Left of what? The role of egocentric coordinates in neglect

Abstract

Objectives: Egocentric coordinate systems centred on the trunk, head, and gaze have been investigated in a patient who displays severe extrapersonal neglect and in five control subjects.

Methods: The subjects were tested with a blind tactile exploration task in five different experimental conditions in which the role of the three distinct frames of reference was individually controlled.

Results: Only the trunk centred coordinates significantly influenced the performance of the patient, therefore proving of paramount importance in determining the boundaries of the neglected field. Similar results emerged from a single word reading task, in which the patient's performance improved when the stimuli were presented to the right of his body's midline.

Conclusion: These findings point to the importance of the body centred coordinate system in determining the area of extrapersonal spatial neglect.