Alterations in corticospinal excitability with imposed vs. voluntary fatigue in human hand muscles

2002 ◽  
Vol 92 (5) ◽  
pp. 2131-2138 ◽  
Author(s):  
Julia B. Pitcher ◽  
Timothy S. Miles
Keyword(s):  
Muscle Activation ◽  
Cortical Plasticity ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Afferent Input ◽  
Voluntary Contraction ◽  
Human Hand ◽  
Motor Point ◽  
Initial Depression ◽  
Spinal Excitability

We aimed to determine whether postexercise depression of motor-evoked potentials (MEPs) could be demonstrated without voluntary muscle activation in humans. Voluntary fatigue was induced with a 2-min maximal voluntary contraction (MVC) of the first dorsal interosseous (FDI) muscle. On another occasion, “electrical fatigue” was induced with trains of shocks delivered for 2 min over the FDI motor point. Five of the twelve subjects also underwent “sequential fatigue” consisting of a 2-min MVC of FDI followed by 20 min of rest and then 2 min of motor point stimulation. Voluntary fatigue induced MEP depression that persisted for at least 20 min. Electrical fatigue induced a transient MEP facilitation that subsided 20 min after the stimulation and became depressed within 30 min. Thus MEP depression can be induced by both voluntary and electrical fatigue. With electrical fatigue, the initial depression is “masked” by transient MEP facilitation, reflecting cortical plasticity induced by the prolonged electrical stimulation. MEP depression probably reflects tonic afferent input from the exercising muscle that alters cortical excitability without altering spinal excitability.

scholarly journals S192. EFFECTS OF NICOTINE INTAKE ON NEUROPLASTICITY IN SMOKING AND NON-SMOKING PATIENTS WITH SCHIZOPHRENIA

2020 ◽  
Vol 46 (Supplement_1) ◽  
pp. S111-S112
Author(s):  
Benjamin Pross ◽  
Patrick Schulz ◽  
Duygu Güler ◽  
Irina Papazova ◽  
Elias Wagner ◽  
...  
Keyword(s):  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Environmental Changes ◽  
Cortical Plasticity ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Receptor Activation ◽  
Pathophysiological Mechanism ◽  
Direct Current Stimulation ◽  
Nicotine Consumption

Abstract Background Cortical plasticity – the ability to reorganize synaptic connections and adapt to environmental changes – appears to be impaired in schizophrenia patients. Results suggest the dysfunctional plasticity to be a key pathophysiological mechanism. Different non-invasive brain stimulation (NIBS) techniques have been used to modulate and induce cortical plasticity. In healthy subjects, nicotine was shown to play an important role in plasticity induction and is capable to alter cortical excitability and plasticity, induced by NIBS techniques. Our goal was to investigate the promising effects of a nicotine receptor activation done by Varenicline and the combination with anodal transcranial direct current stimulation (a-tDCS) on neuroplastic changes in schizophrenia patients. Methods Our sample consisted out of twenty-four individuals with schizophrenia, twelve smokers and twelve non-smokers. Every participant received Varenicline and Placebo, combined with anodal transcranial direct current stimulation (a-tDCS), to induce non-focal plasticity. We inferred plasticity changes by monitoring changes in cortical excitability. This was done via motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS). The MEPs were recorded before and three hours after Varenicline/Placebo intake. Following the direct current stimulation, we monitored excitability changes for up to one hour. Results Significant effects through the mere Varenicline consumption or withdrawal effects could not be found in any group. However, we observed a numeric temporary decrease of excitability after a-tDCS in non-smokers following Varenicline intake. This decrease compared to the placebo condition was visible 20 minutes after a-tDCS but vanished over time. Smokers did not show any excitability changes after a-tDCS and the nicotinic receptor stimulation did not show any influence. Excitability changes after stimulation in contrast to the baseline measurement were not evident. Discussion Our results show that an activation of nicotinic receptors in schizophrenia patients does not induce excitability changes. The modulating effect of nicotine in plasticity induction via anodal transcranial direct current stimulation could not be confirmed for patients with schizophrenia. We could show that chronic nicotine consumption in patients with schizophrenia or nicotine withdrawal does not lead to fundamental excitability changes. Acute nicotine consumption has only small effects on cortical excitability in non-smokers.

Adaptations in the activation of human skeletal muscle induced by short-term isometric resistance training

2007 ◽  
Vol 103 (1) ◽  
pp. 402-411 ◽  
Author(s):  
Christopher Del Balso ◽  
E. Cafarelli
Keyword(s):  
Resistance Training ◽  
Muscle Activation ◽  
Voluntary Contraction ◽  
Spinal Reflex ◽  
Voluntary Activation ◽  
Control Group ◽  
Hoffman Reflex ◽  
V Wave ◽  
Spinal Excitability ◽  
Rate Of Activation

This study employed longitudinal measures of evoked spinal reflex responses (Hoffman reflex, V wave) to investigate changes in the activation of muscle and to determine if there are “linked” neural adaptations in the motor pathway following isometric resistance training. Twenty healthy, sedentary males were randomly assigned to either the trained ( n = 10) or control group ( n = 10). The training protocol consisted of 12 sessions of isometric resistance training of the plantar flexor muscles over a 4-wk period. All subjects were tested prior to and after the 4-wk period. To estimate changes in spinal excitability, soleus Hoffman (H) reflex and M wave recruitment curves were produced at rest and during submaximal contractions. Recruitment curves were analyzed using the slope method (Hslp/Mslp). Modulation of efferent neural drive was assessed through evoked V wave responses (V/Mmax) at 50, 75, and 100% maximal voluntary contraction (MVC). After 4 weeks, MVC torque increased 20.0 ± 13.9% (mean ± SD) in the trained group. The increase in MVC was accompanied by significant increases in the rate of torque development (42.5 ± 13.3%), the soleus surface electromyogram (60.7 ± 30.8%), voluntary activation (2.8 ± 0.1%), and the rate of activation (48.7 ± 24.3%). Hslp/Mslp was not altered by training; however, V/Mmax increased 57.3 ± 34.2% during MVC. These results suggest that increases in MVC observed in the first few days of isometric resistance training can be accounted for by an increase in the rate of activation at the onset of muscle contraction. Augmentation of muscle activation may be due to increased volitional drive from supraspinal centers.

Cortical Excitability in Chronic Stroke and Modulation by Training: A TMS Study

2009 ◽  
Vol 23 (5) ◽  
pp. 486-493 ◽  
Author(s):  
Jakob Udby Blicher ◽  
Johannes Jakobsen ◽  
Grethe Andersen ◽  
Jørgen Feldbæk Nielsen
Keyword(s):  
Inhibitory Activity ◽  
Cortical Plasticity ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Training Session ◽  
Intracortical Inhibition ◽  
Intracortical Circuits ◽  
And Gender ◽  
Healthy Participants ◽  
Pulse Stimulation

Background. A possible role for GABA in regulating cortical plasticity after stroke has been proposed. Objective. To investigate changes in intracortical inhibitory and facilitatory circuits in the affected hemisphere more than 6 months after stroke, as well as modulation of excitability by a single training session. Methods. A total of 22 patients >6 months after stroke were compared to age- and gender-matched healthy participants. Cortical excitability was assessed by transcranial magnetic stimulation (TMS), including paired-pulse stimulation, before and up to 30 minutes after a single 15-minute session of 1 Hz thumb abduction-adduction movements. Results. At baseline, TMS showed decreased intracortical inhibition in the affected hemisphere of patients ( P = .004) compared to healthy participants. After training a short-lasting decline in motor evoked potentials was observed in both patients ( P = .002) and healthy participants ( P = .06). Moreover, in healthy participants, inhibitory activity decreased up to 30 minutes after training whereas no significant change was seen in the patients. Conclusions. The findings indicate that inhibitory intracortical circuits are less active after stroke, and no change in inhibitory activity is evident after a single training session. This may indicate that intracortical disinhibition is beneficial during recovery and that an impaired capacity for modulation remains in the chronic stage of stroke.

Central nervous adaptations following 1 wk of wrist and hand immobilization

2008 ◽  
Vol 105 (1) ◽  
pp. 139-151 ◽  
Author(s):  
Jesper Lundbye-Jensen ◽  
Jens Bo Nielsen
Keyword(s):  
Physical Activity ◽  
Motor Cortex ◽  
Motor Evoked Potentials ◽  
Afferent Input ◽  
Voluntary Contraction ◽  
H Reflex ◽  
Abductor Pollicis Brevis ◽  
Corticomuscular Coherence ◽  
Reduced Physical Activity ◽  
Static Contractions

Plastic neural changes have been documented in relation to different types of physical activity, but little is known about central nervous system plasticity accompanying reduced physical activity and immobilization. In the present study we investigated whether plastic neural changes occur in relation to 1 wk of immobilization of the nondominant wrist and hand and a corresponding period of recovery in 10 able-bodied volunteers. After immobilization, maximal voluntary contraction torque decreased and the variability of submaximal static contractions increased significantly without evidence of changes in muscle contractile properties. Hoffmann (H)-reflex amplitudes and the ratios of H-slope to M-slope increased significantly in flexor carpi radialis and abductor pollicis brevis at rest and during contraction without changes in corticospinal excitability, estimated from motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation. Corticomuscular coherence measures were derived from EEG and EMG obtained during static contractions. After immobilization, corticomuscular coherence in the 15- to 35-Hz range associated with maximum negative cumulant values at lags corresponding to MEP latencies decreased. One week after cast removal, all measurements returned to preimmobilization levels. The increased H-reflex amplitudes without changes in MEPs may suggest that presynaptic inhibition or postactivation depression of Ia afferents is reduced following immobilization. Reduced corticomuscular coherence may be caused by changes in afferent input at spinal and cortical levels or by changes in the descending drive from motor cortex. Further studies are needed to elucidate the mechanisms underlying the observed increased spinal excitability and reduced coupling between motor cortex and spinal motoneuronal activity following immobilization.

An Increase in Cortical Excitability with No Change in Spinal Excitability during Motor Imagery

1996 ◽  
Vol 83 (1) ◽  
pp. 288-290 ◽  
Author(s):  
Susumu Yahagi ◽  
Kuniyoshi Shimura ◽  
Tatsuya Kasai
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Motor Imagery ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Emg Activity ◽  
Electrical Stimuli ◽  
Spinal Excitability ◽  
Flexor Carpi Radialis Muscle

During motor imagery, to estimate changes in excitability of flexor carpi radialis muscle motoneurons of the spinal and cortical levels, electrical stimuli for recording H-reflex and transcranial magnetic stimulation (TMS) for recording motor evoked potentials (MEPs) were used. In the absence of movement or detectable EMG activity during motor magery, there was an increase in cortical excitability with no change in spinal excitability

scholarly journals Modulation of Cerebellar Cortical Plasticity Using Low-Intensity Focused Ultrasound for Poststroke Sensorimotor Function Recovery

2018 ◽  
Vol 32 (9) ◽  
pp. 777-787 ◽  
Author(s):  
Hongchae Baek ◽  
Ki Joo Pahk ◽  
Min-Ju Kim ◽  
Inchan Youn ◽  
Hyungmin Kim
Keyword(s):  
Brain Stimulation ◽  
Focused Ultrasound ◽  
Cortical Plasticity ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Brain Regions ◽  
Adaptive Plasticity ◽  
Alternative Pathways ◽  
Low Intensity

Background. Stroke affects widespread brain regions through interhemispheric connections by influencing bilateral motor activity. Several noninvasive brain stimulation techniques have proved their capacity to compensate the functional loss by manipulating the neural activity of alternative pathways. Over the past few decades, brain stimulation therapies have been tailored within the theoretical framework of modulation of cortical excitability to enhance adaptive plasticity after stroke. Objective. However, considering the vast difference between animal and human cerebral cortical structures, it is important to approach specific neuronal target starting from the higher order brain structure for human translation. The present study focuses on stimulating the lateral cerebellar nucleus (LCN), which sends major cerebellar output to extensive cortical regions. Methods. In this study, in vivo stroke mouse LCN was exposed to low-intensity focused ultrasound (LIFU). After the LIFU exposure, animals underwent 4 weeks of rehabilitative training. Results. During the cerebellar LIFU session, motor-evoked potentials (MEPs) were generated in both forelimbs accompanying excitatory sonication parameter. LCN stimulation group on day 1 after stroke significantly enhanced sensorimotor recovery compared with the group without stimulation. The recovery has maintained for a 4-week period in 2 behavior tests. Furthermore, we observed a significantly decreased level of brain edema and tissue swelling in the affected hemisphere 3 days after the stroke. Conclusions. This study provides the first evidence showing that LIFU-induced cerebellar modulation could be an important strategy for poststroke recovery. A longer follow-up study is, however, necessary in order to fully confirm the effects of LIFU on poststroke recovery.

scholarly journals Strategies to augment volitional and reflex function may improve locomotor capacity following incomplete spinal cord injury

2018 ◽  
Vol 119 (3) ◽  
pp. 894-903
Author(s):  
Kristan A. Leech ◽  
Hyosub E. Kim ◽  
T. George Hornby
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Muscle Activation ◽  
Afferent Input ◽  
Incomplete Spinal Cord Injury ◽  
Locomotor Function ◽  
Cord Injury ◽  
Neurophysiological Mechanisms ◽  
Locomotor Capacity ◽  
Spinal Excitability

Many studies highlight the remarkable plasticity demonstrated by spinal circuits following an incomplete spinal cord injury (SCI). Such plasticity can contribute to improvements in volitional motor recovery, such as walking function, although similar mechanisms underlying this recovery may also contribute to the manifestation of exaggerated responses to afferent input, or spastic behaviors. Rehabilitation interventions directed toward augmenting spinal excitability have shown some initial success in improving locomotor function. However, the potential effects of these strategies on involuntary motor behaviors may be of concern. In this article, we provide a brief review of the mechanisms underlying recovery of volitional function and exaggerated reflexes, and the potential overlap between these changes. We then highlight findings from studies that explore changes in spinal excitability during volitional movement in controlled conditions, as well as altered kinematic and behavioral performance during functional tasks. The initial focus will be directed toward recovery of reflex and volitional behaviors following incomplete SCI, followed by recent work elucidating neurophysiological mechanisms underlying patterns of static and dynamic muscle activation following chronic incomplete SCI during primarily single-joint movements. We will then transition to studies of locomotor function and the role of altered spinal integration following incomplete SCI, including enhanced excitability of specific spinal circuits with physical and pharmacological interventions that can modulate locomotor output. The effects of previous and newly developed strategies will need to focus on changes in both volitional function and involuntary spastic reflexes for the successful translation of effective therapies to the clinical setting.

scholarly journals Shouting strengthens maximal voluntary force and is associated with augmented pupillary dilation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yudai Takarada ◽  
Daichi Nozaki
Keyword(s):  
Pupil Size ◽  
Motor System ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Silent Period ◽  
Voluntary Contraction ◽  
Enhancement Effect ◽  
System State ◽  
Maximal Voluntary Force

AbstractPrevious research has demonstrated that human maximal voluntary force is generally limited by neural inhibition. Producing a shout during maximal exertion effort enhances the force levels of maximal voluntary contraction. However, the mechanisms underlying this enhancement effect on force production remain unclear. We investigated the influence of producing a shout on the pupil-linked neuromodulatory system state by examining pupil size. We also examined its effects on the motor system state by examining motor evoked potentials in response to transcranial magnetic stimulation applied over the contralateral primary motor cortex, and by evaluating handgrip maximal voluntary force. Analysis revealed that producing a shout significantly increased handgrip maximal voluntary force, followed by an increase in pupil size and a reduction of the cortical silent period. Our results indicate that producing a shout increased handgrip maximal voluntary force through the enhancement of motor cortical excitability, possibly via the enhancement of noradrenergic system activity. This study provides evidence that the muscular force-enhancing effect of shouting during maximal force exertion is related to both the motor system state and the pupil-linked neuromodulatory system state.

scholarly journals Investigation of Optimal Afferent Feedback Modality for Inducing Neural Plasticity with A Self-Paced Brain-Computer Interface

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3761 ◽  
Author(s):  
Mads Jochumsen ◽  
Sylvain Cremoux ◽  
Lucien Robinault ◽  
Jimmy Lauber ◽  
Juan Arceo ◽  
...  
Keyword(s):  
Neural Plasticity ◽  
Tibialis Anterior ◽  
Cortical Plasticity ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Passive Movement ◽  
Afferent Feedback ◽  
Computer Interfaces ◽  
Mixed Regression ◽  
Feedback Modalities

Brain-computer interfaces (BCIs) can be used to induce neural plasticity in the human nervous system by pairing motor cortical activity with relevant afferent feedback, which can be used in neurorehabilitation. The aim of this study was to identify the optimal type or combination of afferent feedback modalities to increase cortical excitability in a BCI training intervention. In three experimental sessions, 12 healthy participants imagined a dorsiflexion that was decoded by a BCI which activated relevant afferent feedback: (1) electrical nerve stimulation (ES) (peroneal nerve—innervating tibialis anterior), (2) passive movement (PM) of the ankle joint, or (3) combined electrical stimulation and passive movement (Comb). The cortical excitability was assessed with transcranial magnetic stimulation determining motor evoked potentials (MEPs) in tibialis anterior before, immediately after and 30 min after the BCI training. Linear mixed regression models were used to assess the changes in MEPs. The three interventions led to a significant (p < 0.05) increase in MEP amplitudes immediately and 30 min after the training. The effect sizes of Comb paradigm were larger than ES and PM, although, these differences were not statistically significant (p > 0.05). These results indicate that the timing of movement imagery and afferent feedback is the main determinant of induced cortical plasticity whereas the specific type of feedback has a moderate impact. These findings can be important for the translation of such a BCI protocol to the clinical practice where by combining the BCI with the already available equipment cortical plasticity can be effectively induced. The findings in the current study need to be validated in stroke populations.

scholarly journals Self-Paced Online vs. Cue-Based Offline Brain–Computer Interfaces for Inducing Neural Plasticity

2019 ◽  
Vol 9 (6) ◽  
pp. 127 ◽  
Author(s):  
Mads Jochumsen ◽  
Muhammad Samran Navid ◽  
Rasmus Wiberg Nedergaard ◽  
Nada Signal ◽  
Usman Rashid ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Neural Plasticity ◽  
Stroke Rehabilitation ◽  
Cortical Plasticity ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Brain Computer Interfaces ◽  
Post Intervention ◽  
Computer Interfaces ◽  
The Absolute

Brain–computer interfaces (BCIs), operated in a cue-based (offline) or self-paced (online) mode, can be used for inducing cortical plasticity for stroke rehabilitation by the pairing of movement-related brain activity with peripheral electrical stimulation. The aim of this study was to compare the difference in cortical plasticity induced by the two BCI modes. Fifteen healthy participants participated in two experimental sessions: cue-based BCI and self-paced BCI. In both sessions, imagined dorsiflexions were extracted from continuous electroencephalogram (EEG) and paired 50 times with the electrical stimulation of the common peroneal nerve. Before, immediately after, and 30 min after each intervention, the cortical excitability was measured through the motor-evoked potentials (MEPs) of tibialis anterior elicited through transcranial magnetic stimulation. Linear mixed regression models showed that the MEP amplitudes increased significantly (p < 0.05) from pre- to post- and 30-min post-intervention in terms of both the absolute and relative units, regardless of the intervention type. Compared to pre-interventions, the absolute MEP size increased by 79% in post- and 68% in 30-min post-intervention in the self-paced mode (with a true positive rate of ~75%), and by 37% in post- and 55% in 30-min post-intervention in the cue-based mode. The two modes were significantly different (p = 0.03) at post-intervention (relative units) but were similar at both post timepoints (absolute units). These findings suggest that immediate changes in cortical excitability may have implications for stroke rehabilitation, where it could be used as a priming protocol in conjunction with another intervention; however, the findings need to be validated in studies involving stroke patients.

Sign in / Sign up

Export Citation Format

Share Document