Examining motor evoked potential amplitude and short‐interval intracortical inhibition on the up‐going and down‐going phases of a transcranial alternating current stimulation (tacs) imposed alpha oscillation

Voluntary contraction leads to facilitation of motor-evoked potentials (MEPs) producing greater amplitude, shorter onset latency, and prolonged duration of the electromyography potential. Whereas hyperexcitability of spinal motoneurons and changes in descending corticospinal volleys have been proposed as putative mechanisms for changes in MEP amplitude and onset latency, a contribution of propriospinal interneurons, exerting modulatory effects on α-motoneurons, has been proposed as a potential explanation for prolongation of MEP duration. The aim of the present study is to gain further insight into the physiological processes underlying changes in MEP duration. Transcranial magnetic stimulation (TMS) studies were undertaken on 30 healthy controls, using a 90-mm circular coil, with MEPs recorded at rest and during facilitation, produced by contraction of abductor pollicis brevis. In the same experiment, short interval-intracortical inhibition (SICI) was recorded at rest. Facilitation resulted in a significant prolongation of MEP duration, which increased with stimulus intensity and was accompanied by an increase in MEP amplitude. The main effect (TMS intensity × activation state) was correlated with MEP duration ( F = 10.9, P < 0.001), whereas TMS intensity ( F = 30.5, P < 0.001) and activation state ( F = 125.8, P < 0.001) in isolation were correlated with MEP amplitude. There was a significant inverse relationship between SICI and MEP duration at rest (R2 = 0.141, P = 0.041) and during facilitation (R2 = 0.340, P = 0.001). The present findings suggest that similar physiological processes mediate changes in the facilitated MEP duration and amplitude and that both cortical and nonpropriospinal spinal mechanisms contribute to changes in MEP duration. NEW & NOTEWORTHY Muscle contraction is associated with a significant increase in motor-evoked potential (MEP) duration and amplitude. Whereas the increase in MEP duration was linear, the amplitude increase exhibited a ceiling effect. Importantly, the MEP duration increase strongly correlated with short interval-intracortical inhibition, a biomarker of motor cortical function. This suggests that whereas similar physiological processes contribute to changes in facilitated MEP duration and amplitude, cortical mechanisms appear to contribute to MEP duration changes.

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Influence of Voluntary Contraction Level, Test Stimulus Intensity and Normalization Procedures on the Evaluation of Short-Interval Intracortical Inhibition

Brain Sciences ◽

10.3390/brainsci10070433 ◽

2020 ◽

Vol 10 (7) ◽

pp. 433

Author(s):

Cécilia Neige ◽

Sidney Grosprêtre ◽

Alain Martin ◽

Florent Lebon

Keyword(s):

Healthy Subjects ◽

Compound Muscle Action Potential ◽

Short Interval ◽

Motor Evoked Potential ◽

Intracortical Inhibition ◽

Voluntary Contraction ◽

Experimental Conditions ◽

Specific Level ◽

M Wave ◽

Spinal Motoneurones

Short-interval intracortical inhibition (SICI) represents an inhibitory phenomenon acting at the cortical level. However, SICI estimation is based on the amplitude of a motor-evoked potential (MEP), which depends on the discharge of spinal motoneurones and the generation of compound muscle action potential (M-wave). In this study, we underpin the importance of taking into account the proportion of spinal motoneurones that are activated or not when investigating the SICI of the right flexor carpi radialis (normalization with maximal M-wave (Mmax) and MEPtest, respectively), in 15 healthy subjects. We probed SICI changes according to various MEPtest amplitudes that were modulated actively (four levels of muscle contraction: rest, 10%, 20% and 30% of maximal voluntary contraction (MVC)) and passively (two intensities of test transcranial magnetic stimulation (TMS): 120 and 130% of motor thresholds). When normalized to MEPtest, SICI remained unchanged by stimulation intensity and only decreased at 30% of MVC when compared with rest. However, when normalized to Mmax, we provided the first evidence of a strong individual relationship between SICI and MEPtest, which was ultimately independent from experimental conditions (muscle states and TMS intensities). Under similar experimental conditions, it is thus possible to predict SICI individually from a specific level of corticospinal excitability in healthy subjects.

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Changes in Cortical Excitability and Parkinson Tremor After Botulinum Toxin Therapy

Neurology ◽

10.1212/wnl.0000000000012662 ◽

2021 ◽

Vol 97 (14) ◽

pp. e1413-e1424

Author(s):

Olivia Samotus ◽

Robert Chen ◽

Mandar Jog

Keyword(s):

Botulinum Toxin ◽

De Novo ◽

Cortical Excitability ◽

Botulinum Toxin Type A ◽

Short Interval ◽

Motor Evoked Potential ◽

Botulinum Toxin Type ◽

Intracortical Inhibition ◽

Botulinum Toxin Therapy ◽

Time Point

Background and ObjectivesTo investigate the relationship between botulinum toxin type A (BoNT-A) administration, tremor amplitude, and modulation of intracortical excitability and sensorimotor processing using paired-pulse transcranial magnetic stimulation (pp-TMS) in patients with early, tremor-dominant Parkinson disease (PD).MethodsTwelve de novo (naive to anti-PD medications) and 7 l-dopa (optimized on levodopa) participants with PD with tremor affecting one arm were recruited. All participants received 4 serial BoNT-A treatments for tremor every 12 weeks and peak effect was assessed 6 weeks posttreatment, totaling 8 visits over 42 weeks. Injection measures were based on kinematic tremor analysis. Short interval intracortical inhibition (SICI), intracortical facilitation (ICF), long interval intracortical inhibition (LICI), and measures of sensorimotor interaction (short-latency afferent [SAI] and long-latency afferent [LAI] stimulation) were assessed in both hemispheres using pp-TMS paradigms at each time point. Linear mixed models analyzed the effect of each pp-TMS measure and tremor severity within each cohort and the association between pp-TMS and tremor severity in the de novo cohort over 42 weeks. t Tests compared pp-TMS measures between hemispheres per time point.ResultsBaseline SICI, LICI, and SAI was reduced (higher motor evoked potential [MEP] ratio) on the tremulous/treated side compared to the nontremulous side in de novo participants. On the treated side in the de novo cohort, BoNT-A treatment significantly reduced ICF and increased LICI, SAI, and LAI (lower MEP ratio) at peak BoNT-A time points. The change in tremor severity was significantly associated with changes in SICI, LICI, and LAI.DiscussionOur findings suggest that tremor severity in early PD may be related to impaired intracortical inhibition and defective sensorimotor integration.

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Correction to: Preservation of motor maps with increased motor evoked potential amplitude threshold in RMT determination

Acta Neurochirurgica ◽

10.1007/s00701-018-3591-z ◽

2018 ◽

Vol 160 (8) ◽

pp. 1519-1519

Author(s):

Giuseppe Lucente ◽

Steven Lam ◽

Heike Schneider ◽

Thomas Picht

Keyword(s):

Evoked Potential ◽

Motor Evoked Potential ◽

Potential Amplitude ◽

Motor Maps

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Pathophysiology of Central Poststroke Pain

Stroke ◽

10.1161/strokeaha.119.025692 ◽

2019 ◽

Vol 50 (10) ◽

pp. 2851-2857 ◽

Cited By ~ 4

Author(s):

Sung-Chun Tang ◽

Lukas Jyuhn-Hsiarn Lee ◽

Jiann-Shing Jeng ◽

Sung-Tsang Hsieh ◽

Ming-Chang Chiang ◽

...

Keyword(s):

Quality Of Life ◽

Motor Cortex ◽

Evoked Potential ◽

Short Interval ◽

Intracortical Inhibition ◽

Contact Heat ◽

Sensorimotor Interaction ◽

Motor Cortex Excitability ◽

Impaired Quality

Background and Purpose— Central poststroke pain (CPSP) is a disabling condition in stroke patients, and evidence suggests that altered corticospinal and motor intracortical excitability occurs in neuropathic pain. The objective of this study was to investigate changes in motor cortex excitability and sensorimotor interaction and their correlates with clinical manifestations and alterations in somatosensory systems in CPSP patients. Methods— Fourteen patients with CPSP but no motor weakness were compared with age- and sex-matched healthy controls for motor cortex excitability and sensorimotor interaction assessed by transcranial magnetic stimulation to measure resting motor thresholds, short-interval intracortical inhibition, intracortical facilitation, and afferent inhibitions. The sensory pathway was evaluated by quantitative sensory testing, contact heat evoked potential, and somatosensory evoked potentials. Clinical pain and quality of life were assessed with validated tools. Results— The duration of CPSP was 3.3±3.0 years (ranging 0.5–10 years), and pain significantly impaired quality of life. Compared with the unaffected hemisphere, the stroke hemisphere had higher thermal thresholds, lower contact heat evoked potential amplitudes, and prolonged cortical somatosensory evoked potential latencies. There was no difference in resting motor thresholds between the stroke and unaffected hemisphere or between patients and controls. CPSP patients had a reduction in short-interval intracortical inhibition in the stroke hemisphere compared with that in the unaffected hemispheres of patients and controls. No changes were noted in afferent inhibitions between the stroke and unaffected hemispheres. The short-interval intracortical inhibition of the stroke hemisphere was negatively correlated with self-rated health on a visual analog scale and positively correlated with cortical somatosensory evoked potential latencies. Conclusions— CPSP patients with intact corticospinal tracts showed reduced motor intracortical inhibition in the stroke hemisphere, suggesting defective gamma-aminobutyric acid-ergic inhibition. This disinhibition was associated with impaired quality of life and was related to dorsal column–medial lemniscus pathway dysfunction.

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Proceedings #41: HD-tDCS Effect on Motor Evoked Potential Amplitude Elicited by Neuronavigated TMS

Brain Stimulation ◽

10.1016/j.brs.2018.12.210 ◽

2019 ◽

Vol 12 (2) ◽

pp. e110-e112

Author(s):

Egas Caparelli-Dáquer ◽

Sidário R. Malheiros-Junior ◽

Dylan J. Edwards ◽

Talita Reis ◽

Claudia F. Machado ◽

...

Keyword(s):

Evoked Potential ◽

Motor Evoked Potential ◽

Potential Amplitude

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Different Stimulation Frequencies Alter Synchronous Fluctuations in Motor Evoked Potential Amplitude of Intrinsic Hand Muscles—a TMS Study

Frontiers in Human Neuroscience ◽

10.3389/fnhum.2016.00100 ◽

2016 ◽

Vol 10 ◽

Cited By ~ 3

Author(s):

Martin V. Sale ◽

Nigel C. Rogasch ◽

Michael A. Nordstrom

Keyword(s):

Evoked Potential ◽

Motor Evoked Potential ◽

Hand Muscles ◽

Potential Amplitude ◽

Intrinsic Hand Muscles

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Cortical dysfunction underlies disability in multiple sclerosis

Multiple Sclerosis Journal ◽

10.1177/1352458511424308 ◽

2011 ◽

Vol 18 (4) ◽

pp. 425-432 ◽

Cited By ~ 39

Author(s):

Steve Vucic ◽

Therese Burke ◽

Kerry Lenton ◽

Sudarshini Ramanathan ◽

Lavier Gomes ◽

...

Keyword(s):

Multiple Sclerosis ◽

Cortical Excitability ◽

Short Interval ◽

Motor Evoked Potential ◽

Intracortical Inhibition ◽

Progressive Multiple Sclerosis ◽

Conduction Time ◽

Cortical Function ◽

Resting Motor Threshold ◽

Cortical Dysfunction

Background: Gray matter atrophy has been implicated in the development of secondary progressive multiple sclerosis (SPMS). Cortical function may be assessed by transcranial magnetic stimulation (TMS). Determining whether cortical dysfunction was a feature of SPMS could be of pathophysiological significance. Objectives: Consequently, novel paired-pulse threshold tracking TMS techniques were used to assess whether cortical dysfunction was a feature of SPMS. Methods: Cortical excitability studies were undertaken in 15 SPMS, 25 relapsing–remitting MS patients (RRMS) and 66 controls. Results: Short interval intracortical inhibition (SPMS 3.0 ± 2.1%; RRMS 12.8 ± 1.7%, p < 0.01; controls 10.5 ± 0.7%, p < 0.01) and motor evoked potential (MEP) amplitude (SPMS 11.5 ± 2.2%; RRMS 26.3 ± 3.6%, p <0.05; controls 24.7 ± 1.8%, p < 0.01) were reduced in SPMS, while intracortical facilitation (SPMS -5.2 ± 1.9%; RRMS -2.0 ± 1.4, p < 0.05; controls -0.9 ± 0.7, p < 0.01) and resting motor threshold were increased (SPMS 67.5 ± 4.5%; RRMS 56.0 ± 1.5%, p < 0.01; controls 59.0 ± 1.1%, p < 0.001). Further, central motor conduction time was prolonged in SPMS (9.1 ± 1.2 ms, p < 0.001) and RRMS (7.0 ± 0.9 ms, p < 0.05) patients compared with controls (5.5 ± 0.2 ms). The observed changes in cortical function correlated with the Expanded Disability Status Scale. Conclusion: Together, these findings suggest that cortical dysfunction is associated with disability in MS, and documentation of such cortical dysfunction may serve to quantify disease severity in MS.

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