Egocentric frame of reference: its role in spatial bias after right hemisphere lesions

The reference shift hypothesis of unilateral neglect holds that spatial bia s in left neglect stems from a rightward deviation of patients' egocentric frame of reference (ER). Twenty five unselected right brain-damaged patient s participated in a straight-ahead pointing task to assess the position of their ER (Experiment 1). A rightward ER shift emerged only in the subgroup of patients with extensive parietal lesions. In Experiment 2, we found that the position of the ER did not predict the outcome of various visuospatial neglect tests (r = 0.07 to 0.27). In Experiment 2, no significant positive correlation emerged between the ER position and visual (r = 0.26) or tacti le (r = -0.48) extinction. Two further experiments examined the relationshi ps between the ER position and patients' performance on a reaction time tes t of directional motor bias (Experiment 4), and on a test of response times to lateralised visual stimuli (Experiment 5). Results showed that the ER p osition did not predict the distribution of accuracy scores or response tim es in either task (Experiment 3: accuracy: r = 0.06; response times: r = 0. 16; Experiment 4. accuracy: r = 0.09; response times: r = 0.04). We conclud ed that the position of the ER plays no crucial role in the behavioural con sequences of spatial bias induced by right hemisphere lesions, (C) 1999 Els evier Science Ltd. All rights reserved.