The ventral midline thalamus and long-term memory: What consolidation, what retrieval, what plasticity in rodents?

The ventral midline thalamus, including the reuniens and rhomboid (ReRh) nuclei, connects bidirectionally with the medial prefrontal cortex (mPFC) and hippocampus (Hip), both essential for memory processes. This review compiles and discusses studies on a role for the ReRh nuclei in the system consolidation of memories, also considering their potentially limited participation in memory retrieval or early phases of consolidation. It also examines scientific literature on short- and long-term plasticity in ReRh-mPFC and ReRh-Hip connections, emphasizing plasticity's importance in understanding these nuclei's role in memory. The idea that the two nuclei are at the crossroads of information exchange between the mPFC and the Hip is not new, but the relationship between this status and the plasticity of their connections remains elusive. Since this perspective is relatively recent, our concluding section suggests conceptual and practical avenues for future research, aiming perhaps to bring more order to the apparently multi-functional implication of the ventral midline thalamus in cognition. •Reuniens/rhomboid (ReRh) nuclei connect with medial prefrontal cortex and hippocampus.•ReRh orchestrate hippocampus-cortex interactions supporting systemic consolidation.•ReRh play little role in retrieval and early consolidation of configurational memories.•Fibers to and from ReRH show short- and long-term synaptic plasticity, key for memory.•ReRh lesions disrupt dendritic spine maturation supporting remote not recent memory.