The brain helps us survive by forming internal representations of the external world. Excitatory cortical neurons are often precisely tuned to specific external stimuli. However, inhibitory neurons, such as parvalbumin-positive (PV) interneurons, are generally less selective.
View Article and Find Full Text PDFExperience-driven alterations in neuronal activity are followed by structural-functional modifications allowing cells to adapt to these activity changes. Structural plasticity has been observed for cortical principal cells. However, how GABAergic interneurons respond to experience-dependent network activity changes is not well understood.
View Article and Find Full Text PDFThe dentate gyrus (DG) output plays a key role in the emergence of spatial and contextual map representation within the hippocampus during learning. Differences in neuronal network activity have been observed between left and right CA1-3 areas, implying lateralization in spatial coding properties. Whether bilateral differences of DG granule cell (GC) assemblies encoding spatial and contextual information exist remains largely unexplored.
View Article and Find Full Text PDFThe medial entorhinal cortex (MEC)-hippocampal network plays a key role in the processing, storage, and recall of spatial information. However, how the spatial code provided by MEC inputs relates to spatial representations generated by principal cell assemblies within hippocampal subfields remains enigmatic. To investigate this coding relationship, we employed two-photon calcium imaging in mice navigating through dissimilar virtual environments.
View Article and Find Full Text PDFOver the past twenty years, the reuniens and rhomboid (ReRh) nuclei, which constitute the ventral midline thalamus, have received constantly growing attention. Since our first review article about the functional contributions of ReRh nuclei (Cassel et al., 2013), numerous (>80) important papers have extended anatomical knowledge, including at a developmental level, introduced new and very original electrophysiological insights on ReRh functions, and brought novel results on cognitive and non-cognitive implications of the ReRh.
View Article and Find Full Text PDFThe ventral midline thalamus contributes to hippocampo-cortical interactions supporting systems-level consolidation of memories. Recent hippocampus-dependent memories rely on hippocampal connectivity remodeling. Remote memories are underpinned by neocortical connectivity remodeling.
View Article and Find Full Text PDFExcitotoxic lesions are frequently used to assess the role of cerebral structures in cognitive processes in rodents. However, the precise site and extent of these lesions remain unknown without histological verifications. Using a 7-Teslas MRI system and a T2-weighted turbo-RARE sequence, MR images were acquired at several time points following NMDA lesions (1h, 6h, 24h, 48h, 1 week and 2 weeks).
View Article and Find Full Text PDFThe reuniens (Re) and rhomboid (Rh) nuclei of the ventral midline thalamus are reciprocally connected with the hippocampus (Hip) and the medial prefrontal cortex (mPFC). Growing evidence suggests that these nuclei might play a crucial role in cognitive processes requiring Hip-mPFC interactions, including spatial navigation. Here, we tested the effect of ReRh lesions on the firing properties and spatial activity of dorsal hippocampal CA1 place cells as male rats explored a familiar or a novel environment.
View Article and Find Full Text PDFLesions 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.
View Article and Find Full Text PDFSystems-level consolidation models propose that recent memories are initially hippocampus-dependent. When remote, they are partially or completely dependent upon the medial prefrontal cortex (mPFC). An implication of the mPFC in recent memory, however, is still debated.
View Article and Find Full Text PDFThe reuniens and rhomboid nuclei, located in the ventral midline of the thalamus, have long been regarded as having non-specific effects on the cortex, while other evidence suggests that they influence behavior related to the photoperiod, hunger, stress or anxiety. We summarise the recent anatomical, electrophysiological and behavioral evidence that these nuclei also influence cognitive processes. The first part of this review describes the reciprocal connections of the reuniens and rhomboid nuclei with the medial prefrontal cortex and the hippocampus.
View Article and Find Full Text PDFElectrophysiological and neuroanatomical evidence for reciprocal connections with the medial prefrontal cortex (mPFC) and the hippocampus make the reuniens and rhomboid (ReRh) thalamic nuclei a putatively major functional link for regulations of cortico-hippocampal interactions. In a first experiment using a new water escape device for rodents, the double-H maze, we demonstrated in rats that a bilateral muscimol (MSCI) inactivation (0.70 vs 0.
View Article and Find Full Text PDFThe 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.
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