scholarly journals Intensity Sensitive Modulation Effect of Theta Burst Form of Median Nerve Stimulation on the Monosynaptic Spinal Reflex

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Kuei-Lin Yeh ◽  
Po-Yu Fong ◽  
Ying-Zu Huang
Keyword(s):  
Median Nerve ◽  
Amplitude Ratio ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
H Reflex ◽  
Spinal Reflex ◽  
M Wave ◽  
Therapeutic Benefits ◽  
Median Nerve Stimulation ◽  
Theta Burst

The effects of electrical stimulation of median nerve with a continuous theta burst pattern (EcTBS) on the spinal H-reflex were studied. Different intensities and durations of EcTBS were given to the median nerve to 11 healthy individuals. The amplitude ratio of the H-reflex to maximum M wave (H/M ratio), corticospinal excitability and inhibition measured using motor evoked potentials (MEPs), short-interval intracortical inhibition and facilitation (SICI/ICF), spinal reciprocal inhibition (RI), and postactivation depression (PAD) were measured before and after EcTBS. In result, the H/M ratio was reduced followed by EcTBS at 90% H-reflex threshold, and the effect lasted longer after 1200 pulses than after 600 pulses of EcTBS. In contrast, EcTBS at 110% threshold facilitated the H/M ratio, while at 80% threshold it had no effect. Maximum M wave, MEPs, SICI/ICF, RI, and PAD all remained unchanged after EcTBS. In conclusion, EcTBS produced lasting effects purely on the H-reflex, probably, through effects on postsynaptic plasticity. The effect of EcTBS depends on the intensity and duration of stimulation. EcTBS is beneficial to research on mechanisms of human plasticity. Moreover, its ability to modulate spinal excitability is expected to have therapeutic benefits on neurological disorders involving spinal cord dysfunction.

scholarly journals Indirect Vibration of the Upper Limbs Alters Transmission Along Spinal but Not Corticospinal Pathways

2021 ◽  
Vol 15 ◽  
Author(s):  
Trevor S. Barss ◽  
David F. Collins ◽  
Dylan Miller ◽  
Amit N. Pujari
Keyword(s):  
Median Nerve ◽  
Presynaptic Inhibition ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
H Reflex ◽  
Cutaneous Reflexes ◽  
Spinal Pathways ◽  
Median Nerve Stimulation ◽  
The Right ◽  
Stimulation Of

The use of upper limb vibration (ULV) during exercise and rehabilitation continues to gain popularity as a modality to improve function and performance. Currently, a lack of knowledge of the pathways being altered during ULV limits its effective implementation. Therefore, the aim of this study was to investigate whether indirect ULV modulates transmission along spinal and corticospinal pathways that control the human forearm. All measures were assessed under CONTROL (no vibration) and ULV (30 Hz; 0.4 mm displacement) conditions while participants maintained a small contraction of the right flexor carpi radialis (FCR) muscle. To assess spinal pathways, Hoffmann reflexes (H-reflexes) elicited by stimulation of the median nerve were recorded from FCR with motor response (M-wave) amplitudes matched between conditions. An H-reflex conditioning paradigm was also used to assess changes in presynaptic inhibition by stimulating the superficial radial (SR) nerve (5 pulses at 300Hz) 37 ms prior to median nerve stimulation. Cutaneous reflexes in FCR elicited by stimulation of the SR nerve at the wrist were also recorded. To assess corticospinal pathways, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation of the contralateral motor cortex were recorded from the right FCR and biceps brachii (BB). ULV significantly reduced H-reflex amplitude by 15.7% for both conditioned and unconditioned reflexes (24.0 ± 15.7 vs. 18.4 ± 11.2% Mmax; p < 0.05). Middle latency cutaneous reflexes were also significantly reduced by 20.0% from CONTROL (−1.50 ± 2.1% Mmax) to ULV (−1.73 ± 2.2% Mmax; p < 0.05). There was no significant effect of ULV on MEP amplitude (p > 0.05). Therefore, ULV inhibits cutaneous and H-reflex transmission without influencing corticospinal excitability of the forearm flexors suggesting increased presynaptic inhibition of afferent transmission as a likely mechanism. A general increase in inhibition of spinal pathways with ULV may have important implications for improving rehabilitation for individuals with spasticity (SCI, stroke, MS, etc.).

scholarly journals Indirect Vibration of the Upper Limbs Alters Transmission Along Spinal but not Corticospinal Pathways

2020 ◽  
Author(s):  
Trevor S. Barss ◽  
David F. Collins ◽  
Dylan Miller ◽  
Amit N. Pujari
Keyword(s):  
Median Nerve ◽  
Presynaptic Inhibition ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
H Reflex ◽  
Cutaneous Reflexes ◽  
Spinal Pathways ◽  
Median Nerve Stimulation ◽  
The Right ◽  
Stimulation Of

AbstractThe aim of this study was to investigate whether indirect upper limb vibration (ULV) modulates transmission along spinal and corticospinal pathways that control the human forearm. All measures were assessed under CONTROL (no vibration) and ULV (30 Hz; 0.4 mm displacement) conditions while participants maintained a small contraction of the right flexor carpi radialis (FCR) muscle. To assess spinal pathways, Hoffmann reflexes (H-reflexes) elicited by stimulation of the median nerve were recorded from FCR with motor response (M-wave) amplitudes matched between conditions. An H-reflex conditioning paradigm was also used to assess changes in presynaptic inhibition by stimulating the superficial radial (SR) nerve (5 pulses at 300Hz) 37 ms prior to median nerve stimulation. Cutaneous reflexes in FCR elicited by stimulation of the SR nerve at the wrist were also recorded. To assess corticospinal pathways, motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation of the contralateral motor cortex were recorded from the right FCR and biceps brachii (BB). ULV significantly reduced H-reflex amplitude by 15.7% for both conditioned and unconditioned reflexes (24.0±15.7 vs 18.4±11.2 % Mmax; p<0.05). Middle latency cutaneous reflexes were also significantly reduced by 20.0% from CONTROL (−1.50 ± 2.1 % Mmax) to ULV (−1.73 ± 2.2 % Mmax; p<0.05). There was no significant effect of ULV on MEP amplitude (p>0.05). Therefore, ULV inhibits cutaneous and H-reflex transmission without influencing corticospinal excitability of the forearm flexors suggesting increased presynaptic inhibition of afferent transmission as a likely mechanism. A general increase in inhibition of spinal pathways with ULV may have important implications for improving rehabilitation for individuals with spasticity (SCI, stroke, MS, etc).

The pulse duration of electrical stimulation influences H-reflexes but not corticospinal excitability for tibialis anterior

2014 ◽  
Vol 92 (10) ◽  
pp. 821-825
Author(s):  
Alyssa R. Hindle ◽  
Jenny W.H. Lou ◽  
David F. Collins
Keyword(s):  
Electrical Stimulation ◽  
Pulse Duration ◽  
Peroneal Nerve ◽  
Motor Evoked Potentials ◽  
Common Peroneal Nerve ◽  
H Reflex ◽  
M Wave ◽  
Recruitment Curve ◽  
Afferent Volley ◽  
The Common

The afferent volley generated by neuromuscular electrical stimulation (NMES) influences corticospinal (CS) excitability and frequent NMES sessions can strengthen CS pathways, resulting in long-term improvements in function. This afferent volley can be altered by manipulating NMES parameters. Presently, we manipulated one such parameter, pulse duration, during NMES over the common peroneal nerve and assessed the influence on H-reflexes and CS excitability. We hypothesized that compared with shorter pulse durations, longer pulses would (i) shift the H-reflex recruitment curve to the left, relative to the M-wave curve; and (ii) increase CS excitability more. Using 3 pulse durations (50, 200, 1000 μs), M-wave and H-reflex recruitment curves were collected and, in separate experiments, CS excitability was assessed by comparing motor evoked potentials elicited before and after 30 min of NMES. Despite finding a leftward shift in the H-reflex recruitment curve when using the 1000 μs pulse duration, consistent with a larger afferent volley for a given efferent volley, the increases in CS excitability were not influenced by pulse duration. Hence, although manipulating pulse duration can alter the relative recruitment of afferents and efferents in the common peroneal nerve, under the present experimental conditions it is ineffective for maximizing CS excitability for rehabilitation.

Increased spinal reflex excitability is not associated with neural plasticity underlying the cross-education effect

2006 ◽  
Vol 100 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Olle Lagerquist ◽  
E. Paul Zehr ◽  
David Docherty
Keyword(s):  
Strength Training ◽  
Plantar Flexion ◽  
Exercise Group ◽  
H Reflex ◽  
Spinal Reflex ◽  
Control Group ◽  
M Wave ◽  
Education Effect ◽  
Cross Education ◽  
The Cross

The purpose of this study was to examine the effects of a 5-wk unilateral, isometric strength-training program on plasticity in the spinal Hoffmann (H-) reflex in both the trained and untrained legs. Sixteen participants, 22–42 yr old, were assigned to either a control ( n = 6) or an exercise group ( n = 10). Both groups were tested for plantar flexion maximal voluntary isometric contractions (MVIC) and soleus H-reflex amplitude in both limbs, at the beginning and at the end of a 5-wk interval. Participants in the exercise group showed significantly increased MVIC in both legs after training ( P < 0.05), whereas strength was unchanged in the control group for either leg. Subjects in the exercise group displayed increased ( P < 0.05) H-reflex amplitudes on the ascending limb of the recruitment curve (at an equivalent M wave of 5% of the maximal M wave, HA) only in the trained leg. Maximal H-reflex and M-wave remained unchanged with training. Increased amplitude of HA in the trained limb concurrent with increased strength suggests that spinal mechanisms may underlie the changes in strength, possibly because of increased α-motoneuronal excitability or reduced presynaptic inhibition. Despite a similar increase in strength in the contralateral limb of the exercise group, HA amplitude was unchanged. We conclude that the cross-education effect of strength training may be due to supraspinal to a greater extent than spinal mechanisms.

Changes in Segmental and Motor Cortical Output With Contralateral Muscle Contractions and Altered Sensory Inputs in Humans

2003 ◽  
Vol 90 (4) ◽  
pp. 2451-2459 ◽  
Author(s):  
Tibor Hortobágyi ◽  
Janet L. Taylor ◽  
Nicolas T. Petersen ◽  
Gabrielle Russell ◽  
Simon C. Gandevia
Keyword(s):  
Muscle Contraction ◽  
Nerve Stimulation ◽  
Motor Evoked Potentials ◽  
Muscle Spindles ◽  
Voluntary Contraction ◽  
H Reflex ◽  
Tendon Vibration ◽  
Wrist Flexion ◽  
Median Nerve Stimulation ◽  
Voluntary Contractions

Motor or sensory activity in one arm can affect the other arm. We tested the hypothesis that a voluntary contraction can affect the motor pathway to the contralateral homologous muscle and investigated whether alterations in sensory input might mediate such effects. Responses to transcranial magnetic stimulation [motor-evoked potentials (MEPs)], stimulation of the descending tracts [cervicomedullary MEPs (CMEPs)], and peripheral nerve stimulation (H-reflex) were recorded from the relaxed right flexor carpi radialis (FCR), while the left arm underwent unilateral interventions (5 s duration) that included voluntary contraction, muscle contraction evoked through percutaneous stimulation, tendon vibration, and cutaneous and mixed nerve stimulation. During moderate to strong voluntary wrist flexion on the left, MEPs in the right FCR increased, CMEPs were unaffected, and the H-reflex was depressed. These results are consistent with an increase in excitability of the motor cortex, no effect on the motoneuron pool, and presynaptic inhibition of Ia afferents. In contrast, percutaneous muscle stimulation facilitated both MEPs and the H-reflex. However, muscle contraction produced by a combination of voluntary effort and electrical stimulation also reduced the contralateral H-reflex. After voluntary contractions, the H-reflex remained depressed for 35 s, but after stimulationevoked contractions, it rapidly returned to baseline. Under both conditions, MEPs recovered rapidly. After voluntary contractions, CMEPs were also depressed for approximately 10 s despite their lack of change during contractions. Wrist tendon vibration (100 Hz) did not affect, and 20-Hz median nerve stimulation or forearm medial cutaneous nerve stimulation mildly facilitated, the H-reflex without affecting MEPs. Voluntary wrist extension, similarly to wrist flexion, increased MEPs and depressed H-reflexes. However, ankle dorsiflexion facilitated the H-reflex akin to the Jendrassik maneuver. These data suggest that a unilateral voluntary muscle contraction has contralateral effects at both cortical and segmental levels and that the segmental effects are not replicated by stimulated muscle contraction or by input from muscle spindles or non-nociceptive cutaneous afferents.

scholarly journals Repetitive Peripheral Magnetic Stimulation of Wrist Extensors Enhances Cortical Excitability and Motor Performance in Healthy Individuals

2021 ◽  
Vol 15 ◽  
Author(s):  
Mitsuhiro Nito ◽  
Natsuki Katagiri ◽  
Kaito Yoshida ◽  
Tadaki Koseki ◽  
Daisuke Kudo ◽  
...  
Keyword(s):  
Neural Plasticity ◽  
Motor Performance ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Stimulus Frequency ◽  
Intracortical Inhibition ◽  
Hoffmann Reflex ◽  
M Wave

Repetitive peripheral magnetic stimulation (rPMS) may improve motor function following central nervous system lesions, but the optimal parameters of rPMS to induce neural plasticity and mechanisms underlying its action remain unclear. We examined the effects of rPMS over wrist extensor muscles on neural plasticity and motor performance in 26 healthy volunteers. In separate experiments, the effects of rPMS on motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), direct motor response (M-wave), Hoffmann-reflex, and ballistic wrist extension movements were assessed before and after rPMS. First, to examine the effects of stimulus frequency, rPMS was applied at 50, 25, and 10 Hz by setting a fixed total number of stimuli. A significant increase in MEPs of wrist extensors was observed following 50 and 25 Hz rPMS, but not 10 Hz rPMS. Next, we examined the time required to induce plasticity by increasing the number of stimuli, and found that at least 15 min of 50 and 25 Hz rPMS was required. Based on these parameters, lasting effects were evaluated following 15 min of 50 or 25 Hz rPMS. A significant increase in MEP was observed up to 60 min following 50 and 25 Hz rPMS; similarly, an attenuation of SICI and enhancement of ICF were also observed. The maximal M-wave and Hoffmann-reflex did not change, suggesting that the increase in MEP was due to plastic changes at the motor cortex. This was accompanied by increasing force and electromyograms during wrist ballistic extension movements following 50 and 25 Hz rPMS. These findings suggest that 15 min of rPMS with 25 Hz or more induces an increase in cortical excitability of the relevant area rather than altering the excitability of spinal circuits, and has the potential to improve motor output.

scholarly journals A Re-evaluation of Whether Non-monosynaptic Homonymous H Reflex Facilitation Tests Propriospinal Circuits

2021 ◽  
Vol 15 ◽  
Author(s):  
Karen M. Fisher ◽  
Stuart N. Baker
Keyword(s):  
Median Nerve ◽  
Human Subjects ◽  
Conditioning Stimulus ◽  
Macaque Monkey ◽  
H Reflex ◽  
Healthy Human ◽  
Median Nerve Stimulation ◽  
Important Pathway ◽  
Peripheral Axon ◽  
Forearm Flexor

The C3–C4 propriospinal system is an important pathway mediating movement in cats; it contributes to movements in primates (including humans), and may have a role in recovery after lesion. Validated clinical tests of this system would find many applications, therefore we sought to test whether non-monosynaptic homonymous facilitation of the forearm flexor H reflex is mediated solely via a C3–C4 propriospinal pathway. In one anesthetized macaque monkey, median nerve stimulation elicited an H reflex in the flexor carpi radialis (FCR). Median nerve conditioning stimuli at sub-threshold intensities facilitated the H reflex, for inter-stimulus intervals up to 30 ms. Successive spinal surgical hemisections were then made. C2 lesion left the homonymous facilitation intact, suggesting mediation by spinal, not supraspinal pathways. Facilitation also remained after a second lesion at C5, indicating a major role for segmental (C7–C8) rather than propriospinal (C3–C4) interneurons. In separate experiments in five healthy human subjects, a threshold tracking approach assessed changes in peripheral axon excitability after conditioning stimulation. This was found to be enhanced up to 20 ms after the conditioning stimulus, and could partly, although not completely, underlie the H reflex facilitation seen. We conclude that homonymous facilitation of the H reflex in FCR can be produced by segmental spinal mechanisms, as well as by a supranormal period of nerve excitability. Unfortunately, this straightforward test cannot therefore be used for selective assessment of propriospinal circuits.

scholarly journals Human Theta Burst Stimulation Combined with Subsequent Electroacupuncture Increases Corticospinal Excitability

2020 ◽  
Vol 2020 ◽  
pp. 1-8 ◽  
Author(s):  
Jiali Li ◽  
Meng Ren ◽  
Wenjing Wang ◽  
Shutian Xu ◽  
Sicong Zhang ◽  
...  
Keyword(s):  
Motor Evoked Potentials ◽  
Short Interval ◽  
Silent Period ◽  
Intracortical Inhibition ◽  
Corticospinal Excitability ◽  
Conduction Time ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
Clinical Trial Registry ◽  
Theta Burst

Objective. Intermittent theta burst stimulation (iTBS) is a widely used noninvasive brain stimulation for the facilitation of corticospinal excitability (CSE). Previous studies have shown that acupuncture applied to acupoints associated with motor function in healthy people can reduce the amplitude of the motor-evoked potentials (MEPs), which reflects the inhibition of CSE. In our work, we wanted to test whether the combination of iTBS and electroacupuncture (EA) would have different effects on CSE in humans. Methods. A single-blind sham-controlled crossover design study was conducted on 20 healthy subjects. Subjects received 20 minutes’ sham or real EA stimulation immediately after sham or real iTBS. MEPs, short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), cortical silent period (CSP), and central motor conduction time (CMCT) were recorded before each trial, and immediately, 20 minutes, and 40 minutes after the end of stimulation. Results. In the sham iTBS group, EA produced a reduction in MEPs amplitude, lasting approximately 40 minutes, while in the real iTBS group, EA significantly increased MEPs amplitude beyond 40 minutes after the end of stimulation. In sham EA group, the recorded MEPs amplitude showed no significant trend over time compared to baseline. Among all experiments, there were no significant changes in SICI, ICF, CSP, CMCT, etc. Conclusion. These data indicate that immediate application of EA after iTBS significantly increased corticospinal excitability. This trial was registered in the Chinese Clinical Trial Registry (registration no. ChiCTR1900025348).

scholarly journals Effect of Ankle Angles on the Soleus H-Reflex Excitability During Standing

Motor Control ◽  
2020 ◽  
Vol 24 (2) ◽  
pp. 189-203
Author(s):  
Aviroop Dutt-Mazumder ◽  
Richard L. Segal ◽  
Aiko K. Thompson
Keyword(s):  
Plantar Flexion ◽  
H Reflex ◽  
Spinal Reflex ◽  
System Control ◽  
M Wave ◽  
Reflex Excitability ◽  
Limb Loading ◽  
Upright Standing ◽  
Neurological Injuries ◽  
Full Body

This study investigated effects of ankle joint angle on the Hoffman’s reflex (H-reflex) excitability during loaded (weight borne with both legs) and unloaded (full body weight borne with the contralateral leg) standing in people without neurological injuries. Soleus H-reflex/M-wave recruitment curves were examined during upright standing on three different slopes that imposed plantar flexion (−15°), dorsiflexion (+15°), and neutral (0°) angles at the ankle, with the test leg loaded and unloaded. With the leg loaded and unloaded, maximum H-reflex/maximum M-wave ratio of −15° was significantly larger than those of 0° and +15° conditions. The maximum H-reflex/maximum M-wave ratios were 51%, 43%, and 41% with loaded and 56%, 46%, and 44% with unloaded for −15°, 0°, and +15° slope conditions, respectively. Thus, limb loading/unloading had limited impact on the extent of influence that ankle angles exert on the H-reflex excitability. This suggests that task-dependent central nervous system control of reflex excitability may regulate the influence of sensory input on the spinal reflex during standing.

scholarly journals Motor Cortical Plasticity Induced by Volitional Muscle Activity-Triggered Transcranial Magnetic Stimulation and Median Nerve Stimulation

2020 ◽  
Author(s):  
Pramudika Nirmani Kariyawasam ◽  
Shinya Suzuki ◽  
Susumu Yoshida
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Median Nerve ◽  
Nerve Stimulation ◽  
Magnetic Stimulation ◽  
Primary Motor Cortex ◽  
Short Interval ◽  
Corticospinal Excitability ◽  
Post Intervention ◽  
Median Nerve Stimulation ◽  
Resting Motor Threshold

Abstract BackgroundBilateral motor training (BMT) is a useful method to modify the excitability of the corticospinal system. The effects of artificial symmetrical movement on corticospinal excitability through functional electrical stimulation (FES) or transcranial magnetic stimulation (TMS) have not been reported. Therefore, we compared motor-evoked potentials (MEPs) following TMS over the ipsilateral primary motor cortex (M1) of voluntary movements after conventional BMT and repetitive artificial symmetrical movements generated through FES and TMS.MethodsSurface electromyograms of the abductor pollicis brevis (APB) muscles were recorded bilaterally in 12 healthy participants. Three sessions with different protocols were conducted: (1) bilateral finger training (BFT) involving bilateral thumb abduction, (2) right APB-triggered TMS of the ipsilateral M1 (APB-triggered i-TMS), and (3) right APB-triggered contralateral median nerve stimulation (APB-triggered c-MNS). Each protocol consisted of 360 trials for 30 min. Resting motor threshold (RMT), MEPs induced by single-pulse TMS, short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) induced by paired-pulse TMS were assessed as outcome measures at baseline and at 0, 20, 40, and 60 min after intervention.ResultsRMT showed no significant effect of intervention, time, or interaction. MEP amplitude showed a significant effect with time. MEP amplitude significantly increased at 0, 20, and 40 min post-intervention in BFT; at 0, 20, 40, and 60 min post-intervention in APB-triggered i-TMS; and at 20 and 40 min post-intervention in APB-triggered c-MNS in comparison to the baseline values. SICI was significantly decreased at 0 min post-intervention in the BFT and APB-triggered i-TMS protocols. ICF was significantly increased at 0 min post-intervention in the BFT and at 20 min post-intervention in the APB-triggered c-MNS protocol.ConclusionThe main finding of the present study was the long-lasting increase in MEP amplitude in all three mirror-symmetrical movement protocols. The observed changes are long-lasting and comparatively strong. However, the underlying neural mechanisms seem to be slightly different across the three protocols. Thus, whether voluntarily or artificially caused, repetitive symmetrical mirror movements enhance corticospinal excitability.

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