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Beck MM, Christiansen L, Madsen MAJ, Jadidi AF, Vinding MC, Thielscher A, Bergmann TO, Siebner HR, Tomasevic L. Transcranial magnetic stimulation of primary motor cortex elicits an immediate transcranial evoked potential. Brain Stimul 2024:S1935-861X(24)00114-1. [PMID: 38909748 DOI: 10.1016/j.brs.2024.06.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 06/10/2024] [Accepted: 06/17/2024] [Indexed: 06/25/2024] Open
Abstract
BACKGROUND Transcranial evoked potentials (TEPs) measured via electroencephalography (EEG) are widely used to study the cortical responses to transcranial magnetic stimulation (TMS). Immediate transcranial evoked potentials (i-TEPs) have been obscured by pulse and muscular artifacts. Thus, the TEP peaks that are commonly reported have latencies that are too long to be caused by direct excitation of cortical neurons. METHODS In 25 healthy individuals, we recorded i-TEPs evoked by a single biphasic TMS pulse targeting the primary motor hand area (M1HAND) or parietal or midline control sites. Sampling EEG at 50 kHz enabled us to reduce the duration of the TMS pulse artifact to a few milliseconds, while minor adjustments of the TMS coil tilt or position enabled us to avoid cranial muscular twitches during the experiment. RESULTS We observed an early positive EEG deflection starting after approx. 2 ms followed by a series of superimposed peaks with an inter-peak interval of ∼1.1-1.4 ms in multiple electrodes surrounding the stimulated sensorimotor region. This multi-peak i-TEP response was only evoked by TMS of the M1HAND region and was modified by changes in stimulation intensity and current direction. DISCUSSION Single-pulse TMS of the M1HAND evokes an immediate local multi-peak response at the cortical site of stimulation. Our results suggest that the observed i-TEP patterns are genuine cortical responses evoked by TMS caused by synchronized excitation of pyramidal neurons in the targeted precentral cortex. This notion needs to be corroborated in future studies, including further investigations into the potential contribution of instrumental or physiological artifacts.
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Affiliation(s)
- Mikkel Malling Beck
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
| | - Lasse Christiansen
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark; Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen
| | - Mads Alexander Just Madsen
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
| | - Armita Faghani Jadidi
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
| | - Mikkel Christoffer Vinding
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark
| | - Axel Thielscher
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark; Department of Health Technology, Technical University of Denmark, Kgs Lyngby, Denmark
| | - Til Ole Bergmann
- Neuroimaging Center (NIC), Johannes Gutenberg University Medical Center, Mainz, Germany; Leibniz Institute for Resilience Research, Mainz, Germany
| | - Hartwig Roman Siebner
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark; Department of Neurology, Copenhagen University Hospital Bispebjerg and Frederiksberg; Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen
| | - Leo Tomasevic
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark.
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Assessment of cortical inhibition depends on inter individual differences in the excitatory neural populations activated by transcranial magnetic stimulation. Sci Rep 2022; 12:9923. [PMID: 35705672 PMCID: PMC9200840 DOI: 10.1038/s41598-022-14271-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 06/03/2022] [Indexed: 11/28/2022] Open
Abstract
Transcranial magnetic stimulation (TMS) is used to probe inhibitory intracortical neurotransmission and has been used to infer the neurobiological dysfunction that may underly several neurological disorders. One technique, short-interval intracortical inhibition (SICI), indexes gamma-aminobutyric acid (GABA) mediated inhibitory activity and is a promising biomarker. However emerging evidence suggests SICI does not exclusively represent GABAergic activity because it may be influenced by inter-individual differences in the specific excitatory neural populations activated by TMS. Here we used the latency of TMS motor evoked potentials (MEPs) to index these inter-individual differences, and found that a significant proportion of the observed variability in SICI magnitude was accounted for by MEP latency, r = − 0.57, r2 = 0.33, p = .014. We conclude that SICI is influenced by inter-individual differences in the excitatory neural populations activated by TMS, reducing the precision of this GABAergic probe. Interpreting SICI measures in the context of MEP latency may facilitate a more precise assessment of GABAergic intracortical inhibition. The reduced cortical inhibition observed in some neuropathologies could be influenced by reduced activity in specific excitatory neural populations. Including MEP latency assessment in research investigating SICI in clinical groups could assist in differentiating the cortical circuits impacted by neurological disorders.
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Kahl CK, Giuffre A, Wrightson JG, Kirton A, Condliffe EG, MacMaster FP, Zewdie E. Active versus resting neuro-navigated robotic transcranial magnetic stimulation motor mapping. Physiol Rep 2022; 10:e15346. [PMID: 35748041 PMCID: PMC9226845 DOI: 10.14814/phy2.15346] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 03/30/2022] [Accepted: 05/09/2022] [Indexed: 06/15/2023] Open
Abstract
Transcranial magnetic stimulation (TMS) motor mapping is a safe, non-invasive method that can be used to study corticomotor organization. Motor maps are typically acquired at rest, and comparisons to maps obtained during muscle activation have been both limited and contradictory. Understanding the relationship between functional activation of the corticomotor system as recorded by motor mapping is crucial for their use clinically and in research. The present study utilized robotic TMS paired with personalized neuro-navigation to examine the relationship between resting and active motor map measures and their relationship with motor performance. Twenty healthy right-handed participants underwent resting and active robotic TMS motor mapping of the first dorsal interosseous to 10% maximum voluntary contraction. Motor map parameters including map area, volume, and measures of map centrality were compared between techniques using paired sample tests of difference and Bland-Altman plots and analysis. Map area, volume, and hotspot magnitude were larger in the active motor maps, while map center of gravity and hotspot locations remained consistent between both maps. No associations were observed between motor maps and motor performance as measured by the Purdue Pegboard Test. Our findings support previous suggestions that maps scale with muscle contraction. Differences in mapping outcomes suggest rest and active motor maps may reflect functionally different corticomotor representations. Advanced analysis methods may better characterize the underlying neurophysiology of both types of motor mapping.
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Affiliation(s)
- Cynthia K Kahl
- Department of Psychiatry, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Adrianna Giuffre
- Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - James G Wrightson
- Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Adam Kirton
- Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Elizabeth G Condliffe
- Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Frank P MacMaster
- Department of Psychiatry, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Strategic Clinical Network for Neuroscience, Vision, and Rehabilitation, Calgary, Alberta, Canada
- Strategic Clinical Network for Addictions and Mental Health, Calgary, Alberta, Canada
| | - Ephrem Zewdie
- Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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Gurses A, Boran H, Vuralli D, Cengiz B. Weak transcranial direct current effect on i waves: A single motor unit recording study of healthy controls. NEUROL SCI NEUROPHYS 2022. [DOI: 10.4103/nsn.nsn_221_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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Opie GM, Semmler JG. Preferential Activation of Unique Motor Cortical Networks With Transcranial Magnetic Stimulation: A Review of the Physiological, Functional, and Clinical Evidence. Neuromodulation 2020; 24:813-828. [PMID: 33295685 DOI: 10.1111/ner.13314] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/30/2020] [Accepted: 10/19/2020] [Indexed: 12/16/2022]
Abstract
OBJECTIVES The corticospinal volley produced by application of transcranial magnetic stimulation (TMS) over primary motor cortex consists of a number of waves generated by trans-synaptic input from interneuronal circuits. These indirect (I)-waves mediate the sensitivity of TMS to cortical plasticity and intracortical excitability and can be assessed by altering the direction of cortical current induced by TMS. While this methodological approach has been conventionally viewed as preferentially recruiting early or late I-wave inputs from a given populations of neurons, growing evidence suggests recruitment of different neuronal populations, and this would strongly influence interpretation and application of these measures. The aim of this review is therefore to consider the physiological, functional, and clinical evidence for the independence of the neuronal circuits activated by different current directions. MATERIALS AND METHODS To provide the relevant context, we begin with an overview of TMS methodology, focusing on the different techniques used to quantify I-waves. We then comprehensively review the literature that has used variations in coil orientation to investigate the I-wave circuits, grouping studies based on the neurophysiological, functional, and clinical relevance of their outcomes. RESULTS Review of the existing literature reveals significant evidence supporting the idea that varying current direction can recruit different neuronal populations having unique functionally and clinically relevant characteristics. CONCLUSIONS Further research providing greater characterization of the I-wave circuits activated with different current directions is required. This will facilitate the development of interventions that are able to modulate specific intracortical circuits, which will be an important application of TMS.
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Affiliation(s)
- George M Opie
- Discipline of Physiology, Adelaide Medical School, The University of Adelaide, Adelaide, Australia
| | - John G Semmler
- Discipline of Physiology, Adelaide Medical School, The University of Adelaide, Adelaide, Australia
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Journée SL, Journée HL, Berends HI, Reed SM, de Bruijn CM, Delesalle CJG. Comparison of Muscle MEPs From Transcranial Magnetic and Electrical Stimulation and Appearance of Reflexes in Horses. Front Neurosci 2020; 14:570372. [PMID: 33122992 PMCID: PMC7571265 DOI: 10.3389/fnins.2020.570372] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 08/27/2020] [Indexed: 11/13/2022] Open
Abstract
Introduction Transcranial electrical (TES) and magnetic stimulation (TMS) are both used for assessment of the motor function of the spinal cord in horses. Muscular motor evoked potentials (mMEP) were compared intra-individually for both techniques in five healthy horses. mMEPs were measured twice at increasing stimulation intensity steps over the extensor carpi radialis (ECR), tibialis cranialis (TC), and caninus muscles. Significance was set at p < 0.05. To support the hypothesis that both techniques induce extracranially elicited mMEPs, literature was also reviewed. Results Both techniques show the presence of late mMEPs below the transcranial threshold appearing as extracranially elicited startle responses. The occurrence of these late mMEPs is especially important for interpretation of TMS tracings when coil misalignment can have an additional influence. Mean transcranial motor latency times (MLT; synaptic delays included) and conduction velocities (CV) of the ECR and TC were significantly different between both techniques: respectively, 4.2 and 5.5 ms (MLT TMS --MLT TES ), and -7.7 and -9.9 m/s (CV TMS -CV TES ). TMS and TES show intensity-dependent latency decreases of, respectively, -2.6 (ECR) and -2.7 ms (TC)/30% magnetic intensity and -2.6 (ECR) and -3.2 (TC) ms/30V. When compared to TMS, TES shows the lowest coefficients of variation and highest reproducibility and accuracy for MLTs. This is ascribed to the fact that TES activates a lower number of cascaded interneurons, allows for multipulse stimulation, has an absence of coil repositioning errors, and has less sensitivity for varying degrees of background muscle tonus. Real axonal conduction times and conduction velocities are most closely approximated by TES. Conclusion Both intracranial and extracranial mMEPs inevitably carry characteristics of brainstem reflexes. To avoid false interpretations, transcranial mMEPs can be identified by a stepwise latency shortening of 15-20 ms when exceeding the transcranial motor threshold at increasing stimulation intensities. A ring block around the vertex is advised to reduce interference by extracranial mMEPs. mMEPs reflect the functional integrity of the route along the brainstem nuclei, extrapyramidal motor tracts, propriospinal neurons, and motoneurons. The corticospinal tract appears subordinate in horses. TMS and TES are interchangeable for assessing the functional integrity of motor functions of the spinal cord. However, TES reveals significantly shorter MLTs, higher conduction velocities, and better reproducibility.
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Affiliation(s)
- Sanne Lotte Journée
- Equine Diagnostics, Wyns, Netherlands.,Department of Virology, Parasitology and Immunology, Research Group of Comparative Physiology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Henricus Louis Journée
- Department of Neurosurgery, University Medical Center Groningen, University of Groningen, Groningen, Netherlands.,Department of Orthopedics, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands.,Department of Orthopedics, University Medical Center Amsterdam, Amsterdam, Netherlands
| | - Hanneke Irene Berends
- Department of Orthopedics, University Medical Center Amsterdam, Amsterdam, Netherlands
| | - Steven Michael Reed
- Rood & Riddle Equine Hospital, Lexington, KY, United States.,M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington KY, United States
| | | | - Cathérine John Ghislaine Delesalle
- Department of Virology, Parasitology and Immunology, Research Group of Comparative Physiology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
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Influence of preceding muscle activity on movement-related cortical potential during superimposed ballistic contraction. Neurosci Lett 2020; 735:135193. [PMID: 32565221 DOI: 10.1016/j.neulet.2020.135193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 05/28/2020] [Accepted: 06/17/2020] [Indexed: 11/24/2022]
Abstract
The purpose of current study was to clarify the influence of preceding muscle activity on the force production and movement-related cortical potential (MRCP) during superimposed ballistic contractions. The participants performed the ballistic force production at 40 % of maximum voluntary contraction (MVC) using the isometric abduction force of the metacarpophalangeal joint of the index finger. They were asked to match the peak of force curve with a horizontal target line displayed on the computer monitor. We compared the MRCP amplitude during force exertion detected from Fz, C4, C3, Cz and Pz electrodes during ballistic force production with (active condition) and without (resting condition) preceding muscle activity. The results showed that the MRCP amplitudes of Fz, C4, C3 and Cz electrodes were significantly smaller for the active condition than the resting condition. This was the case even though the peak force values during both conditions were identical. This result suggests that the facilitation of spinal motoneuron excitability by preceding muscle activity could reduce the required central motor command to produce the identical force level. In addition, we examined the MRCP amplitude during ballistic force production of the active condition without a visually displayed target. In this condition, the participants had to perform the force production based on aiming point of target force level (40 %MVC). As a result, the mean of peak force without a visual target was 54 %MVC, which overshot the aiming force level. However, the MRCP amplitudes of five electrodes during the 54 %MVC force production in the active condition were equivalent to the case of the 40 %MVC force production in the resting condition. These results suggest that the MRCP amplitude is consistent with participants' sense of effort involved in the force production, rather than the actual produced force level.
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Electroacupuncture-Induced Plasticity between Different Representations in Human Motor Cortex. Neural Plast 2020; 2020:8856868. [PMID: 32855632 PMCID: PMC7443218 DOI: 10.1155/2020/8856868] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 07/18/2020] [Accepted: 08/01/2020] [Indexed: 11/18/2022] Open
Abstract
Somatosensory stimulation can effectively induce plasticity in the motor cortex representation of the stimulated body part. Specific interactions have been reported between different representations within the primary motor cortex. However, studies evaluating somatosensory stimulation-induced plasticity between different representations within the primary motor cortex are sparse. The purpose of this study was to investigate the effect of somatosensory stimulation on the modulation of plasticity between different representations within the primary motor cortex. Twelve healthy volunteers received both electroacupuncture (EA) and sham EA at the TE5 acupoint (located on the forearm). Plasticity changes in different representations, including the map volume, map area, and centre of gravity (COG) were evaluated by transcranial magnetic stimulation (TMS) before and after the intervention. EA significantly increased the map volume of the forearm and hand representations compared to those of sham EA and significantly reduced the map volume of the face representation compared to that before EA. No significant change was found in the map volume of the upper arm and leg representations after EA, and likewise, no significant changes in map area and COG were observed. These results suggest that EA functions as a form of somatosensory stimulation to effectively induce plasticity between different representations within the primary motor cortex, which may be related to the extensive horizontal intrinsic connectivity between different representations. The cortical plasticity induced by somatosensory stimulation might be purposefully used to modulate human cortical function.
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Abstract
I-waves represent high-frequency (~ 600 Hz) repetitive discharge of corticospinal fibers elicited by single-pulse stimulation of motor cortex. First detected and examined in animal preparations, this multiple discharge can also be recorded in humans from the corticospinal tract with epidural spinal electrodes. The exact underpinning neurophysiology of I-waves is still unclear, but there is converging evidence that they originate at the cortical level through synaptic input from specific excitatory interneuronal circuitries onto corticomotoneuronal cells, controlled by GABAAergic interneurons. In contrast, there is at present no supportive evidence for the alternative hypothesis that I-waves are generated by high-frequency oscillations of the membrane potential of corticomotoneuronal cells upon initial strong depolarization. Understanding I-wave physiology is essential for understanding how TMS activates the motor cortex.
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Affiliation(s)
- Ulf Ziemann
- Department of Neurology and Stroke, University of Tübingen, Hoppe-Seyler-Str. 3, 72076, Tübingen, Germany.
- Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
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Miyamoto T, Kizuka T, Ono S. Influence of preceding muscle activity on perceptually guided force production during superimposed ballistic contraction. Physiol Behav 2020; 222:112933. [PMID: 32376328 DOI: 10.1016/j.physbeh.2020.112933] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/21/2020] [Accepted: 04/21/2020] [Indexed: 10/24/2022]
Abstract
Current study attempted to clarify whether preceding muscle activity influences the perceptually guided force production during superimposed ballistic contractions using isometric abduction of index finger. Subjects were verbally asked to produce ballistic force at requested percentages of their MVC with and without preceding muscle activity at 10% and 20%MVC. Our results showed that the ballistic force and EMG activity were increased significantly with preceding muscle activity at 20%MVC, but no change for 10%MVC. These results suggest that preceding muscle activity at sufficient intensity facilitates spinal motoneuron excitability, which could alter the relationship between the produced force and sense of effort.
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Affiliation(s)
- Takeshi Miyamoto
- Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8574, Japan
| | - Tomohiro Kizuka
- Faculty of Health and Sport Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8574, Japan
| | - Seiji Ono
- Faculty of Health and Sport Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8574, Japan.
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11
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Journée SL, Journée HL, Reed SM, Berends HI, de Bruijn CM, Delesalle CJG. Extramuscular Recording of Spontaneous EMG Activity and Transcranial Electrical Elicited Motor Potentials in Horses: Characteristics of Different Subcutaneous and Surface Electrode Types and Practical Guidelines. Front Neurosci 2020; 14:652. [PMID: 32765207 PMCID: PMC7379335 DOI: 10.3389/fnins.2020.00652] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 05/26/2020] [Indexed: 11/13/2022] Open
Abstract
Introduction Adhesive surface electrodes are worthwhile to explore in detail as alternative to subcutaneous needle electrodes to assess myogenic evoked potentials (MEP) in human and horses. Extramuscular characteristics of both electrode types and different brands are compared in simultaneous recordings by also considering electrode impedances and background noise under not mechanically secured (not taped) and taped conditions. Methods In five ataxic and one non-ataxic horses, transcranial electrical MEPs, myographic activity, and noise were simultaneously recorded from subcutaneous needle (three brands) together with pre-gelled surface electrodes (five brands) on four extremities. In three horses, the impedances of four adjacent-placed surface-electrode pairs of different brands were measured and compared. The similarity between needle and surface EMGs was assessed by cross-correlation functions, pairwise comparison of motor latency times (MLT), and amplitudes. The influence of electrode noise and impedance on the signal quality was assessed by a failure rate (FR) function. Geometric means and impedance ranges under not taped and taped conditions were derived for each brand. Results High coherencies between EMGs of needle-surface pairs degraded to 0.7 at moderate and disappeared at strong noise. MLTs showed sub-millisecond simultaneous differences while sequential variations were several milliseconds. Subcutaneous MEP amplitudes were somewhat lower than epidermal. The impedances of subcutaneous needle electrodes were below 900 Ω and FR = 0. For four brands, the FR for surface electrodes was between 0 and 80% and declined to below 25% after taping. A remaining brand (27G DSN2260 Medtronic) revealed impedances over 100 kΩ and FR = 100% under not taped and taped conditions. Conclusion Subcutaneous needle and surface electrodes yield highly coherent EMGs and TES-MEP signals. When taped and allowing sufficient settling time, adhesive surface-electrode signals may approach the signal quality of subcutaneous needle electrodes but still depend on unpredictable conditions of the skin. The study provides a new valuable practical guidance for selection of extramuscular EMG electrodes. This study on horses shares common principles for the choice of adhesive surface or sc needle electrodes in human applications such as in intraoperative neurophysiological monitoring of motor functions of the brain and spinal cord.
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Affiliation(s)
- Sanne Lotte Journée
- Equine Diagnostics, Wyns, Netherlands.,Research Group of Comparative Physiology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Henricus Louis Journée
- Department of Neurosurgery, University Medical Center Groningen, University of Groningen, Groningen, Netherlands.,Department of Orthopedics, Amsterdam University Medical Center, Amsterdam, Netherlands
| | - Stephen Michael Reed
- Rood & Riddle Equine Hospital, Lexington, KY, United States.,M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, United States
| | - Hanneke Irene Berends
- Department of Orthopedics, Amsterdam University Medical Center, Amsterdam, Netherlands
| | | | - Cathérine John Ghislaine Delesalle
- Research Group of Comparative Physiology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
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12
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Motor corticospinal excitability: a novel facet of pain modulation? Pain Rep 2019; 4:e725. [PMID: 31041424 PMCID: PMC6455687 DOI: 10.1097/pr9.0000000000000725] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Revised: 01/20/2019] [Accepted: 01/30/2019] [Indexed: 12/13/2022] Open
Abstract
Introduction Increase in excitability of the primary motor cortex (M1) is associated with pain inhibition by analgesics, which is, in turn, associated with the psychophysical antinociceptive pain modulation profile. However, the relationship between neurophysiological M1 excitability and psychophysical pain modulation has not yet been explored. Objectives We aim to study these relationships in healthy subjects. Methods Forty-one young healthy subjects (22 women) underwent a wide battery of psychophysical testing that included conditioned pain modulation (CPM) and pain temporal summation, and a transcranial magnetic stimulation neurophysiological assessment of the motor corticospinal excitability, including resting motor threshold, motor-evoked potentials (MEPs), and cortical silent period. Results Increased motor corticospinal excitability in 2 parameters was associated with more efficient CPM: (1) higher MEP amplitude (r = -0.574; P _Bonferroni = 0.02) and (2) longer MEP duration (r = -0.543; P _Bonferroni = 0.02). The latter also correlated with the lower temporal summation magnitude (r = -0.421; P = 0.007); however, on multiplicity adjustment, significance was lost. Conclusions Increased corticospinal excitability of the primary motor cortex is associated with more efficient inhibitory pain modulation as assessed by CPM, in healthy subjects. Motor-evoked potential amplitude and duration may be considered as an additional, objective and easy to measure parameter to allow for better individual assessment of pain modulation profile.
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Ficarella SC, Battelli L. Motor Preparation for Action Inhibition: A Review of Single Pulse TMS Studies Using the Go/NoGo Paradigm. Front Psychol 2019; 10:340. [PMID: 30846954 PMCID: PMC6393403 DOI: 10.3389/fpsyg.2019.00340] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 02/04/2019] [Indexed: 01/15/2023] Open
Abstract
Human behavior must be flexible to respond to environmental and social demands, and to achieve these goals, it requires control. For instance, inhibitory control is used to refrain from executing unwanted or anticipated responses to environmental stimuli. When inhibitory mechanisms are inefficient due to some pathological conditions, such as attention-deficit hyperactivity disorder (ADHD) or pathological gambling, patients show a reduced capability of refraining from executing actions. When planning to execute an action, various inhibitory control mechanisms are activated to prevent the unwanted release of impulses and to ensure that the correct response is produced. A great body of research has used various cognitive tasks to isolate one or more components of inhibitory control (e.g., response selectivity) and to investigate their neuronal underpinnings. However, inter-individual differences in behavior are rarely properly considered, although they often represent a considerable source of noise in the data. In the present review, we will address this issue using the specific case of action inhibition, presenting the results of studies that coupled the so-called Go/NoGo paradigm with non-invasive brain stimulation to directly test the effects of motor inhibition on the excitability of the corticospinal system (CSE). Motor preparation is rarely measured in action inhibition studies, and participants’ compliancy to the task’s requests is often assumed rather than tested. Single pulse transcranial magnetic stimulation (TMS) is a powerful tool to directly measure CSE, whose responsivity depends on both excitatory and inhibitory processes. However, when motor preparation is not measured and the task design does not require participants to prepare responses in advance, fluctuations in CSE levels can be mistaken for active inhibition. One way to isolate motor preparation is to use a carefully designed task that allows to control for excessive variability in the timing of activation of inhibitory control mechanisms. Here, we review single pulse TMS studies that have used variants of the Go/NoGo task to investigate inhibitory control functions in healthy participants. We will identify the specific strategies that likely induced motor preparation in participants, and their results will be compared to current theories of action inhibition.
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Affiliation(s)
- Stefania C Ficarella
- Center for Mind/Brain Sciences, University of Trento, Rovereto, Italy.,Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy.,INSERM U 1127, Institut du Cerveau et de la Moelle épinière, Paris, France
| | - Lorella Battelli
- Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia, Rovereto, Italy.,Berenson-Allen Center for Noninvasive Brain Stimulation and Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
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Rijckaert J, Pardon B, Van Ham L, van Loon G, Deprez P. Magnetic Motor Evoked Potential Recording in Horses Using Intramuscular Needle Electrodes and Surface Electrodes. J Equine Vet Sci 2018; 68:101-107. [PMID: 31256880 DOI: 10.1016/j.jevs.2018.05.218] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 05/08/2018] [Accepted: 05/29/2018] [Indexed: 11/30/2022]
Abstract
To date, motor evoked potential (MEP) recording in animals is often performed using intramuscular monopolar needle electrodes. Their placement and use has several disadvantages. Adhesive surface electrodes appear to be attractive because they are painless and easy to place. Because these are not used in horses, a scouting study is performed to (1) explore the applicability of surface electrodes in horses (2) determine the repeatability of motor latency times (MLTs) and amplitude measurements, and (3) to investigate if MLTs and amplitude values of surface electrode recordings were similar to intramuscular needle electrode recordings. Transcranial MEP recordings were performed by both coated needle and surface electrodes on ten sedated warmblood horses. Mean MLTs for the thoracic limbs were 20.8 ± 1.5 ms for needle and 21.2 ± 1.4 ms for surface electrode recording and 39.4 ± 3.8 ms and 39.2 ± 3.8 ms for the pelvic limbs, respectively. Mean amplitude values were 8.3 ± 4.1 and 7.2 ± 4.7 mV for the thoracic limbs and 4.2 ± 3.1 and 3.8 ± 2.4 mV for the pelvic limbs, respectively. A good agreement and repeatability for MLTs but insufficient agreement and repeatability for amplitude between both recording types were determined by Bland-Altman plots and Passing-Bablok regression and coefficients of variation calculation. In conclusion, this preliminary study shows that surface electrode recording of MEP is possible and well tolerated in horses. Surface recordings were repeatable and look similar to the intramuscular recordings when regarding MLTs, but overshadowing effects of large test-to-test variations precluded a conclusion concerning amplitude.
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Affiliation(s)
- Joke Rijckaert
- Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
| | - Bart Pardon
- Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Luc Van Ham
- Small Animal Department, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Gunther van Loon
- Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Piet Deprez
- Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
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15
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Use of Central Motor Conduction Time and Spinal Cord Evoked Potentials in the Electrophysiological Assessment of Compressive Cervical Myelopathy. Spine (Phila Pa 1976) 2017; 42:895-902. [PMID: 27792117 DOI: 10.1097/brs.0000000000001939] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN A retrospective study. OBJECTIVE This study investigated the pathophysiology of compressive cervical myelopathy (CCM) with prolonged central motor conduction time (CMCT) in the upper limbs (ULs) rather than lower limbs (LLs) and prolonged CMCT at the thoracic level (TL). SUMMARY OF BACKGROUND DATA Earlier reports indicated the usefulness of CMCT to assess preoperative CCM severity. However, little information exists on patients with prolonged CMCT-UL rather than CMCT-LL and prolonged CMCT-TL. METHODS Ninety-four patients (61 men, 33 women; age 28-87 years) with CCM who underwent cervical laminoplasty participated. Fifty-three volunteers provided normal data on CMCT-UL and LL. CMCT-TL was calculated as CMCT-LL - CMCT-UL. We defined three groups: group U, prolonged CMCT-UL rather than CMCT-LL (n = 14); group E, prolonged CMCT-UL and CMCT-LL equality (n = 43); and group L, prolonged CMCT-TL (n = 37). We evaluated intraoperative recording of spinal cord evoked potentials (SCEPs), neurological findings, and surgical outcomes. RESULTS Control mean CMCT-UL was 5.2 ± 0.7 ms, CMCT-LL was 11.8 ± 1.1 ms, and CMCT-TL was 6.6 ± 1.2 ms. SCEPs results were significantly different between CCM patients in group U and L (P < 0.01). Almost all patients in three groups showed hyperreflexia of the patellar tendon reflex, but great toe position sense was abnormal in most patients in group L only. Japanese Orthopedics Association (JOA) scores improved postoperatively in all patients. There was a significant difference in recovery rate of the JOA score between group L and other groups (both P < 0.05). CONCLUSION Multimodal SCEPs, clinical findings, and surgical outcomes showed that patients with CCM and prolonged CMCT-TL had substantial disorders of the gray matter, lateral corticospinal tract, and posterior funiculus. Spine surgeons should be aware that prognosis may be poor even after surgery in patients with severe myelopathy such as prolonged CMCT-TL. LEVEL OF EVIDENCE 4.
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16
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van den Bos MAJ, Geevasinga N, Menon P, Burke D, Kiernan MC, Vucic S. Physiological processes influencing motor-evoked potential duration with voluntary contraction. J Neurophysiol 2016; 117:1156-1162. [PMID: 28031404 DOI: 10.1152/jn.00832.2016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 12/13/2016] [Accepted: 12/27/2016] [Indexed: 11/22/2022] Open
Abstract
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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Affiliation(s)
| | | | - Parvathi Menon
- Sydney Medical School, University of Sydney, Sydney, Australia.,Department of Neurology, Westmead Hospital, New South Wales, Australia
| | - David Burke
- Sydney Medical School, University of Sydney, Sydney, Australia.,Royal Prince Alfred Hospital, Sydney, Australia; and
| | - Matthew C Kiernan
- Sydney Medical School, University of Sydney, Sydney, Australia.,Royal Prince Alfred Hospital, Sydney, Australia; and.,Brain and Mind Centre, University of Sydney, Sydney, Australia
| | - Steve Vucic
- Sydney Medical School, University of Sydney, Sydney, Australia; .,Department of Neurology, Westmead Hospital, New South Wales, Australia
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17
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Kothari M, Baad-Hansen L, Svensson P. Bilateral sensory deprivation of trigeminal afferent fibres on corticomotor control of human tongue musculature: a preliminary study. J Oral Rehabil 2016; 43:656-61. [PMID: 27265155 DOI: 10.1111/joor.12414] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/16/2016] [Indexed: 12/01/2022]
Abstract
Transcranial magnetic stimulation (TMS) has demonstrated changes in motor evoked potentials (MEPs) in human limb muscles following modulation of sensory afferent inputs. The aim of this study was to determine whether bilateral local anaesthesia (LA) of the lingual nerve affects the excitability of the tongue motor cortex (MI) as measured by TMS. The effect on MEPs after bilateral LA of the lingual nerve was studied, while the first dorsal interosseous (FDI) muscle served as a control in ten healthy participants. MEPs were measured on the right side of the tongue dorsum in four different conditions: (i) immediately prior to anaesthesia (baseline), (ii) during bilateral LA block of the lingual nerve, (iii) after anaesthesia had subjectively subsided (recovery) and (iv) 3 h after bilateral lingual block injection. MEPs were assessed using stimulus-response curves in steps of 10% of motor threshold (T). Eight stimuli were given at each stimulus level. The amplitudes of the tongue MEPs were significantly influenced by the stimulus intensity (P < 0·001) but not by condition (P = 0·186). However, post hoc tests showed that MEPS were statistically significantly higher during bilateral LA block condition compared with baseline at T + 40%, T + 50% and T + 60% (P < 0·028) and also compared with recovery at T + 60% (P = 0·010) as well as at 3 h after injection at T + 50% and T + 60% (P < 0·029). Bilateral LA block of the lingual nerve seems to be associated with a facilitation of the corticomotor pathways related to the tongue musculature.
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Affiliation(s)
- M Kothari
- Hammel Neurorehabilitation Centre and University Research Clinic, Aarhus University, Hammel, Denmark
| | - L Baad-Hansen
- Section of Orofacial Pain and Jaw Function, Institute of Odontology and Oral Health, Aarhus University, Aarhus, Denmark.,Scandinavian Center for Orofacial Neurosciences (SCON), Aarhus, Denmark
| | - P Svensson
- Section of Orofacial Pain and Jaw Function, Institute of Odontology and Oral Health, Aarhus University, Aarhus, Denmark.,Scandinavian Center for Orofacial Neurosciences (SCON), Aarhus, Denmark
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van de Ruit M, Grey MJ. The TMS Map Scales with Increased Stimulation Intensity and Muscle Activation. Brain Topogr 2015; 29:56-66. [PMID: 26337508 PMCID: PMC4703616 DOI: 10.1007/s10548-015-0447-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 08/18/2015] [Indexed: 11/27/2022]
Abstract
One way to study cortical organisation, or its reorganisation, is to use transcranial magnetic stimulation (TMS) to construct a map of corticospinal excitability. TMS maps are reported to be acquired with a wide variety of stimulation intensities and levels of muscle activation. Whilst MEPs are known to increase both with stimulation intensity and muscle activation, it remains to be established what the effect of these factors is on the map’s centre of gravity (COG), area, volume and shape. Therefore, the objective of this study was to systematically examine the effect of stimulation intensity and muscle activation on these four key map outcome measures. In a first experiment, maps were acquired with a stimulation intensity of 110, 120 and 130 % of resting threshold. In a second experiment, maps were acquired at rest and at 5, 10, 20 and 40 % of maximum voluntary contraction. Map area and map volume increased with both stimulation intensity (P < 0.01) and muscle activation (P < 0.01). Neither the COG nor the map shape changed with either stimulation intensity or muscle activation (P > 0.09 in all cases). This result indicates the map simply scales with stimulation intensity and muscle activation.
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Affiliation(s)
- Mark van de Ruit
- NIHR Surgical Reconstruction and Microbiology Research Centre, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, B15 2TT, UK.,MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, B15 2TT, UK
| | - Michael J Grey
- NIHR Surgical Reconstruction and Microbiology Research Centre, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, B15 2TT, UK. .,MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, B15 2TT, UK.
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19
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Rusu CV, Murakami M, Ziemann U, Triesch J. A Model of TMS-induced I-waves in Motor Cortex. Brain Stimul 2014; 7:401-14. [DOI: 10.1016/j.brs.2014.02.009] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 02/17/2014] [Accepted: 02/17/2014] [Indexed: 10/25/2022] Open
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20
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ILIC TV, PÖTTER-NERGER M, HOLLER I, SIEBNER HR, ILIC NV, DEUSCHL G, VOLKMANN J. Startle Stimuli Exert Opposite Effects on Human Cortical and Spinal Motor System Excitability in Leg Muscles. Physiol Res 2011; 60:S101-6. [PMID: 21777020 DOI: 10.33549/physiolres.932182] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Increased excitability of the spinal motor system has been observed after loud and unexpected acoustic stimuli (AS) preceding H-reflexes. The paradigm has been proposed as an electrophysiological marker of reticulospinal tract activity in humans. The brainstem reticular formation also maintains dense anatomical interconnections with the cortical motor system. When a startling AS is delivered, prior to transcranial magnetic stimulation (TMS), the AS produces a suppression of motor evoked potential (MEP) amplitude in hand and arm muscles of healthy subjects. Here we analyzed the conditioning effect of a startling AS on MEP amplitude evoked by TMS to the primary motor leg area. Ten healthy volunteers participated in two experiments that used a conditioning-test paradigm. In the first experiment, a startling AS preceded a suprathreshold transcranial test stimulus. The interstimulus interval (ISI) varied between 20 to 160 ms. When given alone, the test stimulus evoked a MEP amplitude of approximately 0.5 mV in the slightly preinervated soleus muscle (SOL). In the second experiment, the startling AS was used to condition the size of the H-reflex in SOL muscle. Mean MEP amplitude was calculated for each ISI. The conditioning AS suppressed MEP amplitude at ISIs of 30-80 ms. By contrast, H-reflex amplitude was augmented at ISIs of 100-200 ms. In conclusions, acoustic stimulation exerts opposite and ISI-specific effects on the amplitude of MEPs and H-reflex in the SOL muscle, indicating different mechanism of auditory-to-motor interactions at cortical and spinal level of motor system.
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Affiliation(s)
- T. V. ILIC
- Department of Clinical Neurophysiology, Military Medical Academy, Belgrade, Serbia
| | | | | | | | | | | | - J. VOLKMANN
- Clinic of Neurology, Universitatklinikum Würzburg, Germany
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21
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Men and women exhibit a similar time to task failure for a sustained, submaximal elbow extensor contraction. Eur J Appl Physiol 2009; 108:1089-98. [PMID: 20024575 DOI: 10.1007/s00421-009-1323-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/03/2009] [Indexed: 10/20/2022]
Abstract
Sex differences in muscle fatigue-resistance have been observed in a variety of muscles and under several conditions. This study compared the time to task failure (TTF) of a sustained isometric elbow extensor (intensity 15% of maximal strength) contraction in young men (n = 12) and women (n = 11), and examined if their neurophysiologic adjustments to fatigue differed. Motor-evoked potential amplitude (MEP), silent period duration, interference electromyogram (EMG) amplitude, maximal muscle action potential (M (max)), heart rate, and mean arterial pressure were measured at baseline, during the task, and during a 2-min ischemia period. Men and women did not differ in TTF (478.2 +/- 31.9 vs. 500.4 +/- 41.3 s; P = 0.67). We also performed an exploratory post hoc cluster analysis, and classified subjects as low (n = 15) or high endurance (n = 8) based on TTF (415.3 +/- 16.0 vs. 626.7 +/- 25.8 s, respectively). The high-endurance group exhibited a lower MEP and EMG at baseline (MEP 16.3 +/- 4.1 vs. 37.2 +/- 3.0% M (max), P < 0.01; EMG 0.98 +/- 0.18 vs. 1.85 +/- 0.26% M (max), P = 0.03). These findings suggest no sex differences in elbow extensor fatigability, in contrast to observations from other muscle groups. The cluster analyses results indicated that high- and low-endurance groups displayed neurophysiologic differences at baseline (before performing the fatigue task), but that they did not differ in fatigue-induced changes in their neurophysiologic adjustments to the task.
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22
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Krutky MA, Perreault EJ. Motor cortical measures of use-dependent plasticity are graded from distal to proximal in the human upper limb. J Neurophysiol 2007; 98:3230-41. [PMID: 17942623 DOI: 10.1152/jn.00750.2007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In humans, it is well established that practicing simple, repetitive movements with the distal upper limb induces short-term plasticity in the neural pathways that control training. It is unknown how the neural response to similar training at more proximal joints differs. The purpose of this study was to quantify how ballistic training at proximal and distal upper limb joints influences measures of corticomotor plasticity. To accomplish this goal, we had subjects repetitively practice simple movements for 30 min using the index finger, wrist, or elbow. Before and after training, transcranial magnetic stimulation (TMS) was used to activate the corticomotor pathways innervating the trained joint. We assessed the effect of training by quantifying changes in TMS-elicited joint movements and motor-evoked potentials in the training agonists and antagonists. These measures of training-induced neural plasticity were graded from distal to proximal in the upper limb. Training had the greatest immediate effect on the pathways controlling the index finger and this effect decreased for more proximal joints. Our results suggest that the relative sizes and properties of the cortical areas controlling the proximal and distal upper limb influence the effect of training on the corticomotor pathways. These results have implications for how training influences the neural pathways controlling movement in the proximal and distal portions of the human upper limb and the degree to which these effects can be quantified using TMS.
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Affiliation(s)
- Matthew A Krutky
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL 60611, USA
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23
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Gelli F, Del Santo F, Popa T, Mazzocchio R, Rossi A. Factors influencing the relation between corticospinal output and muscle force during voluntary contractions. Eur J Neurosci 2007; 25:3469-75. [PMID: 17553016 DOI: 10.1111/j.1460-9568.2007.05590.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mechanisms by which voluntary forces of different strengths are produced in human muscles are not clear. We studied the relation between force and surface electromyography (sEMG) variables over a wide range of voluntary contraction strengths of biceps brachii (BIC) and abductor digiti minimi (ADM). The relation between force and motor evoked potentials (MEPs) to transcranial magnetic stimulation of motor cortex was also assessed. The root mean square of sEMG and median frequency (Mf) of the sEMG power spectrum as well as the MEP area of ADM and BIC were calculated up to the maximum voluntary contraction (MVC). The root mean square of ADM and BIC increased with increasing force levels up to the MVC. The Mf of BIC increased with force levels up to 70% MVC after which it rapidly declined. The Mf of ADM peaked at 40% MVC to slowly decline thereafter. The MEP changes with force were similar to Mf changes. Thus, corticospinal output, as tested by the Mf and MEPs, does not parallel force increments across the contraction range. This decline, which is contingent on the relative contribution of motor unit recruitment and rate coding to force production in each muscle, may depend on reduced motoneurone responsiveness at high firing rates. We suggest that, under controlled conditions, the frequency content of the sEMG signal may be taken to indicate motor unit recruitment range. This information may improve the utility of the Mf to enable evaluation of voluntary activation under different conditions.
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Affiliation(s)
- F Gelli
- Department of Neurological and Behavioural Sciences, Section of Clinical Neurophysiology, University of Siena, Italy
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24
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Martin PG, Gandevia SC, Taylor JL. Output of Human Motoneuron Pools to Corticospinal Inputs During Voluntary Contractions. J Neurophysiol 2006; 95:3512-8. [PMID: 16481454 DOI: 10.1152/jn.01230.2005] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
This study investigated transmission of corticospinal output through motoneurons over a wide range of voluntary contraction strengths in humans. During voluntary contraction of biceps brachii, motor evoked potentials (MEPs) to transcranial magnetic stimulation of the motor cortex grow up to about 50% maximal force and then decrease. To determine whether the decrease reflects events at a cortical or spinal level, responses to stimulation of the cortex and corticospinal tract (cervicomedullary motor evoked potentials, CMEPs) as well as maximal M-waves (Mmax) were recorded during strong contractions at 50 to 100% maximum. In biceps and brachioradialis, MEPs and CMEPs (normalized to Mmax) evoked by strong stimuli decreased during strong elbow flexions. Responses were largest during contractions at 75% maximum and both potentials decreased by about 25% Mmax during maximal efforts ( P < 0.001). Reductions were smaller with weaker stimuli, but again similar for MEPs and CMEPs. Thus the reduction in MEPs during strong voluntary contractions can be accounted for by reduced responsiveness of the motoneuron pool to stimulation. During strong contractions of the first dorsal interosseous, a muscle that increases voluntary force largely by frequency modulation, MEPs declined more than in either elbow flexor muscle (35% Mmax, P < 0.001). This suggests that motoneuron firing rates are important determinants of evoked output from the motoneuron pool. However, motor cortical output does not appear to be limited at high contraction strengths.
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Affiliation(s)
- P G Martin
- Prince of Wales Medical Research Institute, University of New South Wales, Barker Street, Randwick, Sydney, NSW 2031, Australia
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Ni Z, Takahashi M, Yamashita T, Liang N, Tanaka Y, Tsuji T, Yahagi S, Kasai T. Functional demanded excitability changes of human hand motor area. Exp Brain Res 2005; 170:141-8. [PMID: 16328281 DOI: 10.1007/s00221-005-0201-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Accepted: 08/15/2005] [Indexed: 11/27/2022]
Abstract
The present study was performed to examine if there are functional differences between the first dorsal interosseous (FDI) and the abductor digit minimi (ADM) muscles during different muscle contractions, namely dynamic and static contractions of the index and little finger abductions. It was also examined whether these functional differences occur at the cortical level. The motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) and force curves, during the muscle contractions, were simultaneously recorded. Rest motor thresholds (RMTs) and active motor thresholds (AMTs), during dynamic and static contractions, were determined in the two muscles. In all trials, the background EMGs (B.EMGs) were kept at the same level in each muscle. Results showed that the target matching errors of dynamic contractions were statistically smaller in the FDI muscle than those in the ADM. In the FDI muscle, the AMT during dynamic contractions was significantly lower than during static ones and the MEPs elicited by TMS were larger during dynamic contractions than those during static ones. However, such results were not found in the ADM muscle. In order to investigate whether the differences were caused by the excitability changes that occurred in the cortical level, the responses elicited by subcortical stimulations were recorded using the same procedures as the experiment of TMS. Responses to subcortical stimulations during dynamic contractions were similar to those during static ones in either muscle. It is concluded that there are differences in the task-dependent MEP facilitations between the FDI and ADM muscles. And the differences are due to the functional demanded excitability changes accompanied by the cortical activation.
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Affiliation(s)
- Zhen Ni
- Division of Sports and Health Sciences, Graduate School for International Development and Cooperation, Hiroshima University, 1-5-1 Kagamiyama, 739-8529, Higashihiroshima, Japan
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Halkjaer L, Melsen B, McMillan AS, Svensson P. Influence of sensory deprivation and perturbation of trigeminal afferent fibers on corticomotor control of human tongue musculature. Exp Brain Res 2005; 170:199-205. [PMID: 16328282 DOI: 10.1007/s00221-005-0199-3] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2005] [Accepted: 08/14/2005] [Indexed: 11/24/2022]
Abstract
Several recent studies with transcranial magnetic stimulation (TMS) have demonstrated changes in motor evoked potentials (MEPs) in human limb muscles following modulation of sensory afferent inputs, but little is known about the regulation of the human tongue motor control. To test the effect of local anesthesia (LA) of the lingual nerve and topical application of capsaicin stimulation on tongue MEPs. Fourteen volunteers participated (21-30 years) in two randomized sessions; before, during a nerve block of the lingual nerve or topical capsaicin application (30 microl 5%) on the tongue, and after anesthesia or pain had subsided. EMG electrodes were placed on the tongue and the first dorsal interosseous (FDI) muscle (control). EMG signals were amplified, filtered (20 Hz-1 kHz), and sampled at 4 kHz (Nicolet, USA). TMS were delivered with a figure-of-eight coil (Magstim 200, UK). Scalp sites at which EMG responses were evoked in the relaxed tongue or FDI at the lowest stimulus strength were determined, i.e., motor threshold (T). MEPs were assessed using stimulus-response curves in steps of 10% T. Eight stimuli were presented at each stimulus level. The proximal hypoglossal nerve was activated by TMS delivered over the parieto-occipital skull distal to the right ear. Eight stimuli were delivered at 50% of maximum stimulator output. ANOVAs were used to analyze latency and peak-to-peak amplitudes. Capsaicin evoked mild pain (2.8+/-0.5), and a strong burning sensation (6.2+/-0.4) on 0-10 visual analogue scales. MEP amplitudes in tongue and FDI were not influenced by capsaicin (P>0.44) but by stimulus strength (P<0.001). MEP latencies in tongue (8.9+/-0.2 ms) and FDI (22.4+/-0.4 ms) were not affected by capsaicin (P>0.19). Hypoglossal nerve stimulation evoked a short-latency (3.6+/-0.9 ms) response (mean amplitude 65+/-9 microV); but was unaffected by capsaicin (P>0.54). LA did not have any effect on FDI MEPs but was associated with a significant facilitation of tongue MEPs at T+50% and T+60% about 50 min after the nerve block in the recovery phase. Also in this condition, the direct motor responses evoked by hypoglossal nerve stimulation remained constant. No direct effect of a strong burning sensation could be shown on peripheral or central corticomotor pathways to the relaxed tongue musculature, however, LA of the lingual nerve (cranial nerve V) seems able to induce a delayed change in corticomotor control of tongue musculature (cranial nerve XII) possibly related to unmasking effects at the cortical level but not completely excluding excitability changes at the brain stem level.
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Affiliation(s)
- L Halkjaer
- Department of Orthodontics, School of Dentistry, University of Aarhus, Aarhus, Denmark
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Excitability Changes of Motor Evoked Potentials Dependent on Muscle Properties and Contraction Modes. Motor Control 2003. [DOI: 10.1123/mcj.7.4.329] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Chapter 8 Transcranial magnetic stimulation. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1567-4231(09)70156-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Taylor JL, Petersen NT, Butler JE, Gandevia SC. Interaction of transcranial magnetic stimulation and electrical transmastoid stimulation in human subjects. J Physiol 2002; 541:949-58. [PMID: 12068053 PMCID: PMC2290352 DOI: 10.1113/jphysiol.2002.016782] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Transcranial magnetic stimulation activates corticospinal neurones directly and transsynaptically and hence, activates motoneurones and results in a response in the muscle. Transmastoid stimulation results in a similar muscle response through activation of axons in the spinal cord. This study was designed to determine whether the two stimuli activate the same descending axons. Responses to transcranial magnetic stimuli paired with electrical transmastoid stimuli were examined in biceps brachii in human subjects. Twelve interstimulus intervals (ISIs) from -6 ms (magnet before transmastoid) to 5 ms were investigated. When responses to the individual stimuli were set at 10-15 % of the maximal M-wave, responses to the paired stimuli were larger than expected at ISIs of -6 and -5 ms but were reduced in size at ISIs of -2 to 1 ms and at 3 to 5 ms. With individual responses of 3-5 % of maximal M-wave, facilitation still occurred at ISIs of -6 and -5 ms and depression of the paired response at ISIs of 0, 1, 4 and 5 ms. The interaction of the response to transmastoid stimulation with the multiple descending volleys elicited by magnetic stimulation of the cortex is complex. However, depression of the response to the paired stimuli at short ISIs is consistent with an occlusive interaction in which an antidromic volley evoked by the transmastoid stimulus collides with and annihilates descending action potentials evoked by the transcranial magnetic stimulus. Thus, it is consistent with the two stimuli activating some of the same corticospinal axons.
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Affiliation(s)
- Janet L Taylor
- Prince of Wales Medical Research Institute, Barker Street, Randwick, NSW 2031, Australia.
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Ridding MC, Taylor JL. Mechanisms of motor-evoked potential facilitation following prolonged dual peripheral and central stimulation in humans. J Physiol 2001; 537:623-31. [PMID: 11731592 PMCID: PMC2278976 DOI: 10.1111/j.1469-7793.2001.00623.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
1. Repetitive electrical peripheral nerve or muscle stimulation can induce a lasting increase in the excitability of the corticomotor projection. By pairing peripheral stimulation with transcranial magnetic brain stimulation it is possible to shorten the duration of stimulation needed to induce this effect. This ability to induce excitability changes in the motor cortex may be of significance for the rehabilitation of brain-injured patients. The mechanisms responsible for the increases in excitability have not been investigated thoroughly. 2. Using two paired transcranial magnetic stimuli protocols we investigated the excitability of intracortical inhibitory and excitatory systems before and following a period of repetitive dual muscle and brain stimulation. The dual stimulation consisted of motor point stimulation of first dorsal interosseous (FDI; 10 Hz trains of 1 ms square waves for 500 ms) delivered at one train every 10 s, paired with single transcranial magnetic stimulation given 25 ms after the onset of the train. 3. Following 30 min of dual stimulation, motor-evoked potentials (MEPs) were significantly increased in amplitude. During this period of MEP facilitation there was no significant difference in the level of intracortical inhibition. There was, however, a significant increase in the intracortical facilitation demonstrated with paired magnetic stimuli. The increase in facilitation was seen only at short interstimulus intervals (0.8-2.0 ms). These intervals comprised a peak in the time course of facilitation, which is thought to reflect I wave interaction within the motor cortex. 4. The relevance of this finding to the MEP facilitation seen following dual peripheral and central stimulation is discussed.
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Affiliation(s)
- M C Ridding
- Department of Medicine, Royal Adelaide Hospital, Adelaide 5000, Australia.
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Abstract
Muscle fatigue is an exercise-induced reduction in maximal voluntary muscle force. It may arise not only because of peripheral changes at the level of the muscle, but also because the central nervous system fails to drive the motoneurons adequately. Evidence for "central" fatigue and the neural mechanisms underlying it are reviewed, together with its terminology and the methods used to reveal it. Much data suggest that voluntary activation of human motoneurons and muscle fibers is suboptimal and thus maximal voluntary force is commonly less than true maximal force. Hence, maximal voluntary strength can often be below true maximal muscle force. The technique of twitch interpolation has helped to reveal the changes in drive to motoneurons during fatigue. Voluntary activation usually diminishes during maximal voluntary isometric tasks, that is central fatigue develops, and motor unit firing rates decline. Transcranial magnetic stimulation over the motor cortex during fatiguing exercise has revealed focal changes in cortical excitability and inhibitability based on electromyographic (EMG) recordings, and a decline in supraspinal "drive" based on force recordings. Some of the changes in motor cortical behavior can be dissociated from the development of this "supraspinal" fatigue. Central changes also occur at a spinal level due to the altered input from muscle spindle, tendon organ, and group III and IV muscle afferents innervating the fatiguing muscle. Some intrinsic adaptive properties of the motoneurons help to minimize fatigue. A number of other central changes occur during fatigue and affect, for example, proprioception, tremor, and postural control. Human muscle fatigue does not simply reside in the muscle.
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Affiliation(s)
- S C Gandevia
- Prince of Wales Medical Research Institute, Prince of Wales Hospital and University of New South Wales, Randwick, Sydney, Australia.
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Abstract
During exercise, changes occur at many sites in the motor pathway, including the muscle fiber, motoneuron, motor cortex, and "upstream" of the motor cortex. Some of the changes result in fatigue, which can be defined as a decrease in ability to produce maximal muscle force voluntarily. Transcranial magnetic stimulation (TMS) over the human motor cortex reveals changes in both motor evoked potentials (MEPs) and the silent period during and after fatiguing voluntary contractions in normal subjects. The relationship of these changes to loss of force or fatigue is unclear. However, during a sustained maximal contraction TMS evokes extra force from the muscle and thus demonstrates the development of suboptimal output from the motor cortex, that is, fatigue at a supraspinal level. In some patients with symptoms of fatigue, the response to TMS after exercise is altered, but the changed MEP behavior is not yet linked to particular symptoms or pathology.
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Affiliation(s)
- J L Taylor
- Prince of Wales Medical Research Institute and University of New South Wales, Barker Street, Randwick, Sydney, NSW 2031, Australia.
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Romaniello A, Cruccu G, McMillan AS, Arendt-Nielsen L, Svensson P. Effect of experimental pain from trigeminal muscle and skin on motor cortex excitability in humans. Brain Res 2000; 882:120-7. [PMID: 11056191 DOI: 10.1016/s0006-8993(00)02856-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The pathophysiology of many orofacial pain syndromes is still unclear. We investigated the effect of tonic muscle and skin pain on the excitability of the trigeminal motor pathways using transcranial magnetic stimulation (TMS). Motor evoked potentials (MEPs) were recorded in the masseter surface electromyogram (EMG). Magnetic pulses were delivered with a large coil at intensities 1.1 and 1.5 times the motor threshold, and for each intensity, MEPs were recorded at three different clenching levels: 15, 30 and 45% of maximum voluntary contraction (MVC). Baseline, pain and post-baseline recordings were compared in two sessions. Firstly, muscle pain was induced by infusion of hypertonic saline (5.8%) into the left masseter. Secondly, skin pain was induced by topical application of capsaicin (5%) on the left cheek. Muscle and skin pain did not induce significant effects on the amplitude or latency of the MEPs (ANOVAs: P>0.50). In both sessions, the amplitude of the MEPs increased with the increase of the clenching level and stimulus intensity (P<0.0001; P<0.005) whereas the latency was not significantly changed (P>0.05; P=0.11). Muscle pain was associated with an increase in the pre-stimulus EMG activity on the non-painful side compared with baseline (P<0.01), which could be due to compensatory changes in the activation of the painful muscle. The need for voluntary contraction to evoke MEPs in the masseter muscles and compensatory mechanisms both at the brainstem and cortical level might explain the lack of detectable modulation of MEPs. Nonetheless, the present findings did not support the so-called 'vicious cycle' between pain - central hyperexcitability - muscle hyperactivity.
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Affiliation(s)
- A Romaniello
- Center for Sensory-Motor Interaction, Orofacial Pain Laboratory, Aalborg University, Fredrik Bajers Vej 7, D-3 9220, Aalborg S, Denmark
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Abstract
We devised a method to investigate the cortical organization of corticomotoneurons (CMs) to upper limb muscles. A spike-triggering technique was used, in which a tonically discharging single motor unit (SMU) triggered transcranial magnetic stimulation (TMS) of motor cortex, and the probability of producing short-latency discharges (primary excitatory responses [PERs]) was measured. PER probabilities were mapped in 34 SMUs, using a 16 cm(2) scalp grid with the central reference point having a probability of 0.5. Maps showed a single optimum point of scalp stimulation and significant decreases in PER probability with shifts of 2 cm from this point, for all subjects. These findings suggest that the colony of CMs projecting to an individual SMN is contained within a small volume of motor cortex. Changes in PER probability with shifts in stimulation site may reflect the organization of other intracortical neurons mediating TMS activation of these CMs.
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Affiliation(s)
- K A Nithi
- Unit of Clinical Neurophysiology, University Department of Clinical Neurology, The Radcliffe Infirmary, Oxford, UK
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Abstract
I-waves refer to high-frequency (approximately 600 Hz) repetitive discharge of corticospinal fibers produced by single-pulse stimulation of the motor cortex. First detected in animal preparations, this multiple discharge can also be recorded in humans with epidural electrodes over the spinal cord, and with recently developed noninvasive paired-pulse transcranial magnetic stimulation protocols. The exact nature of the generation of I-waves is still unclear, but there is convincing evidence that they originate in the motor cortex, mainly through activation of corticocortical projections onto corticospinal neurons. The ability to measure I-waves in human motor cortex allows one to test the integrity and excitability of the underlying corticocortical circuits in health and disease.
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Affiliation(s)
- U Ziemann
- Clinic of Neurology, J.W. Goethe-University of Frankfurt, Frankfurt am Main, Germany
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Abstract
The present experiment was undertaken to study the change in motor cortex excitability as a function of muscle contraction speed during ramp and step abduction by the index finger. Motor evoked potentials (MEPs) of the first dorsal interosseous muscle elicited by transcranial magnetic stimulation (TMS) were modulated by different muscle contraction speeds. When TMS was delivered at 10% maximum voluntary contraction (MVC), MEP amplitudes were always significantly larger in step than in ramp contractions. These differences were dependent on the amount of background electromyographic activity (EMG), which was significantly larger in step than in ramp contractions. However, using maximum output of TMS (100%) with a trigger level at 10% MVC, these differences disappeared. With a trigger level at 30% MVC, these differences also disappeared in spite of differences in the amount of background EMG between them. These results are attributed to different central motor commands. Motor evoked potential amplitudes are dependent not only on the level of background EMG activity but also on the nature of descending motor commands.
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Affiliation(s)
- T Kasai
- Division of Sports & Health Sciences, Graduate School for International Development, 1-5-1 Kagamiyama, Higashihiroshima, Hiroshima, Japan 739-8529, USA
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Pascual-Leone A, Bartres-Faz D, Keenan JP. Transcranial magnetic stimulation: studying the brain-behaviour relationship by induction of 'virtual lesions'. Philos Trans R Soc Lond B Biol Sci 1999; 354:1229-38. [PMID: 10466148 PMCID: PMC1692644 DOI: 10.1098/rstb.1999.0476] [Citation(s) in RCA: 285] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Transcranial magnetic stimulation (TMS) provides a non-invasive method of induction of a focal current in the brain and transient modulation of the function of the targeted cortex. Despite limited understanding about focality and mechanisms of action, TMS provides a unique opportunity of studying brain-behaviour relations in normal humans. TMS can enhance the results of other neuroimaging techniques by establishing the causal link between brain activity and task performance, and by exploring functional brain connectivity.
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Affiliation(s)
- A Pascual-Leone
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA.
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Stedman A, Davey NJ, Ellaway PH. Facilitation of human first dorsal interosseous muscle responses to transcranial magnetic stimulation during voluntary contraction of the contralateral homonymous muscle. Muscle Nerve 1998; 21:1033-9. [PMID: 9655121 DOI: 10.1002/(sici)1097-4598(199808)21:8<1033::aid-mus7>3.0.co;2-9] [Citation(s) in RCA: 142] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The size of compound motor evoked potentials (cMEPs) to transcranial magnetic stimulation of the motor cortex was measured in the relaxed first dorsal interosseous muscle of the nondominant hand (ndFDI) during different levels of voluntary contraction in the homonymous muscle of the dominant hand (dFDI). cMEP responses in the ndFDI became larger when the dFDI was contracted to forces ranging 10-70% of maximum voluntary contraction. Variability in the amplitude of the cMEP responses in ndFDI decreased when dFDI was contracted. Comparison with cMEPs to spinal cord stimulation suggested a large component of the facilitation was occurring at a cortical level. The amplitude of cMEP responses in ndFDI also increased when the tibialis anterior muscle of the leg on the contralateral side was contracted. The observed facilitation of motoneurons during contraction of contralateral muscles might involve a transcallosal pathway modulating the excitability of one cortex when the other is activated.
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Affiliation(s)
- A Stedman
- Division of Neuroscience and Psychological Medicine, Imperial College School of Medicine, Charing Cross Hospital, London, United Kingdom
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Di Lazzaro V, Restuccia D, Oliviero A, Profice P, Ferrara L, Insola A, Mazzone P, Tonali P, Rothwell JC. Effects of voluntary contraction on descending volleys evoked by transcranial stimulation in conscious humans. J Physiol 1998; 508 ( Pt 2):625-33. [PMID: 9508823 PMCID: PMC2230886 DOI: 10.1111/j.1469-7793.1998.625bq.x] [Citation(s) in RCA: 323] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
1. The spinal volleys evoked by single transcranial magnetic or electric stimulation over the cerebral motor cortex were recorded from a bipolar electrode inserted into the cervical epidural space of three conscious human subjects. These volleys were termed direct (D) and indirect (I) waves according to their latency. 2. We measured the size and number of volleys elicited by magnetic stimulation at various intensities with subjects at rest and during 20 or 100 % maximum contraction of the contralateral first dorsal interosseous muscle (FDI). Surface EMG activity was also recorded. 3. Electrical stimulation evoked a D-wave volley. Magnetic stimulation at intensities up to about 15 % of stimulator output above threshold evoked only I-waves. At higher intensities, a D-wave could be seen in two of the three subjects. 4. At all intensities tested, voluntary contraction increased the number and size of the I-waves, particularly during maximum contractions. However, there was only a small effect on the threshold for evoking descending activity. Voluntary contraction produced large changes in the size of EMG responses recorded from FDI. 5. Because the recorded epidural activity is destined for muscles other than the FDI, it is impossible to say to what extent increased activity contributes to voluntary facilitation of EMG responses. Indeed, our results suggest that the main factor responsible for enhancing EMG responses in the transition from rest to activity is likely to be increased excitability of spinal motoneurones, rather than increases in the corticospinal volley. The latter may be more important in producing EMG facilitation at different levels of voluntary contraction.
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Affiliation(s)
- V Di Lazzaro
- Istituto di Neurologia, Università Cattolica, L.go A. Gemelli 8, 00168 Rome, Italy.
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