Neuroscience
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We have recently shown that folate deficiency induces depression-like behavior and neuronal immaturity in the dentate gyrus (DG) in mice. We also revealed that folate deficiency inhibits neuronal maturation, hypomethylates the promoter of certain neuronal genes and decreases intracellular levels of S-adenosylmethionine (SAM), a methyl donor, in cultured neural stem and progenitor cells. Based on these findings, we hypothesized that SAM reduction may be involved in a folate deficiency-induced depressive state and neural immaturity. ⋯ Furthermore, neurofunctional and neuromorphological abnormalities in the DG of low folate diet-fed mice, such as decreases in stress-induced expression of c-Fos (a neuronal activity marker), dendritic complexity and the number of mature spines, were improved by SAM supplementation. The disrupted expression of transcription factors involved in neuronal differentiation and maturation was also normalized by SAM supplementation. These results suggest that SAM reduction may be involved in a folate deficiency-induced depressive state.
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Several studies have reported similar neural modulations between brain areas of the frontal cortex, such as the dorsolateral prefrontal (DLPFC) and the premotor dorsal (PMd) cortex, in tasks requiring encoding of the abstract rules for selecting the proper action. Here we compared the neuronal modulation of the DLPFC and PMd of monkeys trained to choose the higher rank from a pair of abstract images (target item), selected from an arbitrarily rank-ordered set (A > B > C > D > E > F) in the context of a transitive inference task. Once acquired by trial-and-error, the ordinal relationship between pairs of adjacent images (i.e., A > B; B > C; C > D; D > E; E > F), monkeys were tested in indicating the ordinal relation between items of the list not paired during learning. ⋯ This result is in line with the hypothesis that after learning, the monkeys built an abstract mental representation of the ranked items, where rank comparisons correspond to the items' position comparison on this representation. In both brain areas, we observed higher neuronal activity when the target item appeared in a specific location on the screen with respect to the opposite position and that this difference was particularly enhanced at lower degrees of difficulty. By comparing the time evolution of the activity of the two areas, we observed that the neural encoding of target item spatial position occurred earlier in the DLPFC than in the PMd.
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Hypoxia and ischemia cause neonatal encephalopathy and brain injury and can further result in cerebral palsy, cognitive impairment, growth restriction, and epilepsy. Induction of neuroprotection is a crucial therapeutic strategy for the treatment of perinatal hypoxic-ischaemic encephalopathy (HIE). Hydrogen has neuroprotective effects against brain-related diseases. ⋯ Moreover, the oxidative products reactive oxygen species (ROS) and malondialdehyde (MDA) and the cytokines tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6) and High mobility group box 1 (HMGB1) were reduced and the antioxidant enzymes Superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) were upregulated by hydrogen treatment after HI in WT mice, but not in Nrf2-/- mice. In addition, the absence of Nrf2 abolished the suppressive effect of hydrogen on the expression of Nacht, Lrr, and Pyd domains-containing protein 3 (NLRP3) pathway members and p65 NF-κB after HI. Taken together, our findings showed that hydrogen alleviated cellular injury and apoptosis, neurobehavioural deficits, the inflammatory response and oxidative stress via the Nrf2-mediated NLRP3 and NF-κB pathways.
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The primary motor cortex, a dynamic center for overall motion control and decision making, undergoes significant alterations upon neural stimulation. Over the last few decades, data from numerous studies using rodent models have improved our understanding of the morphological and functional plasticity of the primary motor cortex. ⋯ However, whether the modifications of specific synapses are associated with motor learning should be studied further. In this review, we summarized the findings of prior studies on the features and dynamics of the primary motor cortex in rodents.
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Aging is associated with altered brain connectivity within the default mode network (DMN). Although research using functional magnetic resonance imaging has quantified age-related alterations in functional connectivity within this network during resting state, it is less clear how this may be reflected in electrophysiological measures, and how this relates to cognitive performance in older adults. The aim of this study was to quantify age differences in phase synchrony of the DMN during resting state, with particular focus on connectivity between the anterior node (i.e., medial prefrontal cortex, or mPFC) and other associated regions in this network. ⋯ Findings indicated decreased connectivity in the alpha2 range for older than younger adults between the mPFC and other DMN regions including the left angular gyrus and bilateral lateral temporal cortices, the latter of which were associated with lower performance in semantic fluency and executive functioning in older adults. Furthermore, greater PLV in theta and beta bands between the mPFC and posterior cingulate regions were found in older than younger adults. These results suggest age-related changes in DMN functional connectivity are non-uniform and frequency-dependent, and may reflect poorer performance in cognitive domains thought to decline with aging.