A COMPARISON OF THE INFLUENCES OF BODY AND ENVIRONMENT CENTERED REFERENCE FRAMES ON NEGLECT

Extrapersonal space can be defined by coordinate systems, or frames of reference, that are centred on the body (viewer) or on the environmen t. Although these frames are identical in the upright position, when t he body is placed in positions orthogonal to gravity, the frames may b e dissociable. We compared the influences of environmental and body-ce ntred frames on line bisection in two patients with neglect who, when upright, neglected opposite dimensions of space. Through certain combi nations of line placement and body orientation the body and environmen tal frames were brought into opposition, and each frame predicted line bisection errors in an opposite direction. When the patients were pos itioned so that predictions of the two frames contrasted both bisected fines as predicted by the environmental rather than the body-centred frame.