title: The transition from memory retrieval to extinction.
abstract: Memory is measured by measuring retrieval. Retrieval is often triggered by the conditioned stimulus (CS); however, as known since Pavlov, presentation of the CS alone generates extinction. One-trial avoidance (IA) is a much used conditioned fear paradigm in which the CS is the safe part of a training apparatus, the unconditioned stimulus (US) is a footshock and the conditioned response is to stay in the safe area. In IA, retrieval is measured without the US, as latency to step-down from the safe area (i.e., a platform). Extinction is installed at the moment of the first unreinforced test session, as clearly shown by the fact that many drugs, including PKA, ERK and protein synthesis inhibitors as well as NMDA receptor antagonists, hinder extinction when infused into the hippocampus or the basolateral amygdala at the moment of the first test session but not later. Some, but not all the molecular systems required for extinction are also activated by retrieval, further endorsing the hypothesis that although retrieval is behaviorally and biochemically necessary for the generation of extinction, this last process constitutes a new learning secondary to the unreinforced expression of the original trace.
authors.affiliation: Centro de Memória, ICS, Departamento de Bioquímica, Universidade Federal Do Rio Grande Do Sul, 90035-003 Porto Alegre, RS, Brasil.
authors.forename: Martín
authors.initials: M
authors.lastname: Cammarota
authors.forename: Daniela M
authors.initials: DM
authors.lastname: Barros
authors.forename: Mónica R M
authors.initials: MR
authors.lastname: Vianna
authors.forename: Lia R M
authors.initials: LR
authors.lastname: Bevilaqua
authors.forename: Adriana
authors.initials: A
authors.lastname: Coitinho
authors.forename: Germán
authors.initials: G
authors.lastname: Szapiro
authors.forename: Luciana A
authors.initials: LA
authors.lastname: Izquierdo
authors.forename: Jorge H
authors.initials: JH
authors.lastname: Medina
authors.forename: Iván
authors.initials: I
authors.lastname: Izquierdo
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D001522:Behavior, Animal / Q000502:physiology; D003214:Conditioning, Classical / Q000502:physiology*; D005108:Extinction, Psychological / Q000502:physiology*; D006624:Hippocampus / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008570:Memory, Short-Term / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology