Sustained Muscle Contractions Maintained by Autonomous Neuronal Activity Within the Human Spinal Cord

2003 ◽  
Vol 90 (4) ◽  
pp. 2090-2097 ◽  
Author(s):  
Daichi Nozaki ◽  
Noritaka Kawashima ◽  
Yu Aramaki ◽  
Masami Akai ◽  
Kimitaka Nakazawa ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Muscle Contraction ◽  
Soleus Muscle ◽  
Primary Motor Cortex ◽  
Human Subjects ◽  
Silent Period ◽  
Muscle Contractions ◽  
Electromyographic Activity ◽  
Human Spinal Cord ◽  
Train Stimulation

It is well known that muscle contraction can be easily evoked in the human soleus muscle by applying single-pulse electrical stimulation to the tibial nerve at the popliteal fossa. We herein reveal the unexpected phenomenon of muscle contractions that can be observed when train stimulation is used instead. We found, in 11 human subjects, that transient electrical train stimulation (1-ms pulses, 50 Hz, 2 s) was able to induce sustained muscle contractions in the soleus muscle that outlasted the stimulation period for greater than 1 min. Subjects were unaware of their own muscle activity, suggesting that this is an involuntary muscle contraction. In fact, the excitability of the primary motor cortex (M1) with the sustained muscle contractions evaluated by transcranial magnetic stimulation was lower than the excitability with voluntary muscle contractions even when both muscle contraction levels were matched. This finding indicates that M1 was less involved in maintaining the muscle contractions. Furthermore, the muscle contractions did not come from spontaneous activity of muscle fibers or from reverberating activity within closed neuronal circuits involving motoneurons. These conclusions were made based on the respective evidence: 1) the electromyographic activity was inhibited by stimulation of the common peroneal nerve that has inhibitory connections to the soleus motoneuron pool and 2) it was not abolished after stopping the reverberation (if any) for approximately 100 ms by inducing the silent period that followed an H-reflex. These findings indicate that the sustained muscle contractions induced in this study are most likely to be maintained by autonomous activity of motoneurons and/or interneurons within the human spinal cord.

scholarly journals Corticospinal Reorganization after Locomotor Training in a Person with Motor Incomplete Paraplegia

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Nupur Hajela ◽  
Chaithanya K. Mummidisetty ◽  
Andrew C. Smith ◽  
Maria Knikou
Keyword(s):  
Spinal Cord ◽  
Primary Motor Cortex ◽  
Motor Evoked Potential ◽  
Gait Training ◽  
Spinal Reflex ◽  
Locomotor Training ◽  
Human Spinal Cord ◽  
Flexion Reflex ◽  
Cord Injury ◽  
Before And After

Activity-dependent plasticity as a result of reorganization of neural circuits is a fundamental characteristic of the central nervous system that occurs simultaneously in multiple sites. In this study, we established the effects of subthreshold transcranial magnetic stimulation (TMS) over the primary motor cortex region on the tibialis anterior (TA) long-latency flexion reflex. Neurophysiological tests were conducted before and after robotic gait training in one person with a motor incomplete spinal cord injury (SCI) while at rest and during robotic-assisted stepping. The TA flexion reflex was evoked following nonnociceptive sural nerve stimulation and was conditioned by TMS at 0.9 TA motor evoked potential resting threshold at conditioning-test intervals that ranged from 70 to 130 ms. Subthreshold TMS induced a significant facilitation on the TA flexion reflex before training, which was reversed to depression after training with the subject seated at rest. During stepping, corticospinal facilitation of the flexion reflex at early and midstance phases before training was replaced with depression at early and midswing followed by facilitation at late swing after training. These results constitute the first neurophysiologic evidence that locomotor training reorganizes the cortical control of spinal interneuronal circuits that generate patterned motor activity, modifying spinal reflex function, in the chronic lesioned human spinal cord.

Windup of Flexion Reflexes in Chronic Human Spinal Cord Injury: A Marker for Neuronal Plateau Potentials?

2003 ◽  
Vol 89 (1) ◽  
pp. 416-426 ◽  
Author(s):  
T. G. Hornby ◽  
W. Z. Rymer ◽  
E. N. Benz ◽  
B. D. Schmit
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Reflex Response ◽  
Electromyographic Activity ◽  
Plateau Potentials ◽  
Physiological Basis ◽  
Human Spinal Cord ◽  
Reflex Responses ◽  
Flexion Reflex ◽  
Cord Injury

The physiological basis of flexion spasms in individuals after spinal cord injury (SCI) may involve alterations in the properties of spinal neurons in the flexion reflex pathways. We hypothesize that these changes would be manifested as progressive increases in reflex response with repetitive stimulus application (i.e., “windup”) of the flexion reflexes. We investigated the windup of flexion reflex responses in 12 individuals with complete chronic SCI. Flexion reflexes were triggered using trains of electrical stimulation of plantar skin at variable intensities and inter-stimulus intervals. For threshold and suprathreshold stimulation, windup of both peak ankle and hip flexion torques and of integrated tibialis anterior electromyographic activity was observed consistently in all patients at inter-stimulus intervals ≤3 s. For subthreshold stimuli, facilitation of reflexes occurred only at intervals ≤1 s. Similarly, the latency of flexion reflexes decreased significantly at intervals ≤1 s. Patients that were receiving anti-spasticity medications (e.g., baclofen) had surprisingly larger windup of reflex responses than those who did not take such medications, although this difference may be related to differences of spasm frequency between the groups of subjects. The results indicate that the increase in spinal neuronal excitability following a train of electrical stimuli lasts for ≤3 s, similar to previous studies of nociceptive processing. Such long-lasting increases in flexion reflex responses suggest that cellular mechanisms such as plateau potentials in spinal motoneurons, interneurons, or both, may partially mediate spinal cord hyperexcitability in the absence of descending modulatory input.

scholarly journals Ultrasound stimulation of the motor cortex during tonic muscle contraction

2021 ◽  
Author(s):  
Ian Szwast Heimbuch ◽  
Tiffany Fan ◽  
Allan Wu ◽  
Guido C Faas ◽  
Andrew C Charles ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Motor Cortex ◽  
Muscle Contraction ◽  
Magnetic Stimulation ◽  
Primary Motor Cortex ◽  
Silent Period ◽  
Transcranial Ultrasound ◽  
Emg Activity ◽  
Ultrasound Stimulation ◽  
Tonic Muscle

Transcranial ultrasound stimulation (tUS) shows potential as a noninvasive brain stimulation (NIBS) technique, offering increased spatial precision compared to other NIBS techniques. However, its reported effects on primary motor cortex (M1) are limited. We aimed to better understand tUS effects in human M1 by performing tUS of the hand area of M1 (M1hand) during tonic muscle contraction of the index finger. Stimulation during muscle contraction was chosen because of the transcranial magnetic stimulation-induced phenomenon known as cortical silent period (cSP), in which transcranial magnetic stimulation (TMS) of M1hand involuntarily suppresses voluntary motor activity. Since cSP is widely considered an inhibitory phenomenon, it presents an ideal parallel for tUS, which has often been proposed to preferentially influence inhibitory interneurons. Recording electromyography (EMG) of the first dorsal interosseous (FDI) muscle, we investigated effects on muscle activity both during and after tUS. We found no change in FDI EMG activity concurrent with tUS stimulation. Using single-pulse TMS, we found no difference in M1 excitability before versus after sparsely repetitive tUS exposure. Using acoustic simulations in models made from structural MRI of the participants that matched the experimental setups, we estimated in-brain pressures and generated an estimate of cumulative tUS exposure experienced by M1hand for each subject. We were unable to find any correlation between cumulative M1hand exposure and M1 excitability change. We also present data that suggest a TMS-induced MEP always preceded a near-threshold cSP.

scholarly journals Effects of Noninvasive Low-Intensity Focus Ultrasound Neuromodulation on Spinal Cord Neurocircuits In Vivo

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Ye-Hui Liao ◽  
Mo-Xian Chen ◽  
Shao-Chun Chen ◽  
Kai-Xuan Luo ◽  
Bin Wang ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Muscle Contraction ◽  
Soleus Muscle ◽  
Focused Ultrasound ◽  
Rating Scale ◽  
Coagulation Necrosis ◽  
Enzyme Linked Immunosorbent Assay ◽  
Nissl Staining ◽  
Low Intensity

Although neurocircuits can be activated by focused ultrasound stimulation, it is unclear whether this is also true for spinal cord neurocircuits. In this study, we used low-intensity focused ultrasound (LIFU) to stimulate lumbar 4–lumbar 5 (L4–L5) segments of the spinal cord of normal Sprague Dawley rats with a clapper. The activation of the spinal cord neurocircuits enhanced soleus muscle contraction as measured by electromyography (EMG). Neuronal activation and injury were assessed by EMG, western blotting (WB), immunofluorescence, hematoxylin and eosin (H&E) staining, Nissl staining, enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC), somatosensory evoked potentials (SEPs), motor evoked potentials (MEPs), and the Basso–Beattie–Bresnahan locomotor rating scale. When the LIFU intensity was more than 0.5 MPa, LIFU stimulation induced soleus muscle contraction and increased the EMG amplitudes ( P < 0.05 ) and the number of c-fos- and GAD65-positive cells ( P < 0.05 ). When the LIFU intensity was 3.0 MPa, the LIFU stimulation led to spinal cord damage and decreased SEP amplitudes for electrophysiological assessment ( P < 0.05 ); this resulted in coagulation necrosis, structural destruction, neuronal loss in the dorsal horn by H&E and Nissl staining, and increased expression of GFAP, IL-1β, TNF-α, and caspase-3 by IHC, ELISA, and WB ( P < 0.05 ). These results show that LIFU can activate spinal cord neurocircuits and that LIFU stimulation with an irradiation intensity ≤1.5 MPa is a safe neurostimulation method for the spinal cord.

scholarly journals Competition, Conflict and Change of Mind: A Role of GABAergic Inhibition in the Primary Motor Cortex

2022 ◽  
Vol 15 ◽  
Author(s):  
Bastien Ribot ◽  
Aymar de Rugy ◽  
Nicolas Langbour ◽  
Anne Duron ◽  
Michel Goillandeau ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Silent Period ◽  
Single Pulse ◽  
Electromyographic Activity ◽  
Continuous Control ◽  
Gabaergic Inhibition ◽  
Inhibitory Mechanisms ◽  
Post Onset

Deciding between different voluntary movements implies a continuous control of the competition between potential actions. Many theories postulate a leading role of prefrontal cortices in this executive function, but strong evidence exists that a motor region like the primary motor cortex (M1) is also involved, possibly via inhibitory mechanisms. This was already shown during the pre-movement decision period, but not after movement onset. For this pilot experiment we designed a new task compatible with the dynamics of post-onset control to study the silent period (SP) duration, a pause in electromyographic activity after single-pulse transcranial magnetic stimulation that reflects inhibitory mechanisms. A careful analysis of the SP during the ongoing movement indicates a gradual increase in inhibitory mechanisms with the level of competition, consistent with an increase in mutual inhibition between alternative movement options. However, we also observed a decreased SP duration for high-competition trials associated with change-of-mind inflections in their trajectories. Our results suggest a new post-onset adaptive process that consists in a transient reduction of GABAergic inhibition within M1 for highly conflicting situations. We propose that this reduced inhibition softens the competition between concurrent motor options, thereby favoring response vacillation, an adaptive strategy that proved successful at improving behavioral performance.

Functional difference in short- and long-latency interhemispheric inhibitions from active to resting hemisphere during a unilateral muscle contraction

2014 ◽  
Vol 111 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Kazumasa Uehara ◽  
Takuya Morishita ◽  
Shinji Kubota ◽  
Masato Hirano ◽  
Kozo Funase
Keyword(s):  
Muscle Contraction ◽  
Primary Motor Cortex ◽  
Maximum Voluntary Contraction ◽  
Conditioning Stimulus ◽  
Voluntary Contraction ◽  
Muscle Contractions ◽  
Functional Difference ◽  
Experimental Conditions ◽  
Long Latency ◽  
Significant Difference

The aim of the present study was to investigate whether there is a functional difference in short-latency (SIHI) and long-latency (LIHI) interhemispheric inhibition from the active to the resting primary motor cortex (M1) with paired-pulse transcranial magnetic stimulation during a unilateral muscle contraction. In nine healthy right-handed participants, IHI was tested from the dominant to the nondominant M1 and vice versa under resting conditions or during performance of a sustained unilateral muscle contraction with the right or left first dorsal interosseous muscle at 10% and 30% maximum voluntary contraction. To obtain measurements of SIHI and LIHI, a conditioning stimulus (CS) was applied over the M1 contralateral to the muscle contraction, followed by a test stimulus over the M1 ipsilateral to the muscle contraction at short (10 ms) and long (40 ms) interstimulus intervals. We used four CS intensities to investigate SIHI and LIHI from the active to the resting M1 systematically. The amount of IHI during the unilateral muscle contractions showed a significant difference between SIHI and LIHI, but the amount of IHI during the resting condition did not. In particular, SIHI during the muscle contractions, but not LIHI, significantly increased with increase in CS intensity compared with the resting condition. Laterality of IHI was not detected in any of the experimental conditions. The present study provides novel evidence that a functional difference between SIHI and LIHI from the active to the resting M1 exists during unilateral muscle contractions.

scholarly journals ELECTROGMYOGRAPHIC FEATURES OF MUSCLES SOLEUS IN PEOPLE WITH THE INCREASED SENSITIVITY OF THE VESTIBULAR ANALYZER

2020 ◽  
Vol 2 ◽  
pp. 24-28
Author(s):  
Stepan Vadzyuk ◽  
Roman Shmata ◽  
Nataliia Ulianytska
Keyword(s):  
Spinal Cord ◽  
Semicircular Canals ◽  
Lower Extremities ◽  
Upright Position ◽  
Electromyographic Activity ◽  
Human Spinal Cord ◽  
Before And After ◽  
Increased Sensitivity ◽  
Written Test ◽  
Romberg Test

The article deals with the features of electromyographic indicators of the soleus muscles while maintaining a upright position in people with increased vestibular sensitivity. From the literature, it is concluded that the study of electromyographic features of indicators in the conditions of irritation of the vestibular analyzer in people with different vestibular sensitivity is an important area in physiology. Vestibular sensitivity was determined by the questionnaire, Voyachek's sample and Fukuda's written test. To assess the electromyographic activity of the soleus muscles, a computer DX complex was used for registration of interference electromyography. Registration was carried out during performing Romberg test, before and after vestibular loading. According to the results of the vestibular irritation, there was a greater decrease in the amplitude of the flap muscles of the lower extremities in persons with the increased vestibular sensitivity than in people with the adequate sensitivity. Based on the results achieved, it can be assumed, that in people with the increased sensitivity of the vestibular analyzer, the irritation of the receptors of the semicircular canals alters the activity of extensor motoneurons of the human spinal cord more significantly than in persons with the adequate sensitivity.

scholarly journals Epidural Spinal Electrogram Provides Direct Spinal Recordings in Awake Human Participants

2021 ◽  
Vol 15 ◽  
Author(s):  
John F. Burke ◽  
Nikhita Kunwar ◽  
Maria S. Yaroshinsky ◽  
Kenneth H. Louie ◽  
Prasad Shirvalkar ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Human Subjects ◽  
Movement Control ◽  
Overground Walking ◽  
Kinematic Data ◽  
Human Spinal Cord ◽  
Electrophysiological Activity ◽  
Upper And Lower Extremities ◽  
Novel Method ◽  
Human Participants

Little is known about the electrophysiological activity of the spinal cord during voluntary movement control in humans. We present a novel method for recording electrophysiological activity from the human spinal cord using implanted epidural electrodes during naturalistic movements including overground walking. Spinal electrograms (SEGs) were recorded from epidural electrodes implanted as part of a test trial for patients with chronic pain undergoing evaluation for spinal cord stimulation. Externalized ends of the epidural leads were connected to an external amplifier to capture SEGs. Electromyographic and accelerometry data from the upper and lower extremities were collected using wireless sensors and synchronized to the SEG data. Patients were instructed to perform various arm and leg movements while SEG and kinematic data were collected. This study proves the safety and feasibility of performing epidural spinal recordings from human subjects performing movement tasks.

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