姚 潤宏

INTRODUCTION: Mild cognitive impairment (MCI) is frequently accompanied by impairments in postural control and trunk muscle function. Although gamma-theta rhythmic stimulation has been reported to modulate neural oscillatory activity, its influence on brain-muscle interactions in individuals with MCI remains poorly understood. This exploratory pilot study investigated whether changes in EEG connectivity following gamma-theta stimulation were associated with alterations in trunk muscle electromyographic (EMG) activity in older adults with MCI. METHODS: Nine older adults with MCI underwent two separate 10-min sessions of combined 40 Hz visual flicker and theta-frequency mechanical stimulation. Resting-state EEG and trunk muscle EMG were assessed before and after stimulation. EEG connectivity changes were calculated using Spearman correlations between predefined electrode pairs. Supplementary analyses using phase-lag index (PLI) and imaginary coherence (iCoh) were performed to address potential volume conduction effects. EMG activity was recorded bilaterally from the multifidus and lumbar paraspinal muscles during trunk extension tasks. Correlation analyses examined associations between EEG connectivity changes and EMG changes in RMS amplitude, mean frequency, and spectral power measures. RESULTS: Although no predefined EEG connectivity pair demonstrated significant group-level change following stimulation, several EEG connectivity change scores were significantly associated with concurrent EMG changes. The most robust associations involved left multifidus activity: FC5-F3 connectivity changes were associated with left multifidus RMS amplitude (ρ = +0.800, p = 0.010), and T7-T8 connectivity changes were associated with left multifidus mid-frequency spectral power (ρ = -0.800, p = 0.010). Leave-one-out sensitivity analyses indicated that both associations remained statistically significant in all nine subsets. Supplementary phase-based connectivity analyses provided limited convergent support for the primary findings. Although several contralateral EEG-EMG associations were identified, the overall pattern was characterized by a predominance of ipsilateral associations. DISCUSSION: These findings suggest that gamma-theta stimulation may influence coordinated brain-muscle responses in older adults with MCI, with a predominance of left-hemisphere EEG-EMG associations indicating relative hemispheric predominance rather than strict hemispheric exclusivity. Associations involving broader measures of muscle activation and spectral distribution were more robust than those involving specific spectral indices. Given the small sample size, absence of sham control, non-simultaneous EEG-EMG recording, and exploratory statistical approach, these findings should be interpreted as hypothesis-generating and require confirmation in larger controlled studies.

Mild cognitive impairment (MCI) is associated with age-related alterations in neural oscillatory activity and cerebral hemodynamics, while mobility limitations often restrict participation in conventional exercise-based interventions. This study investigated exploratory, single-arm, within-subject short-term neurovascular and electrophysiological responses to a combined visual and vibration stimulation protocol in older adults with MCI. Cerebral blood flow was assessed using near-infrared spectroscopy (NIRS) in 27 participants, and electroencephalography (EEG) was additionally recorded in a subgroup of nine participants (n = 9) drawn from the same cohort. The intervention consisted of simultaneous 40 Hz visual flicker and low-frequency mechanical vibration delivered during a seated condition. Changes in total hemoglobin concentration and EEG power in predefined frequency bands were analyzed before and after the intervention, with additional time-window analyses to examine temporal dynamics. At baseline, NIRS revealed higher total hemoglobin levels in the left prefrontal cortex compared with the right. Following the intervention, total hemoglobin decreased significantly in both hemispheres, with a larger reduction observed in the right hemisphere. Time-resolved analyses demonstrated an earlier hemodynamic response in the right hemisphere, followed by a delayed response in the left. EEG analyses showed a reduction in frontal gamma-band power accompanied by an increase in theta-band power in temporoparietal regions after the intervention. These electrophysiological changes were stable across time windows. Together, these findings suggest that short-term combined visual and vibration stimulation was associated with asymmetric and time-dependent changes in cerebral hemodynamics and neural oscillatory activity in older adults with MCI. This non-volitional stimulation approach may provide a feasible experimental framework for investigating brain responses in aging populations with limited mobility. Given the exploratory, uncontrolled design, acute measurement window, and small EEG subgroup, these findings should be interpreted as hypothesis-generating rather than as evidence of clinical or neuroplastic efficacy.

INTRODUCTION: The decline in spatial working memory is one of the earliest signs of normal brain aging. OBJECTIVE: We developed a novel physical exercise method, termed the "shaking exercise," to slow down this process. METHODS: The experimental protocol included administering the shaking exercise for 8-32 weeks in male senescence-accelerated mouse prone 10 (SAMP-10). They were subjected to the T-maze test, followed by immunohistochemical analysis, to assess the influence of the shaking exercise on the M1 muscarinic acetylcholine receptor (CHRM1) and α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) of the dorsal hippocampus and medial prefrontal cortex (dHC-mPFC). RESULTS: The T-maze test demonstrated that the shaking group had less hesitation in the face of selecting direction at week 24. In the immunohistochemical analysis, more CHRM1s were in the CA3 subregion and more AMPARs were in the subiculum. CHRM1s and AMPARs were maintained in the CA1 region and the mPFC. The CHRM1s seem to have a positive effect on the AMPAR in the dentate gyrus (DG) region and the CA3 region. In the CA1 region, CHRM1s were negatively correlated with AMPARs. In addition, high-density neurons were expressed in the shaking group in the upstream DG, the middle part and the distal part of CA3, the distal part of CA1, and the mPFC. CONCLUSIONS: Our results raise the possibility that maintenance of the spatial working memory effect observed with the shaking exercise is driven in part by the uneven affection of CHRM1s and AMPARs in the dHC-mPFC circuit system and significantly maintains the neuronal expression in the dHC-mPFC.

INTRODUCTION: The disabling effects of dementia, an incurable disease with little effect on mortality, affect society far more than many other conditions. OBJECTIVE: The aim of this study was to stop or delay the onset of dementia using low-cost methods such as physical exercise. METHODS: Senescence-accelerated model-prone (SAMP) 10 mice were made to perform a user-friendly shaking exercise for 25 weeks. The motor function and hippocampal functions (learning, spatial cognition) of the mice were evaluated using behavioral experiments. The degree of hippocampal aging was evaluated based on brain morphology. The association between behavioral performance of the mice and the degree of hippocampal aging was then evaluated. RESULTS: The behavioral test results showed that the shaking group had higher motor coordination (p < 0.01) and motor learning (p < 0.05). Significantly higher performances in the learning ability were observed in the shaking group at a middle-period experiment (p < 0.05); the spatial cognitive functions also improved (p < 0.05). The shaking group showed delayed ageing of cells in the dentate gyrus (DG; area: p < 0.01) and cornu Ammonis (CA; area: p < 0.01) regions of the hippocampus. CONCLUSIONS: The shaking exercise enhances the activity of mice and reduces age-associated decreases in learning and spatial cognitive functions. Regarding hippocampal morphology, shaking exercise can prevent non-functional protein accumulation, cell atrophy, and cell loss. Specifically, shaking exercise protects cell growth and regeneration in the DG area and enhances the learning function of the hippocampus. Furthermore, shaking exercise maintained the spatial cognitive function of cells in the CA3 and CA1 regions, and prevented the chronic loss of CA2 transmission that decreased the spatial memory decline in mice.

In Japan, 13 million people have osteoporosis, including approximately 9 hundred thousand people who are bedridden owing to bone fractures from falls. Preventing osteoporosis is considered to be an important and effective way of preventing fall-related fractures. Thus, we developed a novel method of locomotor stimulation and analyzed its effectiveness in mice. Specifically, we created a double-loading device that combines vibration and shaking stimulation. The device was used to continuously stimulate ovariectomy-induced decreased bone density mouse models 30 minutes daily for 10 weeks. We then collected femur samples, created undecalcified tissue slices, calculated parameters using bone histomorphomtry, and conducted comparative testing. BS/TV (bone surface/tissue volume), N.Oc/ES (osteoclast number/eroded surface), Oc.S/ES (osteoclast osteoid surface/eroded surface), Omt (osteoid maturation time), Tb.N (trabecular number), Mlt (mineralization lag time) < (p < 0.01), N.Ob (osteoblast number), N.Ob/TV (osteoblast number/tissue volume), sLS (single labeled suface), N.Mu.Oc/ES (multinucle osteoclast number/eroded surface), and N.Mo.Oc/ES (mononucle osteoclast number/eroded surface) (p < 0.05) were significantly higher in the stimulation group than in the non-stimulation group. In addition, BS/BV (bone surface/bone volume), Tb.Sp (trabecular separation), MAR (mineral apposition rate), Aj.Ar (adjusted apposition rate) (p < 0.01), ES (eroded surface ), ES/BS (eroded surface/bone surface), and BRs.R (bone resorption rate) (p < 0.05) were significantly lower in the stimulation group than in the non-stimulation group. These results suggest that stimulation activated osteoblasts and osteoclasts, thereby leading to highly active bone remodeling. We anticipate that bone mineralization will subsequently occur, suggesting that this stimulation technique is effective in preventing osteoporosis by alleviating sudden bone density loss.