title: The ventral midline thalamus (reuniens and rhomboid nuclei) contributes to the persistence of spatial memory in rats.
abstract: The formation of enduring declarative-like memories engages a dialog between the hippocampus and the prefrontal cortex (PFC). Electrophysiological and neuroanatomical evidence for reciprocal connections with both of these structures makes the reuniens and rhomboid nuclei (ReRh) of the thalamus a major functional link between the PFC and hippocampus. Using immediate early gene imaging (c-Fos), fiber-sparing excitotoxic lesion, and reversible inactivation in rats, we provide evidence demonstrating a contribution of the ReRh to the persistence of a spatial memory. Intact rats trained in a Morris water maze showed increased c-Fos expression (vs home cage and visible platform groups: >500%) in the ReRh when tested in a probe trial at a 25 d delay, against no change at a 5 d delay; behavioral performance was comparable at both delays. In rats subjected to excitotoxic fiber-sparing NMDA lesions circumscribed to the ReRh, we found normal acquisition of the water-maze task (vs sham-operated controls) and normal probe trial performance at the 5 d delay, but there was no evidence for memory retrieval at the 25 d delay. In rats having learned the water-maze task, lidocaine-induced inactivation of the ReRh right before the probe trial did not alter memory retrieval tested at the 5 d or 25 d delay. Together, these data suggest an implication of the ReRh in the long-term consolidation of a spatial memory at the system level. These nuclei could then be a key structure contributing to the transformation of a new hippocampal-dependent spatial memory into a remote one also depending on cortical networks.
authors: Laboratoire d'Imagerie et de Neurosciences Cognitives, UMR 7237 Centre National de la Recherche Scientifique, Université de Strasbourg, Institut Fédératif de Recherche 37 de Neurosciences, GDR 2905 du CNRS, Faculté de Psychologie, F-67000 Strasbourg, France.
authors: Michaël
authors: M
authors: Loureiro
authors: Thibault
authors: T
authors: Cholvin
authors: Joëlle
authors: J
authors: Lopez
authors: Nicolas
authors: N
authors: Merienne
authors: Asma
authors: A
authors: Latreche
authors: Brigitte
authors: B
authors: Cosquer
authors: Karine
authors: K
authors: Geiger
authors: Christian
authors: C
authors: Kelche
authors: Jean-Christophe
authors: JC
authors: Cassel
authors: Anne
authors: A
authors: Pereira de Vasconcelos
mesh_terms: D000818:Animals; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D020644:Midline Thalamic Nuclei / Q000187:drug effects / Q000503:physiopathology*; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D016202:N-Methylaspartate / Q000633:toxicity; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D013037:Spatial Behavior / Q000187:drug effects / Q000502:physiology*
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D016202:N-Methylaspartate