title: Error correction in latent inhibition and its disruption by opioid receptor blockade with naloxone.
abstract: Latent inhibition refers to the retardation in the development of conditioned responding when a pre-exposed stimulus is used to signal an unconditioned stimulus. This effect is described by error-correction models as an attentional deficit and is commonly used as an animal model of schizophrenia. A series of experiments studied the role of error-correction mechanism in latent inhibition and its interaction with the endogenous opioid system. Systemic administration of the competitive opioid receptor antagonist naloxone before rats were pre-exposed to a target stimulus prevented latent inhibition of its subsequent fear conditioning; it was without effect on a non-pre-exposed stimulus and did not produce state-dependent learning (Experiments 1a and 1b). Naloxone did not reverse the latent inhibitory effect already accrued to a pre-exposed target. However, it did prevent the enhancement of latent inhibition by a long retention interval interpolated between its initial exposure and re-exposure (Experiment 2) or by a novel stimulus compounded with the pre-exposed target during re-exposure (Experiment 3). These results provide evidence that attentional loss in latent inhibition is instructed by an opioid-mediated error signal which diminishes with repeated stimulus exposures but recovers with the passage of time or reintroduction of novelty.
authors.affiliation: School of Psychology, University of New South Wales, Sydney, NSW, Australia.
authors.forename: Hiu T
authors.initials: HT
authors.lastname: Leung
authors.forename: A S
authors.initials: AS
authors.lastname: Killcross
authors.forename: R Frederick
authors.initials: RF
authors.lastname: Westbrook
mesh_terms: D000818:Animals; D003214:Conditioning, Classical / Q000187:drug effects; D005239:Fear / Q000187:drug effects; D007266:Inhibition, Psychological; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D009292:Narcotic Antagonists; D009270:Naloxone