STRAIGHT-AHEAD POINTING CORRELATES WITH LONG-LINE BISECTION IN NEGLECT PATIENTS

The spatial bias of neglect patients has been assumed to result from the alteration of a body-centred representation which underlies actions within personal and extra-personal spaces. This deficit seems to correspond to the ipsilesional deviation of the subjective straight-ahead (SSA), often described in neglect patients. However, several recent studies have failed to show significant correlations between the SSA deviation and performance in standard visuo-spatial tests of neglect. Since methodological choices could explain these negative results, the present study re-investigated the question. SSA, assessed by manual pointing, was anchored by instructions to a precise median body part. A body-centred line bisection task was also carried out, during the same session and in similar experimental conditions. Sixteen right brain-damaged patients with (n=8) or without (n=8) neglect, and 8 control subjects free of any neurological problem were included. Taken as a group, the neglect group stood out from the others in both tasks. Moreover, in neglect patients only, SSA position significantly correlated with bisection error for long lines, even if dissociations between SSA shift and bisection error were found in two cases. Results are discussed with regard to the nature of the tasks proposed in the different studies and to methodological aspects that could at least partly explain the aforementioned failures.