An examination of the suppression of overlearned responses in schizophrenia

Individuals often experience interference from overlearned responses. This phenomenon is reported to be increased in patients with schizophrenia.

In order to determine the generality of such interference in these patients, the frequency of repetitive responses in simple tasks was manipulated. It was hypothesised that patients' performance would be disproportionately impaired when a strong response tendency needed to be overridden. This was expected to be the case especially where task rules had to be maintained for a period of time in order to respond appropriately.

A spatial analogue of the Stroop test, with a response bias to a side of space, produced stronger expectancy in patients than in controls. A similar manipulation of expectancy in a variant of the Continuous Performance Test, in which subjects were to respond to sequentially presented pairs of letters, did not result in a difference between patients and controls in terms of inhibiting inappropriate responses. In this test, patients' deficits were associated with the delay period between stimulus and target.

The cognitive impairment in patients with schizophrenia is not simply a general deficit in the suppression of overlearned responses, rather, the susceptibility to interference appears more task specific.