| dc.description | Orienting visual attention involves disengaging attention from its current focus, moving it, and engaging it at a new location. A deficit in disengaging attention from the ipsilesional (right) space in order to re-orient toward the contralesional (left) space occurs after right-hemisphere stroke and has been related to the severity of visuospatial neglect. Active and passive left limb movements in left hemispace improve visual scanning and reduce rightward bias on visual extinction and line bisection tasks in individuals with neglect, but the effect of limb movements on the disengage mechanism underlying covert orienting of attention is unknown. Orienting was assessed with no limb movement and after unilateral active and passive limb movements in groups of younger (n=20) and older (n=20) healthy adults and in right-hemisphere stroke patients with (n=3) and without (n=13) neglect. It was hypothesized that left limb movements would reduce the disengage deficit in some right-hemisphere stroke patients by decreasing reaction time to detect left targets after a right exogenous spatial cue. Results showed no effect of limb movement on covert visuospatial orienting in healthy young adults but active limb movements reduced cueing effects in healthy older adults. A disengage deficit in orienting was observed after right-hemisphere stroke that was related in size to neglect severity. As hypothesized, left limb movement reduced the disengage deficit in one neglect participant with a severe disengage deficit. Left limb movements, however, had little effect on orienting in individual neglect participants with a spatial attention bias (i.e., slower overall left target detection, n=2), a mild-to-moderate disengage deficit (n=2) or no disengage deficit (n=11). The left limb movement effect on orienting was restricted to a neglect participant with ventral fronto-parietal orienting network damage and spared superior parietal lobe and subcortical structures involved in right-hemisphere attention and motor pathways. The efficacy of contralesional limb activation in ameliorating orienting deficits in spatial neglect may be dependent upon the presence of a severe disengage deficit and the availability of neural resources in attentional and motor pathways that are capable of facilitating activation in the orienting network and rebalancing neural activity between the two hemispheres. | en_US |
