Can Visual Neglect Operate in Object-centred Co-ordinates? An Affirmative Single-case Study

Abstract

Clinical evidence from visuospatial neglect suggests that some patients neglect one side of each individual object in a scene, rather than just one side of the scene as a whole. For example, in copying they may produce only the right side of objects from both the right and left of the original drawing. One interpretation of this phenomenon is that neglect may operate in object-centred co-ordinates. We examined this hypothesis in a right-hemisphere damaged patient, PP, who shows severe and intractable left neglect. Her task was to judge whether two elongated nonsense shapes, presented one above the other, were the same or different. When the principal axis of each shape was vertical PP missed differences on the left. When the shapes were both rotated 45° clockwise or anticlockwise, she continued to neglect differences on the left of the objects' axes, even when these differences fell on the right of the sagittal midline. This demonstrates that neglect can be object-centred in the sense of operating relative to principal axes.