Perioperative neurocognitive disorder (PND) is a common complication after anesthesia and surgery, particularly in older individuals, and is associated with oxidative stress and ferroptosis. Krüppel-like factor 4 (KLF4) has been implicated in neuronal injury, but its role in PND remains unclear. Using a mouse model of sevoflurane anesthesia plus tibial fracture surgery and sevoflurane-exposed HT22 cells, we found that KLF4 was upregulated in the hippocampus after anesthesia and surgery, as well as in HT22 cells. KLF4 knockdown alleviated cognitive impairment and neuronal injury in vivo and improved cell viability while reducing apoptosis in vitro. Mechanistically, KLF4 depletion attenuated oxidative stress and ferroptosis-related changes, including reduced ROS, iron accumulation, MDA, LDH, and ACSL4 expression, together with restored GSH, antioxidant activity, GPX4, and SLC7A11 levels. Multiplex immunofluorescence showed that surgery-induced GPX4 loss and ACSL4 upregulation occurred predominantly in hippocampal neurons, whereas 4-HNE accumulation was observed in both neurons and microglia. KLF4 directly bound to the SMAD7 promoter and enhanced SMAD7 transcription. Rescue experiments showed that KLF4 overexpression reversed the protective effects of SMAD7 knockdown, and in the absence of sevoflurane, KLF4 overexpression alone induced toxicity that was only partially rescued by SMAD7 knockdown. Together, these findings suggest that KLF4 is associated with PND-related neuronal injury, potentially through SMAD7-linked oxidative stress and ferroptosis-related signaling.

Temperature profoundly influences brain physiology and pathology. Accumulating evidence indicates that microglia, the resident immune cells of the central nervous system, are highly sensitive to temperature changes. Experimental evidence indicates that temperature modulates microglial motility, inflammatory signaling, and phagocytic activity through thermosensitive ion channels and, potentially, through broader biophysical mechanisms. In parallel, advances in intracellular thermometry have revealed the potential for local heat generation within organelles and heat propagation between subcellular compartments, raising the possibility that temperature may function not only as a consequence of cellular activity but also as a biologically meaningful signal. Although direct evidence for microglial heat generation remains limited, the unique metabolic and lysosomal activities of microglia make them a compelling target for investigating how local thermal dynamics are generated and regulated within the brain. In this review, we summarize current knowledge regarding the bidirectional relationship between temperature and microglial biology. We discuss temperature-dependent microglial responses and their underlying mechanisms, examine temperature dynamics in physiological and pathological conditions, and review recent advances in thermal measurement and interventions. Finally, we highlight key unresolved questions and future directions for understanding temperature-microglia interactions and their therapeutic implications.

Mechanical stimulation to periodontal ligament (PDL) by orthodontic force is received by the peripheral mechanoreceptors of trigeminal ganglion (TG) neurons and/or trigeminal mesencephalic nucleus (MesV) neurons, which are the primary sensory neurons. In this study, we examined changes in the expression of mechanosensitive plasma membrane proteins in TG and MesV neurons innervating the PDL labeled with cholera toxin B subunit (CTB) in response to orthodontic force as a sustained mechanical stimulation of molar tooth in nine-week-old Wistar rats. We also evaluated changes in body weight and food intake in non-orthodontic force-treated and orthodontic force-treated rats. In CTB-positive TG neurons innervating the PDL, we observed significantly higher expression levels of ion channels involved in mechanical sensing. Notably, in CTB-labeled MesV neurons, we observed that the expression level of Piezo2 channels was significantly higher in the group subjected to orthodontic force than in those not subjected to orthodontic force. Body weight did not change after 3 days of orthodontic force application, but food intake decreased. These results suggest that continuous mechanical stimulation by orthodontic force increases the mechanosensitive response in the PDL during proprioception via Piezo2-positive MesV neuron activation.

Dementia poses a substantial global health burden, necessitating public health focus on modifiable risk factors. While sleep duration has been linked to dementia risk, studies specifically addressing middle-aged and older Chinese adults remain limited. Using cross-sectional (n = 12,187) and longitudinal (n = 9030, 4-year follow-up) data from CHARLS, along with two-sample Mendelian randomization (MR), we examined associations between sleep duration and dementia, and causality between insomnia and dementia. We observed the strongest dementia risk among individuals reporting extreme sleep durations (<5 h or >10 h), both cross-sectional (OR=2.99, 95% CI: 2.47-3.62, P < 0.001) and longitudinally (HR=1.55, 95% CI: 1.25-1.91, P < 0.001). Restricted cubic spline analyses demonstrated a significant U-shaped dose-response association (P for nonlinearity <0.001). MR findings provided suggestive evidence for a potential causal effect of insomnia on dementia risk (OR=1.06, 95% CI: 1.01-1.13, P = 0.029). Sensitivity analyses confirmed robustness. Optimizing sleep duration and managing insomnia may help reduce dementia risk in Chinese middle-aged and older adults.

Decoding visual information based on machine learning has the potential to reveal the neural mechanisms of visual information processing in the brain. Although most highly precise decoding methods require highly invasive electrodes, these electrodes make long-term use difficult because they cause brain damage. To address this issue, we recorded local field potentials (LFPs) from the mouse cortex using custom-made low-invasive electrodes (ECoG with six recording sites) and verified how convolutional neural network (CNN) can decode visual stimulus positions from the LFP signals recorded by these electrodes. We found that the discrimination accuracies based on the cross-validation (39-70%) were significantly higher than the chance level (25%) for all animals. This confirmed that CNNs can extract the neural features of visual stimulus positions, even from low-spatial-resolution LFPs. Furthermore, we showed that visual positional information was primarily encoded during specific time periods of LFPs by using surrogate datasets. Our findings suggest that CNN enables low-invasive electrodes to analyze the visual information processing system and provide tools to understand the neural mechanisms in the brain.

Myelin, a multilamellar membrane structure enwrapping axons, is essential for rapid saltatory conduction, metabolic support, and long-term axonal integrity in the central nervous system (CNS). Myelination by oligodendrocytes (OLs) constitutes a highly dynamic and orchestrated process, encompassing distinct stages: target axon recognition, axonal wrapping, membrane expansion, and compaction. This review comprehensively summarizes recent advances in understanding the dynamics of CNS myelination which is spatiotemporally regulated through a complex interplay of membrane protein interaction, neuronal activity, metabolic checkpoints, and mechanosensory mechanisms. We highlight how adhesive molecules, cytoskeletal dynamics, and polarized membrane trafficking collectively drive the precise spiraling of myelin around axons. Furthermore, we emphasize the indispensable non-cell autonomous roles of astrocytes and microglia, which contribute critically through lipid transfer, phagocytic refinement, and modulation of the extracellular matrix. Beyond development, we discuss mechanisms that sustain myelin homeostasis, such as autophagy-lysosomal clearance. By integrating these mechanistic insights, we not only underscore the exquisite precision of CNS myelination but also illuminate potential therapeutic targets for demyelinating disorders.

Microtubules support neuronal morphology, intracellular transport, and neurite growth, but how microtubule turnover is regulated across neuronal compartments remains incompletely understood. To examine microtubule dynamics under physiological expression conditions, we expressed EGFP-tagged βIII-tubulin from the endogenous Tubb3 locus in cultured rat hippocampal neurons and measured tubulin turnover using fluorescence recovery after photobleaching (FRAP). FRAP analysis revealed pronounced spatial differences in microtubule dynamics at 9 days in vitro (DIV), with the highest turnover observed in growth cones and substantially slower turnover in dendrites, axons, and the axon initial segment (AIS). Microtubule turnover further decreased between 9 and 17 DIV in dendrites and axons, indicating progressive stabilization during neuronal maturation, whereas turnover in the AIS remained largely unchanged. Analysis of EB3 comet dynamics suggested that microtubule polymerization contributes substantially to tubulin turnover. In addition, manipulation of the dendritic microtubule-associated protein MAP-2 altered tubulin FRAP, indicating that MAP-2 contributes to the regulation of neuronal microtubule dynamics. Together, these results demonstrate that microtubule turnover is spatially and developmentally regulated in neurons.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by elevated concentrations of amyloid β1-42 (Aβ1-42) in the brain, where it exerts neurotoxic effects. A recent study demonstrated that medium flow at approximately 10 μm/s reduces Aβ1-42 neurotoxicity in explant brain cultures containing neurons and beating ependymal cilia; however, the underlying mechanisms remain unclear. Neurons migrating from the explant and located within 300 μm of the beating cilia were exposed to cilia-generated medium flow, allowing analysis of Aβ1-42 toxicity under fluid flow conditions. Aβ1-42-containing putative EV-related extracellular particles (putative EV-related Eps), with diameters of 100-400 nm were detected in the culture medium and exhibited neurotoxic effects. Pharmacological inhibition of EV release and endocytosis reduced intracellular accumulation of Aβ1-42 and attenuated neuronal toxicity. Under medium flow, fewer putative EV-related EPs bound to neurons, and their binding duration was significantly shortened. Rhodamine-conjugated concanavalin A staining revealed enhanced cell-surface glycan labeling in damaged neurons on the non-ciliated side compared with neurons on the ciliated side. These results suggest that shear stress reduces neuronal accumulation of Aβ1-42-containing putative EV-related EPs, likely through modulation of cell-surface glycosylation composition.

How damaged mitochondrial DNA (mtDNA) affects gene expression in mtDNA-related diseases is not well understood. Here, we investigated the changes in the transcriptome and chromatin modifications associated with the accumulation of mtDNA mutations in a proof-reading-deficient mitochondrial DNA polymerase transgenic mouse (Polg1 mutant mice), which accumulate mtDNA mutations preferentially in the paraventricular thalamic nucleus (PVT) and exhibit depressive-like episodes. We examined PVT neurons that were positive or negative for cytochrome oxidase (COX) in the mutant mice in depressive-like or euthymic states. The genes that were upregulated in the COX-negative PVT neurons during the depressive-like state were enriched for mitophagy or interferon signalling pathways. We observed no differentially accessible regions between WT and Polg1 mutant mice by ATAC (Assay for Transposase-Accessible Chromatin), but the loss of H3K27Ac signal in Polg1 mutant mice was associated with a higher number of ATAC tags. The change in H3K27Ac signal was seen only in brain regions that accumulate mtDNA mutations. In addition, we found that mtDNA, especially partially deleted mtDNA, was released from mitochondria upon opening of the mitochondrial permeability transition pore. These findings altogether suggest that mutated mtDNA molecules are released from mitochondria, which may contribute to the depression-specific transcriptomic alterations in the PVT neurons of the mood disorder animal model.

This study proposes an electroencephalography (EEG) analysis method using second-order derivatives of the alpha-band envelope to characterize task-related brain dynamics. An open dataset including EEG data from 60 healthy participants was analyzed during rest and three eyes-closed tasks: calculation, memory, and music. Sixty-second epochs were extracted, alpha-band activity (8-13 Hz) was filtered, and amplitude envelopes were computed via the Hilbert transform. Second-order derivatives were derived and separated into positive (Ap) and negative (An) components. Source-localized EEG signals were mapped to 68 cortical regions using the Desikan-Killiany atlas. Regional differences in Ap, An, their ratio, envelope amplitude, and peak alpha frequency were tested using corrected Wilcoxon signed-rank tests. The calculation task increased Ap, An, and amplitude in prefrontal and cingulate cortices, while reducing An in medial parietal regions. The memory task showed increased An in the left fusiform gyrus, whereas the music task showed no significant changes. Peak alpha frequency and Ap-An ratio were unchanged. These results suggest that derivative-based features capture task- and region-specific brain dynamics not detected by conventional measures, providing complementary descriptors of EEG activity in healthy individuals. Conceptual illustration of the present study. We hypothesized that the second-order derivatives of fluctuations in the alpha-band envelope, which are relatively preserved after the Fourier-based filtering process, may contain biologically relevant information. In this study, we examined whether the second-order derivatives (force, shown in red), in addition to conventional amplitude (green) and frequency (blue) measures, exhibit task-related changes in healthy individuals. By incorporating second-order derivative measures into node-wise functional descriptors of brain regions within an intracerebral network framework, the present results provide a complementary perspective for characterizing brain function. Ap and An denote the positive and negative components of the second-order derivative, respectively.

Benign adult familial myoclonus epilepsy (BAFME) is caused by intronic TTTCA and TTTTA repeat expansions in SAMD12 and other genes; the neuronal basis of cortical hyperexcitability, however, remains unclear. We generated induced pluripotent stem cell (iPSC)-derived glutamatergic and GABAergic neurons from three BAFME1 patients and examined functional and transcriptomic phenotypes. Patient-derived neurons retained the pathogenic repeat expansions and showed a tendency toward upstream intronic RNA accumulation. Calcium imaging revealed increased spontaneous Ca[2 +] transient frequency in both neuronal subtypes, indicating heightened activity. Pharmacological profiling demonstrated attenuated responses to calcium-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor (CP-AMPAR) blockade and GABAA receptor antagonism in GABAergic neurons, suggesting altered inhibitory signaling. RNA sequencing revealed transcriptomic alterations without differential expression of ion channels and neurotransmitter receptors. In glutamatergic neurons, ATF4-regulated genes, including SLC7A5 encoding LAT1, a Kv1.2 channel modulator, were downregulated. Reduced SLC7A5 expression was validated at both mRNA and protein levels. In GABAergic neurons, synapse-associated genes PTPRD and GPC6 were upregulated. TCERG1L and NLRP2 were suppressed across both neuronal subtypes. These findings suggest subtype-specific alterations may contribute to neuronal hyperexcitability in BAFME and provide a platform for mechanistic studies of repeat expansion-associated epilepsies.

The hippocampus is one of the most important brain regions for memory formation. Memory information is stored in cell populations called memory traces or engrams. However, how these cell populations are formed and selected from among many neurons is unclear. Here, to verify the hypothesis that cell populations are configured by the cellular adhesion molecule clustered protocadherins (Pcdhs), we investigated neuronal activity using immunostaining of the neuronal activity marker c-Fos in hippocampal-cortical regions of mice in which cells expressing Pcdhβ3 are labeled with a fluorescent protein. Reducing Pcdhβ repertoires increased the number of Pcdhβ3[+] cells expressing c-Fos. The number of c-Fos[+] Pcdhβ3[+] cells correlated between hippocampal subregions and between the entorhinal cortex (EC) and hippocampal subregions. Artificial activation of Pcdhβ3[+] neurons in the EC induced c-Fos expression in the activated neurons of the EC and Pcdhβ3[+] cells of the hippocampus in a projection-dependent manner. These results indicate that cell populations expressing the same Pcdhβ isoforms form functional cell populations and functionally connect hippocampal-cortical regions. These findings suggest that a specific subset of molecules within individual cells latently defines the neuronal populations that encode memory information. SIGNIFICANCE STATEMENT: The hippocampus is an important brain region for memory formation. Memory information is stored in cell populations called memory traces or engrams. However, the mechanisms underlying the formation of functional cell populations in the hippocampus remain unclear. Here, we show that functional cell populations are latently defined by the molecules clustered protocadherins (Pcdhs) in the hippocampal-cortical regions by observing and manipulating neuronal activity in mice whose cells expressing a specific isoform of Pcdhs are labeled with a fluorescent protein. This study suggests that latent cell populations can function as a fundamental unit for processing information.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by loss of upper and lower motor neurons that gradually causes muscle weakness and paralysis, eventually resulting in death. While ALS was once believed to specifically target motor neurons, recent clinical studies have revealed sensory involvement. The pathological hallmark of ALS is TAR DNA-binding protein 43 (TDP-43) aggregation in cytoplasm, with increasing evidence of its presence in both motor and sensory neurons. However, sensory abnormalities remain poorly characterized. To address this research gap, we analyzed the effects of TDP-43 expression on layer 2/3 (L2/3) pyramidal neurons of the primary somatosensory cortex in mice projecting through corpus callosum. In utero electroporation (IUE) was performed to express GFP alone (control) or in combination with TDP-43. Compared with the control, mice co-expressing GFP and TDP-43 showed disturbed callosal axonal projections of L2/3 neurons. Mutant TDP-43 variants displayed a more pronounced phenotype, indicating pathogenic role during fetal cortical development. To distinguish developmental from maintenance effects, tamoxifen-inducible TDP-43 expression was used to initiate postnatal TDP-43 expression. Postnatal induction resulted in shorter axonal length and reduced branching rather than gross projections disturbance. Taken together, these results demonstrate that TDP-43 expression can disturb the integrity of axonal projections, such as callosal projections of L2/3 neurons in the somatosensory cortex.

Microglia are the resident immune cells of the central nervous system (CNS) with a unique developmental origin distinct from other tissue macrophages. They arise from progenitors generated in the yolk sac during early embryogenesis, subsequently colonize the developing brain, and persist throughout life via self-renewal. Following brain entry, microglial progenitors undergo stepwise differentiation and maturation under the influence of the local microenvironment, giving rise to the transcriptional and functional diversity observed in mature microglia. In recent years, substantial progress has been made in elucidating the molecular and developmental mechanisms governing microglial ontogeny, from early progenitor specification to brain colonization and maturation. In parallel, in vitro approaches for generating microglia have advanced rapidly. These include the use of immortalized cell lines, primary microglial cultures, and, more recently, microglia-like cells derived from human induced pluripotent stem cells (iPSCs), which are increasingly used for disease modeling. While these systems do not fully recapitulate the in vivo environment, they provide powerful and complementary platforms for dissecting specific aspects of microglial biology. Recent efforts to incorporate microglia into transplantation and brain organoid models have enhanced their physiological relevance and applicability to human systems. In this review, we integrate current knowledge of microglial development with in vitro models and discuss how these insights can be leveraged to further refine experimental systems and advance human disease research.

Neural circuits mature through coordinated assembly of excitatory and inhibitory synapses, yet quantitative frameworks that preserve laminar and dorsoventral coordinates remain limited. Here, we establish a layer boundary-based pipeline for wide-field tiled immunohistochemistry to quantify PSD-95 and gephyrin puncta across stratum oriens, stratum radiatum, and stratum lacunosum-moleculare within mouse hippocampal CA1. In dorsal CA1, analysis across P8, P16, P24, and P80 revealed layer-dependent maturation patterns, with SLM exhibiting temporally inverted excitatory and inhibitory synaptic trajectories. Because prenatal valproic acid exposure is widely used to model autism-associated neurodevelopmental abnormalities and has been linked to hippocampal circuit disruption, we next examined whether synaptic organization is altered across CA1 layers and along the dorsoventral axis. At P56, a 2 × 2 design comparing control and prenatal VPA exposure across dorsal and ventral axes to assess axis dependent synaptic remodeling. Prenatal valproic acid exposure produced layer- and axis specific alterations in puncta density, mean area, and total area, suggesting nonuniform vulnerability of synaptic architecture. A conductance-based leaky integrate-and-fire model further provided a heuristic translation framework, highlighting membrane potential fluctuations as a candidate readout when excitatory and inhibitory components co-vary. These findings provides a practical foundation for integrating histological, functional, and developmental analyses of hippocampal CA1 circuits.