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Kudina LP, Andreeva RE. Human motoneuron firing behavior and single motor unit F-wave. J Electromyogr Kinesiol 2022; 63:102641. [DOI: 10.1016/j.jelekin.2022.102641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 01/31/2022] [Accepted: 02/03/2022] [Indexed: 10/19/2022] Open
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Christiansen L, Chen B, Lei Y, Urbin MA, Richardson MSA, Oudega M, Sandhu M, Rymer WZ, Trumbower RD, Mitchell GS, Perez MA. Acute intermittent hypoxia boosts spinal plasticity in humans with tetraplegia. Exp Neurol 2020; 335:113483. [PMID: 32987000 DOI: 10.1016/j.expneurol.2020.113483] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 08/31/2020] [Accepted: 09/22/2020] [Indexed: 12/19/2022]
Abstract
Paired corticospinal-motoneuronal stimulation (PCMS) elicits spinal synaptic plasticity in humans with chronic incomplete cervical spinal cord injury (SCI). Here, we examined whether PCMS-induced plasticity could be potentiated by acute intermittent hypoxia (AIH), a treatment also known to induce spinal synaptic plasticity in humans with chronic incomplete cervical SCI. During PCMS, we used 180 pairs of stimuli where corticospinal volleys evoked by transcranial magnetic stimulation over the hand representation of the primary motor cortex were timed to arrive at corticospinal-motoneuronal synapses of the first dorsal interosseous (FDI) muscle ~1-2 ms before the arrival of antidromic potentials elicited in motoneurons by electrical stimulation of the ulnar nerve. During AIH, participants were exposed to brief alternating episodes of hypoxic inspired gas (1 min episodes of 9% O2) and room air (1 min episodes of 20.9% O2). We examined corticospinal function by measuring motor evoked potentials (MEPs) elicited by cortical and subcortical stimulation of corticospinal axons and voluntary motor output in the FDI muscle before and after 30 min of PCMS combined with AIH (PCMS+AIH) or sham AIH (PCMS+sham-AIH). The amplitude of MEPs evoked by magnetic and electrical stimulation increased after both protocols, but most after PCMS+AIH, consistent with the hypothesis that their combined effects arise from spinal plasticity. Both protocols increased electromyographic activity in the FDI muscle to a similar extent. Thus, PCMS effects on spinal synapses of hand motoneurons can be potentiated by AIH. The possibility of different thresholds for physiological vs behavioral gains needs to be considered during combinatorial treatments.
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Affiliation(s)
- Lasse Christiansen
- University of Miami, Department of Neurological Surgery, The Miami Project to Cure Paralysis and Miami VA Medical Center, Miami, FL, 33136, United States of America; Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital, Amager and Hvidovre, Denmark
| | - Bing Chen
- University of Miami, Department of Neurological Surgery, The Miami Project to Cure Paralysis and Miami VA Medical Center, Miami, FL, 33136, United States of America; Shirley Ryan AbilityLab, Northwestern University, Chicago, IL 60611, United States of America
| | - Yuming Lei
- University of Miami, Department of Neurological Surgery, The Miami Project to Cure Paralysis and Miami VA Medical Center, Miami, FL, 33136, United States of America
| | - M A Urbin
- University of Miami, Department of Neurological Surgery, The Miami Project to Cure Paralysis and Miami VA Medical Center, Miami, FL, 33136, United States of America
| | | | - Martin Oudega
- University of Miami, Department of Neurological Surgery, The Miami Project to Cure Paralysis and Miami VA Medical Center, Miami, FL, 33136, United States of America; Shirley Ryan AbilityLab, Northwestern University, Chicago, IL 60611, United States of America; Edward Jr. Hines VA Hospital, Chicago, IL 60141, United States of America; Department of Physical Therapy and Human Movement Sciences, Northwestern University, Northwestern University, Chicago, IL 60611, United States of America; Affiliated Cancer Hospital & Institute, Guangzhou Medical University, Guangzhou, Guangdong 510095, PR China
| | - Milap Sandhu
- Shirley Ryan AbilityLab, Northwestern University, Chicago, IL 60611, United States of America
| | - W Zev Rymer
- Shirley Ryan AbilityLab, Northwestern University, Chicago, IL 60611, United States of America
| | - Randy D Trumbower
- Spaulding Rehabilitation Hospital, Cambridge Street, Cambridge, MA 02138, United States of America; Harvard Medical School, Department of Physical Medicine & Rehabilitation, Boston, MA 02115, United States of America
| | - Gordon S Mitchell
- Center for Respiratory Research and Rehabilitation, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL 32610, United States of America
| | - Monica A Perez
- University of Miami, Department of Neurological Surgery, The Miami Project to Cure Paralysis and Miami VA Medical Center, Miami, FL, 33136, United States of America; Shirley Ryan AbilityLab, Northwestern University, Chicago, IL 60611, United States of America; Edward Jr. Hines VA Hospital, Chicago, IL 60141, United States of America; Department of Physical Therapy and Human Movement Sciences, Northwestern University, Northwestern University, Chicago, IL 60611, United States of America.
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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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4
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Velázquez-Pérez L, Rodríguez-Labrada R, Torres-Vega R, Ortega-Sánchez R, Medrano-Montero J, González-Piña R, Vázquez-Mojena Y, Auburger G, Ziemann U. Progression of corticospinal tract dysfunction in pre-ataxic spinocerebellar ataxia type 2: A two-years follow-up TMS study. Clin Neurophysiol 2018; 129:895-900. [PMID: 29550649 DOI: 10.1016/j.clinph.2018.01.066] [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: 10/21/2017] [Revised: 01/13/2018] [Accepted: 01/23/2018] [Indexed: 01/06/2023]
Abstract
OBJECTIVE Corticospinal tract (CST) dysfunction is common in the pre-ataxic stage of spinocerebellar ataxia type 2 (SCA2) but quantitative assessment of its progression over time has not been explored. The aim of this study was to quantify the progression of CST dysfunction in pre-ataxic SCA2 using transcranial magnetic stimulation (TMS). METHODS Thirty-three pre-ataxic SCA2 mutation carriers and a 33 age- and gender-matched healthy controls were tested at baseline and 2-years follow-up by standardized clinical exams, validated clinical scales, and TMS. RESULTS Pre-ataxic SCA2 mutation carriers showed a significant increase of resting motor thresholds (RMT) to abductor pollicis brevis (APB) and tibialis anterior (TA) muscles, and of central motor conduction time (CMCT) to TA at 2-years follow-up, over and above changes in healthy controls. The changes in the pre-ataxic SCA2 mutation carriers were independent of the presence of clinical signs of CST dysfunction at baseline, and independent of conversion to clinically definite SCA2 at 2-years follow-up. CONCLUSIONS TMS markers of CST dysfunction progress significantly during the pre-ataxic stage of SCA2. SIGNIFICANCE TMS measures of CST dysfunction may provide biomarkers of disease progression prior to clinical disease expression that have potential utility for monitoring neuroprotective therapies in future clinical trials.
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Affiliation(s)
- Luis Velázquez-Pérez
- Dept. Clinical Neurophysiology, Centre for the Research and Rehabilitation of Hereditary Ataxias, Holguín, Cuba; Medical University of Holguin "Mariana Grajales", Holguín, Cuba.
| | - Roberto Rodríguez-Labrada
- Dept. Clinical Neurophysiology, Centre for the Research and Rehabilitation of Hereditary Ataxias, Holguín, Cuba; School of Physical Culture, University of Holguín, Holguín, Cuba
| | - Reidenis Torres-Vega
- Dept. Clinical Neurophysiology, Centre for the Research and Rehabilitation of Hereditary Ataxias, Holguín, Cuba
| | - Ricardo Ortega-Sánchez
- Dept. Clinical Neurophysiology, Centre for the Research and Rehabilitation of Hereditary Ataxias, Holguín, Cuba
| | - Jacqueline Medrano-Montero
- Dept. Clinical Neurophysiology, Centre for the Research and Rehabilitation of Hereditary Ataxias, Holguín, Cuba; School of Physical Culture, University of Holguín, Holguín, Cuba
| | | | - Yaimeé Vázquez-Mojena
- Dept. Molecular Neurobiology, Centre for the Research and Rehabilitation of Hereditary Ataxias, Cuba
| | - Georg Auburger
- Exp. Neurology, Building 89, Goethe University Medical School, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
| | - Ulf Ziemann
- Dept. Neurology & Stroke, and Hertie Institute for Clinical Brain Research, University Tübingen, Hoppe-Seyler-Straße 3, 72076 Tübingen, Germany.
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5
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Welniarz Q, Morel MP, Pourchet O, Gallea C, Lamy JC, Cincotta M, Doulazmi M, Belle M, Méneret A, Trouillard O, Ruiz M, Brochard V, Meunier S, Trembleau A, Vidailhet M, Chédotal A, Dusart I, Roze E. Non cell-autonomous role of DCC in the guidance of the corticospinal tract at the midline. Sci Rep 2017; 7:410. [PMID: 28341853 PMCID: PMC5428661 DOI: 10.1038/s41598-017-00514-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 02/28/2017] [Indexed: 11/13/2022] Open
Abstract
DCC, a NETRIN-1 receptor, is considered as a cell-autonomous regulator for midline guidance of many commissural populations in the central nervous system. The corticospinal tract (CST), the principal motor pathway for voluntary movements, crosses the anatomic midline at the pyramidal decussation. CST fails to cross the midline in Kanga mice expressing a truncated DCC protein. Humans with heterozygous DCC mutations have congenital mirror movements (CMM). As CMM has been associated, in some cases, with malformations of the pyramidal decussation, DCC might also be involved in this process in human. Here, we investigated the role of DCC in CST midline crossing both in human and mice. First, we demonstrate by multimodal approaches, that patients with CMM due to DCC mutations have an increased proportion of ipsilateral CST projections. Second, we show that in contrast to Kanga mice, the anatomy of the CST is not altered in mice with a deletion of DCC in the CST. Altogether, these results indicate that DCC controls CST midline crossing in both humans and mice, and that this process is non cell-autonomous in mice. Our data unravel a new level of complexity in the role of DCC in CST guidance at the midline.
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Affiliation(s)
- Quentin Welniarz
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France.,Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de Biologie Paris Seine, Neuroscience Paris Seine, F-75005, Paris, France
| | - Marie-Pierre Morel
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de Biologie Paris Seine, Neuroscience Paris Seine, F-75005, Paris, France
| | - Oriane Pourchet
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France.,Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de Biologie Paris Seine, Neuroscience Paris Seine, F-75005, Paris, France
| | - Cécile Gallea
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France
| | - Jean-Charles Lamy
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France
| | - Massimo Cincotta
- Unità Operativa di Neurologia-Firenze, Azienda USL Toscana Centro, Ospedale San Giovanni di Dio, 50143, Firenze, Italy
| | - Mohamed Doulazmi
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de Biologie Paris Seine, Adaptation Biologique et vieillissement, F-75005, Paris, France
| | - Morgane Belle
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, F-75012, Paris, France
| | - Aurélie Méneret
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France.,Département de Neurologie, AP-HP, Hôpital Pitié Salpêtrière, Paris, France
| | - Oriane Trouillard
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France
| | - Marta Ruiz
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France
| | - Vanessa Brochard
- Centre d'Investigation Clinique 14-22, INSERM/AP-HP, Paris, France
| | - Sabine Meunier
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France
| | - Alain Trembleau
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de Biologie Paris Seine, Neuroscience Paris Seine, F-75005, Paris, France
| | - Marie Vidailhet
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France.,Département de Neurologie, AP-HP, Hôpital Pitié Salpêtrière, Paris, France
| | - Alain Chédotal
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, F-75012, Paris, France
| | - Isabelle Dusart
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de Biologie Paris Seine, Neuroscience Paris Seine, F-75005, Paris, France
| | - Emmanuel Roze
- Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle épinière, F-75013, Paris, France. .,Département de Neurologie, AP-HP, Hôpital Pitié Salpêtrière, Paris, France.
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Turton A. Mechanisms for Recovery of Hand and Arm Function after Stroke: A Review of Evidence from Studies Using Non-Invasive Investigative Techniques. Br J Occup Ther 2016. [DOI: 10.1177/030802269806100804] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The mechanisms for recovery of motor function after stroke are largely unknown. New non-invasive techniques of Positron Emission Tomography (PET) and Transcranial Magnetic Stimulation (TMS) have provided evidence for changes within the cortical motor areas and descending pathways after stroke in adult subjects. Reorganisation of the corticospinal tract originating from the damaged hemisphere is important for recovery of hand function. Some implications for occupational therapy are discussed.
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7
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Input-Output Characteristics of Late Corticospinal Silent Period Induced by Transcranial Magnetic Stimulation. J Clin Neurophysiol 2015; 32:346-51. [PMID: 25784001 DOI: 10.1097/wnp.0000000000000177] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE Corticospinal silent period (SP) may be interrupted by a burst of muscle activity followed by a second (late) SP, generally assumed to be a continuation from the primary SP. Our objective was to characterize the input-output behavior of the late SP. METHODS Transcranial magnetic stimulation was applied on the cortical representation area of the right-hand muscles of 12 healthy subjects. Single-pulse transcranial magnetic stimulation was given with varying stimulation intensities normalized to the individual resting motor threshold (60% to 130% of the resting motor threshold) during voluntary muscle contraction. Electromyogram was recorded from first dorsal interosseous and abductor pollicis brevis muscles. Primary and late SPs were analyzed as absolute SPs, and input-output characteristics were assessed. RESULTS The late SP exhibited fundamentally different input-output characteristics from that of the primary SP. The late SP most likely presented itself at stimulation intensities of 90% to 100% of the resting motor threshold. CONCLUSIONS Different input-output characteristics of the late SP compared with the primary SP indicate that the late SP possess mechanisms different from the primary SP. The exact origin of the late SP remains unclear. Understanding the origins of the late SP could provide valuable insight on corticospinal inhibitory processes.
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Caliandro P, Padua L, Rossi A, Rossini PM, Stalberg E, Feurra M, Ulivelli M, Bartalini S, Giannini F, Rossi S. Jitter of Corticospinal Neurons During Repetitive Transcranial Magnetic Stimulation. Method and Possible Clinical Implications. Brain Stimul 2014; 7:580-6. [DOI: 10.1016/j.brs.2014.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 04/08/2014] [Accepted: 05/01/2014] [Indexed: 12/19/2022] Open
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9
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Vicario CM, Candidi M, Aglioti SM. Cortico-spinal embodiment of newly acquired, action-related semantic associations. Brain Stimul 2013; 6:952-8. [PMID: 23856556 DOI: 10.1016/j.brs.2013.05.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 01/22/2013] [Accepted: 05/31/2013] [Indexed: 10/26/2022] Open
Abstract
BACKGROUND Behavioral and neurophysiological studies indicate that the semantic derivation of the motor skills of a given model (e.g., famous tennis or soccer athlete) modulates the reactivity of arm and leg cortico-spinal representations of an onlooker who performs a categorization task. Information on the possible plastic nature of the sensorimotor mapping of action-related knowledge is still lacking. OBJECTIVE/HYPOTHESIS Here we explored the time course of any cortico-spinal excitability modulation induced by the creation of arbitrary associations between a personal name and tennis- or soccer-related motor skills. METHODS We recorded the amplitude of Transcranial Magnetic Stimulation (TMS) Motor Evoked Potentials (MEPs) from arm and leg muscles during a categorization task concerning names that were learned in association with either soccer players, tennis players or control, non-motor, identities (actors). We stimulated the cortico-spinal system and recorded the MEPs at three different time points (0-24-72 h) after the association learning. RESULTS Coherently with previous literature we found a relative dissociation of leg muscles MEPs during reading of soccer-associated personal names with respect to tennis ones. Importantly this modulation was measured only 72 h after having learned the association. This effect was not found in the arm muscle. CONCLUSION The results suggest that for the process of embodying semantic associations in the motor system to take place, the strength of the association itself needs to rise above some level of consolidation.
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Affiliation(s)
- Carmelo Mario Vicario
- Department of Psychology, University of Rome "La Sapienza", Rome, Italy; IRCCS, Santa Lucia Foundation, Rome, Italy; School of Psychology, The University of Queensland, St. Lucia, Australia.
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10
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Change in the ipsilateral motor cortex excitability is independent from a muscle contraction phase during unilateral repetitive isometric contractions. PLoS One 2013; 8:e55083. [PMID: 23383063 PMCID: PMC3561368 DOI: 10.1371/journal.pone.0055083] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Accepted: 12/17/2012] [Indexed: 11/19/2022] Open
Abstract
The aim of this study was to investigate the difference in a muscle contraction phase dependence between ipsilateral (ipsi)- and contralateral (contra)-primary motor cortex (M1) excitability during repetitive isometric contractions of unilateral index finger abduction using a transcranial magnetic stimulation (TMS) technique. Ten healthy right-handed subjects participated in this study. We instructed them to perform repetitive isometric contractions of the left index finger abduction following auditory cues at 1 Hz. The force outputs were set at 10, 30, and 50% of maximal voluntary contraction (MVC). Motor evoked potentials (MEP) were obtained from the right and left first dorsal interosseous muscles (FDI). To examine the muscle contraction phase dependence, TMS of ipsi-M1 or contra-M1 was triggered at eight different intervals (0, 20, 40, 60, 80, 100, 300, or 500 ms) after electromyogram (EMG) onset when each interval had reached the setup triggering level. Furthermore, to demonstrate the relationships between the integrated EMG (iEMG) in the active left FDI and the ipsi-M1 excitability, we assessed the correlation between the iEMG in the left FDI for the 100 ms preceding TMS onset and the MEP amplitude in the resting/active FDI for each force output condition. Although contra-M1 excitability was significantly changed after the EMG onset that depends on the muscle contraction phase, the modulation of ipsi-M1 excitability did not differ in response to any muscle contraction phase at the 10% of MVC condition. Also, we found that contra-M1 excitability was significantly correlated with iEMG in all force output conditions, but ipsi-M1 excitability was not at force output levels of below 30% of MVC. Consequently, the modulation of ipsi-M1 excitability was independent from the contraction phase of unilateral repetitive isometric contractions at least low force output.
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11
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Stump nerve signals during transcranial magnetic motor cortex stimulation recorded in an amputee via longitudinal intrafascicular electrodes. Exp Brain Res 2011; 210:1-11. [DOI: 10.1007/s00221-011-2571-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 01/24/2011] [Indexed: 10/18/2022]
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Abstract
During the last decades, transcranial magnetic stimulation (TMS) has been used as a noninvasive method to investigate motor cortical reorganization and neuroplasticity in humans after stroke. An increasing number of studies in the field of motor control have used TMS to gain an understanding of the different aspects of stroke cortical physiology and motor recovery. This review addresses the effects of corticospinal tract (CST) lesions in humans and nonhuman primates on the functional organization of the motor system. We review information on the physiological mechanisms by which the CST contributes to normal motor control and to central nervous system reorganization following stroke when the CST is injured as measured using TMS. Insight into these physiological mechanisms has led to the development of scientifically sound interventional proposals in the field of neurorehabilitation.
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Affiliation(s)
- Monica A Perez
- Department of Physical Medicine and Rehabilitation, Center for the Neural Basis of Cognition, University of Pittsburgh, Pennsylvania, USA
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13
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Lazzaro VD, Ziemann U, Lemon RN. State of the art: Physiology of transcranial motor cortex stimulation. Brain Stimul 2008; 1:345-62. [DOI: 10.1016/j.brs.2008.07.004] [Citation(s) in RCA: 214] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Revised: 07/23/2008] [Accepted: 07/31/2008] [Indexed: 10/21/2022] Open
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14
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Pitcher JB, Robertson AL, Clover EC, Jaberzadeh S. Facilitation of cortically evoked potentials with motor imagery during post-exercise depression of corticospinal excitability. Exp Brain Res 2004; 160:409-17. [PMID: 15502993 DOI: 10.1007/s00221-004-2021-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2003] [Accepted: 05/14/2004] [Indexed: 11/28/2022]
Abstract
This study examined whether muscle fatigue alters the facilitatory effect of motor imagery on corticospinal excitability. We aimed to determine if post-exercise depression of potentials evoked magnetically from the motor cortex is associated with alterations in internally generated movement plans. In experiment 1, motor-evoked potentials (MEPs) were recorded from two right hand and two right forearm muscles, at rest and during motor imagery of a maximal handgrip contraction, in eight neurologically normal subjects, before and after a 2-min maximal voluntary handgrip contraction. Resting MEP amplitude was facilitated by motor imagery in three of the four muscles, but consistently only in two. Motor imagery also reduced the trial-to-trial variability of resting MEPs. Following the exercise, resting MEP amplitude was depressed reliably in only one muscle engaged in the task, although two other muscles exhibited some depression. Motor imagery MEPs were smaller after exercise, but the degree of facilitation compared to the rest MEP was unchanged. In experiment 2, TMS intensity was increased after exercise-induced MEP depression so that the MEP amplitude matched the pre-exercise baseline. The amplitude of the MEP facilitated with motor imagery was not altered by MEP depression, nor was it increased when the TMS intensity was increased. These results suggest, at least with a simple motor task, that while post-exercise depression reduces corticospinal excitability, it does not appear to significantly affect the strength of the input to the motor cortex from those areas of the brain responsible for the storage and generation of internal representations of movement.
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Affiliation(s)
- Julia B Pitcher
- Discipline of Physiology, School of Molecular and Biomedical Sciences, The University of Adelaide, 5005, Adelaide, South Australia, Australia.
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15
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Rodríguez M, Muñiz R, González B, Sabaté M. Hand movement distribution in the motor cortex: the influence of a concurrent task and motor imagery. Neuroimage 2004; 22:1480-91. [PMID: 15275905 DOI: 10.1016/j.neuroimage.2004.02.040] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2003] [Revised: 01/20/2004] [Accepted: 02/28/2004] [Indexed: 11/17/2022] Open
Abstract
The aim of this work was to study the relevance of the primary motor cortex (M1) for motor functions different to the simple execution of motor orders. The M1 activity during the performance with individual fingers of a simple motor task (tonic flexion), a motor task that includes a complex motor computation but not motor execution (motor imagery), and a motor task that involves both the computation and execution of movements (phasic movement) was evaluated by functional magnetic resonance imaging (fMRI). The possible influence of other cortical tasks on the M1 activation induced by finger movements was assessed by evaluating the effect of a distracting concurrent task (numeric calculation). Data show that both the dimension of the area activated and the intensity of response were higher during motor planning than during motor execution. There is a mosaic-like distribution for motor-planning M1 functions, with the movement of individual fingers being controlled from several M1 loci. The concurrent mental-task induces a rapid functional reconfiguration of M1, adding M1 subsets to motor programming but excluding others. Present data support the involvement of the M1 in more than just simple motor execution, showing broader and more intense modifications during motor tasks not accompanied by movements (motor imagery) than during the execution of simple motor acts (tonic flexion).
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Affiliation(s)
- Manuel Rodríguez
- Department of Physiology, Faculty of Medicine, University of La Laguna, Spain.
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16
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Petersen NT, Pyndt HS, Nielsen JB. Investigating human motor control by transcranial magnetic stimulation. Exp Brain Res 2003; 152:1-16. [PMID: 12879177 DOI: 10.1007/s00221-003-1537-y] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2002] [Accepted: 05/21/2003] [Indexed: 12/22/2022]
Abstract
In this review we discuss the contribution of transcranial magnetic stimulation (TMS) to the understanding of human motor control. Compound motor-evoked potentials (MEPs) may provide valuable information about corticospinal transmission, especially in patients with neurological disorders, but generally do not allow conclusions regarding the details of corticospinal function to be made. Techniques such as poststimulus time histograms (PSTHs) of the discharge of single, voluntarily activated motor units and conditioning of H reflexes provide a more optimal way of evaluating transmission in specific excitatory and inhibitory pathways. Through application of such techniques, several important issues have been clarified. TMS has provided the first real evidence that direct monosynaptic connections from the motor cortex to spinal motoneurons exist in man, and it has been revealed that the distribution of these projections roughly follows the same proximal-distal gradient as in other primates. However, pronounced differences also exist. In particular, the tibialis anterior muscle appears to receive as significant a monosynaptic corticospinal drive as muscles in the hand. The reason for this may be the importance of this muscle in controlling the foot trajectory in the swing phase of walking. Conditioning of H reflexes by TMS has provided evidence of changes in cortical excitability prior to and during various movements. These experiments have generally confirmed information obtained from chronic recording of the activity of corticospinal cells in primates, but information about the corticospinal contribution to movements for which information from other primates is sparse or lacking has also been obtained. One example is walking, where TMS experiments have revealed that the corticospinal tract makes an important contribution to the ongoing EMG activity during treadmill walking. TMS experiments have also documented the convergence of descending corticospinal projections and peripheral afferents on spinal interneurons. Current investigations of the functional significance of this convergence also rely on TMS experiments. The general conclusion from this review is that TMS is a powerful technique in the analysis of motor control, but that care is necessary when interpreting the data. Combining TMS with other techniques such as PSTH and H reflex testing amplifies greatly the power of the technique.
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Affiliation(s)
- Nicolas T Petersen
- Department of Medical Physiology, The Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
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Tröger M, Vøllestad N, Dengler R, Mills KR. Clinical neurophysiological approaches to neuromuscular fatigue. SUPPLEMENTS TO CLINICAL NEUROPHYSIOLOGY 2003; 53:433-42. [PMID: 12741031 DOI: 10.1016/s1567-424x(09)70192-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- M Tröger
- Department of Neurology, Medical School Hannover, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
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Pearce SL, Miles TS, Thompson PD, Nordstrom MA. Responses of single motor units in human masseter to transcranial magnetic stimulation of either hemisphere. J Physiol 2003; 549:583-96. [PMID: 12692177 PMCID: PMC2342953 DOI: 10.1113/jphysiol.2002.035352] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The corticobulbar inputs to single masseter motoneurons from the contra- and ipsilateral motor cortex were examined using focal transcranial magnetic stimulation (TMS) with a figure-of-eight stimulating coil. Fine-wire electrodes were inserted into the masseter muscle of six subjects, and the responses of 30 motor units were examined. All were tested with contralateral TMS, and 87 % showed a short-latency excitation in the peristimulus time histogram at 7.0 +/- 0.3 ms. The response was a single peak of 1.5 +/- 0.2 ms duration, consistent with monosynaptic excitation via a single D- or I1-wave volley elicited by the stimulus. Increased TMS intensity produced a higher response probability (n = 13, paired t test, P < 0.05) but did not affect response latency. Of the remaining motor units tested with contralateral TMS, 7 % did not respond at intensities tested, and 7 % had reduced firing probability without any preceding excitation. Sixteen of these motor units were also tested with ipsilateral TMS and four (25 %) showed short-latency excitation at 6.7 +/- 0.6 ms, with a duration of 1.5 +/- 0.3 ms. Latency and duration of excitatory peaks for these four motor units did not differ significantly with ipsilateral vs. contralateral TMS (paired t tests, P > 0.05). Of the motor units tested with ipsilateral TMS, 56 % responded with a reduced firing probability without a preceding excitation, and 19 % did not respond. These data suggest that masseter motoneurons receive monosynaptic input from the motor cortex that is asymmetrical from each hemisphere, with most low threshold motoneurons receiving short-latency excitatory input from the contralateral hemisphere only.
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Affiliation(s)
- Sophie L Pearce
- Department of Physiology, The University of Adelaide, Adelaide, South Australia 5005, Australia
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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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Mall V, Glocker FX, Fietzek U, Heinen F, Berweck S, Korinthenberg R, Rösler KM. Inhibitory conditioning stimulus in transcranial magnetic stimulation reduces the number of excited spinal motor neurons. Clin Neurophysiol 2001; 112:1810-3. [PMID: 11595138 DOI: 10.1016/s1388-2457(01)00638-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To study the mechanisms of amplitude attenuation caused by a transcranial magnetic conditioning stimulus. Both conventional MEPs and the recently described triple stimulation technique (TST) were applied; the latter to improve the quantification of the response size decrease. METHODS TST uses a peripheral collision method to eliminate the effects of desynchronization of the transcranial magnetic stimulation (TMS) induced spinal motor neuron discharges. The attenuation of motor evoked potentials (MEPs) and responses to TST was studied in 10 healthy volunteers using the conditioning-test paradigm with 2 ms interstimulus intervals. RESULTS Conventional MEPs and responses to TST demonstrated a marked attenuation by the preceding conditioning stimulus in all subjects. The ratio of MEP to TST amplitudes was the same in conditioned and unconditioned responses. CONCLUSIONS Our findings suggest that the transcranial conditioning stimulus does not change the degrees of desynchronization of spinal motor neuron discharges, but results in a reduced number of excited alpha motor neurons. This reduction can be estimated by both MEPs and TST.
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Affiliation(s)
- V Mall
- Department of Neuropediatrics and Muscle Diseases, Children's Hospital, University of Freiburg, Mathildenstrasse 1, D-79106, Freiburg, Germany.
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Amiaz R, Stein O, Schreiber S, Danon PN, Dolberg OT, Grunhaus L. Magnetic and seizure thresholds before and after six electroconvulsive treatments. J ECT 2001; 17:195-7. [PMID: 11528311 DOI: 10.1097/00124509-200109000-00009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Electroconvulsive therapy (ECT) is a well-established treatment in psychiatry. It has been reported that in patients with nondelusional major depression, transcranial magnetic stimulation (TMS) may substitute for ECT. To explore whether ECT and TMS share mechanisms of action, we studied the effects of ECT on both seizure threshold (ST) and magnetic motor threshold (MT). METHODS We measured ST and MT in 10 patients referred for ECT. MT was defined as the minimal power of the TMS equipment at which a motor evoked potential (MEP) response could be detected 50% of the time. ST was defined as the minimal intensity of electrical stimulation needed to elicit an adequate seizure. ECT was performed following the methods recommended by the American Psychiatric Association. All subjects signed an informed consent for participation in the research. RESULTS We measured MT and ST in 10 patients before and after 6 ECT treatments. No changes in MT were detected from the treatment (paired t-test: t = 1.05, SD = 4.78, p = 0.25). ST, on the other hand, increased significantly with treatment (paired t-test: t = 2.99, SD = 190.20, p < 0.001). CONCLUSIONS ECT and TMS do not share a common mechanism at least with regard to MT and ST.
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Affiliation(s)
- R Amiaz
- Psychiatry Department C, The Chaim Sheba Medical Center, Tel-Hashomer, Israel.
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Bühler R, Magistris MR, Truffert A, Hess CW, Rösler KM. The triple stimulation technique to study central motor conduction to the lower limbs. Clin Neurophysiol 2001; 112:938-49. [PMID: 11336912 DOI: 10.1016/s1388-2457(01)00506-5] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE To quantify the percentage of motor units of a foot muscle that can be activated by transcranial magnetic stimulation (TMS) in normal subjects and patients. METHODS We adapted the recently described triple stimulation technique (TST) for recordings from abductor hallucis (AH). Conventional motor evoked potentials (MEPs) of this muscle are usually small and variable in shape, because of an important temporal desynchronization of the TMS induced spinal motor neuron discharges. The TST allows 'resynchronization' of these discharges and thereby a quantification of the proportion of motor units activated by TMS. The lower limb (LL-) TST was applied to 33 sides of 18 normal subjects and 51 sides of 46 patients with multiple sclerosis, amyotrophic lateral sclerosis, or spinal cord disorders. RESULTS In healthy subjects, the LL-TST demonstrated that TMS achieves activation of virtually all motor neurons supplying the AH. In 33 of 51 patient sides, abnormal LL-TST responses suggested corticospinal conduction failures of various degrees. The LL-TST was 2.54 times more sensitive to detect central conduction failures than the conventional LL-MEPs. Combining the LL-TST with TST of the upper limbs further increased the sensitivity to detect a conduction failure by 1.50 times. CONCLUSION The LL-TST markedly improves the examination of corticospinal pathways.
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Affiliation(s)
- R Bühler
- Department of Neurology, University of Berne, Inselspital, CH-3010, Berne, Switzerland
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Azanza MJ, Calvo AC. SNAIL NEURON BIOELECTRIC ACTIVITY INDUCED UNDER STATIC OR SINUSOIDAL MAGNETIC FIELDS REPRODUCES MAMMAL NEURON RESPONSES UNDER TRANSCRANIAL MAGNETIC STIMULATION. ACTA ACUST UNITED AC 2000. [DOI: 10.1081/jbc-100102121] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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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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Spinal cord-evoked potentials and muscle responses evoked by transcranial magnetic stimulation in 10 awake human subjects. J Neurosci 1999. [PMID: 10024369 DOI: 10.1523/jneurosci.19-05-01855.1999] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Transcranial magnetic stimulation (TCMS) causes leg muscle contractions, but the neural structures in the brain that are activated by TCMS and their relationship to these leg muscle responses are not clearly understood. To elucidate this, we concomitantly recorded leg muscle responses and thoracic spinal cord-evoked potentials (SCEPs) after TCMS for the first time in 10 awake, neurologically intact human subjects. In this report we provide evidence of direct and indirect activation of corticospinal neurons after TCMS. In three subjects, SCEP threshold (T) stimulus intensities recruited both the D wave (direct activation of corticospinal neurons) and the first I wave (I1, indirect activation of corticospinal neurons). In one subject, the D, I1, and I2 waves were recruited simultaneously, and in another subject, the I1 and I2 waves were recruited simultaneously. In the remaining five subjects, only the I1 wave was recruited first. More waves were recruited as the stimulus intensity increased. The presence of D and I waves in all subjects at low stimulus intensities verified that TCMS directly and indirectly activated corticospinal neurons supplying the lower extremities. Leg muscle responses were usually contingent on the SCEP containing at least four waves (D, I1, I2, and I3).
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Ziemann U, Tergau F, Wassermann EM, Wischer S, Hildebrandt J, Paulus W. Demonstration of facilitatory I wave interaction in the human motor cortex by paired transcranial magnetic stimulation. J Physiol 1998; 511 ( Pt 1):181-90. [PMID: 9679173 PMCID: PMC2231091 DOI: 10.1111/j.1469-7793.1998.181bi.x] [Citation(s) in RCA: 338] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/1997] [Accepted: 05/08/1998] [Indexed: 11/30/2022] Open
Abstract
1. Transcranial magnetic stimulation (TMS) of the human motor cortex results in multiple discharges (D and I waves) in the corticospinal tract. We tested whether these volleys can be explored non-invasively with paired TMS. The intensity of the first stimulus (S1) was set to produce a motor-evoked potential (MEP) of 1 mV in the resting contralateral abductor digiti minimi (ADM) muscle; the second stimulus (S2) was set to 90 % of the resting motor threshold. At interstimulus intervals of 1.1-1.5, 2.3-2.9 and 4.1-4.4 ms the MEP elicited by S1 plus S2 was larger than that produced by S1 alone. 2. Varying the S1 intensity between 70 and 130 % resting motor threshold with S2 held constant at 90 % resting motor threshold showed that the threshold for the first MEP peak was <= 70 % resting motor threshold. The second and third MEP peaks appeared only at higher S1 intensities. The latency of all peaks decreased with increasing S1 intensity. 3. Varying the S2 intensity with S1 held constant to produce a MEP of 1 mV on its own showed that the amplitude of all MEP peaks increased with S2 intensity, but that their timing remained unchanged. 4. Paired TMS in the active ADM (S1 clearly suprathreshold, S2 just above threshold; interstimulus interval, 1 ms) produced strong MEP facilitation. The onset of this facilitation occurred later by about 1.5 ms than the onset of the MEP evoked by S2 alone. No MEP facilitation was seen if the magnetic S2 was replaced by anodal or cathodal transcranial electrical stimulation. 5. It is concluded that the MEP facilitation after paired TMS, at least for the first MEP peak, is due to facilitatory interaction between I waves, and takes place in the motor cortex at or upstream from the corticospinal neurone.
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Affiliation(s)
- U Ziemann
- Department of Clinical Neurophysiology, University of Gottingen, Human Motor Control Section, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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Ziemann U, Steinhoff BJ, Tergau F, Paulus W. Transcranial magnetic stimulation: its current role in epilepsy research. Epilepsy Res 1998; 30:11-30. [PMID: 9551841 DOI: 10.1016/s0920-1211(97)00079-x] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This paper reviews the current role of transcranial magnetic stimulation (TMS) in epilepsy research. After a brief introduction to the technical principles, the physiology and the safety aspects of TMS, emphasis is put on how human cortex excitability can be assessed by TMS and how this may improve our understanding of pathophysiological mechanisms in epilepsy and the mode of action of antiepileptic drugs (AEDs). Also, potential therapeutical applications of TMS are reviewed. For all aspects of this paper, a clear distinction was made between single-/paired-pulse TMS and repetitive TMS, since these two techniques have fundamentally different scopes and applications.
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Affiliation(s)
- U Ziemann
- Department of Clinical Neurophysiology, University of Gottingen, Germany
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Thomas CK, Zaidner EY, Calancie B, Broton JG, Bigland-Ritchie BR. Muscle weakness, paralysis, and atrophy after human cervical spinal cord injury. Exp Neurol 1997; 148:414-23. [PMID: 9417821 DOI: 10.1006/exnr.1997.6690] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Muscle weakness and failure of central motor drive were assessed in triceps brachii muscles of individuals with chronic cervical spinal cord injury (SCI) and able-bodied controls. Electrical stimuli were applied to the radial nerve during rest and during triceps submaximal and maximal voluntary contractions (MVCs). The mean forces and integrated EMGs generated by SCI subjects during MVCs were significantly less than those produced by controls (P < 0.01), with 74 and 71% of muscles generating <10% control force and EMG, respectively. There was an inverse linear relationship between the evoked and voluntary forces (n = 32 muscles of SCI subjects) which, when extrapolated to zero evoked force, also showed significant whole muscle weakness for SCI compared to control subjects (P < 0. 01). Severe muscle atrophy was revealed which might reflect disuse and/or muscle denervation subsequent to motoneuron loss. Many triceps muscles of SCI subjects showed no force occlusion (n = 41) or were impossible to stimulate selectively (n = 61). Force was always evoked when the radial nerve was stimulated during MVCs of SCI subjects. The force elicited by single magnetic shocks applied to the motor cortex at Cz' during voluntary contractions of SCI subjects was also inversely related to the voluntary triceps force exerted (n = 18), but usually no force could be elicited during MVCs. Thus central motor drive was probably maximal to these muscles, and the force evoked during MVCs by below-lesion stimulation must come from activation of paralyzed muscle. SCI subjects also had significantly longer mean central nervous system (CNS) conduction times to triceps (P < 0.01) suggesting that the measured deficits reflect CNS rather than peripheral nervous system factors. Thus, the weak voluntary strength of these partially paralyzed muscles is not due to submaximal excitation of higher CNS centers, but results mainly from reduction of this input to triceps motoneurons.
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Affiliation(s)
- C K Thomas
- Department of Neurological Surgery, University of Miami School of Medicine, Miami, Florida 33136, USA
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Capaday C. Neurophysiological methods for studies of the motor system in freely moving human subjects. J Neurosci Methods 1997; 74:201-18. [PMID: 9219889 DOI: 10.1016/s0165-0270(97)02250-4] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In this paper, the following experimental methods for studies of the motor system in freely moving human subjects will be considered: (i) eliciting the H-reflex and understanding its use as a test response, (ii) methods to measure reciprocal inhibition between antagonist muscles, (iii) methods to measure presynaptic inhibition of Ia-afferent terminals in the spinal cord, (iv) certain aspects of the interpretation of peri-stimulus time histograms (PSTH) of single motor unit discharge, and finally, (v) stimulation of the motor cortex and the measurement of response parameters that may reflect task dependent changes. Two closely related ideas bearing directly on these methods will be emphasized--the influence of the background level of motor activity on input output properties of the neural pathway investigated and the operating point on the input-output curves at which the experimental variable is measured. Finally, in the discussion a simple model that is easily understandable in geometric terms is presented to help predict and interpret the outcome of these sorts of experiments.
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Affiliation(s)
- C Capaday
- Centre de recherche en Neurobiologie, Universitè Laval, Québec City, Canada.
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Lemon RN, Johansson RS, Westling G. Modulation of corticospinal influence over hand muscles during gripping tasks in man and monkey. Can J Physiol Pharmacol 1996. [DOI: 10.1139/y96-030] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Olivier E, Bawa P, Lemon RN. Excitability of human upper limb motoneurones during rhythmic discharge tested with transcranial magnetic stimulation. J Physiol 1995; 485 ( Pt 1):257-69. [PMID: 7658379 PMCID: PMC1157988 DOI: 10.1113/jphysiol.1995.sp020728] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. The activity of thirty-one single motor units (SMUs) was recorded from forearm and hand muscles of three volunteers. The excitability of the rhythmically firing motoneurones supplying these SMUs was examined after voluntary discharge using transcranial magnetic stimulation (TMS). 2. The magnetic stimulus was delivered either at a fixed delay (range: 1-60 ms) after SMU discharge (triggered mode) or at random with respect to voluntary SMU discharge (random mode). Post-stimulus time histograms (PSTHs) of responses to 50-100 stimuli were constructed for each experimental condition. 3. In the triggered mode, the probability of response to TMS progressively decreased as the spike-to-stimulus interval was shortened. Shortening of the interval also resulted in redistribution of responses within the different subpeaks characterizing the short-latency response of motor units to TMS: the relative response probability of the first subpeak decreased with the shorter spike-to-stimulus intervals. 4. In the triggered mode, the probability of SMU responding to TMS was significantly higher when the firing rate of the motor unit was increased from a slow rate (< 10 impulses s-1) to a faster rate (> 12 impulses s-1), irrespective of the spike-to-stimulus interval. In contrast, in the random mode, the response probability was greater at the slower discharge rate. 5. The higher excitability of motoneurones at the fast rate in the triggered mode is consistent with findings in cat motoneurones suggesting a shallower after-hyperpolarization, but other mechanisms could contribute. Furthermore, our results suggest that there is an asymptotic recovery in the excitability of slow firing motoneurones towards the end of the interspike interval.
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Affiliation(s)
- E Olivier
- Department of Anatomy, University of Cambridge, UK
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Sabatino M, Sardo P, Iurato L, La Grutta V. Cortical stimulation and reflex excitability of spinal cord neurones in man. J Neural Transm (Vienna) 1995; 101:159-68. [PMID: 8695046 DOI: 10.1007/bf01271553] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The H reflex technique was used to evaluate the influence exerted by cortical conditioning on the excitability of the alpha-motoneurone pool and on IA interneuronal activity (reciprocal inhibition). In ten subjects at absolute rest electrical and magnetic stimulation of the motor cortex was transcranially applied during flexor carpi radialis H reflex eliciting and in conditions of reciprocal inhibition induced by radial nerve stimulation. The time courses showed that at intensities below motor threshold, electrical brain conditioning induced an increase in the amplitude of the test reflex when the cortical shock was given 4 ms after the test H reflex. On the contrary, reciprocal inhibition was reduced by electrical cortical conditioning when the scalp stimulation was applied 2-3 ms after the test stimulus. Magnetic transcranial stimulation induced an increase of H reflex amplitude when the test shock was administered 5 and 2 ms prior to the scalp shock; it did not modify the degree of reciprocal inhibition. The experimental findings could be considered the electrophysiological manifestation of a differential cortico-spinal control on the pathway alpha-motoneurone/IA interneurone. Considerations on the delay allow the hypothesis of a further synapse between the cortico-spinal ending and the IA interneurone. Discrepancies with magnetic conditioning might be ascribed to a preferential transsynaptic action of magnetic mode of neural activation.
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Affiliation(s)
- M Sabatino
- Istituto di Fisiologia umana, Università di Palermo, Italy
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Burke D, Gracies JM, Mazevet D, Meunier S, Pierrot-Deseilligny E. Non-monosynaptic transmission of the cortical command for voluntary movement in man. J Physiol 1994; 480 ( Pt 1):191-202. [PMID: 7853222 PMCID: PMC1155789 DOI: 10.1113/jphysiol.1994.sp020352] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
1. The possibility was investigated that, in man, some of the descending command for tonic voluntary wrist extension is transmitted to extensor motoneurones over a non-monosynaptic pathway. 2. Stimulation of the cutaneous superficial radial nerve at 3 times perceptual threshold depressed the electromyogram (EMG) of extensor carpi radialis (ECR) and the discharge of single ECR motor units, both with a mean central delay of 4.2 ms. Such stimuli depressed the response to transcranial magnetic stimulation of the motor cortex, but had little effect on the H reflex. 3. The possibility that the relative sparing of the H reflex was due to an alteration in transmission of the afferent volley for the H reflex was excluded. 4. The central latency of the cutaneous-induced depression of the discharge of single motor units in biceps brachii (C5-C6) was shorter by about 1 ms than that of the more caudal wrist and finger extensor motor units. This suggests that the locus for the cutaneous-induced effects was spinal but above the cervical enlargement. 5. The pattern of EMG depression (evoked by superficial radial but not palmar stimuli, in wrist extensors but not wrist flexors) is that previously described for the presumed propriospinal system of human subjects. 6. It is concluded that a significant component of the voluntary command for tonic wrist extension reaches the relevant motoneurone pool via a non-monosynaptic pathway. It is suggested that the interposed neurones could be C3-C4 propriospinal neurones.
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Affiliation(s)
- D Burke
- Département de Rééducation Neurologique, Hôpital de la Salpétrière, Paris, France
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Awiszus F, Feistner H. Abnormal EPSPs evoked by magnetic brain stimulation in hand muscle motoneurons of patients with amyotrophic lateral sclerosis. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1993; 89:408-14. [PMID: 7507427 DOI: 10.1016/0168-5597(93)90114-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Using cross-correlation between magnetic brain stimulation and discharges of a motoneuron made active by a slight voluntary contraction, an indirect estimate of the EPSP evoked by magnetic brain stimulation in single hand muscle motoneurons was obtained in patients with amyotrophic lateral sclerosis (ALS) and normal controls. In total, 60 motoneurons of 3 normal subjects and 70 motoneurons of 7 patients with ALS were investigated. All motoneurons of normal subjects responded to the magnetic brain stimulus with a short-latency EPSP with a rise time between 1 and 5 msec. In contrast, only 67% of the motoneurons from ALS patients responded with an EPSP while the remaining 33% exhibited a clear short-latency inhibition in response to the brain stimulus. For those units of ALS patients showing an EPSP, both latency and EPSP amplitude were indistinguishable from those of normal subjects. The EPSP rise time, however, was massively prolonged in some units (up to 18 msec). These results provide a physiological basis for the interpretation of surface EMG responses in patients with ALS.
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Affiliation(s)
- F Awiszus
- Abteilung Neurophysiologie, Medizinische Hochschule Hannover, FRG
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38
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Abstract
1. Short-latency responses of single motor units (SMUs) and surface electromyographic activity (EMG) to transcranial magnetic stimulation (TMS) were examined in five different hand and forearm muscles of human subjects. 2. The response probability, P (number of extra spikes in the response peak above background per stimulus), was, in general, higher at the lower voluntary discharge rate of the motor unit than at the higher rate. 3. Increasing the strength of TMS increased the response probability of a tonically firing motor unit and at the same time recruited new units which discharged phasically during the response peak. This demonstrates rate coding and recruitment of motor units by excitatory inputs resulting from TMS when the motoneurone pool is tonically facilitated by a constant voluntary drive. 4. Next, TMS was delivered without any voluntary facilitation of motoneurones. The order of recruitment for up to four different motor units discharged by TMS was compared to that observed with voluntary input. The threshold of recruitment for each of the two inputs was estimated from the surface EMG value at which the unit was recruited. For these motoneurone pools (eleven sets of observations), the order of recruitment was the same with TMS and voluntary inputs. 5. From these data it is concluded that, despite the complex and phasic nature of the descending corticospinal volleys generated by TMS, it produces orderly recruitment and rate coding of motoneurones similar to that found for voluntary activation.
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Affiliation(s)
- P Bawa
- Department of Kinesiology, Smith Fraser University, Burnaby, Vancouver, British Columbia, Canada
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39
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Schubert M, Dengler R, Wohlfarth K, Elek J, Stallkamp A. Activation of high-threshold motor units in man by transcranial magnetic stimulation. Neurosci Lett 1993; 150:21-4. [PMID: 8469397 DOI: 10.1016/0304-3940(93)90098-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Motor units (MUs) with low voluntary recruitment thresholds are the first to be activated by transcranial magnetic stimulation. It is not clear, however, if high-threshold MUs can also be activated and if they contribute to motor evoked potentials (MEPs). We therefore studied 11 high-threshold motor units in the first dorsal interosseous muscle of 11 healthy subjects. Voluntary recruitment thresholds ranged from 22 to 41% (29.5 +/- 5.6%; mean +/- S.D.) of maximal muscle force. When MUs were driven at their recruitment thresholds, transcranial magnetic stimuli were applied to the vertex. Peri-stimulus time histograms of MU discharges were constructed. All MUs studied revealed a period of increased firing probability at 19-27 ms after the stimulus (primary peak). Stimulus intensities were lower by 10-57% of the maximal stimulator output than required to produce near maximal MEPs in conventional surface EMG recordings in the same subjects. We conclude that high-threshold MUs can be activated by transcranial magnetic stimulation and that they contribute to conventionally recorded MEPs.
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Affiliation(s)
- M Schubert
- Department of Neurology, University of Bonn, FRG
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