Focal and global attention modulate the expression of visuo-spatial neglect: a case study.

We report a case of severe left visuo-spatial neglect consequent upon right-hemisphere stroke. In Experiment 1, we show that while the patient bisects lines significantly to the right of true centre, he is extremely accurate in placing a mark at the centre of an equivalent outlined square. Experiment 2 confirms that the lateral and radial accuracy obtained in the latter (square) task cannot be predicted from the lateral and radial displacements found in horizontal and vertical (radial) line bisection; the experiment also shows that the individual horizontal lines of a square can be bisected significantly more accurately than the same lines presented individually. Experiment 3 shows that the crucial figural component requisite for the accurate estimation of lateral extent is a large vertical (radial) line in right space. The obtained figural modulation of neglect is consistent with the model in which a large, unitary stimulus in right space engages and enhances the lesioned right hemisphere's intrinsic capacity to deploy global attention.