Impaired conditional discrimination learning in schizophrenia

Learning deficits have repeatedly been found in patients with schizophrenia. Eyelid conditional discrimination learning (ECDL) is a test of discriminative aversive conditioning and places minimal demands on motivation. An ECDL task was used to examine residual and paranoid type individuals with schizophrenia and age- and gender-equivalent healthy controls. In the experiment two differently colored light stimuli were randomly presented. Only one of the stimuli (in reinforced trials) was followed by an aversive airpuff to the cornea, as opposed to unreinforced trials where the stimulus was not followed by an aversive airpuff. Conditioned responses develop to both trial types during the course of the experiment. These conditioned responses consist of reflectory eyelid closures already upon light presentation. The patients showed significantly impaired conditional discrimination learning abilities. There was no significant difference between the results in the two schizophrenia subtypes. Patients failed to increase response frequencies on reinforced trials during the course of the experiment, while controls showed appropriate conditional discrimination ability. Thus the results show an impairment of adequate behavior modification in an aversive conditioning task in individuals with schizophrenia. It is concluded that ECDL might be a trait marker for schizophrenia.