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Abstract:
Abstract: Patients with unilateral strokes, especially in the
right hemisphere, exhibit a bias towards stimuli in the
ipsilesional part of visual space (unilateral neglect). To
accurately map this bias, we used a paradigm in which patients
responded to targets that appeared shortly between many visual
distractors blinking randomly all around the visual display
('starry night' display). Attention distribution, indexed by
reaction time and hit rate, was mapped in 2D in left- and
right-hemisphere damaged (LHD and RHD, respectively) patients, and
healthy controls. Controls showed the normal advantage for
center-screen targets over the periphery, whereas LHD patients
showed a small ipselesional bias. RHD patients performed worst
towards the left of the display while exhibiting 'hyperattention'
on the right (faster RTs on the right than in the center),
supporting the attention gradient hypothesis. While on the average,
RHD patients' most severe deficit was in the left lower quadrant,
patients varied in this vertical dimension of neglect. In our
paradigm, 'vertical neglect' cannot be ascribed to fatigue effects
as argued for the conventional scanning tests. Our test was more
sensitive than popular pencil and paper tests in assessing the
spatial distribution of attention over the recovery period
following stroke, and may be used for on-line assessment of the
effect of experimental manipulations on the distribution of
attention. The high resolution of mapping additionally allows
testing of mathematical formulation of attention
distribution.
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