“Paradoxical neglect”: spatial representations, hemisphere-specific activation, and spatial cueing

Abstract

Several recent studies have reported neglect of both the left and right sides of space ("dual neglect"), depending upon particular circumstances, within single patients. A further case, EL, who sustained a unilateral lesion of the left parietal lobe, is reported here. EL shows left neglect in reading and object naming tasks, and right neglect in cancellation, drawing, oral spelling, and copying tasks. In addition, the side neglected can be altered by cueing EL to start copying on the right rather than the left, and by parsing visual displays so that they contain single or multiple objects. EL neglected the left side of single object representations and the right side of representations in which stimuli were coded as separate perceptual objects. We discuss relations between representations of space within and between perceptual objects, the effects of attentional cueing on these spatial representations, and their relation to activation within each cerebral hemisphere.

The interaction of spatial reference frames and hierarchical object representations: Evidence from figure copying in hemispatial neglect

“…We extend the account in the second experiment by including empirical data on a more complex figure-copying task and by showing that the critical assumptions underlying the computational model are sufficiently general to account for neglect performance under these more challenging conditions. Burroughs, & Bateman, 1995). Interestingly, some of these same patients show neglect for entire words on the right in multiple-stimulus displays, simultaneous with the object-based effects, providing support for accounts that posit the involvement of multiple spatial frames and coding between as well as within objects (see Haywood & Coltheart, 2000, for further discussion of neglect dyslexia and other examples of object-based findings).…”

Oculographic analysis of word reading in hemispatial neglect

“…Although most patients with neglect dyslexia also exhibit visuospatial neglect on these standard tasks [4,14], patients may show neglect dyslexia but not neglect on the other standard tasks [15 -18] and vice versa [10,19,20]. The dissociation between neglect dyslexia and visuospatial neglect is also apparent after bilateral lesions in that some patients show left neglect dyslexia but right visuospatial neglect [6,21,22]. Understanding the apparent independence of visuospatial neglect and neglect dyslexia is critical as it suggests that the spatial representation of words may differ from the spatial representations used in other kinds of visual tasks.…”

Visual Neglect in Horizontal and Radial Space: When Left Goes Right, Proximal Goes Distal

“…'s horizontal neglect. Based on studies reviewed above Na et al, 2000;Riddoch et al, 1995), we administered a bisection task in which the physical dimensions and configuration of stimuli were manipulated. Assuming that these stimulus changes reversed the direction of bias, it would then be possible (in a second experiment) to re-orient stimuli along the radial plane to determine if a similar reversal occurred during radial bisection.…”

“…However, a minority of sufferers show a bi-directional pattern of impairment within peri-personal space, neglecting the left-side under some conditions and the right-side under others. Cases include those who ignore the left-hand side of displays when reading but the right side during copying and drawing , or ignore the left side during picture naming, but the right side when spelling (Riddoch, Humphreys, Luckhurst, Burroughs, & Bateman, 1995). This reversible spatial bias is taken to reflect a quality that runs to the heart of neglect.…”