scholarly journals Transcutaneous Electrical Neuromodulation of the Cervical Spinal Cord Depends Both on the Stimulation Intensity and the Degree of Voluntary Activity for Training. A Pilot Study

2021 ◽  
Vol 10 (15) ◽  
pp. 3278
Author(s):  
Hatice Kumru ◽  
María Rodríguez-Cañón ◽  
Victor R. Edgerton ◽  
Loreto García ◽  
África Flores ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Motor Evoked Potentials ◽  
Cervical Spinal Cord ◽  
Handgrip Strength ◽  
Short Interval ◽  
Voluntary Contraction ◽  
Voluntary Activity ◽  
Abductor Pollicis Brevis ◽  
Recruitment Curve ◽  
F Wave

Electrical enabling motor control (eEmc) through transcutaneous spinal cord stimulation offers promise in improving hand function. However, it is still unknown which stimulus intensity or which muscle force level could be better for this improvement. Nine healthy individuals received the following interventions: (i) eEmc intensities at 80%, 90% and 110% of abductor pollicis brevis motor threshold combined with hand training consisting in 100% handgrip strength; (ii) hand training consisting in 100% and 50% of maximal handgrip strength combined with 90% eEmc intensity. The evaluations included box and blocks test (BBT), maximal voluntary contraction (MVC), F wave persistency, F/M ratio, spinal and cortical motor evoked potentials (MEP), recruitment curves of spinal MEP and cortical MEP and short-interval intracortical inhibition. The results showed that: (i) 90% eEmc intensity increased BBT, MVC, F wave persistency, F/M ratio and cortical MEP recruitment curve; 110% eEmc intensity increased BBT, F wave persistency and cortical MEP and recruitment curve of cortical MEP; (ii) 100% handgrip strength training significantly modulated MVC, F wave persistency, F/M wave and cortical MEP recruitment curve in comparison to 50% handgrip strength. In conclusion, eEmc intensity and muscle strength during training both influence the results for neuromodulation at the cervical level.

scholarly journals Changes in motoneuron excitability during voluntary muscle activity in humans with spinal cord injury

2020 ◽  
Vol 123 (2) ◽  
pp. 454-461 ◽  
Author(s):  
Roberta Vastano ◽  
Monica A. Perez
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Electrical Stimulation ◽  
Muscle Activity ◽  
Voluntary Contraction ◽  
Voluntary Activity ◽  
Voluntary Muscle ◽  
Motoneuron Excitability ◽  
Cord Injury ◽  
F Wave

The excitability of resting motoneurons increases following spinal cord injury (SCI). The extent to which motoneuron excitability changes during voluntary muscle activity in humans with SCI, however, remains poorly understood. To address this question, we measured F waves by using supramaximal electrical stimulation of the ulnar nerve at the wrist and cervicomedullary motor-evoked potentials (CMEPs) by using high-current electrical stimulation over the cervicomedullary junction in the first dorsal interosseous muscle at rest and during 5 and 30% of maximal voluntary contraction into index finger abduction in individuals with chronic cervical incomplete SCI and aged-matched control participants. We found higher persistence (number of F waves present in each set) and amplitude of F waves at rest in SCI compared with control participants. With increasing levels of voluntary contraction, the amplitude, but not the persistence, of F waves increased in both groups but to a lesser extent in SCI compared with control participants. Similarly, the CMEP amplitude increased in both groups but to a lesser extent in SCI compared with controls. These results were also found at matched absolutely levels of electromyographic activity, suggesting that these changes were not related to decreases in voluntary motor output after SCI. F-wave and CMEP amplitudes were positively correlated across conditions in both groups. These results support the hypothesis that the responsiveness of the motoneuron pool during voluntary activity decreases following SCI, which could alter the generation and strength of voluntary muscle contractions. NEW & NOTEWORTHY How the excitability of motoneurons changes during voluntary muscle activity in humans with spinal cord injury (SCI) remains poorly understood. We found that F-wave and cervicomedullary motor-evoked potential amplitude, outcomes reflecting motoneuronal excitability, increased during voluntary activity compared with rest in SCI participants but to a lesser extent that in controls. These results suggest that the responsiveness of motoneurons during voluntary activity decreases following SCI, which might affect functionally relevant plasticity after the injury.

scholarly journals Physiological changes underlying bilateral isometric arm voluntary contractions in healthy humans

2011 ◽  
Vol 105 (4) ◽  
pp. 1594-1602 ◽  
Author(s):  
Demetris S. Soteropoulos ◽  
Monica A. Perez
Keyword(s):  
Tibialis Anterior ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Intracortical Inhibition ◽  
Voluntary Contraction ◽  
Triceps Brachii ◽  
Hand Muscles ◽  
Healthy Humans ◽  
Simultaneous Activation ◽  
The Right

Many bilateral motor tasks engage simultaneous activation of distal and proximal arm muscles, but little is known about their physiological interactions. Here, we used transcranial magnetic stimulation to examine motor-evoked potentials (MEPs), interhemispheric inhibition at a conditioning-test interval of 10 (IHI10) and 40 ms (IHI40), and short-interval intracortical inhibition (SICI) in the left first dorsal interosseous (FDI) muscle during isometric index finger abduction. The right side remained at rest or performed isometric voluntary contraction with the FDI, biceps or triceps brachii, or the tibialis anterior. Left FDI MEPs were suppressed to a similar extent during contraction of the right FDI and biceps and triceps brachii but remained unchanged during contraction of the right tibialis anterior. IHI10 and IHI40 were decreased during contraction of the right biceps and triceps brachii compared with contraction of the right FDI. SICI was increased during activation of the right biceps and triceps brachii and decreased during activation of the right FDI. The present results indicate that an isometric voluntary contraction with either a distal or a proximal arm muscle, but not a foot dorsiflexor, decreases corticospinal output in a contralateral active finger muscle. Transcallosal inhibitory effects were strong during bilateral activation of distal hand muscles and weak during simultaneous activation of a distal and a proximal arm muscle, whereas GABAergic intracortical activity was modulated in the opposite manner. These findings suggest that in intact humans crossed interactions at the level of the motor cortex involved different physiological mechanisms when bilateral distal hand muscles are active and when a distal and a proximal arm muscle are simultaneously active.

Objective assessment of cervical spinal cord injury levels by transcranial magnetic motor-evoked potentials

2006 ◽  
Vol 66 (5) ◽  
pp. 475-483 ◽  
Author(s):  
Christopher B. Shields ◽  
Yi Ping Zhang ◽  
Lisa B.E. Shields ◽  
Darlene A. Burke ◽  
Steven D. Glassman
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Evoked Potentials ◽  
Motor Evoked Potentials ◽  
Cervical Spinal Cord ◽  
Objective Assessment ◽  
Cervical Spinal Cord Injury ◽  
Cord Injury

scholarly journals A common neural element receiving rhythmic arm and leg activity as assessed by reflex modulation in arm muscles

2016 ◽  
Vol 115 (4) ◽  
pp. 2065-2075 ◽  
Author(s):  
Syusaku Sasada ◽  
Toshiki Tazoe ◽  
Tsuyoshi Nakajima ◽  
Genki Futatsubashi ◽  
Hiroyuki Ohtsuka ◽  
...  
Keyword(s):  
Nerve Stimulation ◽  
Motor Evoked Potentials ◽  
Cervical Spinal Cord ◽  
Voluntary Contraction ◽  
Reflex Modulation ◽  
Neural Element ◽  
Single Motor Unit ◽  
Arm Cycling ◽  
Leg Cycling ◽  
Arm Muscles

Neural interactions between regulatory systems for rhythmic arm and leg movements are an intriguing issue in locomotor neuroscience. Amplitudes of early latency cutaneous reflexes (ELCRs) in stationary arm muscles are modulated during rhythmic leg or arm cycling but not during limb positioning or voluntary contraction. This suggests that interneurons mediating ELCRs to arm muscles integrate outputs from neural systems controlling rhythmic limb movements. Alternatively, outputs could be integrated at the motoneuron and/or supraspinal levels. We examined whether a separate effect on the ELCR pathways and cortico-motoneuronal excitability during arm and leg cycling is integrated by neural elements common to the lumbo-sacral and cervical spinal cord. The subjects performed bilateral leg cycling (LEG), contralateral arm cycling (ARM), and simultaneous contralateral arm and bilateral leg cycling (A&L), while ELCRs in the wrist flexor and shoulder flexor muscles were evoked by superficial radial (SR) nerve stimulation. ELCR amplitudes were facilitated by cycling tasks and were larger during A&L than during ARM and LEG. A low stimulus intensity during ARM or LEG generated a larger ELCR during A&L than the sum of ELCRs during ARM and LEG. We confirmed this nonlinear increase in single motor unit firing probability following SR nerve stimulation during A&L. Furthermore, motor-evoked potentials following transcranial magnetic and electrical stimulation did not show nonlinear potentiation during A&L. These findings suggest the existence of a common neural element of the ELCR reflex pathway that is active only during rhythmic arm and leg movement and receives convergent input from contralateral arms and legs.

scholarly journals Examination of Relativity of Injury of Cervical Spinal Cord, Nerves, and F-wave of Upper Extremity

2012 ◽  
Vol 61 (1) ◽  
pp. 81-85
Author(s):  
Yohei Takahashi ◽  
Shinjiro Moriwaki ◽  
Yasuhiro Ochi ◽  
Yoshihiko Kunishi ◽  
Kenji Kido
Keyword(s):  
Spinal Cord ◽  
Upper Extremity ◽  
Cervical Spinal Cord ◽  
F Wave

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.

scholarly journals Writing's Shadow: Corticospinal Activation during Letter Observation

2012 ◽  
Vol 24 (5) ◽  
pp. 1138-1148 ◽  
Author(s):  
Masahiro Nakatsuka ◽  
Mohamed Nasreldin Thabit ◽  
Satoko Koganemaru ◽  
Ippei Nojima ◽  
Hidenao Fukuyama ◽  
...  
Keyword(s):  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Single Pulse ◽  
Random Order ◽  
Intracortical Inhibition ◽  
Corticospinal Excitability ◽  
Motor Memory ◽  
F Wave ◽  
The Right

We can recognize handwritten letters despite the variability among writers. One possible strategy is exploiting the motor memory of orthography. By using TMS, we clarified the excitatory and inhibitory neural circuits of the motor corticospinal pathway that might be activated during the observation of handwritten letters. During experiments, participants looked at the handwritten or printed single letter that appeared in a random order. The excitability of the left and right primary motor cortex (M1) was evaluated by motor-evoked potentials elicited by single-pulse TMS. Short interval intracortical inhibition (SICI) of the left M1 was evaluated using paired-pulse TMS. F waves were measured for the right ulnar nerve. We found significant reduction of corticospinal excitability only for the right hand at 300–400 msec after each letter presentation without significant changes in SICI. This suppression is likely to be of supraspinal origin, because of no significant alteration in F-wave amplitudes. These findings suggest that the recognition of handwritten letters may include the implicit knowledge of “writing” in M1. The M1 activation associated with that process, which has been shown in previous neuroimaging studies, is likely to reflect the active suppression of the corticospinal excitability.

Corticomotor plasticity and learning of a ballistic thumb training task are diminished in older adults

2009 ◽  
Vol 107 (6) ◽  
pp. 1874-1883 ◽  
Author(s):  
Nigel C. Rogasch ◽  
Tamara J. Dartnall ◽  
John Cirillo ◽  
Michael A. Nordstrom ◽  
John G. Semmler
Keyword(s):  
Older Adults ◽  
Primary Motor Cortex ◽  
Motor Evoked Potentials ◽  
Short Interval ◽  
Intracortical Inhibition ◽  
Training Task ◽  
Abductor Pollicis Brevis ◽  
Corticomotor Excitability ◽  
Old Adults ◽  
Young Subjects

This study examined changes in corticomotor excitability and plasticity after a thumb abduction training task in young and old adults. Electromyographic (EMG) recordings were obtained from right abductor pollicis brevis (APB, target muscle) and abductor digiti minimi (ADM, control muscle) in 14 young (18–24 yr) and 14 old (61–82 yr) adults. The training task consisted of 300 ballistic abductions of the right thumb to maximize peak thumb abduction acceleration (TAAcc). Transcranial magnetic stimulation (TMS) of the left primary motor cortex was used to assess changes in APB and ADM motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) before, immediately after, and 30 min after training. No differences in corticomotor excitability (resting and active TMS thresholds, MEP input-output curves) or SICI were observed in young and old adults before training. Motor training resulted in improvements in peak TAAcc in young (177% improvement, P < 0.001) and old (124%, P = 0.005) subjects, with greater improvements in young subjects ( P = 0.002). Different thumb kinematics were observed during task performance, with increases in APB EMG related to improvements in peak TAAcc in young ( r2 = 0.46, P = 0.008) but not old ( r2 = 0.09, P = 0.3) adults. After training, APB MEPs were 50% larger ( P < 0.001 compared with before) in young subjects, with no change after training in old subjects ( P = 0.49), suggesting reduced use-dependent corticomotor plasticity with advancing age. These changes were specific to APB, because no training-related change in MEP amplitude was observed in ADM. No significant association was observed between change in APB MEP and improvement in TAAcc with training in individual young and old subjects. SICI remained unchanged after training in both groups, suggesting that it was not responsible for the diminished use-dependent corticomotor plasticity for this task in older adults.

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