Loss of the Kamin blocking effect in acute but not chronic schizophrenics.

Jones, Steven H. and Gray, Jeffrey A. and Hemsley, David R. (1992) Loss of the Kamin blocking effect in acute but not chronic schizophrenics. Biological Psychiatry, 32 (9). pp. 739-755. ISSN 1873-2402

Abstract

Differences between research diagnostic criteria (RDC)-diagnosed acute and chronic schizophrenics and normal controls were studied using a Kamin blocking procedure. Blocking is an established animal learning procedure, thought by some researchers to reflect selective attention; decreased blocking indicates increased processing of irrelevant stimuli. It was predicted that this pattern would be obtained in acute schizophrenics, tested soon after admission, for two reasons: (1) evidence from previous clinical studies indicates that acute schizophrenics are more aware of nonsalient aspects of their environment than controls; and (2) blocking is disrupted in animals in a hyperdopaminergic state and restored by neuroleptic medication. This was the case: acute, but not chronic, schizophrenics showed disrupted blocking. This disruption was especially clear in those acute schizophrenics tested within 2 weeks of hospital admission. By the second test session (in a cross-over design), there was some evidence of normalization in performance in the acute schizophrenics. These findings are considered with regard to the dopamine hypothesis of schizophrenia.