Paired-pulse interactions

2021 ◽  
Author(s):  
Robin F. H. Cash ◽  
Ulf Ziemann
Keyword(s):  
Evoked Potential ◽  
Cortical Excitability ◽  
Conditioning Stimulus ◽  
Motor Evoked Potential ◽  
Pharmacological Profile ◽  
Activation Threshold ◽  
Human Cortex ◽  
Paired Pulse ◽  
Inhibitory Circuitry ◽  
Health And Disease

Paired-pulse transcranial magnetic stimulation (TMS) techniques provide an opportunity to examine and better understand the excitatory and inhibitory circuitry in the human cortex in health and disease. Typically, a conditioning stimulus is applied and the effect on cortical excitability is inferred by the change in motor evoked potential (MEP) amplitude elicited by a test stimulus delivered shortly (milliseconds) thereafter. This approach has revealed a range of distinct, but generally overlapping, excitatory and inhibitory phenomena, which have been characterized according to their temporal and pharmacological profile, activation threshold, and various other properties. These phenomena have provided new pathophysiological insights into neurological and psychiatric disorders, and paired-pulse TMS measures have demonstrated clinical diagnostic utility. More recently, via implementation of TMS-evoked electroencephalography (TMS-EEG), paired-pulse TMS protocols have started to expand into nonmotor regions.

scholarly journals The effects of forearm position and contraction intensity on cortical and spinal excitability during a submaximal force steadiness task of the elbow flexors

2020 ◽  
Vol 123 (2) ◽  
pp. 522-528
Author(s):  
Alexandra F. Yacyshyn ◽  
Samantha Kuzyk ◽  
Jennifer M. Jakobi ◽  
Chris J. McNeil
Keyword(s):  
Evoked Potential ◽  
Biceps Brachii ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Elbow Flexor ◽  
Elbow Flexors ◽  
Neural Excitability ◽  
Force Steadiness ◽  
Maximal Force ◽  
Spinal Excitability

Elbow flexor force steadiness is less with the forearm pronated (PRO) compared with neutral (NEU) or supinated (SUP) and may relate to neural excitability. Although not tested in a force steadiness paradigm, lower spinal and cortical excitability was observed separately for biceps brachii in PRO, possibly dependent on contractile status at the time of assessment. This study aimed to investigate position-dependent changes in force steadiness as well as spinal and cortical excitability at a variety of contraction intensities. Thirteen males (26 ± 7 yr; means ± SD) performed three blocks (PRO, NEU, and SUP) of 24 brief (~6 s) isometric elbow flexor contractions (5, 10, 25 or 50% of maximal force). During each contraction, transcranial magnetic stimulation or transmastoid stimulation was delivered to elicit a motor-evoked potential (MEP) or cervicomedullary motor-evoked potential (CMEP), respectively. Force steadiness was lower in PRO compared with NEU and SUP ( P ≤ 0.001), with no difference between NEU and SUP. Similarly, spinal excitability (CMEP/maximal M wave) was lower in PRO than NEU (25 and 50% maximal force; P ≤ 0.010) and SUP (all force levels; P ≤ 0.004), with no difference between NEU and SUP. Cortical excitability (MEP/CMEP) did not change with forearm position ( P = 0.055); however, a priori post hoc testing for position showed excitability was 39.8 ± 38.3% lower for PRO than NEU at 25% maximal force ( P = 0.006). The data suggest that contraction intensity influences the effect of forearm position on neural excitability and that reduced spinal and, to a lesser extent, cortical excitability could contribute to lower force steadiness in PRO compared with NEU and SUP. NEW & NOTEWORTHY To address conflicting reports about the effect of forearm position on spinal and cortical excitability of the elbow flexors, we examine the influence of contraction intensity. For the first time, excitability data are considered in a force steadiness context. Motoneuronal excitability is lowest in pronation and this disparity increases with contraction intensity. Cortical excitability exhibits a similar pattern from 5 to 25% of maximal force. Lower corticospinal excitability likely contributes to relatively poor force steadiness in pronation.

Design and analysis of motor-evoked potential data in pediatric neurobehavioral disorder investigations

2012 ◽  
Author(s):  
Donald L. Gilbert
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Research Methods ◽  
Magnetic Stimulation ◽  
Evoked Potential ◽  
Motor Evoked Potential ◽  
Experimental Designs ◽  
Future Research ◽  
Paired Pulse ◽  
Practical Guidance

This article discusses how transcranial magnetic stimulation (TMS) can be used to study the pathophysiological substrata of pediatric neurological and neurobehavioural disorders and to provide practical guidance for future research. It outlines the substantial challenges inherent in studying in vivo the neurobiology of pediatric neurobehavioural disorders, such as safety, quantitative versus categorical measures, and challenges in correlational studies. It discusses ways in which TMS generates quantitative measures that may function as endophenotypes for neurobehavioural disorders. Combining TMS with other modalities may also be informative. Single- and paired-pulse TMS is safe and well tolerated in children. The application of rigorous experimental designs and a combination of TMS with other research methods may increase the knowledge of pathophysiology and treatment of pediatric neurobehavioural disorders.

Paired-pulse measures

2012 ◽  
Author(s):  
Ritsuko Hanajima ◽  
Yoshikazu Ugawa
Keyword(s):  
Motor Cortex ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Paired Pulse ◽  
Motor Cortical Excitability ◽  
Interhemispheric Connectivity ◽  
Conditioned Motor ◽  
Human Motor ◽  
Motor Cortical ◽  
Insight Into

This article reviews the physiology and application of the currently available paired-pulse protocols. Paired-pulse transcranial magnetic stimulation (TMS) techniques study the modulation of human motor cortical excitability. Paired-pulse experiments are designed to give insight into the nature of the cortical circuitry activated by TMS. Changes in motor cortical excitability produced by the conditioning pulse are estimated by changes in the size of the conditioned motor-evoked potential (MEP). It is possible to identify specific abnormalities in the balance between inhibitory and facilitatory processes, even if the pathology lies in abnormal afferent signalling to the motor cortex rather than in the motor cortex itself. The conclusion that emerges from the studies on interhemispheric interactions is that it is now possible by means of TMS protocols to chart long-range functional interhemispheric connectivity of remote areas of the human brain.

scholarly journals A new measure of cortical inhibition by mechanomyography and paired-pulse transcranial magnetic stimulation in unanesthetized rats

2012 ◽  
Vol 107 (3) ◽  
pp. 966-972 ◽  
Author(s):  
Tsung-Hsun Hsieh ◽  
Sameer C. Dhamne ◽  
Jia-Jin J. Chen ◽  
Alvaro Pascual-Leone ◽  
Frances E. Jensen ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Time Course ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Single Pulse ◽  
Cortical Inhibition ◽  
Testing Time ◽  
Paired Pulse ◽  
Awake Rats

Paired-pulse transcranial magnetic stimulation (ppTMS) is a safe and noninvasive tool for measuring cortical inhibition in humans, particularly in patients with disorders of cortical inhibition such as epilepsy. However, ppTMS protocols in rodent disease models, where mechanistic insight into the ppTMS physiology and into disease processes may be obtained, have been limited due to the requirement for anesthesia and needle electromyography. To eliminate the confounding factor of anesthesia and to approximate human ppTMS protocols in awake rats, we adapted the mechanomyogram (MMG) method to investigate the ppTMS inhibitory phenomenon in awake rats and then applied differential pharmacology to test the hypothesis that long-interval cortical inhibition is mediated by the GABAA receptor. Bilateral hindlimb-evoked MMGs were elicited in awake rats by long-interval ppTMS protocols with 50-, 100-, and 200-ms interstimulus intervals. Acute changes in ppTMS-MMG were measured before and after intraperitoneal injections of saline, the GABAA agonist pentobarbital (PB), and GABAA antagonist pentylenetetrazole (PTZ). An evoked MMG was obtained in 100% of animals by single-pulse stimulation, and ppTMS resulted in predictable inhibition of the test-evoked MMG. With increasing TMS intensity, MMG amplitudes increased in proportion to machine output to produce reliable input-output curves. Simultaneous recordings of electromyography and MMG showed a predictable latency discrepancy between the motor-evoked potential and the evoked MMG (7.55 ± 0.08 and 9.16 ± 0.14 ms, respectively). With pharmacological testing, time course observations showed that ppTMS-MMG inhibition was acutely reduced following PTZ ( P < 0.05), acutely enhanced after PB ( P < 0.01) injection, and then recovered to pretreatment baseline after 1 h. Our data support the application of the ppTMS-MMG technique for measuring the cortical excitability in awake rats and provide the evidence that GABAA receptor contributes to long-interval paired-pulse cortical inhibition. Thus ppTMS-MMG appears a well-tolerated biomarker for measuring GABAA-mediated cortical inhibition in rats.

Direct corticospinal pathways contribute to neuromuscular control of perturbed stance

2006 ◽  
Vol 101 (2) ◽  
pp. 420-429 ◽  
Author(s):  
Wolfgang Taube ◽  
Martin Schubert ◽  
Markus Gruber ◽  
Sandra Beck ◽  
Michael Faist ◽  
...  
Keyword(s):  
Magnetic Stimulation ◽  
Evoked Potential ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Neuromuscular Control ◽  
H Reflex ◽  
Compensatory Response ◽  
Long Latency Responses ◽  
Long Latency ◽  
Posterior Translation

The antigravity soleus muscle (Sol) is crucial for compensation of stance perturbation. A corticospinal contribution to the compensatory response of the Sol is under debate. The present study assessed spinal, corticospinal, and cortical excitability at the peaks of short- (SLR), medium- (MLR), and long-latency responses (LLR) after posterior translation of the feet. Transcranial magnetic stimulation (TMS) and peripheral nerve stimulation were individually adjusted so that the peaks of either motor evoked potential (MEP) or H reflex coincided with peaks of SLR, MLR, and LLR, respectively. The influence of specific, presumably direct, corticospinal pathways was investigated by H-reflex conditioning. When TMS was triggered so that the MEP arrived in the Sol at the same time as the peaks of SLR and MLR, EMG remained unaffected. Enhanced EMG was observed when the MEP coincided with the LLR peak ( P < 0.001). Similarly, conditioning of the H reflex by subthreshold TMS facilitated H reflexes only at LLR ( P < 0.001). The earliest facilitation after perturbation occurred after 86 ms. The TMS-induced H-reflex facilitation at LLR suggests that increased cortical excitability contributes to the augmentation of the LLR peaks. This provides evidence that the LLR in the Sol muscle is at least partly transcortical, involving direct corticospinal pathways. Additionally, these results demonstrate that ∼86 ms after perturbation, postural compensatory responses are cortically mediated.

scholarly journals Effect of Therapy on Motor Cortical Excitability in Parkinson’s Disease

2008 ◽  
Vol 35 (2) ◽  
pp. 166-172 ◽  
Author(s):  
Aysun Soysal ◽  
Ismail Sobe ◽  
Turan Atay ◽  
Aysu Sen ◽  
Baki Arpaci
Keyword(s):  
Parkinson’S Disease ◽  
Late Stage ◽  
Evoked Potential ◽  
Cortical Excitability ◽  
Early Stage ◽  
Motor Evoked Potential ◽  
Motor Threshold ◽  
Potential Amplitude ◽  
Motor Cortical Excitability ◽  
Motor Cortical

Objective:To assess the impact of the disease stage and therapy on motor cortical excitability in Parkinson’s disease (PD).Methods:Twenty newly diagnosed and medication-free, early stage patients, 20 late stage patients under antiparkinsonian therapy and 20 normal healthy controls were included. Motor threshold (MT), amplitudes of motor evoked potential (MEP), motor evoked potential amplitude/compound muscle action potential amplitude (MEP/CMAP) ratio, central motor conduction time (CMCT) and cortical silent period (CSP) were measured by stimulation of the motor cortex using a 13.5 cm circular coil and recordings from abductor digiti minimi muscle. Following the first study protocol, early stage patients were given therapy and the same protocol was repeated three months later.Results:Motor threshold was lower; and the MEP/CMAP ratio was higher in early and late stage patients than normals. In early stage patients after proper therapy, the MTs became higher than before therapy, but still remained lower than normals. In late stage patients, the CMCTs were shorter than the early stage patients before therapy and normals, but there was no difference between the early stage patients and normals. In early stage patients after therapy, the CMCT became longer than before therapy and this difference was significant in both late stage patients and normals. Although more prominent in late stage patients, the CSP duration in both PD groups was found shorter than normals. In early stage patients, after therapy, the CSP durations became significantly longer compared with before therapy.Conclusion:These findings suggest that the motor cortical excitability increases in PD because of the impairment of the corticomotoneuronal inhibitory system.

scholarly journals Evidence for a Window of Enhanced Plasticity in the Human Motor Cortex Following Ischemic Stroke

2021 ◽  
pp. 154596832199233
Author(s):  
Brenton Hordacre ◽  
Duncan Austin ◽  
Katlyn E. Brown ◽  
Lynton Graetz ◽  
Isabel Pareés ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Synaptic Plasticity ◽  
Motor Cortex ◽  
Human Brain ◽  
Evoked Potential ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Stroke Survivors ◽  
Behavioral Training ◽  
Human Motor Cortex

Background In preclinical models, behavioral training early after stroke produces larger gains compared with delayed training. The effects are thought to be mediated by increased and widespread reorganization of synaptic connections in the brain. It is viewed as a period of spontaneous biological recovery during which synaptic plasticity is increased. Objective To look for evidence of a similar change in synaptic plasticity in the human brain in the weeks and months after ischemic stroke. Methods We used continuous theta burst stimulation (cTBS) to activate synapses repeatedly in the motor cortex. This initiates early stages of synaptic plasticity that temporarily reduces cortical excitability and motor-evoked potential amplitude. Thus, the greater the effect of cTBS on the motor-evoked potential, the greater the inferred level of synaptic plasticity. Data were collected from separate cohorts (Australia and UK). In each cohort, serial measurements were made in the weeks to months following stroke. Data were obtained for the ipsilesional motor cortex in 31 stroke survivors (Australia, 66.6 ± 17.8 years) over 12 months and the contralesional motor cortex in 29 stroke survivors (UK, 68.2 ± 9.8 years) over 6 months. Results Depression of cortical excitability by cTBS was most prominent shortly after stroke in the contralesional hemisphere and diminished over subsequent sessions ( P = .030). cTBS response did not differ across the 12-month follow-up period in the ipsilesional hemisphere ( P = .903). Conclusions Our results provide the first neurophysiological evidence consistent with a period of enhanced synaptic plasticity in the human brain after stroke. Behavioral training given during this period may be especially effective in supporting poststroke recovery.

scholarly journals Evidence of Neuroplasticity: A Robotic Hand Exoskeleton Study for Post-Stroke Rehabilitation

2020 ◽  
Author(s):  
Neha Singh ◽  
Megha Saini ◽  
Nand Kumar ◽  
M.V. Padma Srivast ◽  
Amit Mehndiratta
Keyword(s):  
Evoked Potential ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Clinical Scales ◽  
Robotic Therapy ◽  
Active Range Of Motion ◽  
Modified Ashworth Scale ◽  
Resting Motor Threshold ◽  
Motor Outcomes ◽  
Ashworth Scale

Abstract Background: A novel electromechanical robotic-exoskeleton was designed in-house for rehabilitation of wrist joint and Metacarpophalangeal (MCP) joint. Objective: The objective was to compare the rehabilitation effectiveness (clinical-scales and neurophysiological-measures) of robotic-therapy training-sessions with dose-matched control in patients with stroke. Methods: An observational pilot study was designed with patients within 2 years of chronicity. Patients received an intervention of 20 sessions of 45-minutes each, five days a week for four-weeks) in Robotic-therapy Group (RG) (n=12) and conventional upper-limb rehabilitation in Control-Group (CG) (n=11). Clinical-scales– Modified Ashworth Scale, Active Range of Motion, Barthel-Index, Brunstrom-stage and Fugl-Meyer scale (Shoulder/Elbow and Wrist/Hand component), and neurophysiological-measures of cortical-excitability (using Transcranial Magnetic Stimulation) –Motor Evoked Potential and Resting Motor-threshold, were acquired pre and post-therapy. Results: RG and CG showed significant improvement in all clinical motor-outcomes (p<0.05) except Modified Ashworth Scale in CG. RG showed significantly higher improvement over CG in Modified Ashworth Scale, Active Range of Motion and Fugl-Meyer (FM) scale and FM Wrist-/Hand component) (p<0.05). Increase in cortical-excitability in ipsilesional-hemisphere was found to be statistically significant in RG over CG, as indexed by decrease in Resting Motor-Threshold and increase in amplitude of Motor Evoked Potential (p<0.05). No significant changes were shown by the contralesional-hemisphere. Interhemispheric RMT-asymmetry evidenced significant changes in RG over CG (p<0.05) indicating increased cortical-excitability in ipsilesional-hemisphere along with interhemispheric changes.Conclusion: Neurophysiological-changes in RG could be most likely a consequence of plastic-reorganization and use-dependent plasticity. Robotic-exoskeleton training could significantly improve motor-outcomes and cortical-excitability in patients with stroke.Registry number: IEC/NP-99/13.03.2015

scholarly journals Obesity is Associated with Reduced Plasticity of the Human Motor Cortex

2020 ◽  
Vol 10 (9) ◽  
pp. 579
Author(s):  
Sophia X. Sui ◽  
Michael C. Ridding ◽  
Brenton Hordacre
Keyword(s):  
Motor Cortex ◽  
Evoked Potential ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Healthy Weight ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
Weight Group ◽  
Theta Burst ◽  
Continuous Theta Burst Stimulation

Obesity is characterised by excessive body fat and is associated with several detrimental health conditions, including cardiovascular disease and diabetes. There is some evidence that people who are obese have structural and functional brain alterations and cognitive deficits. It may be that these neurophysiological and behavioural consequences are underpinned by altered plasticity. This study investigated the relationship between obesity and plasticity of the motor cortex in people who were considered obese (n = 14, nine males, aged 35.4 ± 14.3 years) or healthy weight (n = 16, seven males, aged 26.3 ± 8.5 years). A brain stimulation protocol known as continuous theta burst transcranial magnetic stimulation was applied to the motor cortex to induce a brief suppression of cortical excitability. The suppression of cortical excitability was quantified using single-pulse transcranial magnetic stimulation to record and measure the amplitude of the motor evoked potential in a peripheral hand muscle. Therefore, the magnitude of suppression of the motor evoked potential by continuous theta burst stimulation was used as a measure of the capacity for plasticity of the motor cortex. Our results demonstrate that the healthy-weight group had a significant suppression of cortical excitability following continuous theta burst stimulation (cTBS), but there was no change in excitability for the obese group. Comparing the response to cTBS between groups demonstrated that there was an impaired plasticity response for the obese group when compared to the healthy-weight group. This might suggest that the capacity for plasticity is reduced in people who are obese. Given the importance of plasticity for human behaviour, our results add further emphasis to the potentially detrimental health effects of obesity.

Reduced cortical excitability in depression

1999 ◽  
Vol 174 (5) ◽  
pp. 449-454 ◽  
Author(s):  
P. M. Shajahan ◽  
M. F. Glabus ◽  
P. A. Gooding ◽  
P. J. Shah ◽  
K. P. Ebmeier
Keyword(s):  
Magnetic Stimulation ◽  
Evoked Potential ◽  
Primary Motor Cortex ◽  
Cortical Excitability ◽  
Motor Evoked Potential ◽  
Abductor Pollicis Brevis ◽  
Post Exercise ◽  
Significant Difference ◽  
Dsm Iv ◽  
The Mean

BackgroundIn healthy controls, preactivation of muscles by exercise results in enhanced motor-evoked potential (MEP) responses to transcranial magnetic stimulation (TMS).AimsWe tested the hypothesis that medicated, depressed patients would show reduced post-exercise MEP facilitation compared with controls.MethodTen patients with DSM-IV depression (two male, eight female) and ten controls (three male, seven female) participated. MEPs were elicited at rest, then after exercising the contralateral abductor pollicis brevis muscle, using TMS of the primary motor cortex.ResultsThe mean MEP amplitude recorded after exercise (expressed as a percentage of baseline) was 210% in controls and 130% in patients. There was a significant difference in post-exercise MEP between patients and controls (P=0.03).ConclusionsPost-exercise MEP facilitation was demonstrated in controls but not in patients. This supports the hypothesis that the modulation of cortical excitability may be impaired in depression.

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