Due to the COVID-19 pandemic in 2020, medical resources (especially ICU beds with advanced life support, such as respirators) have become scarce around the world, and the necessity of their ...allocation/rationing is discussed as an ICU triage. This paper reviews the bioethical discussions on ICU triage during the pandemic and addresses three issues: (1) treatment of the elderly, (2) priorities for medical resource allocation, and (3) medical resource re-allocation. Our analysis showed (1) that using age as exclusion criteria for ICU can be discrimination against the elderly, (2) that there were mainly three policies guiding the allocation; no triage, triage by medical needs, and triage by medical utility, while lacking the evidence-based medical assessments on the utility of the triage, and (3) that the reallocation of scarce medical resources in a utilitarian ICU triage scheme might not be legally secure. Finally, we discussed the social implications of utilitarian triage during the state of exception such as the COVID-19 pandemic in the framework of biopolitics theory.
•Transcranial Static Magnetic Stimulation (tSMS) can modulate cortical excitability by acting on the oscillatory activity.•tSMS may alter motor learning through modulating cortical ...excitability.•Neuromodulation induced by tSMS may be a useful clinical tool for the treatment.
Non-invasive brain stimulation (NIBS) techniques are extensively applied for the treatment of neuropsychiatric disorders and offer a powerful tool for addressing fundamental questions in neuroscience research. Recently, the use of static magnetic fields (SMFs) as a tool of NIBS has led to the development of a safe and promising method of neuromodulation called transcranial static magnetic stimulation (tSMS). However, the neurophysiological mechanisms regarding the effect of tSMS on the cortical elements are not yet fully understood. Here, we focus on the modulation of cortical excitability and oscillatory brain activity induced by tSMS. We believe that understanding the physiological mechanisms of this novel method is an important step for developing these techniques into potentially useful tools for the treatment of specific patient groups. Reviewing the neurophysiological evidence provided by human and animal studies suggests that tSMS may affect brain oscillations and alter behavioral parameters through the modulation of cortical excitability. In this review, we outline possible accounts and future directions to better understand the link between neural modification and accompanied behavioral changes.
Control of movements using visual information is crucial for many daily activities, and such visuomotor control has been revealed to be supported by alpha and beta cortical oscillations. However, it ...has been remained to be unclear how midfrontal theta and occipital gamma oscillations, which are associated with high-level cognitive functions, would be involved in this process to facilitate performance. Here we addressed this fundamental open question in healthy young adults by measuring high-density cortical activity during a precision force-matching task. We manipulated the amount of error by changing visual feedback gain (low, medium, and high visual gains) and analyzed event-related spectral perturbations. Increasing the visual feedback gain resulted in a decrease in force error and variability. There was an increase in theta synchronization in the midfrontal area and also in beta desynchronization in the sensorimotor and posterior parietal areas with higher visual feedback gains. Gamma de/synchronization was not evident during the task. In addition, we found a moderation effect of midfrontal theta on the positive relationship between the beta oscillations and force error. Subsequent simple slope analysis indicated that the effect of beta oscillations on force error was weaker when midfrontal theta was high. Our findings suggest that the midfrontal area signals the increased need of cognitive control to refine behavior by modulating the visuomotor processing at theta frequencies.
Beta-band (15–30 Hz) corticomuscular and intermuscular coherences are important markers of the corticospinal interaction. The purpose of this study was to investigate whether amount of visual ...feedback during an isometric pinch grip contraction would influence these coherences in young and elderly adults. Thirty-three healthy young and elderly subjects performed pinch grip force-matching task with right thumb and index finger, while scalp electroencephalogram (EEG) and electromyogram (EMG) from the first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles were recorded. The amount of visual feedback was altered by manipulation of visual gain (low and high). Beta-band corticomuscular coherence was computed between EEG over the sensorimotor cortex and EMG from the FDI muscle and between EEG and EMG from the APB muscle (EEG-FDI and EEG-APB coherences). Also, beta-band intermuscular coherence was computed between EMG signals from the FDI and APB muscles (EMG-EMG coherence). Task performance was quantified as standard deviation (SD) of force and mean force error (MFE). EEG-FDI coherence was larger at high than low visual gain in the elderly but not in the young subjects, whereas there was no effect of age or visual gain on EEG-APB coherence. EMG-EMG coherence was smaller at high than low visual gain in the young and elderly subjects. The MFE was smaller at high than low visual gain in the young and elderly subjects, but the SD of force was smaller at high than low visual gain only in the young subjects. These results suggest that the effect of aging on beta-band coherence depends on the amount of visual feedback and further that visual feedback modulates beta-band corticomuscular and intermuscular coherences differently.
Highlights • Homogeneous and inhomogeneous static magnetic fields suppress the human motor cortex. • Short-latency intracortical inhibition was increased after magnetic exposure. • The enhancement of ...the GABAergic system can be used for clinical purposes.
Transcranial static magnetic stimulation (tSMS) has been focused as a new non-invasive brain stimulation, which can suppress the human cortical excitability just below the magnet. However, the ...non-regional effects of tSMS via brain network have been rarely studied so far. We investigated whether tSMS over the left primary motor cortex (M1) can facilitate the right M1 in healthy subjects, based on the hypothesis that the functional suppression of M1 can cause the paradoxical functional facilitation of the contralateral M1 via the reduction of interhemispheric inhibition (IHI) between the bilateral M1. This study was double-blind crossover trial. We measured the corticospinal excitability in both M1 and IHI from the left to right M1 by recording motor evoked potentials from first dorsal interosseous muscles using single-pulse and paired-pulse transcranial magnetic stimulation before and after the tSMS intervention for 30 min. We found that the corticospinal excitability of the left M1 decreased, while that of the right M1 increased after tSMS. Moreover, the evaluation of IHI revealed the reduced inhibition from the left to the right M1. Our findings provide new insights on the mechanistic understanding of neuromodulatory effects of tSMS in human.
Transcranial static magnetic stimulation (tSMS) is a novel non-invasive brain stimulation technique that reduces cortical excitability at the stimulation site. We investigated the effects of tSMS ...over the left primary motor cortex (M1) for 20 min on the local electroencephalogram (EEG) power spectrum and interregional EEG coupling. Twelve right-handed healthy subjects participated in this crossover, double-blind, sham-controlled study. Resting-state EEG data were recorded for 3 min before the intervention and 17 min after the beginning of the intervention. The power spectrum at the left central electrode (C3) and the weighted phase lag index (wPLI) between C3 and the other electrodes was calculated for theta (4-8 Hz), alpha (8-12 Hz), and beta (12-30 Hz) frequencies. The tSMS significantly increased theta power at C3 and the functional coupling in the theta band between C3 and the parietal midline electrodes. The tSMS over the left M1 for 20 min exhibited modulatory effects on local cortical activity and interregional functional coupling in the theta band. The neural oscillations in the theta band may have an important role in the neurophysiological effects induced by tSMS over the frontal cortex.
•tACS was given on left cerebellum during over-ground walking in healthy subjects.•The frequency of tACS were set close to that of their gait cycle.•It significantly entrained their gait rhythm.•The ...entrainment phase was inverted with the inverted direction of the tACS currents.•It suggests that tACS modulates rhythm generation system in cerebellum.
Although specific brain regions are important for regularly patterned limb movements, the rhythm generation system that governs bipedal locomotion in humans is not thoroughly understood. We investigated whether rhythmic transcranial brain stimulation over the cerebellum could alter walking rhythm. Fourteen healthy subjects performed over-ground walking for 10 min during which they were given, in a random order, transcranial alternating current stimulation (tACS) over the left cerebellum at the approximated frequency of their gait cycle, tACS over the skin of the scalp, and during sham stimulation. Cerebellar tACS showed a significant entrainment of gait rhythm compared with the control conditions. When the direction of the tACS currents was symmetrically inverted, some subjects showed entrainment at an approximately 180° inverted phase, suggesting that gait modulation is dependent on current orientation. These findings indicate that tACS over cerebellum can modulate gait generation system in cerebellum and become an innovative approach for the recovery of locomotion in patients with gait disturbances caused by CNS disorders.
•We investigated the effect of transcranial static magnetic stimulation (tSMS) on motor learning in implicit sequential task.•tSMS applied to the primary motor cortex improved reaction times compared ...to DLPFC and Sham stimulations at 24 h after practice.•The neural modulation of the M1 using tSMS may enhance human offline motor learning.
Transcranial static magnetic stimulation (tSMS) is a recently introduced noninvasive brain stimulation technique that can modulate brain excitability. Here, we investigated a hypothesis that motor learning would be altered by tSMS applied to the primary motor cortex (M1). For motor task, we chose a serial reaction time task consisting of sequential trials and random trials in which the visual cue doesn’t play out a repeating pattern of positions to evaluate an implicit motor learning, where the M1 is a key structure for skill acquisition and early consolidation. Forty-four healthy right-handed volunteers participated in the present study. TSMS was placed over the right M1 or dorsolateral prefrontal cortex (DLPFC). The control group received Sham stimulation over the right M1. Reaction times (RTs) of left hand were analyzed before (Pre session) and after (Post session) practice to examine online learning, and were also assessed 24 h later to examine offline learning (Cons session). The results showed that the RTs became faster in Post than Pre session regardless of the stimulation location. Interestingly, the RTs were significantly faster with the M1 stimulation than the DLPFC or Sham stimulation in Cons session. There was not significant difference in error rate among sessions or stimulation locations. These findings suggest that the modulation of the M1 using tSMS can enhance offline motor learning in an implicit task.
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