Pigache, Robert M.; (1995) The attention deficit of schizophrenia. Doctoral thesis (M.D), UCL (University College London).

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Abstract

Attention is known to be impaired in schizophrenia but the reason remains unclear. A new auditory test was devised (PAT) that measures simultaneously selective attention, sustained attention and the rate of information processing. It was validated by a longitudinal (two year), double-blind, cross-over study of chlorpromazine (CPZ) versus placebo in 20 schizophrenic in-patients, who were tested fortnightly and compared to healthy subjects. The results showed that the essential attention deficit in schizophrenia is intermittent sustained attention. PAT errors increased significantly with placebo and responded to CPZ. The errors discriminated patients from healthy subjects; correlated with parallel clinical ratings; and measured the absolute severity of illness, since normal errors 'predicted' which patients were ready for hospital discharge. Current models of attention are inadequate to explain the PAT findings. Possible causes of the attention defect were examined. It was argued that attention is deployed by plans that are constantly challenged by rival options. Distraction causes a switch of plan when a rival option is adopted. However, increased distractibility does not explain schizophrenia. The defect lies in the selection and maintenance of plans. A new cognitive model was proposed whereby bottom-up 'meaning' and 'top-down' plans are selected by integration with the context. The model was provided with a neurological counterpart. Schizophrenia was presented as an organic psychosis with neuropathology affecting the cortico-thalamic basal ganglia circuit. Derangement of this anatomical circuit impairs working-memory and degrades context. Evidence was insufficient to support a primary integration failure, but degraded context would cause analogous defects. Defects of plan selection (integration with the context) and plan maintenance (working-memory) would disrupt attention. All three aspects of planning are deficient in schizophrenia. The model explained multiple behavioural and cognitive deficits produced by schizophrenia and other neurological conditions, and the PAT results.

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