title: Extinction partially reverts structural changes associated with remote fear memory.
abstract: Structural synaptic changes occur in medial prefrontal cortex circuits during remote memory formation. Whether extinction reverts or further reshapes these circuits is, however, unknown. Here we show that the number and the size of spines were enhanced in anterior cingulate (aCC) and infralimbic (ILC) cortices 36 d following contextual fear conditioning. Upon extinction, aCC spine density returned to baseline, but the enhanced proportion of large spines did not. Differently, ILC spine density remained elevated, but the size of spines decreased dramatically. Thus, extinction partially erases the remote memory network, suggesting that the preserved network properties might sustain reactivation of extinguished conditioned fear.
authors.affiliation: Cell Biology and Neurobiology Institute, National Research Council of Italy, Rome, Italy.
authors.forename: Gisella
authors.initials: G
authors.lastname: Vetere
authors.forename: Leonardo
authors.initials: L
authors.lastname: Restivo
authors.forename: Giovanni
authors.initials: G
authors.lastname: Novembre
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Aceti
authors.forename: Massimo
authors.initials: M
authors.lastname: Lumaca
authors.forename: Martine
authors.initials: M
authors.lastname: Ammassari-Teule
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000502:physiology*; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D049229:Dendritic Spines / Q000502:physiology*; D005108:Extinction, Psychological / Q000502:physiology*; D005239:Fear; D006179:Gyrus Cinguli / Q000166:cytology / Q000502:physiology; D008297:Male; D008568:Memory / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology