Fig. 4.

Neglect patients have difficulty locating objects in diverse frames of reference. a, In a line cancellation task, subjects with left neglect typically miss many of the targets on the left side of the display. b and c, Stimuli used by Driver and others (1994) to test for object-centered coordinates. The cross indicates the location where subjects had to fixate. The task consisted in detecting a gap like the one shown, except much smaller. In b, the triangles appear to point up and to the right, whereas in c they appear to point up and to the left. Left neglect patients performed significantly better in condition c, where the gap appears to the right of an axis parallel to the pointing direction, even though the central triangle containing the gap is identical in the two situations (Driver and others 1994). This indicates that the location of the gap is at least partly specified in object-centered coordinates.