task in five different experimental conditions inwhich the role of the three distinct frames of reference wasindividually controlled.
RESULTS—Only the trunk centred coordinatessignificantly influenced the performance of the patient, thereforeproving of paramount importance in determining the boundaries of theneglected field. Similar results emerged from a single word readingtask, in which the patient's performance improved when the stimuliwere presented to the right of his body's midline.
CONCLUSION—These findings point to the importanceof the body centred coordinate system in determining the area ofextrapersonal spatial neglect.