Grey Scales uncover similar attentional effects in homonymous hemianopia and visual hemi-neglect

Grey Scales uncover similar attentional effects in homonymous hemianopia and visual hemi-neglect * 1. Abstract Multi-component models of visual hemi-neglect have postulated that visual hemi-neglect is characterised by various attentional deficits. A Grey Scales-task has been developed to quantify the early, automatic, (perhaps obligatory) ipsilesional orienting of visual attention, frequently assumed as the first of these attentional deficits. Explanations for this attentional imbalance are up until now mainly formulated in terms of right hemisphere activation. This lateral attentional bias has also been demonstrated in controls, in whom it is expressed as a leftward perceptual asymmetry. We reproduced previous literature findings on a Grey Scales-task, considering controls and neglect patients. Three patients with neglect showed an extreme ipsilesional lateral bias. This bias did not change during or after cognitive rehabilitation. Additionally, we presented this Grey Scale-task to 32 patients with left-and right-sided homonymous hemianopia (HH). Homonymous hemianopia is the loss of sight in one visual hemi-field. The HH patients had no clinical signs of impaired lateralised attention. Results revealed that HH patients showed a similar ipsilesional bias, albeit to a lesser degree than in neglect. Left-sided HH patients presented a quantitatively similar, but qualitatively opposite bias than the right-sided HH patients. We suggest that sensory effects can be an alternative source of attentional imbalance, which can interact with the previously proposed (right) hemispheric effects. This suggests that the perceptual asymmetry in the Grey Scales-task is not necessarily an indicator of impaired right hemisphere attention. It rather suggests a pattern of functional cerebral asymmetry, which can also be caused by asymmetric sensory input. suggested that the clinical syndrome of unilateral visual spatial neglect (UN) can be described/explained as a series of successive attentional events beginning with (1) an early, automatic, chronic, perhaps obligatory, orienting of attention toward the ipsilesional half space, followed by (2) a deficit in disengaging attention from that side in order to reorient it toward the contralateral half space. In addition to these two deficits, (3) a generalised (i.e. directionally non-specific) reduction in attentional-information processing capacity is assumed. The first component underlies an anomalous lateral preference. The second component gives rise to the clinical signs of UN (e.g. left-sided omissions on cancellation tasks) [23]. Karnath [16] proposed that this second component (reorienting) recovers faster than the other two, and this has been confirmed by several authors (e.g. [28, 23]). Mattingley and colleagues [23] concluded that the apparent recovery of …