Dynamics of longitudinal dentate gyrus axons associated with seizure

Neurodiagnostic and neurotherapeutic potential of graphene nanomaterials

Graphene has emerged as a highly promising nanomaterial for a variety of advanced technologies, including batteries, energy, electronics, and biotechnologies. Its recent contribution to neurotechnology is particularly noteworthy because its superior conductivity, chemical resilience, biocompatibility, thermal stability, and scalable nature make it well-suited for measuring brain activity and plasticity in health and disease. Graphene-mediated compounds are microfabricated in two central methods: chemical processes with natural graphite and chemical vapor deposition of graphene in a film form. They are widely used as biosensors and bioelectronics for neurodiagnostic and neurotherapeutic purposes in several brain disorders, such as Parkinson's disease, stroke, glioma, epilepsy, tinnitus, and Alzheimer's disease. This review provides an overview of studies that have demonstrated the technical advances of graphene nanomaterials in neuroscientific and clinical applications. We also discuss current limitations and future demands in relation to the clinical application of graphene, highlighting its potential technological and clinical significance for treating brain disorders. Our review underscores the potential of graphene nanomaterials as powerful tools for advancing the understanding of the brain and developing new therapeutic strategies.

Cortical surface plasticity promotes map remodeling and alleviates tinnitus in adult mice

Tinnitus induced by hearing loss is caused primarily by irreversible damage to the peripheral auditory system, which results in abnormal neural responses and frequency map disruption in the central auditory system. It remains unclear whether and how electrical rehabilitation of the auditory cortex can alleviate tinnitus. We hypothesize that stimulation of the cortical surface can alleviate tinnitus by enhancing neural responses and promoting frequency map reorganization. To test this hypothesis, we assessed and activated cortical maps using our newly designed graphene-based electrode array with a noise-induced tinnitus animal model. We found that cortical surface stimulation increased cortical activity, reshaped sensory maps, and alleviated hearing loss-induced tinnitus behavior in adult mice. These effects were likely due to retained long-term synaptic potentiation capabilities, as shown in cortical slices from the mice model. These findings suggest that cortical surface activation can be used to facilitate practical functional recovery from phantom percepts induced by sensory deprivation. They also provide a working principle for various treatment methods that involve electrical rehabilitation of the cortex.

Electrophysiological measurements of synaptic connectivity and plasticity in the longitudinal dentate gyrus network from mouse hippocampal slices

Longitudinal synaptic connections between dentate gyrus (DG) granule neurons in the hippocampus have been found to be correlated with increased anxiety. Here, we present a protocol to assess synaptic connectivity and plasticity in the longitudinal DG network. We detail the steps for (1) obtaining acute mouse hippocampal slices that contain longitudinal DG-DG connections, (2) measuring excitatory postsynaptic potentials using whole-cell patch clamp recording combined with two-photon microscopy and glutamate uncaging, and (3) assessing synaptic plasticity using extracellular field recording. For complete details on the use and execution of this protocol, please refer to Pak et al. (2022).1.

Hippocampal interlamellar cell-cell connectome that counts

The hippocampus is regarded as a cognition hub, particularly for learning and memory. Previously, neuronal mechanisms underlying various cognitive functions are delineated with the lamellar hippocampal circuitry, dentate gyrus-CA3 or CA2-CA1, within the transverse plane. More recently, interlamellar (often referred to as longitudinal) projections have received intensive attention to help understand signal convergence and divergence in cognition and behavior. Signal propagation along the longitudinal axis is evidenced by axonal arborization patterns and synaptic responses to electro- and photo-stimulation, further demonstrating that information flow is more enriched in the longitudinal plane than the transverse plane. Here, we review the significance of longitudinal connections for cognition, discuss a putative circuit mechanism of place coding, and suggest the reconceptualization of the hippocampal circuitry.

Altered synaptic plasticity of the longitudinal dentate gyrus network in noise-induced anxiety

Anxiety is characteristic comorbidity of noise-induced hearing loss (NIHL), which causes physiological changes within the dentate gyrus (DG), a subfield of the hippocampus that modulates anxiety. However, which DG circuit underlies hearing loss-induced anxiety remains unknown. We utilize an NIHL mouse model to investigate short- and long-term synaptic plasticity in DG networks. The recently discovered longitudinal DG-DG network is a collateral of DG neurons synaptically connected with neighboring DG neurons and displays robust synaptic efficacy and plasticity. Furthermore, animals with NIHL demonstrate increased anxiety-like behaviors similar to a response to chronic restraint stress. These behaviors are concurrent with enhanced synaptic responsiveness and suppressed short- and long-term synaptic plasticity in the longitudinal DG-DG network but not in the transverse DG-CA3 connection. These findings suggest that DG-related anxiety is typified by synaptic alteration in the longitudinal DG-DG network.

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Traumatic noise-induced hearing loss enhances anxiety-like behaviors

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The longitudinal DG-DG network displays robust synaptic efficacy and plasticity

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Abnormal anxiety is associated with synaptic alterations of the DG-DG network

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DG-related brain disorders might stem from dysfunctional DG-DG networks