A study of conditioned inhibition procedures in relation to individual differences and disorder

Classical conditioning and conditioned inhibition are fundamental for cognitive processes in both animals and humans. Conditioned inhibition is involved in a wide range of normal behaviour – and its disruption could produce a wide range of behavioural deficits. For example, lack of inhibitory control has been argued to lie at the core of impulsivity (Buss & Plomin, 1975). Impulsivity is one of the core features in some of the clinical groups, such as schizophrenic patients and patients with cluster B personality disorders (PD), especially patients with PD within forensic populations (Hare et al., 1991; Munro et al., 2007). Previous research studied impulsivity by using some laboratory behaviour learning tasks (e.g. Go-NoGo tasks). People with higher impulsivity have difficulty withholding responding which is demonstrated by poor performances in these tasks. Such tasks measured participants’ ability to inhibit pre-potent motor responses, and these tasks are usually thought to involve inhibition of stimulus-response (S-R) association. To date, little research has explored the inhibition of stimulus-stimulus (S-S) associations (formally ‘conditioned inhibition’, CI) in relation to individual differences, and no research has explicitly examined CI learning in any clinical groups. The present study developed a suitable procedure to examine human participants’ conditioned inhibition in a summation test and explored CI learning performance in relation to individual differences and disorders. Two hundred and thirty-seven participants in the University of Nottingham completed a set of questionnaires [BIS/BAS, UPPS, EPQ-RS, O-LIFE (short) and STB] to assess their individual differences and a computer-based experiment to test their excitatory and conditioned inhibitory learning. The results suggested various correlations between the scores of questionnaires and the measures of excitatory and inhibitory learning, which confirmed that the higher impulsivity, neuroticism and schizotypy levels, the less evidence of the excitatory learning. At the same time, the higher anxiety, neuroticism and schizotypy levels, the less evidence of the conditioned inhibition. Twenty-five schizophrenic patients in community-based and 24 patients with PD in forensic settings were also tested using the CI learning task. The results suggested that schizophrenic patients showed a clear reduction in their excitatory and inhibitory learning performance. Moreover, schizophrenic patients with higher negative scores on PANSS, perform worse on the CI learning task. For PD patients at Rampton hospital, the CI effect was abolished in the samples. There was also a significant difference in the CI effect between patients in the PD and the DSPD units. Specifically participants in the DSPD unit showed significantly less CI. Within the clinical samples used in the present study, it was unable to demonstrate any relationship between the levels of CI and medication. Implications of these findings for personality dimensions affect learning in normal populations and clinical groups would be discussed, and further research would be suggested in this thesis.