Evidence from unilateral visual neglect

Abstract

We report the case of a patient, JR, who manifests left neglect in reading single words but right neglect in copying and drawing tasks. We show that left neglect is not confined to reading, but is also found in picture naming and in line-bisection tasks. In each of these tasks, JR neglected the right side of multiple stimulus displays. We show that neglect is manifest on the left or right side as a function of whether visual stimuli are encoded as parts of a single perceptual object or as separate perceptual objects. JR's left neglect in reading words can be switched to right neglect by having him read aloud all the letters in the string. He also showed left neglect in a search task in which the visual elements configure into a coherent object, but right neglect in displays using similar elements which did not so configure. JR's case demonstrates that the visual system employs separate representations to encode the spatial relations between the parts of single objects (within-object spatial coding) and between separate perceptual objects (between-object spatial coding). These two forms of spatial representation are encoded independently and in parallel.