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Abstract:
Several studies have suggested working memory (WM) capacity
deficits in patients with schizophrenia (SC). In normals, Luck
(1997) demonstrated that visual WM capacity is limited to 3-4
objects, with no impact of multiple features on capacity estimates.
The purpose of the present study was 1) to determine WM capacity in
SC and 2) to determine how this visual WM paradigm relates to
commonly used neuropsychological measures. Twenty SC patients and
18 healthy controls were studied in a change-detection task
involving displays (100ms or 500ms) of 2, 3, 4, and 6 colored bars.
In 50% of the test arrays, one item in the array differed in color,
orientation, or either feature. Patients with SC revealed deficits
in all set sizes, in all conditions, and at both exposure
durations. A lack of higher order interactions involving group
suggests that both groups performed in a qualitatively similar
manner, coding multiple features as integrated objects. Group
differences at all set sizes suggests that the impairment is not
simply a reduction in maximal capacity, but also involves a basic
attentional/encoding deficit. In exploratory regression analyses of
subsamples, performance on this paradigm was related to WMS-III
Spatial Span, and other psychometric measures of WM in controls. In
patients it was related to processing speed only, further
suggesting that visual WM in SC is mediated by attentional/encoding
deficits.
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