Biology subjects

Shimba, K.

Publications and source records attributed to Shimba, K..

3 recordsLinked to original sources

bioRxiv2025

Chronic social defeat causes dysregulation of systemic glucose metabolism via the cerebellar fastigial nucleus

Chronic psychological stress leads to hyperglycemia through the endocrine and sympathetic nervous systems, which contributes to the development of type II diabetes mellitus (T2DM). Higher plasma corticosteroids after stress is one well-established driver of insulin resistance in peripheral tissues. However, previous studies have indicated that only a fraction of patients with depression and post-traumatic disorder (PTSD) who develop T2DM exhibit hypocortisolism, so corticosteroids do not fully explain psychological stress-induced T2DM. Here, we find that chronic social defeat stress (CSDS) in mice enhances gluconeogenesis, which is accompanied by a decrease in plasma insulin, an increase in plasma catecholamines, and a drop in plasma corticosterone levels. We further reveal that these metabolic and endocrinological changes are mediated by the activation of neurons projecting from the cerebellar fastigial nucleus (FN) to the medullary parasolitary nucleus (PSol). These neurons are crucial in shifting the bodys primary energy source from glucose to lipids. Additionally, data from patients with depression reveal correlations between the presence of cerebellar abnormalities and both worsening depressive symptoms and elevated HbA1c levels. These findings highlight a previously unappreciated role of the cerebellum in metabolic regulation and its importance as a potential therapeutic target in depression, PTSD, and similar psychological disorders.

neuroscience↗

bioRxiv2024

After-effects of Parieto-occipital Gamma Transcranial Alternating Current Stimulation on Behavioral Performance and Neural Activity in Visuo-spatial Attention Task

Visuo-spatial attention enables selective focus on spatial locations while ignoring irrelevant stimuli, involving both endogenous and exogenous attention. Recent advancements in transcranial alternating current stimulation (tACS) have shown promise in modulating these attentional processes by targeting electrical oscillations in specific brain areas. Despite evidence of online effects of tACS on visuo-spatial attention performance, whether tACS can produce lasting after-effects on behavioral performance and neural activity remains unknown. This study explored these after-effects using a single-blind, sham-controlled, between-group design. Eighteen young healthy participants were equally divided into two groups receiving either sham or active gamma tACS at 40 Hz targeted at the right parieto-occipital region. Each participant performed a version of the Posner cueing task with EEG recording before and after the tACS intervention. The active tACS group exhibited greater reductions in reaction time compared to the sham group. These changes were not uniform across different attention types, suggesting specific enhancements in cognitive processing. EEG analyses revealed trial-type-specific modulation of event-related potentials, including amplitude and latency of N1 and P3 components, that paralleled the behavioral effects. Additionally, frequency-specific changes in oscillatory power during the cue-target interval--decreased alpha power and increased gamma power--as well as reduced long-range temporal correlations were observed more broadly across conditions. While limited by a small sample size, these preliminary findings provide convergent behavioral and electrophysiological evidence that parieto-occipital gamma tACS can induce lasting, condition-specific after-effects on visuo-spatial attentional networks.

neuroscience↗

bioRxiv2021

Acoustic frequency-dependent physical mechanism of sub-MHz ultrasound neurostimulation

Ultrasound is an innovative physical modality allowing non-invasive and reversible modulation of neural circuit activity in the brain with high spatial resolution. Despite growing interest in clinical applications, the safe and effective use of ultrasound neuromodulation has been limited by a lack of understanding of the physical mechanisms underlying its effects. Here, we demonstrate acoustic frequency-dependent physical effects that underlie ultrasound neuromodulation, where cavitation and radiation forces are the dominant sources of low- and high-frequency stimulation, respectively. We used 39.5 kHz and 500 kHz acoustic frequencies to stimulate cultured neural and glial cells, excised from rat cortex, to study acoustic frequency-dependent neural responses. We demonstrate increased evoked responses due to increased cavitation activity at the 39.5 kHz acoustic frequency. In contrast, notable cavitation activity was not detected at 500 kHz despite detection of evoked responses. Our work highlights the dependence of ultrasound neuromodulation on acoustic frequencies, with different physical effects underlying cell responses to low and high sub-MHz acoustic frequency ranges.

bioengineering↗