The reuniens and rhomboid nuclei are necessary for contextual fear memory persistence in rats

Etienne Quet, Monique Majchrzak, Brigitte Cosquer, Thomas Morvan, Mathieu Wolff, Jean-Christophe Cassel, Anne Pereira de Vasconcelos, Aline Stéphan
Brain Struct Funct. 2020-03-07; :
DOI: 10.1007/s00429-020-02048-z

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Quet E(1)(2), Majchrzak M(1)(2), Cosquer B(1)(2), Morvan T(1)(2), Wolff M(3)(4), Cassel JC(1)(2), Pereira de Vasconcelos A(1)(2), Stéphan A(5)(6).

Author information:
(1)Laboratoire de Neurosciences Cognitives et Adaptatives, LNCA, UMR7364, CNRS, Université de Strasbourg, 67000, Strasbourg, France.
(2)Centre National de la Recherche Scientifique, LNCA UMR 7364, 67000, Strasbourg, France.
(3)Centre National de la Recherche Scientifique, INCIA, Unité Mixte de Recherche 5287, Bordeaux, France.
(4)Université de Bordeaux, INCIA, Unité Mixte de Recherche 5287, Bordeaux, France.
(5)Laboratoire de Neurosciences Cognitives et Adaptatives, LNCA, UMR7364, CNRS, Université de Strasbourg, 67000, Strasbourg, France.
(6)Centre National de la Recherche Scientifique, LNCA UMR 7364, 67000, Strasbourg, France.

Memory persistence refers to the process by which a temporary, labile memory is transformed into a stable and long-lasting state. This process involves a reorganization of brain networks at systems level, which requires functional interactions between the hippocampus (HP) and medial prefrontal cortex (mPFC). The reuniens (Re) and rhomboid (Rh) nuclei of the ventral midline thalamus are bidirectionally connected with both regions, and we previously demonstrated their crucial role in spatial memory persistence. We now investigated, in male rats, whether specific manipulations of ReRh activity also affected contextual and cued fear memory persistence. We showed that the permanent ReRh lesion impaired remote, but not recent contextual fear memory. Tone-cued recent and remote fear memory were spared by the lesion. In intact rats, acute chemogenetic ReRh inhibition conducted before recall of either recent or remote contextual fear memories produced no effect, indicating that the ReRh nuclei are not required for retrieval of such memories. This was also suggested by a functional cellular imaging approach, as retrieval did not alter c-fos expression in the ReRh. Collectively, these data are compatible with a role for the ReRh in ‘off-line’ consolidation of a contextual fear memory and support the crucial importance of ventral midline thalamic nuclei in systems consolidation of memories.

 


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