Intracortical inhibition of lower limb motor-evoked potentials after paired transcranial magnetic stimulation

1997 ◽  
Vol 117 (3) ◽  
pp. 437-443 ◽  
Author(s):  
D. S. Stokic´ ◽  
W. Barry McKay ◽  
Lillian Scott ◽  
Arthur M. Sherwood ◽  
Milan R. Dimitrijevic´
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Lower Limb ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
Intracortical Inhibition

scholarly journals Intermittent single-joint fatiguing exercise reduces TMS-EEG measures of cortical inhibition

2019 ◽  
Vol 121 (2) ◽  
pp. 471-479 ◽  
Author(s):  
Lavender A. Otieno ◽  
George M. Opie ◽  
John G. Semmler ◽  
Michael C. Ridding ◽  
Simranjit K. Sidhu
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
Global Analysis ◽  
Intracortical Inhibition ◽  
Corticospinal Excitability ◽  
Cortical Inhibition ◽  
Relaxation Period ◽  
Fatiguing Exercise

Fatiguing intermittent single-joint exercise causes an increase in corticospinal excitability and a decrease in intracortical inhibition when measured with peripherally recorded motor evoked potentials (MEPs) after transcranial magnetic stimulation (TMS). Combined TMS and electroencephalography (TMS-EEG) allows for more direct recording of cortical responses through the TMS-evoked potential (TEP). The aim of this study was to investigate the changes in the excitatory and inhibitory components of the TEP during fatiguing single-joint exercise. Twenty-three young (22 ± 2 yr) healthy subjects performed intermittent 30-s maximum voluntary contractions of the right first dorsal interosseous muscle, followed by a 30-s relaxation period repeated for a total of 15 min. Six single-pulse TMSs and one peripheral nerve stimulation (PNS) to evoke maximal M wave (Mmax) were applied during each relaxation period. A total of 90 TMS pulses and 5 PNSs were applied before and after fatiguing exercise to record MEP and TEP. The amplitude of the MEP (normalized to Mmax) increased during fatiguing exercise ( P < 0.001). There were no changes in local and global P30, N45, and P180 of TEPs during the development of intermittent single-joint exercise-induced fatigue. Global analysis, however, revealed a decrease in N100 peak of the TEP during fatiguing exercise compared with before fatiguing exercise ( P = 0.02). The decrease in N100 suggests a fatigue-related decrease in global intracortical GABAB-mediated inhibition. The increase in corticospinal excitability typically observed during single-joint fatiguing exercise may be mediated by a global decrease in intracortical inhibition. NEW & NOTEWORTHY Fatiguing intermittent single-joint exercise causes an increase in corticospinal excitability and a decrease in intracortical inhibition when measured with transcranial magnetic stimulation (TMS)-evoked potentials from the muscle. The present study provides new and direct cortical evidence, using TMS-EEG to demonstrate that during single-joint fatiguing exercise there is a global decrease in intracortical GABAB-mediated inhibition.

scholarly journals Modeling motor-evoked potentials from neural field simulations of transcranial magnetic stimulation

2019 ◽  
Author(s):  
Marcus T Wilson ◽  
Bahar Moezzi ◽  
Nigel C Rogasch
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Outcome Measures ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
Intracortical Inhibition ◽  
Population Based ◽  
Neural Field ◽  
List Type ◽  
Single Motor Unit

AbstractObjectiveTo develop a population-based biophysical model of motor-evoked potentials (MEPs) following transcranial magnetic stimulation (TMS).MethodsWe combined an existing MEP model with population-based cortical modeling. Layer 2/3 excitatory and inhibitory neural populations, modeled with neural-field theory, are stimulated with TMS and feed layer 5 corticospinal neurons, which also couple directly but weakly to the TMS pulse. The layer 5 output controls mean motoneuron responses, which generate a series of single motor-unit action potentials that are summed to estimate a MEP.ResultsA MEP waveform was generated comparable to those observed experimentally. The model captured TMS phenomena including a sigmoidal input-output curve, common paired pulse effects (short interval intracortical inhibition, intracortical facilitation, long interval intracortical inhibition) including responses to pharmacological interventions, and a cortical silent period. Changes in MEP amplitude following theta burst paradigms were observed including variability in outcome direction.ConclusionsThe model reproduces effects seen in common TMS paradigms.SignificanceThe model allows population-based modeling of changes in cortical dynamics due to TMS protocols to be assessed in terms of changes in MEPs, thus allowing a clear comparison between population-based modeling predictions and typical experimental outcome measures.HighlightsA model of motor-evoked potential formation gives a realistic electromyogram in response to TMS.The model reproduces effects of SICI, ICF and LICI.A link between existing neural field modeling and realistic outcome measures of TMS is provided.

scholarly journals Reliability of diaphragmatic motor-evoked potentials induced by transcranial magnetic stimulation

2020 ◽  
Vol 129 (6) ◽  
pp. 1393-1404
Author(s):  
Joseph F. Welch ◽  
Patrick J. Argento ◽  
Gordon S. Mitchell ◽  
Emily J. Fox
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Evoked Potentials ◽  
Magnetic Stimulation ◽  
Motor Evoked Potentials ◽  
Surface Emg ◽  
Noninvasive Technique ◽  
Large Variability ◽  
Adult Men ◽  
Latency Duration ◽  
Excellent Reproducibility

Transcranial magnetic stimulation (TMS) is a noninvasive technique to assess neural impulse conduction along the cortico-diaphragmatic pathway. The reliability of diaphragm motor-evoked potentials (MEP) induced by TMS is unknown. Notwithstanding large variability in MEP amplitude, we found good-to-excellent reproducibility of all MEP characteristics (latency, duration, amplitude, and area) both within- and between-day in healthy adult men and women. Our findings support the use of TMS and surface EMG to assess diaphragm activation in humans.

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