Line bisection in visuo-spatial neglect: disproof of a conjecture.

We describe two patients with left neglect who show a linear relationship between the magnitude of their line bisection displacements and the veridical length of the line presented. For lines smaller than those typically employed in previous investigations, the patients' mean performance is fairly accurate; with even smaller lines, the direction of displacement crosses over true centre to give a leftward displacement ('right neglect'). In both cases, the slope of the regression line falsifies the conjecture that (intact) left hemisphere mechanisms (correctly) bisect the (subtotal or supertotal) line length that is available in right hemispace.