Perceptual and Action Systems in Unilateral Visual Neglect

In this chapter, an attentional view of neglect is elaborated in which neglect is attributed to a breakdown in the processes enabling stimul on the contralateral side of space to a lesion to “ capture” visual attention.

Abstract

In this chapter we review three different accounts of unilateral neglect: one maintaining that neglect is due to early visual processing deficits; one maintaining that neglect is due to a disorder of an internal representation of space; and one maintaining that neglect is due to a disorder of visual attention. An attentional view of neglect is elaborated in which neglect is attributed to a breakdown in the processes enabling stimul on the contralateral side of space to a lesion to “capture” visual attention. This attentional account predicts that contralateral stimuli may vary according to the ease with which they “capture” the attention of neglect patients. Further, even when “attentional capture” does not occur, attention may nevertheless be consciously directed to the neglected side. Data supporting this position are reported from visual search tasks where targets are defined either by single feature differences relative to distractors or by some combination of local feature information, and where neglect patients are either free to adopt their own search strategy or they are cued to the neglected side. Neglect was more marked in the combined-feature searches than the single-feature searches, and it tended to be reduced by spatial cueing. Implications for understanding unilateral visual neglect and for understanding the operation of normal visual attention are discussed.