Time-dependent effect of acute hypoxia on corticospinal excitability in healthy humans

Contradictory results regarding the effect of hypoxia on cortex excitability have been reported in healthy subjects, possibly depending on hypoxia exposure duration. We evaluated the effects of 1- and 3-h hypoxia on motor corticospinal excitability, intracortical inhibition, and cortical voluntary activation (VA) using transcranial magnetic stimulation (TMS). TMS to the quadriceps cortex area and femoral nerve electrical stimulations were performed in 14 healthy subjects. Motor-evoked potentials (MEPs at 50–100% maximal voluntary contraction; MVC), recruitment curves (MEPs at 30–100% maximal stimulator power output at 50% MVC), cortical silent periods (CSP), and VA were measured in normoxia and after 1 ( n = 12) or 3 ( n = 10) h of hypoxia (FiO2 = 0.12). One-hour hypoxia did not modify any parameters of corticospinal excitability but reduced slightly VA, probably due to the repetition of contractions 1 h apart (96 ± 4% vs. 94 ± 4%; P = 0.03). Conversely, 3-h hypoxia significantly increased 1) MEPs of the quadriceps muscles at all force levels (+26 ± 14%, +24 ± 12%, and +27 ± 17% at 50, 75, and 100% MVC, respectively; P = 0.01) and stimulator power outputs (e.g., +21 ± 14% at 70% maximal power), and 2) CSP at all force levels (+20 ± 18%, +18 ± 19%, and +14 ± 22% at 50, 75, and 100% MVC, respectively; P = 0.02) and stimulator power outputs (e.g., +9 ± 8% at 70% maximal power), but did not modify VA (98 ± 1% vs. 97 ± 3%; P = 0.42). These data demonstrate a time-dependent hypoxia-induced increase in motor corticospinal excitability and intracortical inhibition, without changes in VA. The impact of these cortical changes on physical or psychomotor performances needs to be elucidated to better understand the cerebral effects of hypoxemia.

Download Full-text

On the Implication of Dietary Nitrate Supplementation for the Hemodynamic and Fatigue Response to Cycling Exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00400.2021 ◽

2021 ◽

Author(s):

Taylor S. Thurston ◽

Joshua C. Weavil ◽

Thomas J. Hureau ◽

Jayson R. Gifford ◽

Vincent P. Georgescu ◽

...

Keyword(s):

Muscle Fatigue ◽

Femoral Nerve ◽

Voluntary Activation ◽

Peak Power Output ◽

Cycling Exercise ◽

Dietary Nitrate ◽

Task Failure ◽

Nitrate Supplementation ◽

The Impact ◽

Cycling Time

This study investigated the impact of dietary nitrate supplementation on peripheral hemodynamics, the development of neuromuscular fatigue, and time to task failure during cycling exercise. Eleven recreationally active male participants (27±5 years, VO2max: 42±2ml/kg/min) performed two experimental trials following 3 days of either dietary nitrate-rich beetroot juice (4.1mmol NO3-/day; DNS) or placebo (PLA) supplementation in a blinded, counterbalanced order. Exercise consisted of constant-load cycling at 50, 75, and 100 W (4-min each) and, at ~80% of peak power output (218±12W), to task-failure. All participants returned to repeat the shorter of the two trials performed to task-failure, but with the opposite supplementation regime (ISO-time comparison). Mean arterial pressure (MAP), leg blood flow (QL; Doppler ultrasound), leg vascular conductance (LVC), and pulmonary gas exchange were continuously assessed during exercise. Locomotor muscle fatigue was determined by the change in pre- to post-exercise quadriceps twitch-torque (∆Qtw) and voluntary activation (∆VA; electrical femoral nerve stimulation). Following DNS, plasma [nitrate] (~670 vs ~180 nmol) and [nitrite] (~775 vs ~11 nmol) were significantly elevated compared to PLA. Unlike PLA, DNS lowered both QL and MAP by ~8% (P<0.05), but did not alter LVC (P=0.31). VO2 across work rates, as well as cycling time to task-failure (~7min) and locomotor muscle fatigue following the ISO-time comparison were not different between the two conditions (∆Qtw ~42%, ∆VA ~4%). Thus, despite significant hemodynamic changes, DNS did not alter the development of locomotor muscle fatigue and, ultimately, cycling time to task failure.

Download Full-text

Neurophysiological correlates of aging-related muscle weakness

Journal of Neurophysiology ◽

10.1152/jn.00205.2013 ◽

2013 ◽

Vol 110 (11) ◽

pp. 2563-2573 ◽

Cited By ~ 11

Author(s):

Ela B. Plow ◽

David A. Cunningham ◽

Corin Bonnett ◽

Dina Gohar ◽

Mehmed Bayram ◽

...

Keyword(s):

Older Adults ◽

Muscle Weakness ◽

Muscle Activation ◽

Primary Motor Cortex ◽

Biceps Brachii ◽

Short Interval ◽

Intracortical Inhibition ◽

Corticospinal Excitability ◽

Voluntary Activation ◽

Interhemispheric Inhibition

Muscle weakness associated with aging implicates central neural degeneration. However, role of the primary motor cortex (M1) is poorly understood, despite evidence that gains in strength in younger adults are associated with its adaptations. We investigated whether weakness of biceps brachii in aging analogously relates to processes in M1. We enrolled 20 young (22.6 ± 0.87 yr) and 28 old (74.79 ± 1.37 yr) right-handed participants. Using transcranial magnetic stimulation, representation of biceps in M1 was identified. We examined the effect of age and sex on strength of left elbow flexion, voluntary activation of biceps, corticospinal excitability and output, and short-interval intracortical and interhemispheric inhibition. Interhemispheric inhibition was significantly exaggerated in the old ( P = 0.047), while strength tended to be lower ( P = 0.075). Overall, women were weaker ( P < 0.001). Processes of M1 related to strength or voluntary activation of biceps, but only in older adults. Corticospinal excitability was lower in weaker individuals ( r = 0.38), and corticospinal output, intracortical inhibition and interhemispheric inhibition were reduced too in individuals who poorly activated biceps ( r = 0.43, 0.54 and 0.38). Lower intracortical inhibition may reflect compensation for reduced corticospinal excitability, allowing weaker older adults to spread activity in M1 to recruit synergists and attempt to sustain motor output. Exaggerated interhemispheric inhibition, however, conflicts with previous evidence, potentially related to greater callosal damage in our older sample, our choice of proximal vs. distal muscle and differing influence of measurement of inhibition in rest vs. active states of muscle. Overall, age-specific relation of M1 to strength and muscle activation emphasizes that its adaptations only emerge when necessitated, as in a weakening neuromuscular system in aging.

Download Full-text

The Impact of Glucose on Corticospinal and Intracortical Excitability

Brain Sciences ◽

10.3390/brainsci9120339 ◽

2019 ◽

Vol 9 (12) ◽

pp. 339 ◽

Cited By ~ 2

Author(s):

Stephen L. Toepp ◽

Claudia V. Turco ◽

Mitchell B. Locke ◽

Chiara Nicolini ◽

Roshni Ravi ◽

...

Keyword(s):

Blood Glucose ◽

Short Interval ◽

Motor Evoked Potential ◽

Intracortical Inhibition ◽

Corticospinal Excitability ◽

Controlled Study ◽

Glucose Response ◽

Afferent Inhibition ◽

Intracortical Excitability ◽

The Impact

Neurotransmission is highly dependent on the availability of glucose-derived energy, although it is unclear how glucose availability modulates corticospinal and intracortical excitability as assessed via transcranial magnetic stimulation (TMS). In this double-blinded placebo-controlled study, we tested the effect of acute glucose intake on motor-evoked potential (MEP) recruitment curves, short-interval intracortical inhibition (SICI), short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI). Eighteen healthy males participated in four sessions. Session 1 involved acquisition of an individualized blood glucose response curve. This allowed measurements to be time-locked to an individualized glucose peak after consuming one of three drinks during the subsequent three sessions. Participants were administered a 300 mL concealed solution containing 75 g of glucose, sucralose, or water in separate sessions. Dependent measures were assessed at baseline and twice after drinking the solution. Secondary measures included blood glucose and mean arterial pressure. Corticospinal excitability and blood pressure increased following the drink across all treatments. No changes were observed in SICI, SAI or LAI. There was no rise in corticospinal excitability that was specific to the glucose drink, suggesting that acute changes in glucose levels do not necessarily alter TMS measures of corticospinal or intracortical excitability.

Download Full-text

Motor excitability in bilateral moyamoya vasculopathy and the impact of revascularization

Neurosurgical FOCUS ◽

10.3171/2021.6.focus21280 ◽

2021 ◽

Vol 51 (3) ◽

pp. E7

Author(s):

Gueliz Acker ◽

Davide Giampiccolo ◽

Kerstin Rubarth ◽

Robert Mertens ◽

Anna Zdunczyk ◽

...

Keyword(s):

Intracortical Inhibition ◽

Relative Effect ◽

Corticospinal Excitability ◽

Cerebral Revascularization ◽

Study Results ◽

Resting Motor Threshold ◽

Before And After ◽

Revascularization Surgery ◽

The Impact

OBJECTIVE Motor cortical dysfunction has been shown to be reversible in patients with unilateral atherosclerotic disease after cerebral revascularization. Moyamoya vasculopathy (MMV) is a rare bilateral stenoocclusive cerebrovascular disease. The aim of this study was to analyze the corticospinal excitability and the role of bypass surgery in restoring cortical motor function in patients by using navigated transcranial magnetic stimulation (nTMS). METHODS Patients with bilateral MMV who met the criteria for cerebral revascularization were prospectively included. Corticospinal excitability, cortical representation area, and intracortical inhibition and facilitation were assessed by nTMS for a small hand muscle (first dorsal interosseous) before and after revascularization. The clinically and/or hemodynamically more severely affected hemisphere was operated first as the leading hemisphere. Intra- and interhemispheric differences were analyzed before and after direct or combined revascularization. RESULTS A total of 30 patients with bilateral MMV were examined by nTMS prior to and after revascularization surgery. The corticospinal excitability was higher in the leading hemisphere compared with the non-leading hemisphere prior to revascularization. This hyperexcitability was normalized after revascularization as demonstrated in the resting motor threshold ratio of the hemispheres (preoperative median 0.97 [IQR 0.89–1.08], postoperative median 1.02 [IQR 0.94–1.22]; relative effect = 0.61, p = 0.03). In paired-pulse paradigms, a tendency for a weaker inhibition of the leading hemisphere was observed compared with the non-leading hemisphere. Importantly, the paired paradigm also demonstrated approximation of excitability patterns between the two hemispheres after surgery. CONCLUSIONS The study results suggested that, in the case of a bilateral chronic ischemia, a compensation mechanism between both hemispheres seemed to exist that normalized after revascularization surgery. A potential role of nTMS in predicting the efficacy of revascularization must be further assessed.

Download Full-text

The impact of statin therapy after surgical or endovascular treatment of cerebral aneurysms

Journal of Neurosurgery ◽

10.3171/2019.3.jns183500 ◽

2020 ◽

Vol 133 (1) ◽

pp. 182-189

Author(s):

Tae-Jin Song ◽

Seung-Hun Oh ◽

Jinkwon Kim

Keyword(s):

Statin Therapy ◽

Coil Embolization ◽

Primary Outcome ◽

Cox Regression ◽

Cerebral Aneurysms ◽

Time Dependent ◽

Lipid Lowering ◽

Surgical Clipping ◽

The Impact

OBJECTIVECerebral aneurysms represent the most common cause of spontaneous subarachnoid hemorrhage. Statins are lipid-lowering agents that may expert multiple pleiotropic vascular protective effects. The authors hypothesized that statin therapy after coil embolization or surgical clipping of cerebral aneurysms might improve clinical outcomes.METHODSThis was a retrospective cohort study using the National Health Insurance Service–National Sample Cohort Database in Korea. Patients who underwent coil embolization or surgical clipping for cerebral aneurysm between 2002 and 2013 were included. Based on prescription claims, the authors calculated the proportion of days covered (PDC) by statins during follow-up as a marker of statin therapy. The primary outcome was a composite of the development of stroke, myocardial infarction, and all-cause death. Multivariate time-dependent Cox regression analyses were performed.RESULTSA total of 1381 patients who underwent coil embolization (n = 542) or surgical clipping (n = 839) of cerebral aneurysms were included in this study. During the mean (± SD) follow-up period of 3.83 ± 3.35 years, 335 (24.3%) patients experienced the primary outcome. Adjustments were performed for sex, age (as a continuous variable), treatment modality, aneurysm rupture status (ruptured or unruptured aneurysm), hypertension, diabetes mellitus, household income level, and prior history of ischemic stroke or intracerebral hemorrhage as time-independent variables and statin therapy during follow-up as a time-dependent variable. Consistent statin therapy (PDC > 80%) was significantly associated with a lower risk of the primary outcome (adjusted hazard ratio 0.34, 95% CI 0.14–0.85).CONCLUSIONSConsistent statin therapy was significantly associated with better prognosis after coil embolization or surgical clipping of cerebral aneurysms.

Download Full-text

Faculty Opinions recommendation of Continuous femoral nerve blocks: the impact of catheter tip location relative to the femoral nerve (anterior versus posterior) on quadriceps weakness and cutaneous sensory block.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.718015776.793477714 ◽

2013 ◽

Author(s):

Peter Gerner ◽

Thomas Danninger

Keyword(s):

Femoral Nerve ◽

Sensory Block ◽

Nerve Blocks ◽

Quadriceps Weakness ◽

Catheter Tip ◽

The Impact

Download Full-text

COVID-19: Time-Dependent Effective Reproduction Number and Sub-notification Effect Estimation Modeling (Preprint)

10.2196/preprints.23997 ◽

2020 ◽

Author(s):

Eduardo Atem De Carvalho ◽

Rogerio Atem De Carvalho

Keyword(s):

New York ◽

Reproduction Number ◽

Moving Average ◽

Real Data ◽

Time Dependent ◽

Initial Value ◽

Health Authorities ◽

Reproduction Numbers ◽

Effect Estimation ◽

The Impact

BACKGROUND Since the beginning of the COVID-19 pandemic, researchers and health authorities have sought to identify the different parameters that govern their infection and death cycles, in order to be able to make better decisions. In particular, a series of reproduction number estimation models have been presented, with different practical results. OBJECTIVE This article aims to present an effective and efficient model for estimating the Reproduction Number and to discuss the impacts of sub-notification on these calculations. METHODS The concept of Moving Average Method with Initial value (MAMI) is used, as well as a model for Rt, the Reproduction Number, is derived from experimental data. The models are applied to real data and their performance is presented. RESULTS Analyses on Rt and sub-notification effects for Germany, Italy, Sweden, United Kingdom, South Korea, and the State of New York are presented to show the performance of the methods here introduced. CONCLUSIONS We show that, with relatively simple mathematical tools, it is possible to obtain reliable values for time-dependent, incubation period-independent Reproduction Numbers (Rt). We also demonstrate that the impact of sub-notification is relatively low, after the initial phase of the epidemic cycle has passed.

Download Full-text

Evaluation and Validation of a Joint Stress Test to Induce Activity-Related Knee Joint Discomfort — a Prospective Case-Control Study

Sports Medicine - Open ◽

10.1186/s40798-021-00317-7 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Christiane Schön ◽

Claudia Reule ◽

Katharina Knaub ◽

Antje Micka ◽

Manfred Wilhelm ◽

...

Keyword(s):

Knee Joint ◽

Healthy Subjects ◽

Stress Test ◽

Osteoarthritis Of The Knee ◽

Time Interval ◽

Short Time Interval ◽

Joint Stress ◽

Joint Health ◽

The Impact ◽

Health Function

Abstract Background The assessment of improvement or maintenance of joint health in healthy subjects is a great challenge. The aim of the study was the evaluation of a joint stress test to assess joint discomfort in subjects with activity-related knee joint discomfort (ArJD). Results Forty-five subjects were recruited to perform the single-leg-step-down (SLSD) test (15 subjects per group). Subjects with ArJD of the knee (age 22–62 years) were compared to healthy subjects (age 24–59 years) with no knee joint discomfort during daily life sporting activity and to subjects with mild-to-moderate osteoarthritis of the knee joint (OA, Kellgren score 2–3, age 42–64 years). The subjects performed the SLSD test with two different protocols: (I) standardization for knee joint discomfort; (II) standardization for load on the knee joint. In addition, range of motion (ROM), reach test, acute pain at rest and after a single-leg squat and knee injury, and osteoarthritis outcome score (KOOS) were assessed. In OA and ArJD subjects, knee joint discomfort could be reproducibly induced in a short time interval of less than 10 min (200 steps). In healthy subjects, no pain was recorded. A clear differentiation between study groups was observed with the SLSD test (maximal step number) as well as KOOS questionnaire, ROM, and reach test. In addition, a moderate to good intra-class correlation was shown for the investigated outcomes. Conclusions These results suggest the SLSD test is a reliable tool for the assessment of knee joint health function in ArJD and OA subjects to study the improvements in their activities. Further, this model can be used as a stress model in intervention studies to study the impact of stress on knee joint health function.

Download Full-text

Impact of Matrix Metalloproteinase-9 during Periodontitis and Cardiovascular Diseases

Molecules ◽

10.3390/molecules26061777 ◽

2021 ◽

Vol 26 (6) ◽

pp. 1777

Author(s):

Gaetano Isola ◽

Alessandro Polizzi ◽

Vincenzo Ronsivalle ◽

Angela Alibrandi ◽

Giuseppe Palazzo ◽

...

Keyword(s):

Matrix Metalloproteinase ◽

Healthy Subjects ◽

Multivariate Regression Analysis ◽

Matrix Metalloproteinase 9 ◽

C Reactive Protein ◽

Reactive Protein ◽

Hs Crp ◽

The Impact ◽

Negative Predictor ◽

Metalloproteinase 9

Matrix metalloproteinase-9 (MMP-9) has been shown to play a key role in endothelial function and perhaps pivotal in the correlation between periodontal disease and cardiovascular disease (CVD). For the study, the impact of MMP-9 of periodontitis and CVD on serum and saliva concentrations was analyzed. For the study patients with periodontitis (n = 31), CVD (n = 31), periodontitis + CVD (n = 31), and healthy patients (n = 31) were enrolled. Clinical and demographic characteristics as well as serum and salivary MMP-9 were evaluated. MMP-9 concentrations in serum and saliva were statistically elevated in patients with CVD (p < 0.01) and in patients with periodontitis plus CVD (p < 0.001) compared to patients with periodontitis and healthy subjects. Multivariate regression analysis showed that c-reactive protein (hs-CRP) was the only significant predictor for MMP-9 serum (p < 0.001), whereas hs-CRP (p < 0.001) and total cholesterol (p = 0.029) were the statistically significant salivary MMP-9 predictors. This study evidenced that patients with CVD and periodontitis + CVD presented elevated MMP-9 concentrations in serum and saliva compared to patients with periodontitis and healthy subjects. Furthermore, hs-CRP was a negative predictor of serum and salivary MMP-9.

Download Full-text