title: Extinction and Latent Inhibition Involve a Similar Form of Inhibitory Learning that is Stored in and Retrieved from the Infralimbic Cortex.
abstract: Extinction and latent inhibition each refer to a reduction in conditioned responding: the former occurs when pairings of a conditioned stimulus (CS) and an unconditioned stimulus (US) are followed by repeated presentations of the CS alone; the latter occurs when CS alone presentations precede its pairings with the US. The present experiments used fear conditioning to test the hypothesis that both phenomena involve a similar form of inhibitory learning that recruits common neuronal substrates. We found that the initial inhibitory memory established by extinction is reactivated in the infralimbic (IL) cortex during additional extinction. Remarkably, this reactivation also occurs when the initial inhibitory memory had been established by latent inhibition. In both cases, the inhibitory memory was strengthened by pharmacological stimulation of the IL. Moreover, NMDA receptor blockade in the IL disrupted the weakening in conditioned responding produced by either latent inhibition or extinction. These findings, therefore, indicate that latent inhibition and extinction produce a similar inhibitory memory that is retrieved from the IL. They also demonstrate that the IL plays a wide role in fear regulation by promoting the retrieval of inhibitory memories generated by CS alone presentations either before or after this CS has been rendered dangerous.
authors: School of Psychology, University of New South Wales, Sydney NSW 2052, Australia.
authors: Nura W
authors: NW
authors: Lingawi
authors: School of Psychology, University of New South Wales, Sydney NSW 2052, Australia.
authors: R Fredrick
authors: RF
authors: Westbrook
authors: School of Psychology, University of New South Wales, Sydney NSW 2052, Australia.
authors: Vincent
authors: V
authors: Laurent
mesh_terms: D000818:Animals; D001307:Auditory Perception / Q000187:drug effects / Q000502:physiology; D002408:Catheters, Indwelling; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology*; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology*; D004597:Electroshock; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005108:Extinction, Psychological / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D007266:Inhibition, Psychological; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate
keywords: Pavlovian fear conditioning; extinction; infralimbic cortex; inhibition; latent inhibition