Abstract
Impairment of sustained attention is assumed to be a core cognitive abnormality in schizophrenia. However, this seems inconsistent with a recent hypothesis that in schizophrenia the implementation of selection (i.e., sustained attention) is intact but the control of selection (i.e., switching the focus of attention) is impaired. Mounting evidence supports this hypothesis, indicating that switching of attention is a bigger problem in schizophrenia than maintaining the focus of attention. To shed more light on this hypothesis, we tested whether schizophrenia patients are impaired relative to controls in sustaining attention, switching attention, or both. Fifteen patients with recent-onset schizophrenia and fifteen healthy volunteers, matched on age and intelligence, performed sustained attention and attention switching tasks, while performance and brain potential measures of selective attention were recorded. In the sustained attention task, patients did not differ from the controls on these measures. In the attention switching task, however, patients showed worse performance than the controls, and early selective attention related brain potentials were absent in the patients while clearly present in the controls. These findings support the hypothesis that schizophrenia is associated with an impairment of the mechanisms that control the direction of attention (attention switching), while the mechanisms that implement a direction of attention (sustained attention) are intact.
Highlights
There is consensus that impairment of attention is a separable and core cognitive abnormality in schizophrenia [1]
It has been argued that schizophrenia is associated with an impairment of the control of information selection while the implementation of information selection is intact [4]. This hypothesis predicts that schizophrenia patients would be impaired in attention switching, but not in sustaining attention, because, as we argue below, attention switching, but not sustaining attention, engages mechanisms required to control the selection of information, while in both types of tasks a specified selection must be implemented
Patients had a smaller CNV (F1,24 = 6.89, p=0.015, η2 = .22) than controls. This experiment evaluates the hypothesis that schizophrenia is associated with a deficit in switching the focus of attention but not with a deficit in sustaining the focus of attention
Summary
There is consensus that impairment of attention is a separable and core cognitive abnormality in schizophrenia [1]. Findings of impaired performance in schizophrenia patients on the classic Stroop color-word test of selective attention [5], are hard to allocate to a deficit at a specific level or in a specific mechanism [6,7,8]. Another example is that early Event-Related brain Potentials (ERPs) associated with selection in the visual modality [9,10,11] and the auditory modality [12,13] are diminished in schizophrenia patients when they perform sequential objectbased selective attention tasks. When they perform spatial selection tasks, the ERPs suggest that early selective attention [14] and selection for visual working memory storage are intact [15]
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