Perceptual and visuomotor processing in spatial neglect

This chapter reviews recent progress on a series of studies in which the phenomena of size and distance distortion in neglect patients are examined. The data agree with the proposal by Bisiach et al. that the enhancement of neglect typically observed for gap bisection relates to the attentional cueing inherent in such tasks and does not reflect differential processing of filled and unfilled spatial intervals. Certainly, the study of neglect has provided compelling evidence that the mechanisms underlying the allocation of spatial attention within single objects may be separable from those governing the distribution of attention between discrete objects. Moreover, a hypothesis predicts that relative lateralization within the environmental frame of reference should be the dominant determinant of size distortion effects. Furthermore, preliminary evidence that neglect patients may indeed show preserved visuomotor guidance despite pronounced perceptual biases is reported. In addition, it is briefly considered how the recent observations on the heterogeneity of size distortion may fit within the general theoretical framework of this chapter.