Article

In visual hemi-neglect, non-spatial deficits such as reduced intrinsic alertness
can significantly modulate the degree of left visual field inattention. However,
to date, the precise mechanisms mediating this effect are hardly understood. In
the present study, we assessed the influence of increased alertness on both
general attentional capacity (perceptual processing speed) and spatial
attentional selection processes (spatial distribution of attentional weighting).
For this purpose, a whole-report paradigm based on Bundesen's 'theory of visual
attention' (TVA) was combined with a non-spatial, visual alerting cue. Three
different cue-target stimulus onset asynchronies (SOAs; of 80, 200, and 650 ms),
allowed us to observe the time course of the alerting-cue effects. A group of six
patients with visual hemi-neglect was examined and their performance compared
with six healthy control subjects matched for age, gender, and education. In
neglect patients, the alerting cue evoked a phasic increase of perceptual
processing speed. However, this effect was mainly found in the ipsilateral, i.e.
in the "preserved" hemifield. Importantly, however, patients displayed a
fast-evolving and short-lasting, phasic modulation of spatial attentional
weighting, with a re-distribution of attentional weights from the pathological
rightward bias to a normal, more balanced distribution of visual attention. In
control participants, the cueing effects on perceptual processing speed and
spatial weighting were generally less pronounced than in neglect patients.
Replicating results of a prior study, cueing induced a stable, slightly leftward,
distribution of attentional weights, whilst in the no-cue condition, a temporary
rightward shift of attentional weights was found. This pattern of effects
suggests a close interaction between alertness and spatial-attentional weighting
in the syndrome of visual hemi-neglect. It supports the hypothesis that the
manifestation of spatial neglect involves at least in part intrinsic alertness
deficits. It also provides clues to a more detailed account of the mechanisms
responsible for alleviating neglect in patients following manipulations of the
alertness level, both in the short (cueing) and in the long term (alertness
training).
CI - Copyright (c) 2012 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS