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Cognitive mechanisms of response initiation in schizophrenia Caissie, Stephanie Leanne


Psychomotor poverty is one syndrome of the three-syndrome model of schizophrenia, and refers to a subset of symptoms which includes flat affect, underactivity, and poverty of speech. The hallmark of psychomotor poverty is diminished mental and physical activity. It has been proposed that deficits in initiation are the core problem in psychomotor poverty (Liddle, 1994; Frith, 1987), although little is understood about the cognitive mechanisms mediating initiation impairments. The current study sought to investigate the role of cognitive set in response initiation using a basic choice reaction time task. The non-designated stimulus reaction time (NDSRT) task involves two conditions. In one condition, subjects are explicitly given a stimulusresponse mapping, thus they have a strong set. In the other, the stimulus-response mapping is implicit and the set is weak. Pilot data indicates that both healthy controls and schizophrenia patients are slower to respond when the set is weak. It addition to replicating this result, it was hypothesized that patients would show more slowing on this condition than controls, and that this slowing would be correlated with psychomotor poverty. This would suggest that responding with a weak, incomplete set is related to symptoms of psychomotor poverty. The results support the above hypotheses. Both patients and controls were significantly slower at responding with a weak set than with a strong set, and this difference was greater in patients. The magnitude of the difference correlated significantly with psychomotor poverty score. These results support the hypothesis that responding with an incompletely mapped set may underlie the initiation deficits of the psychomotor poverty syndrome. These findings have implications for the rehabilitation of individuals with schizophrenia.

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