title: Environmental enrichment enhances systems-level consolidation of a spatial memory after lesions of the ventral midline thalamus.
abstract: Lesions of the reuniens and rhomboid (ReRh) thalamic nuclei in rats do not alter spatial learning but shorten the period of memory persistence (Loureiro et al. 2012). Such persistence requires a hippocampo-cortical (prefrontal) dialog leading to memory consolidation at the systems level. Evidence for reciprocal connections with the hippocampus and the medial prefrontal cortex (mPFC) makes the ReRh a potential hub for regulating hippocampo-cortical interactions. As environmental enrichment (EE) fosters recovery of declarative-like memory functions after diencephalic lesions (e.g., anterior thalamus), we studied the possibility of triggering recovery of systems-level consolidation in ReRh lesioned rats using a 40-day postsurgical EE. Remote memory was tested 25days post-acquisition in a Morris water maze. The functional activity associated with retrieval was quantified using c-Fos imaging in the dorsal hippocampus, mPFC, intralaminar thalamic nuclei, and amygdala. EE enhanced remote memory in ReRh rats. Conversely, ReRh rats housed in standard conditions were impaired. C-Fos immunohistochemistry showed a higher recruitment of the mPFC in enriched vs. standard rats with ReRh lesions during retrieval. ReRh rats raised in standard conditions showed weaker c-Fos expression than their sham-operated counterparts. The reinstatement of memory capacity implicated an EE-triggered modification of functional connectivity: EE reduced a marked lesion-induced increase in baseline c-Fos expression in the amygdala. Thus, enriched housing conditions counteracted the negative impact of ReRh lesions on spatial memory persistence. These effects could be the EE-triggered consequence of an enhanced neuronal activation in the mPFC, along with an attenuation of a lesion-induced hyperactivity in the amygdala.
authors.affiliation: Laboratoire de Neurosciences Cognitives et Adaptatives, Université de Strasbourg, F-67000 Strasbourg, France; LNCA, UMR 7364 - CNRS, F-67000 Strasbourg, France.
authors.forename: Mohamad
authors.initials: M
authors.lastname: Ali
authors.affiliation: Laboratoire de Neurosciences Cognitives et Adaptatives, Université de Strasbourg, F-67000 Strasbourg, France; LNCA, UMR 7364 - CNRS, F-67000 Strasbourg, France.
authors.forename: Thibault
authors.initials: T
authors.lastname: Cholvin
authors.affiliation: Laboratoire de Neurosciences Cognitives et Adaptatives, Université de Strasbourg, F-67000 Strasbourg, France; LNCA, UMR 7364 - CNRS, F-67000 Strasbourg, France.
authors.forename: Marc Antoine
authors.initials: MA
authors.lastname: Muller
authors.affiliation: Laboratoire de Neurosciences Cognitives et Adaptatives, Université de Strasbourg, F-67000 Strasbourg, France; LNCA, UMR 7364 - CNRS, F-67000 Strasbourg, France.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Cosquer
authors.affiliation: Laboratoire de Neurosciences Cognitives et Adaptatives, Université de Strasbourg, F-67000 Strasbourg, France; LNCA, UMR 7364 - CNRS, F-67000 Strasbourg, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Kelche
authors.affiliation: Laboratoire de Neurosciences Cognitives et Adaptatives, Université de Strasbourg, F-67000 Strasbourg, France; LNCA, UMR 7364 - CNRS, F-67000 Strasbourg, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Cassel
authors.affiliation: Laboratoire de Neurosciences Cognitives et Adaptatives, Université de Strasbourg, F-67000 Strasbourg, France; LNCA, UMR 7364 - CNRS, F-67000 Strasbourg, France. Electronic address: pereira@unistra.fr.
authors.forename: Anne
authors.initials: A
authors.lastname: Pereira de Vasconcelos
mesh_terms: D000679:Amygdala / Q000378:metabolism; D000818:Animals; D004777:Environment; D006624:Hippocampus / Q000378:metabolism; D006799:Housing, Animal; D008297:Male; D018782:Maze Learning / Q000502:physiology; D000069077:Memory Consolidation / Q000502:physiology*; D020644:Midline Thalamic Nuclei / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D065852:Spatial Memory / Q000502:physiology*
chemical_list: D016760:Proto-Oncogene Proteins c-fos
keywords: Enriched environment; Hippocampus; Prefrontal cortex; Rat; Reuniens and rhomboid nuclei; Systems-level consolidation