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Heemels RE, Ademi S, Hehl M. Test-retest reliability of intrahemispheric dorsal premotor and primary motor cortex dual-site TMS connectivity measures. Clin Neurophysiol 2024; 165:64-75. [PMID: 38959537 DOI: 10.1016/j.clinph.2024.06.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 05/23/2024] [Accepted: 06/02/2024] [Indexed: 07/05/2024]
Abstract
OBJECTIVE Investigating the optimal interstimulus interval (ISI) and the 24-hour test-retest reliability for intrahemispheric dorsal premotor cortex (PMd) - primary motor cortex (M1) connectivity using dual-site transcranial magnetic stimulation (dsTMS). METHODS In 21 right-handed adults, left intrahemispheric PMd-M1 connectivity has been investigated with a stacked-coil dsTMS setup (conditioning stimulus: 75% of resting motor threshold; test stimulus: eliciting MEPs of 1-1.5 mV) at ISIs of 3, 5-8, and 10 ms. Additionally, M1-M1 short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were investigated to assess comparability to standard paired-pulse setups. RESULTS Conditioning PMd led to significant inhibition of M1 output at ISIs of 3 and 5 ms, whereas 10 ms resulted in facilitation (all, p < 0.001), with a fair test-retest reliability for 3 (ICC: 0.47) and 6 ms (ICC: 0.44) ISIs. Replication of SICI (p < 0.001) and ICF (p = 0.017) was successful, with excellent test-retest reliability for SICI (ICC: 0.81). CONCLUSION This dsTMS setup can probe the inhibitory and facilitatory PMd-M1 connections, as well as reliably replicate SICI and ICF paradigms. SIGNIFICANCE The stacked-coil dsTMS setup for investigating intrahemispheric PMd-M1 connectivity offers promising possibilities to better understand motor control.
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Affiliation(s)
- Robin E Heemels
- Movement Control & Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, Heverlee, Belgium; KU Leuven, Leuven Brain Institute (LBI), Leuven, Belgium
| | - Sian Ademi
- Movement Control & Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, Heverlee, Belgium; KU Leuven, Leuven Brain Institute (LBI), Leuven, Belgium
| | - Melina Hehl
- Movement Control & Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, Heverlee, Belgium; KU Leuven, Leuven Brain Institute (LBI), Leuven, Belgium; Neuroplasticity and Movement Control Research Group, Rehabilitation Research Institute (REVAL), Hasselt University, Diepenbeek, Belgium.
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2
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Kolbaşı EN, Huseyinsinoglu BE, Ozdemir Z, Bayraktaroglu Z, Soysal A. Priming constraint-induced movement therapy with intermittent theta burst stimulation to enhance upper extremity recovery in patients with stroke: protocol for a randomized controlled study. Acta Neurol Belg 2024; 124:887-893. [PMID: 38329642 DOI: 10.1007/s13760-024-02472-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 01/03/2024] [Indexed: 02/09/2024]
Abstract
BACKGROUND The treatments based on motor control and motor learning principles have gained popularity in the last 20 years, as well as non-invasive brain stimulations that enhance neuroplastic changes after stroke. However, the effect of intermittent theta burst stimulation (iTBS) in addition to evidence-based, intensive neurorehabilitation approaches such as modified constraint-induced movement therapy (mCIMT) is yet to be investigated. AIM We aim to establish a protocol for a randomized controlled study investigating the efficiency of mCIMT primed with iTBS after stroke. METHODS In this randomized controlled, single-blind study, patients with stroke (N = 17) will be divided into 3 groups: (a) mCIMT + real iTBS, (b) mCIMT + sham iTBS, and (c) mCIMT alone. 600-pulse iTBS will be delivered to the primary motor cortex on the ipsilesional hemisphere, and then, patients will receive mCIMT for 1 h/session, 3 sessions/week for 5 weeks. Upper extremity recovery will be assessed with Fugl-Meyer Test-Upper Extremity and Wolf Motor Function Test. Electrophysiological assessments, such as Motor-Evoked Potentials, Resting Motor Threshold, Short-Intracortical Inhibition, and Intracortical Facilitation, will also be included. CONCLUSIONS In this study, a protocol of an ongoing intervention study investigating the effectiveness of iTBS on ipsilesional M1 prior to the mCIMT in patients with stroke is proposed. This will be the first study to research priming mCIMT with iTBS and it may have the potential to reveal the true effect of the iTBS when it is added to the high-quality neurorehabilitation approaches. TRIAL REGISTRATION Trial registration number: NCT05308667.
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Affiliation(s)
- Esma Nur Kolbaşı
- Department of Physiotherapy and Rehabilitation, Istanbul Medeniyet University, Istanbul, Turkey
- Institute of Graduate Studies, Physiotherapy and Rehabilitation Department, Istanbul University-Cerrahpaşa, Istanbul, Turkey
| | - Burcu Ersoz Huseyinsinoglu
- Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Marmara University, Istanbul, Turkey.
| | - Zeynep Ozdemir
- Department of Neurology, Bakırkoy Prof. Dr. Mazhar Osman Training and Research Hospital for Psychiatric, Neurologic and Neurosurgical Diseases, University of Health Sciences, Istanbul, Turkey
| | - Zubeyir Bayraktaroglu
- Department of Physiology, International School of Medicine, Istanbul Medipol University, Istanbul, Turkey
| | - Aysun Soysal
- Department of Neurology, Bakırkoy Prof. Dr. Mazhar Osman Training and Research Hospital for Psychiatric, Neurologic and Neurosurgical Diseases, University of Health Sciences, Istanbul, Turkey
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3
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Strunge K, Bostock H, Howells J, Cengiz B, Samusyte G, Koltzenburg M, Tankisi H. Caffeine and cortical excitability, as measured with paired-pulse transcranial magnetic stimulation. Muscle Nerve 2024; 69:206-212. [PMID: 38124685 DOI: 10.1002/mus.28027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 11/27/2023] [Accepted: 12/12/2023] [Indexed: 12/23/2023]
Abstract
INTRODUCTION/AIMS The transcranial magnetic stimulation tests of short-interval intracortical inhibition (SICI) by both conventional amplitude measurements (A-SICI) and threshold-tracking (T-SICI) are important methods to investigate intracortical inhibitory circuits, and T-SICI has been proposed to aid the diagnosis of amyotrophic lateral sclerosis. Beverages containing caffeine are widely consumed, and caffeine has been reported to affect cortical excitability. The aim of this study was to determine whether these SICI tests are affected by caffeine. METHODS Twenty-four healthy subjects (13 females, 11 males, aged from 19 to 31, mean: 26.2 ± 2.4 years) were studied in a single fixed-dose randomized double-blind placebo-controlled cross-over trial of 200 mg caffeine or placebo ingested as chewing gum. A-SICI and T-SICI, using parallel tracking (T-SICIp), were performed before and after chewing gum. RESULTS There was no significant change in SICI parameters after placebo in A-SICI (p > .10) or T-SICIp (p > .30), and no significant effect of caffeine was found on A-SICI (p > .10) or T-SICIp (p > .50) for any of the interstimulus intervals. DISCUSSION There is no need for caffeine abstention before measurements of SICI by either the T-SICI or A-SICI measurements.
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Affiliation(s)
- Kristine Strunge
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Ankara, Turkey
| | - Gintaute Samusyte
- Department of Neurology, Hospital of Lithuanian University of Health Sciences Kauno Klinikos, Kaunas, Lithuania
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Martin Koltzenburg
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, London, UK
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
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4
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Hehl M, Van Malderen S, Geraerts M, Meesen RLJ, Rothwell JC, Swinnen SP, Cuypers K. Probing intrahemispheric interactions with a novel dual-site TMS setup. Clin Neurophysiol 2024; 158:180-195. [PMID: 38232610 DOI: 10.1016/j.clinph.2023.12.128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 12/02/2023] [Accepted: 12/19/2023] [Indexed: 01/19/2024]
Abstract
OBJECTIVE Using dual-site transcranial magnetic stimulation (dsTMS), the effective connectivity between the primary motor cortex (M1) and adjacent brain areas such as the dorsal premotor cortex (PMd) can be investigated. However, stimulating two brain regions in close proximity (e.g., ±2.3 cm for intrahemispheric PMd-M1) is subject to considerable spatial restrictions that potentially can be overcome by combining two standard figure-of-eight coils in a novel dsTMS setup. METHODS After a technical evaluation of its induced electric fields, the dsTMS setup was tested in vivo (n = 23) by applying a short-interval intracortical inhibition (SICI) protocol. Additionally, the intrahemispheric PMd-M1 interaction was probed. E-field modelling was performed using SimNIBS. RESULTS The technical evaluation yielded no major alterations of the induced electric fields due to coil overlap. In vivo, the setup reliably elicited SICI. Investigating intrahemispheric PMd-M1 interactions was feasible (inter-stimulus interval 6 ms), resulting in modulation of M1 output. CONCLUSIONS The presented dsTMS setup provides a novel way to stimulate two adjacent brain regions with fewer technical and spatial limitations than previous attempts. SIGNIFICANCE This dsTMS setup enables more accurate and repeatable targeting of brain regions in close proximity and can facilitate innovation in the field of effective connectivity.
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Affiliation(s)
- Melina Hehl
- Movement Control & Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, 3001 Heverlee, Belgium; KU Leuven, Leuven Brain Institute (LBI), Leuven, Belgium; Neuroplasticity and Movement Control Research Group, Rehabilitation Research Institute (REVAL), Hasselt University, Diepenbeek, Belgium
| | - Shanti Van Malderen
- Movement Control & Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, 3001 Heverlee, Belgium; KU Leuven, Leuven Brain Institute (LBI), Leuven, Belgium; Neuroplasticity and Movement Control Research Group, Rehabilitation Research Institute (REVAL), Hasselt University, Diepenbeek, Belgium
| | - Marc Geraerts
- Neuroplasticity and Movement Control Research Group, Rehabilitation Research Institute (REVAL), Hasselt University, Diepenbeek, Belgium
| | - Raf L J Meesen
- Movement Control & Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, 3001 Heverlee, Belgium; Neuroplasticity and Movement Control Research Group, Rehabilitation Research Institute (REVAL), Hasselt University, Diepenbeek, Belgium
| | - John C Rothwell
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, United Kingdom
| | - Stephan P Swinnen
- Movement Control & Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, 3001 Heverlee, Belgium; KU Leuven, Leuven Brain Institute (LBI), Leuven, Belgium
| | - Koen Cuypers
- Movement Control & Neuroplasticity Research Group, Department of Movement Sciences, Group Biomedical Sciences, KU Leuven, 3001 Heverlee, Belgium; KU Leuven, Leuven Brain Institute (LBI), Leuven, Belgium; Neuroplasticity and Movement Control Research Group, Rehabilitation Research Institute (REVAL), Hasselt University, Diepenbeek, Belgium.
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5
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Mroczek M, de Grado A, Pia H, Nochi Z, Tankisi H. Effects of sleep deprivation on cortical excitability: A threshold-tracking TMS study and review of the literature. Clin Neurophysiol Pract 2023; 9:13-20. [PMID: 38223850 PMCID: PMC10787222 DOI: 10.1016/j.cnp.2023.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Revised: 11/09/2023] [Accepted: 12/01/2023] [Indexed: 01/16/2024] Open
Abstract
Objective Insufficient sleep is linked to several health problems. Previous studies on the effects of sleep deprivation on cortical excitability using conventional transcranial magnetic stimulation (TMS) included a limited number of modalities, and few inter-stimulus intervals (ISIs) and showed conflicting results. This study aimed to investigate the effects of sleep deprivation on cortical excitability through threshold-tracking TMS, using a wide range of protocols at multiple ISIs. Methods Fifteen healthy subjects (mean age ± SD: 36 ± 3.34 years) were included. The following tests were performed before and after 24 h of sleep deprivation using semi-automated threshold-tacking TMS protocols: short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) at 11 ISIs between 1 and 30 ms, short interval intracortical facilitation (SICF) at 14 ISIs between 1 and 4.9 ms, long interval intracortical inhibition (LICI) at 6 ISIs between 50 and 300 ms, and short-latency afferent inhibition (SAI) at 12 ISIs between 16 and 30 ms. Results No significant differences were observed between pre- and post-sleep deprivation measurements for SICI, ICF, SICF, or LICI at any ISIs (p < 0.05). As for SAI, we found a difference at 28 ms (p = 0.007) and 30 ms (p = 0.04) but not at other ISIs. Conclusions Sleep deprivation does not affect cortical excitability except for SAI. Significance This study confirms some of the previous studies while contradicting others.
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Affiliation(s)
- Magdalena Mroczek
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Amedeo de Grado
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
- Neurophysiology Unit, IRCCS Fondazione Istituto Neurologico “Carlo Besta”, Università degli Studi di Milano, Milano, Italy
| | - Hossain Pia
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Zahra Nochi
- Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
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Xie M, Pallegar PN, Parusel S, Nguyen AT, Wu LJ. Regulation of cortical hyperexcitability in amyotrophic lateral sclerosis: focusing on glial mechanisms. Mol Neurodegener 2023; 18:75. [PMID: 37858176 PMCID: PMC10585818 DOI: 10.1186/s13024-023-00665-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Accepted: 10/05/2023] [Indexed: 10/21/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by the loss of both upper and lower motor neurons, resulting in muscle weakness, atrophy, paralysis, and eventually death. Motor cortical hyperexcitability is a common phenomenon observed at the presymptomatic stage of ALS. Both cell-autonomous (the intrinsic properties of motor neurons) and non-cell-autonomous mechanisms (cells other than motor neurons) are believed to contribute to cortical hyperexcitability. Decoding the pathological relevance of these dynamic changes in motor neurons and glial cells has remained a major challenge. This review summarizes the evidence of cortical hyperexcitability from both clinical and preclinical research, as well as the underlying mechanisms. We discuss the potential role of glial cells, particularly microglia, in regulating abnormal neuronal activity during the disease progression. Identifying early changes such as neuronal hyperexcitability in the motor system may provide new insights for earlier diagnosis of ALS and reveal novel targets to halt the disease progression.
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Affiliation(s)
- Manling Xie
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA
| | - Praveen N Pallegar
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA
- Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN, USA
| | - Sebastian Parusel
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA
| | - Aivi T Nguyen
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Long-Jun Wu
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA.
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.
- Department of Immunology, Mayo Clinic, Rochester, MN, USA.
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7
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Romare M, Elcadi GH, Johansson E, Tsaklis P. Relative Neuroadaptive Effect of Resistance Training along the Descending Neuroaxis in Older Adults. Brain Sci 2023; 13:brainsci13040679. [PMID: 37190644 DOI: 10.3390/brainsci13040679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 04/01/2023] [Accepted: 04/16/2023] [Indexed: 05/17/2023] Open
Abstract
Age-related decline in voluntary force production represents one of the main contributors to the onset of physical disability in older adults and is argued to stem from adverse musculoskeletal alterations and changes along the descending neuroaxis. The neural contribution of the above is possibly indicated by disproportionate losses in voluntary activation (VA) compared to muscle mass. For young adults, resistance training (RT) induces muscular and neural adaptations over several levels of the central nervous system, contributing to increased physical performance. However, less is known about the relative neuroadaptive contribution of RT in older adults. The aim of this review was to outline the current state of the literature regarding where and to what extent neural adaptations occur along the descending neuroaxis in response to RT in older adults. We performed a literature search in PubMed, Google Scholar and Scopus. A total of 63 articles met the primary inclusion criteria and following quality analysis (PEDro) 23 articles were included. Overall, neuroadaptations in older adults seemingly favor top-down adaptations, where the preceding changes of neural drive from superior levels affect the neural output of lower levels, following RT. Moreover, older adults appear more predisposed to neural rather than morphological adaptations compared to young adults, a potentially important implication for the improved maintenance of neuromuscular function during aging.
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Affiliation(s)
- Mattias Romare
- ErgoMech-Lab, Department of Physical Education and Sport Science, University of Thessaly, 42100 Trikala, Greece
| | - Guilherme H Elcadi
- ErgoMech-Lab, Department of Physical Education and Sport Science, University of Thessaly, 42100 Trikala, Greece
- Division of Ergonomics, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, 14157 Huddinge, Sweden
| | - Elin Johansson
- Pain in Motion Research Group, Departments of Human Physiology and Rehabilitation Sciences, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, PC 1050 Brussel, Belgium
| | - Panagiotis Tsaklis
- ErgoMech-Lab, Department of Physical Education and Sport Science, University of Thessaly, 42100 Trikala, Greece
- Centre of Orthopaedics and Regenerative Medicine, C.O.R.E.-C.I.R.I., Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
- Department of Molecular Medicine and Surgery, Karolinska Institute, SE-171 76 Solna, Sweden
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8
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Guerra A, D'Onofrio V, Asci F, Ferreri F, Fabbrini G, Berardelli A, Bologna M. Assessing the interaction between L-dopa and γ-transcranial alternating current stimulation effects on primary motor cortex plasticity in Parkinson's disease. Eur J Neurosci 2023; 57:201-212. [PMID: 36382537 PMCID: PMC10100043 DOI: 10.1111/ejn.15867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 10/18/2022] [Accepted: 11/08/2022] [Indexed: 11/17/2022]
Abstract
L-dopa variably influences transcranial magnetic stimulation (TMS) parameters of motor cortex (M1) excitability and plasticity in Parkinson's disease (PD). In patients OFF dopaminergic medication, impaired M1 plasticity and defective GABA-A-ergic inhibition can be restored by boosting gamma (γ) oscillations via transcranial alternating current stimulation (tACS) during intermittent theta-burst stimulation (iTBS). However, it is unknown whether L-dopa modifies the beneficial effects of iTBS-γ-tACS on M1 in PD. In this study, a PD patients group underwent combined iTBS-γ-tACS and iTBS-sham-tACS, each performed both OFF and ON dopaminergic therapy (four sessions in total). Motor evoked potentials (MEPs) elicited by single TMS pulses and short-interval intracortical inhibition (SICI) were assessed before and after iTBS-tACS. We also evaluated possible SICI changes during γ-tACS delivered alone in OFF and ON conditions. The amplitude of MEP elicited by single TMS pulses and the degree of SICI inhibition significantly increased after iTBS-γ-tACS. The amount of change produced by iTBS-γ-tACS was similar in patients OFF and ON therapy. Finally, γ-tACS (delivered alone) modulated SICI during stimulation and this effect did not depend on the dopaminergic condition of patients. In conclusion, boosting cortical γ oscillatory activity via tACS during iTBS improved M1 plasticity and enhanced GABA-A-ergic transmission in PD patients to the same extent regardless of dopaminergic state. These results suggest a lack of interaction between L-dopa and γ-tACS effects at the M1 level. The possible neural substrate underlying iTBS-γ tACS effects, that is, γ-resonant GABA-A-ergic interneurons activity, may explain our findings.
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Affiliation(s)
| | - Valentina D'Onofrio
- Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy.,Unit of Neurology, Unit of Clinical Neurophysiology and Study Center for Neurodegeneration (CESNE), Department of Neuroscience, University of Padua, Padua, Italy
| | | | - Florinda Ferreri
- Unit of Neurology, Unit of Clinical Neurophysiology and Study Center for Neurodegeneration (CESNE), Department of Neuroscience, University of Padua, Padua, Italy.,Department of Clinical Neurophysiology, Kuopio University Hospital, University of Eastern Finland, Kuopio, Finland
| | - Giovanni Fabbrini
- IRCCS Neuromed, Pozzilli, Italy.,Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy
| | - Alfredo Berardelli
- IRCCS Neuromed, Pozzilli, Italy.,Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy
| | - Matteo Bologna
- IRCCS Neuromed, Pozzilli, Italy.,Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy
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Rehsi RS, Ramdeo KR, Foglia SD, Turco CV, Adams FC, Toepp SL, Nelson AJ. Investigating the intra-session reliability of short and long latency afferent inhibition. Clin Neurophysiol Pract 2022; 8:16-23. [PMID: 36632369 PMCID: PMC9826929 DOI: 10.1016/j.cnp.2022.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 11/24/2022] [Accepted: 12/05/2022] [Indexed: 12/24/2022] Open
Abstract
Objective To establish the intrasession relative and absolute reliability of Short (SAI) and Long-Latency Afferent Inhibition (LAI). These findings will allow us to guide future explorations of changes to these measures. Methods 31 healthy individuals (21.06 ± 2.85 years) had SAI and LAI obtained thrice at 30-minute intervals in one session. To identify the minimum number of trials required to reliably elicit SAI and LAI, relative reliability was assessed at running intervals of 5 trials. Results SAI had moderate-high, and LAI had high-excellent relative reliability. Both SAI and LAI had high amounts of measurement error. LAI had high relative reliability when only 5 frames of data were included, whereas SAI required ∼20-30 frames of data for the same. For both SAI and LAI, individual smallest detectable change was large but was reduced at the group level. Conclusions SAI and LAI can be used for both diagnostic purposes and to assess group level change but have limited utility in assessing within-individual changes. Significance These results can be used to inform future work regarding the utility of SAI and LAI, particularly in terms of their ability to identify particularly high or low values of afferent inhibition.
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Affiliation(s)
| | | | | | - Claudia V. Turco
- Faculty of Medicine and Dentistry, University of Alberta, Canada
| | | | | | - Aimee J. Nelson
- Department of Kinesiology, McMaster University, Canada,School of Biomedical Engineering, McMaster University, Canada,Corresponding author at: Department of Kinesiology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada.
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10
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Neige C, Ciechelski V, Lebon F. The recruitment of indirect waves within primary motor cortex during motor imagery: A directional transcranial magnetic stimulation study. Eur J Neurosci 2022; 56:6187-6200. [PMID: 36215136 PMCID: PMC10092871 DOI: 10.1111/ejn.15843] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 09/15/2022] [Accepted: 09/28/2022] [Indexed: 12/29/2022]
Abstract
Motor imagery (MI) refers to the mental simulation of an action without overt movement. While numerous transcranial magnetic stimulation (TMS) studies provided evidence for a modulation of corticospinal excitability and intracortical inhibition during MI, the neural signature within the primary motor cortex is not clearly established. In the current study, we used directional TMS to probe the modulation of the excitability of early and late indirect waves (I-waves) generating pathways during MI. Corticospinal responses evoked by TMS with posterior-anterior (PA) and anterior-posterior (AP) current flow within the primary motor cortex evoke preferentially early and late I-waves, respectively. Seventeen participants were instructed to stay at rest or to imagine maximal isometric contractions of the right flexor carpi radialis. We demonstrated that the increase of corticospinal excitability during MI is greater with PA than AP orientation. By using paired-pulse stimulations, we confirmed that short-interval intracortical inhibition (SICI) increased during MI in comparison to rest with PA orientation, whereas we found that it decreased with AP orientation. Overall, these results indicate that the pathways recruited by PA and AP orientations that generate early and late I-waves are differentially modulated by MI.
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Affiliation(s)
- Cécilia Neige
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, Dijon, France.,Centre Hospitalier Le Vinatier, Université Claude Bernard Lyon 1, INSERM, CNRS, CRNL U1028 UMR5292, PsyR2 Team, Bron, France
| | - Valentin Ciechelski
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, Dijon, France
| | - Florent Lebon
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, Dijon, France
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11
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van den Bos MAJ, Menon P, Vucic S. Cortical hyperexcitability and plasticity in Alzheimer's disease: developments in understanding and management. Expert Rev Neurother 2022; 22:981-993. [PMID: 36683586 DOI: 10.1080/14737175.2022.2170784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
INTRODUCTION Transcranial magnetic stimulation (TMS) is a non-invasive neurophysiological tool that provides important insights into Alzheimer's Disease (AD). A significant body of work utilizing TMS techniques has explored the pathophysiological relevance of cortical hyperexcitability and plasticity in AD and their modulation in novel therapies. AREAS COVERED This review examines the technique of TMS, the use of TMS to examine specific features of cortical excitability and the use of TMS techniques to modulate cortical function. A search was performed utilizing the PubMed database to identify key studies utilizing TMS to examine cortical hyperexcitability and plasticity in Alzheimer's dementia. We then translate this understanding to the study of Alzheimer's disease pathophysiology, examining the underlying neurophysiologic links contributing to these twin signatures, cortical hyperexcitability and abnormal plasticity, in the cortical dysfunction characterizing AD. Finally, we examine utilization of TMS excitability to guide targeted therapies and, through the use of repetitive TMS (rTMS), modulate cortical plasticity. EXPERT OPINION The examination of cortical hyperexcitability and plasticity with TMS has potential to optimize and expand the window of therapeutic interventions in AD, though remains at relatively early stage of development.
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Affiliation(s)
- Mehdi A J van den Bos
- Brain and Nerve Research Centre, Concord Repatriation General Hospital, Sydney, Australia
| | - Parvathi Menon
- Brain and Nerve Research Centre, Concord Repatriation General Hospital, Sydney, Australia
| | - Steve Vucic
- Brain and Nerve Research Centre, Concord Repatriation General Hospital, Sydney, Australia
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12
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Sasaki R, Semmler JG, Opie GM. Threshold Tracked Short-Interval Intracortical Inhibition More Closely Predicts the Cortical Response to Transcranial Magnetic Stimulation. Neuromodulation 2022; 25:614-623. [DOI: 10.1016/j.neurom.2021.11.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 10/19/2021] [Accepted: 10/26/2021] [Indexed: 01/14/2023]
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13
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Cengiz B, Boran HE, Alaydın HC, Tankisi H, Samusyte G, Howells J, Koltzenburg M, Bostock H. Short latency afferent inhibition: comparison between threshold-tracking and conventional amplitude recording methods. Exp Brain Res 2022; 240:1241-1247. [PMID: 35192042 DOI: 10.1007/s00221-022-06327-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 02/05/2022] [Indexed: 11/04/2022]
Abstract
Short-latency afferent inhibition (SAI), which is conventionally measured as a reduction in motor evoked potential amplitude (A-SAI), is of clinical interest as a potential biomarker for cognitive impairment. Since threshold-tracking has some advantages for clinical studies of short-interval cortical inhibition, we have compared A-SAI with a threshold-tracking alternative method (T-SAI). In the T-SAI method, inhibition was calculated by tracking the required TMS intensity for the targeted MEP amplitude (200 uV) both for the test (TMS only) and paired (TMS and peripheral stimulation) stimuli. A-SAI and T-SAI were recorded from 31 healthy subjects using ten stimuli at each of 12 inter-stimulus intervals, once in the morning and again in the afternoon. There were no differences between morning and afternoon recordings. When A-SAI was normalized by log conversion it was closely related to T-SAI. Between subjects, variability was similar for the two techniques, but within-subject variability was significantly smaller for normalized A-SAI. Conventional amplitude measurements appear more sensitive for detecting changes within-subjects, such as in interventional studies, but threshold-tracking may be as sensitive as detecting abnormal SAI in a patient.
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Affiliation(s)
- Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey.
| | - H Evren Boran
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey
| | - Halil Can Alaydın
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Martin Koltzenburg
- Department of Clinical and Movement Neuroscience, UCL Queen Square Institute of Neurology, Queen Square, London, WC1N 3BG, UK.,Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG, UK
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London, WC1N 3BG, UK
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14
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Intracortical facilitation and inhibition in human primary motor cortex during motor skill acquisition. Exp Brain Res 2022; 240:3289-3304. [PMID: 36308563 PMCID: PMC9678989 DOI: 10.1007/s00221-022-06496-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 10/20/2022] [Indexed: 01/15/2023]
Abstract
The primary motor cortex (M1) is critical for movement execution, but its role in motor skill acquisition remains elusive. Here, we examine the role of M1 intracortical circuits during skill acquisition. Paired-pulse transcranial magnetic stimulation (TMS) paradigms of short-interval intracortical facilitation (SICF) and inhibition (SICI) were used to assess excitatory and inhibitory circuits, respectively. We hypothesised that intracortical facilitation and inhibition circuits in M1 would be modulated to support acquisition of a novel visuomotor skill. Twenty-two young, neurologically healthy adults trained with their nondominant hand on a skilled and non-skilled sequential visuomotor isometric finger abduction task. Electromyographic recordings were obtained from the nondominant first dorsal interosseous (FDI) muscle. Corticomotor excitability, SICF, and SICI were examined before, at the midway point, and after the 10-block motor training. SICI was assessed using adaptive threshold-hunting procedures. Task performance improved after the skilled, but not non-skilled, task training, which likely reflected the increase in movement speed during training. The amplitudes of late SICF peaks were modulated with skilled task training. There was no modulation of the early SICF peak, SICI, and corticomotor excitability with either task training. There was also no association between skill acquisition and SICF or SICI. The findings indicate that excitatory circuitries responsible for the generation of late SICF peaks, but not the early SICF peak, are modulated in motor skill acquisition for a sequential visuomotor isometric finger abduction task.
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15
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Neva JL, Brown KE, Peters S, Feldman SJ, Mahendran N, Boisgontier MP, Boyd LA. Acute Exercise Modulates the Excitability of Specific Interneurons in Human Motor Cortex. Neuroscience 2021; 475:103-116. [PMID: 34487820 DOI: 10.1016/j.neuroscience.2021.08.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 08/25/2021] [Accepted: 08/26/2021] [Indexed: 10/20/2022]
Abstract
Acute exercise can modulate the excitability of the non-exercised upper-limb representation in the primary motor cortex (M1). Accumulating evidence demonstrates acute exercise affects measures of M1 intracortical excitability, with some studies also showing altered corticospinal excitability. However, the influence of distinct M1 interneuron populations on the modulation of intracortical and corticospinal excitability following acute exercise is currently unknown. We assessed the impact of an acute bout of leg cycling exercise on unique M1 interneuron excitability of a non-exercised intrinsic hand muscle using transcranial magnetic stimulation (TMS) in young adults. Specifically, posterior-to-anterior (PA) and anterior-to-posterior (AP) TMS current directions were used to measure the excitability of distinct populations of interneurons before and after an acute bout of exercise or rest. Motor evoked potentials (MEPs) and short-interval intracortical inhibition (SICI) were measured in the PA and AP current directions in M1 at two time points separated by 25 min of rest, as well as immediately and 30 min after a 25-minute bout of moderate-intensity cycling exercise. Thirty minutes after exercise, MEP amplitudes were significantly larger than other timepoints when measured with AP current, whereas MEP amplitudes derived from PA current did not show this effect. Similarly, SICI was significantly decreased immediately following acute exercise measured with AP but not PA current. Our findings suggest that the excitability of unique M1 interneurons are differentially modulated by acute exercise. These results indicate that M1 interneurons preferentially activated by AP current may play an important role in the exercise-induced modulation of intracortical and corticospinal excitability.
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Affiliation(s)
- Jason L Neva
- Université de Montréal, École de kinésiologie et des sciences de l'activité physique, Faculté de médecine, Montréal, QC, Canada; Centre de recherche de l'institut universitaire de gériatrie de Montréal, Montréal, QC, Canada.
| | - Katlyn E Brown
- University of Waterloo, Department of Kinesiology, Applied Health Sciences, Waterloo, ON, Canada
| | - Sue Peters
- Rehabilitation Research Program, GF Strong Rehabilitation Centre, Vancouver Coastal Health Research Institute, Vancouver, BC, Canada; University of British Columbia, Department of Physical Therapy, Faculty of Medicine, Vancouver, BC, Canada
| | - Samantha J Feldman
- Graduate Program in Clinical Developmental Neuropsychology, Department of Psychology, York University, Toronto, ON, Canada
| | - Niruthikha Mahendran
- University of Queensland, Discipline of Physiotherapy, School of Health and Rehabilitation Sciences, Brisbane, Australia
| | - Matthieu P Boisgontier
- School of Rehabilitation Sciences, Faculty of Health Sciences, University of Ottawa, Ottawa ON, Canada; Bruyère Research Institute, Ottawa, ON, Canada
| | - Lara A Boyd
- University of British Columbia, Department of Physical Therapy, Faculty of Medicine, Vancouver, BC, Canada; Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
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16
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Test-Retest Reliability of Short-Interval Intracortical Inhibition Assessed by Threshold-Tracking and Automated Conventional Techniques. eNeuro 2021; 8:ENEURO.0103-21.2021. [PMID: 34561238 PMCID: PMC8528507 DOI: 10.1523/eneuro.0103-21.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 08/09/2021] [Accepted: 08/20/2021] [Indexed: 11/21/2022] Open
Abstract
Two novel short-interval intracortical inhibition (SICI) protocols, assessing SICI across a range of interstimulus intervals (ISIs) using either parallel threshold-tracking transcranial magnetic stimulation (TT-TMS) or automated conventional TMS (cTMS), were recently introduced. However, the test-retest reliability of these protocols has not been investigated, which is important if they are to be introduced in the clinic. SICI was recorded in 18 healthy subjects using TT-TMS (T-SICI) and cTMS (A-SICI). All subjects were examined at four identical sessions, i.e., morning and afternoon sessions on 2 d, 5-7 d apart. Both SICI protocols were performed twice at each session by the same observer. In one of the sessions, another observer performed additional examinations. Neither intraobserver nor interobserver measures of SICI differed significantly between examinations, except for T-SICI at ISI 3 ms (p = 0.00035) and A-SICI at ISI 2.5 ms (p = 0.0103). Intraday reliability was poor-to-good for A-SICI and moderate-to-good for T-SICI. Interday and interobserver reliabilities of T-SICI and A-SICI were moderate-to-good. Although between-subject variation constituted most of the total variation, SICI repeatability in an individual subject was poor. The two SICI protocols showed no considerable systematic bias across sessions and had a comparable test-retest reliability profile. Findings from the present study suggest that both SICI protocols may be reliably and reproducibly employed in research studies, but should be used with caution for individual decision-making in clinical settings. Studies exploring reliability in patient cohorts are warranted to investigate the clinical utility of these two SICI protocols.
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17
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Suzuki YI, Ma Y, Shibuya K, Misawa S, Suichi T, Tsuneyama A, Nakamura K, Matamala JM, Dharmadasa T, Vucic S, Fan D, Kiernan MC, Kuwabara S. Effect of racial background on motor cortical function as measured by threshold tracking transcranial magnetic stimulation. J Neurophysiol 2021; 126:840-844. [PMID: 34406906 DOI: 10.1152/jn.00083.2021] [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] [Indexed: 11/22/2022] Open
Abstract
A previous study using traditional paired-pulse TMS methods (amplitude-tracking) has reported differences in resting motor threshold (RMT) and short-interval intracortical inhibition (SICI) between healthy subjects of Caucasian and Han Chinese backgrounds, probably due to differences in the skull shape. The amplitude-tracking method delivers stimuli with constant intensity and causes substantial variabilities in motor-evoked potential amplitudes. To overcome this variability, threshold tracking transcranial magnetic stimulation (TT-TMS) has been developed. The present study aimed to investigate whether racial differences in motor cortical function exist, using TT-TMS. A total of 83 healthy volunteers (30 Caucasians, 25 Han Chinese, and 28 Japanese) were included in the present series. In TT-TMS and nerve conduction studies, electrodes were placed on the dominant limb, with measures recorded from the abductor pollicis brevis muscle. Stimulations were delivered with a circular coil, directly above the primary motor cortex. There were no significant differences at all the SICI intervals between races. Similarly, there were no significant differences in other measures of excitability including mean RMT, intracortical facilitation, and cortical silent period. Contrary to traditional amplitude-tracking TMS, motor cortical excitability and thereby motor cortical function is minimally influenced by racial differences when measured by TT-TMS. Recent studies have disclosed that SICI measured by TT-TMS differentiates amyotrophic lateral sclerosis (ALS) from ALS mimic disorders, with high sensitivity and specificity, in Caucasians. This study suggested that TT-TMS can be applied for the ALS diagnosis in Asian patients, as well as Caucasians.NEW & NOTEWORTHY Threshold tracking transcranial magnetic stimulation (TT-TMS) was applied for Caucasians, Han Chinese, and Japanese. No significant differences were found in TMS excitability indexes among races. Recent studies have disclosed that TT-TMS indexes differentiate amyotrophic lateral sclerosis (ALS) from ALS mimic disorders, with high sensitivity and specificity, in Caucasians. This study suggested that TT-TMS can be applied for the ALS diagnosis in Asian patients, as well as Caucasians.
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Affiliation(s)
- Yo-Ichi Suzuki
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Yan Ma
- Brain and Mind Centre, University of Sydney, Sydney, New South Wales, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia.,Department of Neurology, Peking University Third Hospital, Beijing, China
| | - Kazumoto Shibuya
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan.,Brain and Mind Centre, University of Sydney, Sydney, New South Wales, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Sonoko Misawa
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Tomoki Suichi
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Atsuko Tsuneyama
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Keigo Nakamura
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - José Manuel Matamala
- Brain and Mind Centre, University of Sydney, Sydney, New South Wales, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Thanuja Dharmadasa
- Brain and Mind Centre, University of Sydney, Sydney, New South Wales, Australia.,Department of Neurology, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
| | - Steve Vucic
- Westmead Clinical School, University of Sydney, Sydney, New South Wales, Australia
| | - Dongsheng Fan
- Department of Neurology, Peking University Third Hospital, Beijing, China
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney, Sydney, New South Wales, Australia
| | - Satoshi Kuwabara
- Department of Neurology, Graduate School of Medicine, Chiba University, Chiba, Japan
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18
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The reliability of cerebellar brain inhibition. Clin Neurophysiol 2021; 132:2365-2370. [PMID: 34454263 DOI: 10.1016/j.clinph.2021.06.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 06/21/2021] [Accepted: 06/29/2021] [Indexed: 01/03/2023]
Abstract
OBJECTIVE Connectivity between the cerebellum and primary motor cortex (M1) can be assessed by using transcranial magnetic stimulation to measure cerebellar brain inhibition (CBI). The aim of the present study was to determine the intra- and inter-day measurment error and relative reliability of CBI. The former informs the degree to which repeated measurements vary, whereas the latter informs how well the measure can distinguish individuals from one another within a sample. METHODS We obtained CBI data from 83 healthy young participants (n = 55 retrospective). Intra-day measurements were separated by ~ 30 min. Inter-day measurmenets were separated by a minimum of 24 h. RESULTS We show that CBI has low measurement error (~15%) within and between sessions. Using the measurment error, we demonstrate that change estimates which exceed measurment noise are large at an individual level, but can be detected with modest sample sizes. Finally, we demonstrate that the CBI measurement has fair to good relative reliability in healthy individuals, which may be deflated by low sample heterogeneity. CONCLUSIONS CBI has low measurement error supporting its use for tracking intra- and inter-day changes in cerebellar-M1 connectivity. SIGNIFICANCE Our findings provide clear reliability guidelines for future studies assessing modulation of cerebellar-M1 connectivity with intervention or disease progression.
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19
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Tankisi H, Nielsen CSZ, Howells J, Cengiz B, Samusyte G, Koltzenburg M, Blicher JU, Møller AT, Pugdahl K, Fuglsang-Frederiksen A, de Carvalho M, Bostock H. Early diagnosis of amyotrophic lateral sclerosis by threshold tracking and conventional transcranial magnetic stimulation. Eur J Neurol 2021; 28:3030-3039. [PMID: 34233060 PMCID: PMC9291110 DOI: 10.1111/ene.15010] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 06/30/2021] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND PURPOSE Short-interval intracortical inhibition by threshold tracking (T-SICI) has been proposed as a diagnostic tool for amyotrophic lateral sclerosis (ALS) but has not been compared directly with conventional amplitude measurements (A-SICI). This study compared A-SICI and T-SICI for sensitivity and clinical usefulness as biomarkers for ALS. METHODS In all, 104 consecutive patients referred with suspicion of ALS were prospectively included and were subsequently divided into 62 patients with motor neuron disease (MND) and 42 patient controls (ALS mimics) by clinical follow-up. T-SICI and A-SICI recorded in the first dorsal interosseus muscle (index test) were compared with recordings from 53 age-matched healthy controls. The reference standard was the Awaji criteria. Clinical scorings, conventional nerve conduction studies and electromyography were also performed on the patients. RESULTS Motor neuron disease patients had significantly reduced T-SICI and A-SICI compared with the healthy and patient control groups, which were similar. Sensitivity and specificity for discriminating MND patients from patient controls were high (areas under the receiver operating characteristic curves 0.762 and 0.810 for T-SICI and A-SICI respectively at 1-3.5 ms). Paradoxically, T-SICI was most reduced in MND patients with the fewest upper motor neuron (UMN) signs (Spearman ρ = 0.565, p = 4.3 × 10-6 ). CONCLUSIONS Amplitude-based measure of cortical inhibition and T-SICI are both sensitive measures for the detection of cortical involvement in MND patients and may help early diagnosis of ALS, with T-SICI most abnormal before UMN signs have developed. The gradation in T-SICI from pathological facilitation in patients with minimal UMN signs to inhibition in those with the most UMN signs may be due to progressive degeneration of the subset of UMNs experiencing facilitation.
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Affiliation(s)
- Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | | | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Ankara, Turkey
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Martin Koltzenburg
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, London, UK.,Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK
| | - Jakob U Blicher
- Department of Neurology, Aarhus University Hospital, Aarhus, Denmark.,Centre of Functionally Integrated Neuroscience, Aarhus University, Aarhus, Denmark
| | - Anette T Møller
- Department of Neurology, Aarhus University Hospital, Aarhus, Denmark
| | - Kirsten Pugdahl
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | | | - Mamede de Carvalho
- Instituto de Fisiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Univeridade de Lisboa, Lisbon, Portugal.,Department of Neurosciences and Mental Health, Hospital de Santa Maria, Centro Hospitalar Universitário de Lisboa Norte, Lisbon, Portugal
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
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20
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Germanidis EI, Schulz R, Quandt F, Mautner VF, Gerloff C, Timmermann JE. Intact procedural learning and motor intracortical inhibition in adult neurofibromatosis type 1 gene carriers. Clin Neurophysiol 2021; 132:2037-2045. [PMID: 34284238 DOI: 10.1016/j.clinph.2021.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Revised: 05/22/2021] [Accepted: 06/12/2021] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Neurofibromatosis type 1 (NF1)1 is known to cause learning deficits in affected individuals. There has been evidence linking altered gamma-aminobutyric acid (GABA)2 mediated inhibition to learning impairments in rodent models and humans with NF1. Still, evidence on the role of GABA in learning deficits associated with NF1 is inconclusive. METHODS We examined procedural learning and motor cortex excitability through intracortical facilitation and short interval intracortical inhibition and its activity dependent modulation while performing a procedural sequence learning task in 16 asymptomatic NF1 gene carriers. We aimed to analyze potential brain-behavior correlations in a carefully selected sample of gene carriers in order to minimize confounding factors. RESULTS Gene carriers did not differ from healthy controls when learning the task with their non-dominant hand over three days of training. Electrophysiological data did not reveal alterations in patients' inhibitory function of the motor cortex. CONCLUSIONS In contrast with previous publications reporting various cognitive deficits in clinically asymptomatic individuals with NF1, here asymptomatic gene carriers did not show major neuropsychological or behavioral abnormalities. SIGNIFICANCE Our results support the concept that gene carriers may not always be impaired by the condition and the population of individuals with NF1 most likely comprises different subgroups according to patients' phenotype severity.
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Affiliation(s)
- Eirene I Germanidis
- Experimental Electrophysiology and Neuroimaging (xENi) Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Robert Schulz
- Experimental Electrophysiology and Neuroimaging (xENi) Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Fanny Quandt
- Experimental Electrophysiology and Neuroimaging (xENi) Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Victor F Mautner
- Section for Neurofibromatosis, Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christian Gerloff
- Experimental Electrophysiology and Neuroimaging (xENi) Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Jan E Timmermann
- Experimental Electrophysiology and Neuroimaging (xENi) Laboratory, Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
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21
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Mooney RA, Bastian AJ, Celnik PA. Training at asymptote stabilizes motor memories by reducing intracortical excitation. Cortex 2021; 143:47-56. [PMID: 34375797 DOI: 10.1016/j.cortex.2021.06.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 06/21/2021] [Accepted: 06/22/2021] [Indexed: 10/20/2022]
Abstract
Learning similar motor skills in close succession is limited by interference, a phenomenon that takes place early after acquisition when motor memories are unstable. Interference can be bidirectional, as the first memory can be disrupted by the second (retrograde interference), or the second memory can be disrupted by the first (anterograde interference). The heightened plastic state of primary motor cortex after learning is thought to underlie interference, as unstable motor memories compete for neural resources. While time-dependent consolidation processes reduce interference, the passage of time (~6 h) required for memory stabilization limits our capacity to learn multiple motor skills at once. Here, we demonstrate in humans that prolonged training at asymptote of an initial motor skill reduces both retrograde and anterograde interference when a second motor skill is acquired in close succession. Neurophysiological assessments via transcranial magnetic stimulation reflect this online stabilization process. Specifically, excitatory neurotransmission in primary motor cortex increased after short training and decreased after prolonged training at performance asymptote. Of note, this reduction in intracortical excitation after prolonged training was proportional to better skill retention the following day. Importantly, these neurophysiological effects were not observed after motor practice without learning or after a temporal delay. Together, these findings indicate that prolonged training at asymptote improves the capacity to learn multiple motor skills in close succession, and that downregulation of excitatory neurotransmission in primary motor cortex may be a marker of online motor memory stabilization.
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Affiliation(s)
- Ronan A Mooney
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University, Baltimore, MD, USA
| | - Amy J Bastian
- Kennedy Krieger Institute, Baltimore, MD, USA; Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
| | - Pablo A Celnik
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University, Baltimore, MD, USA.
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22
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Vucic S, Pavey N, Haidar M, Turner BJ, Kiernan MC. Cortical hyperexcitability: Diagnostic and pathogenic biomarker of ALS. Neurosci Lett 2021; 759:136039. [PMID: 34118310 DOI: 10.1016/j.neulet.2021.136039] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 03/04/2021] [Accepted: 06/01/2021] [Indexed: 02/06/2023]
Abstract
Cortical hyperexcitability is an early and intrinsic feature of both sporadic and familial forms of amyotrophic lateral sclerosis (ALS).. Importantly, cortical hyperexcitability appears to be associated with motor neuron degeneration, possibly via an anterograde glutamate-mediated excitotoxic process, thereby forming a pathogenic basis for ALS. The presence of cortical hyperexcitability in ALS patients may be readily determined by transcranial magnetic stimulation (TMS), a neurophysiological tool that provides a non-invasive and painless method for assessing cortical function. Utilising the threshold tracking TMS technique, cortical hyperexcitability has been established as a robust diagnostic biomarker that distinguished ALS from mimicking disorders at early stages of the disease process. The present review discusses the pathophysiological and diagnostic utility of cortical hyperexcitability in ALS.
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Affiliation(s)
- Steve Vucic
- Western Clinical School, University of Sydney, Sydney, Australia.
| | - Nathan Pavey
- Western Clinical School, University of Sydney, Sydney, Australia
| | - Mouna Haidar
- Florey Institute of Neuroscieace and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Bradley J Turner
- Florey Institute of Neuroscieace and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, Australia
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23
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Ørskov S, Bostock H, Howells J, Pugdahl K, Fuglsang-Frederiksen A, Nielsen CSZ, Cengiz B, Samusyte G, Koltzenburg M, Tankisi H. Comparison of figure-of-8 and circular coils for threshold tracking transcranial magnetic stimulation measurements. Neurophysiol Clin 2021; 51:153-160. [PMID: 33468370 DOI: 10.1016/j.neucli.2021.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/05/2021] [Accepted: 01/05/2021] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVES The transcranial magnetic stimulation (TMS) technique of threshold-tracking short-interval intracortical inhibition (T-SICI) has been proposed as a diagnostic tool for amyotrophic lateral sclerosis (ALS). Most of these studies have used a circular coil, whereas a figure-of-8 coil is usually recommended for paired-pulse TMS measurements. The aim of this study was to compare figure-of-8 and circular coils for T-SICI in the upper limb, with special attention to reproducibility, and the pain or discomfort experienced by the subjects. METHODS Twenty healthy subjects (aged: 45.5 ± 6.7, mean ± SD, 9 females, 11 males) underwent two examinations with each coil, in morning and afternoon sessions on the same day, with T-SICI measured at interstimulus intervals (ISIs) from 1-7 ms. After each examination the subjects rated degree of pain/discomfort from 0 to 10 using a numerical rating scale (NRS). RESULTS Mean T-SICI was higher for the figure-of-8 than for the circular coil at ISI of 2 ms (p < 0.05) but did not differ at other ISIs. Intra-subject variability did not differ between coils, but mean inhibition from 1-3.5 ms was less variable between subjects with the figure-of-8 coil (SD 7.2% vs. 11.2% RMT, p < 0.05), and no such recordings were without inhibition (vs. 6 with the circular coil). The subjects experienced less pain/discomfort with the figure-of-8 coil (mean NRS: 1.9 ± 1.28 vs 2.8 ± 1.60, p < 0.005). DISCUSSION The figure-of-8 coil may have better applicability in patients, due to the lower incidence of lack of inhibition in healthy subjects, and the lower experience of pain or discomfort.
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Affiliation(s)
- Søren Ørskov
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Hugh Bostock
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, WC1N 3BG, London, United Kingdom
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Kirsten Pugdahl
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | | | | | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Martin Koltzenburg
- Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, WC1N 3BG, London, United Kingdom; Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, WC1N 3BG, London, United Kingdom
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark.
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van den Bos MAJ, Higashihara M, Geevasinga N, Menon P, Kiernan MC, Vucic S. Pathophysiological associations of transcallosal dysfunction in ALS. Eur J Neurol 2020; 28:1172-1180. [PMID: 33220162 DOI: 10.1111/ene.14653] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 11/05/2020] [Indexed: 12/28/2022]
Abstract
AIM Involvement of the corpus callosum has been identified as a feature of amyotrophic lateral sclerosis (ALS), particularly through neuropathological studies. The aim of the present study was to determine whether alteration in transcallosal function contributed to the development of ALS, disease progression and thereby functional disability. METHODS Transcallosal function and motor cortex excitability were assessed in 17 ALS patients with results compared to healthy controls. Transcallosal inhibition (interstimulus intervals (ISI) of 8-40 ms), short interval intracortical facilitation (SICF) and inhibition (SICI) were assessed in both cerebral hemispheres. Patients were staged utilising clinical and neurophysiological staging assessments. RESULTS In ALS, there was prominent reduction of transcallosal inhibition (TI) when recorded from the primary and secondary motor cortices compared to controls (F = 23.255, p < 0.001). This reduction of TI was accompanied by features indicative of cortical hyperexcitability, including reduction of SICI and increase in SICF. There was a significant correlation between the reduction in TI and the rate of disease progression (R = -0.825, p < 0.001) and reduction in muscle strength (R = 0.54, p = 0.031). CONCLUSION The present study has established that dysfunction of transcallosal circuits was an important pathophysiological mechanism in ALS, correlating with greater disability and a faster rate of disease progression. Therapies aimed at restoring the function of transcallosal circuits may be considered for therapeutic approaches in ALS.
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Affiliation(s)
| | - Mana Higashihara
- Westmead Clinical School, University of Sydney, Sydney, NSW, Australia.,Department of Neurology, Tokyo Metropolitan Geriatric Hospital, Tokyo, Japan
| | | | - Parvathi Menon
- Westmead Clinical School, University of Sydney, Sydney, NSW, Australia
| | - Matthew C Kiernan
- Department of Neurology, Brain and Mind Centre, Royal Prince Alfred Hospital, University of Sydney, Sydney, NSW, Australia
| | - Steve Vucic
- Westmead Clinical School, University of Sydney, Sydney, NSW, Australia
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Tankisi H, Cengiz B, Howells J, Samusyte G, Koltzenburg M, Bostock H. Short-interval intracortical inhibition as a function of inter-stimulus interval: Three methods compared. Brain Stimul 2020; 14:22-32. [PMID: 33166726 DOI: 10.1016/j.brs.2020.11.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 10/28/2020] [Accepted: 11/01/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Short-interval intracortical inhibition (SICI), as measured by threshold-tracking as a function of inter-stimulus interval (ISI), has been proposed as a useful biomarker for amyotrophic lateral sclerosis (ALS), but its relationship to conventional amplitude measurements has not been established. METHODS Serial tracking of SICI at increasing ISIs from 1 to 7 ms (T-SICIs) was compared in 50 healthy control subjects with the same ISIs tracked in parallel (T-SICIp), and with conventional amplitude measurements (A-SICI). For T-SICIp and A-SICI, pairs of conditioning and test stimuli with different ISIs were pseudo-randomised and interspersed with test-alone stimuli given at regular intervals. Thresholds were estimated by regression of log peak-to-peak amplitude on stimulus. RESULTS T-SICIp and A-SICI were closely related: a ten-fold reduction in amplitude corresponding to an approximately 18% increase in threshold. Threshold increases were greater for T-SICIs than for T-SICIp at 3.5-5 ms (P < 0.001). This divergence depended on the initial settings and whether ISIs were progressively increased or decreased, and was attributed to the limitations of the serial tracking protocol. SICI variability between subjects was greatest for T-SICIs estimates and least for A-SICI, and only A-SICI estimates revealed a significant decline in inhibition with age. CONCLUSIONS The serial tracking protocol did not accurately show the dependence of inhibition on ISI. Randomising ISIs gives corresponding SICI measures, whether tracking thresholds or measuring amplitude measurements. SICI variability suggested that A-SICI measurements may be the most sensitive to loss of inhibition.
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Affiliation(s)
- Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Bülent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, 06500, Ankara, Turkey
| | - James Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - Gintaute Samusyte
- Department of Neurology, Medical Academy, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Martin Koltzenburg
- Department of Clinical and Movement Neuroscience, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG, London, United Kingdom; Department of Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, Queen Square, WC1N 3BG, London, United Kingdom
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG, London, United Kingdom.
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Pellegrini M, Zoghi M, Jaberzadeh S. Can genetic polymorphisms predict response variability to anodal transcranial direct current stimulation of the primary motor cortex? Eur J Neurosci 2020; 53:1569-1591. [PMID: 33048398 DOI: 10.1111/ejn.15002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 09/17/2020] [Accepted: 10/02/2020] [Indexed: 11/28/2022]
Abstract
Genetic mediation of cortical plasticity and the role genetic variants play in previously observed response variability to transcranial direct current stimulation (tDCS) have become important issues in the tDCS literature in recent years. This study investigated whether inter-individual variability to tDCS was in-part genetically mediated. In 61 healthy males, anodal-tDCS (a-tDCS) and sham-tDCS were administered to the primary motor cortex at 1 mA for 10-min via 6 × 4 cm active and 7 × 5 cm return electrodes. Twenty-five single-pulse transcranial magnetic stimulation (TMS) motor evoked potentials (MEP) were recorded to represent corticospinal excitability (CSE). Twenty-five paired-pulse MEPs were recorded with 3 ms inter-stimulus interval (ISI) to assess intracortical inhibition (ICI) via short-interval intracranial inhibition (SICI) and 10 ms ISI for intracortical facilitation (ICF). Saliva samples were tested for specific genetic polymorphisms in genes encoding for excitatory and inhibitory neuroreceptors. Individuals were sub-grouped based on a pre-determined threshold and via statistical cluster analysis. Two distinct subgroups were identified, increases in CSE following a-tDCS (i.e. Responders) and no increase or even reductions in CSE (i.e. Non-responders). No changes in ICI or ICF were reported. No relationships were reported between genetic polymorphisms in excitatory receptor genes and a-tDCS responders. An association was reported between a-tDCS responders and GABRA3 gene polymorphisms encoding for GABA-A receptors suggesting potential relationships between GABA-A receptor variations and capacity to undergo tDCS-induced cortical plasticity. In the largest tDCS study of its kind, this study presents an important step forward in determining the contribution genetic factors play in previously observed inter-individual variability to tDCS.
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Affiliation(s)
- Michael Pellegrini
- Non-Invasive Brain Stimulation and Neuroplasticity Laboratory, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, Australia
| | - Maryam Zoghi
- Department of Rehabilitation, Nutrition and Sport, School of Allied Health, Discipline of Physiotherapy, La Trobe University, Melbourne, Australia
| | - Shapour Jaberzadeh
- Non-Invasive Brain Stimulation and Neuroplasticity Laboratory, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, Australia
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The Effects of 1 mA tACS and tRNS on Children/Adolescents and Adults: Investigating Age and Sensitivity to Sham Stimulation. Neural Plast 2020; 2020:8896423. [PMID: 32855633 PMCID: PMC7443018 DOI: 10.1155/2020/8896423] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/10/2020] [Accepted: 07/14/2020] [Indexed: 12/24/2022] Open
Abstract
The aim of this study was to investigate the effect of transcranial random noise (tRNS) and transcranial alternating current (tACS) stimulation on motor cortex excitability in healthy children and adolescents. Additionally, based on our recent results on the individual response to sham in adults, we explored this effect in the pediatric population. We included 15 children and adolescents (10-16 years) and 28 adults (20-30 years). Participants were stimulated four times with 20 Hz and 140 Hz tACS, tRNS, and sham stimulation (1 mA) for 10 minutes over the left M1HAND. Single-pulse MEPs (motor evoked potential), short-interval intracortical inhibition, and facilitation were measured by TMS before and after stimulation (baseline, 0, 30, 60 minutes). We also investigated aspects of tolerability. According to the individual MEPs response immediately after sham stimulation compared to baseline (Wilcoxon signed-rank test), subjects were regarded as responders or nonresponders to sham. We did not find a significant age effect. Regardless of age, 140 Hz tACS led to increased excitability. Incidence and intensity of side effects did not differ between age groups or type of stimulation. Analyses on responders and nonresponders to sham stimulation showed effects of 140 Hz, 20 Hz tACS, and tRNS on single-pulse MEPs only for nonresponders. In this study, children and adolescents responded to 1 mA tRNS and tACS comparably to adults regarding the modulation of motor cortex excitability. This study contributes to the findings that noninvasive brain stimulation is well tolerated in children and adolescents including tACS, which has not been studied before. Finally, our study supports a modulating role of sensitivity to sham stimulation on responsiveness to a broader stimulation and age range.
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28
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Electrodiagnosis of Amyotrophic Lateral Sclerosis: A Review of Existing Guidelines. J Clin Neurophysiol 2020; 37:294-298. [DOI: 10.1097/wnp.0000000000000682] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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29
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Unravelling the Modulation of Intracortical Inhibition During Motor Imagery: An Adaptive Threshold-Hunting Study. Neuroscience 2020; 434:102-110. [DOI: 10.1016/j.neuroscience.2020.03.038] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 03/22/2020] [Accepted: 03/23/2020] [Indexed: 12/13/2022]
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30
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Higashihara M, Van den Bos MA, Menon P, Kiernan MC, Vucic S. Interneuronal networks mediate cortical inhibition and facilitation. Clin Neurophysiol 2020; 131:1000-1010. [DOI: 10.1016/j.clinph.2020.02.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 01/23/2020] [Accepted: 02/04/2020] [Indexed: 12/13/2022]
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31
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Howells J, Sangari S, Matamala JM, Kiernan MC, Marchand-Pauvert V, Burke D. Interrogating interneurone function using threshold tracking of the H reflex in healthy subjects and patients with motor neurone disease. Clin Neurophysiol 2020; 131:1986-1996. [PMID: 32336595 DOI: 10.1016/j.clinph.2020.03.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 02/21/2020] [Accepted: 03/15/2020] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The excitability of the lower motoneurone pool is traditionally tested using the H reflex and a constant-stimulus paradigm, which measures changes in the amplitude of the reflex response. This technique has limitations because reflex responses of different size must involve the recruitment or inhibition of different motoneurones. The threshold-tracking technique ensures that the changes in excitability occur for an identical population of motoneurones. We aimed to assess this technique and then apply it in patients with motor neurone disease (MND). METHODS The threshold-tracking approach was assessed in 17 healthy subjects and 11 patients with MND. The soleus H reflex was conditioned by deep peroneal nerve stimulation producing reciprocal Ia and so-called D1 and D2 inhibitions, which are believed to reflect presynaptic inhibition of soleus Ia afferents. RESULTS Threshold tracking was quicker than the constant-stimulus technique and reliable, properties that may be advantageous for clinical studies. D1 inhibition was significantly reduced in patients with MND. CONCLUSIONS Threshold tracking is useful and may be preferable under some conditions for studying the excitability of the motoneurone pool. The decreased D1 inhibition in the patients suggests that presynaptic inhibition may be reduced in MND. SIGNIFICANCE Reduced presynaptic inhibition could be evidence of an interneuronopathy in MND. It is possible that the hyperreflexia is a spinal pre-motoneuronal disorder, and not definitive evidence of corticospinal involvement in MND.
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Affiliation(s)
- James Howells
- Brain & Mind Centre, The University of Sydney, N.S.W. 2006, Australia
| | - Sina Sangari
- Sorbonne Université, INSERM, CNRS, Laboratoire d'Imagerie Biomédicale, LIB, F-75006 Paris, France
| | - José Manuel Matamala
- Department of Neurological Science and Biomedical Neuroscience Institute, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Matthew C Kiernan
- Brain & Mind Centre, The University of Sydney, N.S.W. 2006, Australia; Department of Neurology, Royal Prince Alfred Hospital and The University of Sydney, N.S.W. 2006, Australia
| | | | - David Burke
- Department of Neurology, Royal Prince Alfred Hospital and The University of Sydney, N.S.W. 2006, Australia.
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Dharmadasa T, Matamala JM, Howells J, Vucic S, Kiernan MC. Early focality and spread of cortical dysfunction in amyotrophic lateral sclerosis: A regional study across the motor cortices. Clin Neurophysiol 2020; 131:958-966. [DOI: 10.1016/j.clinph.2019.11.057] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/13/2019] [Accepted: 11/18/2019] [Indexed: 11/15/2022]
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Primary motor cortex function and motor skill acquisition: insights from threshold-hunting TMS. Exp Brain Res 2020; 238:1745-1757. [DOI: 10.1007/s00221-020-05791-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 03/18/2020] [Indexed: 12/11/2022]
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34
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Cirillo J, Mooney RA, Ackerley SJ, Barber PA, Borges VM, Clarkson AN, Mangold C, Ren A, Smith MC, Stinear CM, Byblow WD. Neurochemical balance and inhibition at the subacute stage after stroke. J Neurophysiol 2020; 123:1775-1790. [PMID: 32186435 DOI: 10.1152/jn.00561.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Stroke is a leading cause of death and disability worldwide with many people left with impaired motor function. Evidence from experimental animal models of stroke indicates that reducing motor cortex inhibition may facilitate neural plasticity and motor recovery. This study compared primary motor cortex (M1) inhibition measures over the first 12 wk after stroke with a cohort of age-similar healthy controls. The excitation-inhibition ratio and gamma-aminobutyric acid (GABA) neurotransmission within M1 were assessed using magnetic resonance spectroscopy and threshold hunting paired-pulse transcranial magnetic stimulation respectively. Upper limb impairment and function were assessed with the Fugl-Meyer Upper Extremity Scale and Action Research Arm Test. Patients with a functional corticospinal pathway had motor-evoked potentials on the paretic side and exhibited better recovery from upper limb impairment and recovery of function than patients without a functional corticospinal pathway. Compared with age-similar controls, the neurochemical balance in terms of the excitation-inhibition ratio was greater within contralesional M1 in patients with a functional corticospinal pathway. There was evidence for elevated long-interval inhibition in both ipsilesional and contralesional M1 compared with controls. Short-interval inhibition measures differed between the first and second phases, with evidence for elevation of the former only in ipsilesional M1 and no evidence of disinhibition for the latter. Overall, findings from transcranial magnetic stimulation indicate an upregulation of GABA-mediated tonic inhibition in M1 early after stroke. Therapeutic approaches that aim to normalize inhibitory tone during the subacute period warrant further investigation.NEW & NOTEWORTHY Magnetic resonance spectroscopy indicated higher excitation-inhibition ratios within motor cortex during subacute recovery than age-similar healthy controls. Measures obtained from adaptive threshold hunting paired-pulse transcranial magnetic stimulation indicated greater tonic inhibition in patients compared with controls. Therapeutic approaches that aim to normalize motor cortex inhibition during the subacute stage of recovery should be explored.
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Affiliation(s)
- John Cirillo
- Department of Exercise Sciences, University of Auckland, Auckland, New Zealand.,Centre for Brain Research, University of Auckland, Auckland, New Zealand
| | - Ronan A Mooney
- Department of Exercise Sciences, University of Auckland, Auckland, New Zealand.,Centre for Brain Research, University of Auckland, Auckland, New Zealand
| | - Suzanne J Ackerley
- Centre for Brain Research, University of Auckland, Auckland, New Zealand.,Department of Medicine, University of Auckland, Auckland, New Zealand
| | - P Alan Barber
- Centre for Brain Research, University of Auckland, Auckland, New Zealand.,Department of Medicine, University of Auckland, Auckland, New Zealand
| | - Victor M Borges
- Department of Exercise Sciences, University of Auckland, Auckland, New Zealand.,Centre for Brain Research, University of Auckland, Auckland, New Zealand
| | | | - Christine Mangold
- Centre for Brain Research, University of Auckland, Auckland, New Zealand
| | - April Ren
- Department of Exercise Sciences, University of Auckland, Auckland, New Zealand
| | - Marie-Claire Smith
- Centre for Brain Research, University of Auckland, Auckland, New Zealand.,Department of Medicine, University of Auckland, Auckland, New Zealand
| | - Cathy M Stinear
- Centre for Brain Research, University of Auckland, Auckland, New Zealand.,Department of Medicine, University of Auckland, Auckland, New Zealand
| | - Winston D Byblow
- Department of Exercise Sciences, University of Auckland, Auckland, New Zealand.,Centre for Brain Research, University of Auckland, Auckland, New Zealand
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Longitudinal assessment of 1H-MRS (GABA and Glx) and TMS measures of cortical inhibition and facilitation in the sensorimotor cortex. Exp Brain Res 2019; 237:3461-3474. [PMID: 31734787 DOI: 10.1007/s00221-019-05691-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Accepted: 11/09/2019] [Indexed: 01/05/2023]
Abstract
The purpose of the present study was to investigate the long-term stability of water-referenced GABA and Glx neurometabolite concentrations in the sensorimotor cortex using MRS and to assess the long-term stability of GABA- and glutamate-related intracortical excitability using transcranial magnetic stimulation (TMS). Healthy individuals underwent two sessions of MRS and TMS at a 3-month interval. A MEGA-PRESS sequence was used at 3 T to acquire MRS signals in the sensorimotor cortex. Metabolites were quantified by basis spectra fitting and metabolite concentrations were derived using unsuppressed water reference scans accounting for relaxation and partial volume effects. TMS was performed using published standards. After performing stability and reliability analyses for MRS and TMS, reliable change indexes were computed for all measures with a statistically significant test-retest correlation. No significant effect of time was found for GABA, Glx and TMS measures. There was an excellent ICC and a strong correlation across time for GABA and Glx. Analysis of TMS measure stability revealed an excellent ICC for rMT CSP and %MSO and a fair ICC for 2 ms SICI. There was no significant correlation between MRS and TMS measures at any time point. This study shows that MRS-GABA and MRS-Glx of the sensorimotor cortex have good stability over a 3-month period, with variability across time comparable to that reported in other brain areas. While resting motor threshold, %MSO and CSP were found to be stable and reliable, other TMS measures had greater variability and lesser reliability.
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Theme 8 Clinical imaging and electrophysiology. Amyotroph Lateral Scler Frontotemporal Degener 2019; 20:246-261. [DOI: 10.1080/21678421.2019.1646996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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37
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Reliability of transcranial magnetic stimulation measures of afferent inhibition. Brain Res 2019; 1723:146394. [DOI: 10.1016/j.brainres.2019.146394] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Revised: 07/09/2019] [Accepted: 08/14/2019] [Indexed: 12/19/2022]
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He JL, Fuelscher I, Coxon J, Chowdhury N, Teo WP, Barhoun P, Enticott P, Hyde C. Individual differences in intracortical inhibition predict motor-inhibitory performance. Exp Brain Res 2019; 237:2715-2727. [DOI: 10.1007/s00221-019-05622-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 08/06/2019] [Indexed: 10/26/2022]
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Pathophysiology and Diagnosis of ALS: Insights from Advances in Neurophysiological Techniques. Int J Mol Sci 2019; 20:ijms20112818. [PMID: 31185581 PMCID: PMC6600525 DOI: 10.3390/ijms20112818] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 05/27/2019] [Accepted: 06/06/2019] [Indexed: 12/28/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and fatal neurodegenerative disorder of the motor neurons, characterized by focal onset of muscle weakness and incessant disease progression. While the presence of concomitant upper and lower motor neuron signs has been recognized as a pathognomonic feature of ALS, the pathogenic importance of upper motor neuron dysfunction has only been recently described. Specifically, transcranial magnetic stimulation (TMS) techniques have established cortical hyperexcitability as an important pathogenic mechanism in ALS, correlating with neurodegeneration and disease spread. Separately, ALS exhibits a heterogeneous clinical phenotype that may lead to misdiagnosis, particularly in the early stages of the disease process. Cortical hyperexcitability was shown to be a robust diagnostic biomarker if ALS, reliably differentiating ALS from neuromuscular mimicking disorders. The present review will provide an overview of key advances in the understanding of ALS pathophysiology and diagnosis, focusing on the importance of cortical hyperexcitability and its relationship to advances in genetic and molecular processes implicated in ALS pathogenesis.
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Abstract
PURPOSE OF REVIEW Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative disorder of the motor neurons, characterized by upper motor neuron (UMN) and lower motor neuron (LMN) dysfunction. There have been significant technological advances in the development of neurophysiological biomarkers of UMN and LMN dysfunction in ALS. In this review, we discuss major advances in development of neurophysiological biomarkers in ALS, critiquing their potential in diagnosis and prognosis of ALS, as well as utility in monitoring treatment effects. RECENT FINDINGS The threshold tracking transcranial magnetic stimulation (TMS) technique has established cortical hyperexcitability as an early and specific biomarker of UMN dysfunction in ALS, and associated with neurodegeneration. In addition to establishing cortical hyperexcitability as a pathophysiological mechanism, threshold tracking TMS has enabled an earlier diagnosis of ALS and provided a means of monitoring effects of therapeutic agents. Biomarkers of LMN dysfunction, including motor unit number estimation, the neurophysiological index, electrical impedance myography and axonal excitability techniques, have all exhibited utility in monitoring disease progression. SUMMARY In addition to enhancing ALS diagnosis, the development of novel neurophysiological biomarkers has implications for clinical trials research and drug development, enabling the assessment of biological efficacy of agents in early stages of drug development.
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Short-latency afferent-induced facilitation and inhibition as predictors of thermally induced variations in corticomotor excitability. Exp Brain Res 2019; 237:1445-1455. [DOI: 10.1007/s00221-019-05522-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/13/2019] [Indexed: 01/02/2023]
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42
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The effect of coil type and limb dominance in the assessment of lower-limb motor cortex excitability using TMS. Neurosci Lett 2019; 699:84-90. [PMID: 30710665 DOI: 10.1016/j.neulet.2019.01.050] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 01/25/2019] [Accepted: 01/30/2019] [Indexed: 12/13/2022]
Abstract
PURPOSE Clinical application of transcranial magnetic stimulation (TMS) has rapidly increased but the majority of studies have targeted upper limb muscles, with few exploring the lower-limb. Differences of coil choice have added to methodological difficulties of lower-limb studies and have challenged consistent interpretation of these parameters. The aims of this study were to determine the optimal coil choice for assessing lower-limb cortical excitability and assess laterality of normal cortical function. METHODS 69 recordings were undertaken from the tibialis anterior muscle from 48 healthy participants. Three coil types currently used in lower-limb studies (90 mm circular; 70 mm figure-of-8; and 110 mm double cone) were explored using single pulse TMS and paired-pulse threshold tracking TMS (TT-TMS) paradigms, with peripheral function also assessed. Cortical symmetry was ascertained with bilateral recordings (dominant versus non-dominant muscles). RESULTS The double-cone coil showed greatest efficacy, with significantly lower resting motor thresholds (49.0 ± 2.3%, p<0.0005) and greater intracortical facilitation compared to the alternate coil choices. Using the double-cone coil, paired-pulse TT-TMS generated an averaged short interval intracortical inhibition of 11.3 ± 1.2%, with an averaged intracortical facilitation of -6.1 ± 1.9%. There were no differences between dominant and non-dominant hemispheres. CONCLUSIONS The present study identified key differences in cortical parameters between the currently utilised coils for lower-limb TMS. Specifically, this indicates the importance of standardizing the lower-limb TMS protocol, particularly for accurate interpretation in disease pathology.
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Vucic S, van den Bos M, Menon P, Howells J, Dharmadasa T, Kiernan MC. Utility of threshold tracking transcranial magnetic stimulation in ALS. Clin Neurophysiol Pract 2018; 3:164-172. [PMID: 30560220 PMCID: PMC6275211 DOI: 10.1016/j.cnp.2018.10.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 10/17/2018] [Accepted: 10/29/2018] [Indexed: 12/21/2022] Open
Abstract
Upper motor neuron [UMN] and lower motor neuron [LMN] dysfunction, in the absence of sensory features, is a pathognomonic feature of amyotrophic lateral sclerosis [ALS]. Although the precise mechanisms have yet to be elucidated, one leading hypothesis is that UMN precede LMN dysfunction, which is induced by anterograde glutamatergic excitotoxicity. Transcranial magnetic stimulation (TMS) is a neurophysiological tool that provides a non-invasive and painless assessment of cortical function. Threshold tracking methodologies have been recently adopted for TMS, whereby changes in threshold rather than motor evoked potential (MEP) amplitude serve as outcome measures. This technique is reliable and provides a rapid assessment of cortical function in ALS. Utilisng the threshold tracking TMS technique, cortical hyperexcitability was demonstrated as an early feature in sporadic ALS preceding the onset of LMN dysfunction and possibly contributing to disease spread. Separately, cortical hyperexcitability was reported to precede the clinical onset of familial ALS. Of further relevance, the threshold tracking TMS technique was proven to reliably distinguish ALS from mimicking disorders, even in the presence of a comparable degree of LMN dysfunction, suggesting a diagnostic utility of TMS. Taken in total, threshold tracking TMS has provided support for a cortical involvement at the earliest detectable stages of ALS, underscoring the utility of the technique for probing the underlying pathophysiology. The present review will discuss the physiological processes underlying TMS parameters, while further evaluating the pathophysiological and diagnostic utility of threshold tracking TMS in ALS.
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Affiliation(s)
- Steve Vucic
- Western Clinical School, University of Sydney, Sydney, Australia
| | | | - Parvathi Menon
- Western Clinical School, University of Sydney, Sydney, Australia
| | - James Howells
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, Australia
| | - Thanuja Dharmadasa
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, Australia
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Conventional or threshold-hunting TMS? A tale of two SICIs. Brain Stimul 2018; 11:1296-1305. [DOI: 10.1016/j.brs.2018.07.047] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 07/11/2018] [Accepted: 07/15/2018] [Indexed: 12/14/2022] Open
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Menon P, Kiernan MC, Vucic S. Cortical excitability varies across different muscles. J Neurophysiol 2018; 120:1397-1403. [PMID: 29975162 DOI: 10.1152/jn.00148.2018] [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] [Indexed: 12/13/2022] Open
Abstract
The aim of the present study was to determine whether significant differences in cortical excitability were evident across different body regions in healthy humans. Threshold tracking transcranial magnetic stimulation (TMS) was undertaken in 28 healthy controls. Short-interval intracortical inhibition [SICI between interstimulus intervals (ISI) 1-7 ms], intracortical facilitation (ICF, between ISI 10-30 ms), resting motor threshold (RMT), cortical silent period (CSP) duration (generated at stimulus intensity 150% RMT), and motor evoked potential amplitude were recorded from the abductor pollicis brevis (APB), tibialis anterior (TA), and trapezius muscles. These muscles were selected as they are frequently affected in neurodegenerative diseases, such as amyotrophic lateral sclerosis. SICI and ICF are measured as a percentage difference between conditioned and an unconditioned test response. SICI was significantly greater when recorded over the APB (9.9 ± 1.5%) and TA (8.6 ± 1.4%) muscles compared with the trapezius (4.5 ± 1.9%, P < 0.05). The CSP duration was significantly shorter (CSPtrapezius, 131.0 ± 6.3 ms; CSPTA, 175.7 ± 9.9 ms; CSPAPB, 188.3 ± 4.0 ms; P < 0.001) and ICF greater ( P < 0.01) in the trapezius muscle. There were no significant correlations between inhibitory and facilitatory processes recorded across the three muscles. The present study established significant differences in cortical excitability across three body regions, with evidence of more prominent inhibition and less facilitation in the limb muscles. NEW & NOTEWORTHY Cortical excitability of muscles with differing motor functions was assessed using threshold tracking transcranial magnetic stimulation. Significantly greater intracortical inhibition and less facilitation were evident over the limb muscles. These findings could relate to differences in the functional organization of the corticomotoneuronal system innervating different muscle regions.
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Affiliation(s)
- Parvathi Menon
- Western Clinical School, University of Sydney , Sydney , Australia.,Westmead Hospital, University of Sydney , Sydney , Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Royal Prince Alfred Hospital , Sydney , Australia
| | - Steve Vucic
- Western Clinical School, University of Sydney , Sydney , Australia.,Westmead Hospital, University of Sydney , Sydney , Australia
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Van den Bos MAJ, Menon P, Howells J, Geevasinga N, Kiernan MC, Vucic S. Physiological Processes Underlying Short Interval Intracortical Facilitation in the Human Motor Cortex. Front Neurosci 2018; 12:240. [PMID: 29695952 PMCID: PMC5904283 DOI: 10.3389/fnins.2018.00240] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 03/27/2018] [Indexed: 11/24/2022] Open
Abstract
Short interval intracortical facilitation (SICF) may be elicited by a paired pulse transcranial magnetic stimulation (TMS) paradigm, whereby a suprathreshold first stimulus (S1) precedes a perithreshold second stimulus (S2). Other facilitatory circuits can be probed by TMS such as intracranial facilitation, however the cortical contributions to these circuits may lie partially outside of M1. SICF as such represents a unique analog to M1 inhibitory circuits such as short interveal intracortical circuits. The aim of the present study was to provide insight into the physiological processes underlying the development of SICF using the threshold tracking TMS technique which was recently demonstrated to have significant reliability. TMS studies were undertaken on 35 healthy controls, using either a 90 mm circular and 70 mm figure of eight coil, and one of two targets (0.2 and 1.0 mV) tracked. The motor evoked potential (MEP) responses were recorded from the abductor pollicis brevis. SICF was consistently evident between interstimulus intervals (ISI) of 1–5 ms (P < 0.001), with two peaks occurring ISIs 1.5 and 3 ms when using the circular coil. A significant SICF reduction (F = 5.631, P < 0.05) was evident with the higher tracking target, while SICF increased when stimulating with the figure of eight coil. While there was a correlation between SICF and CSP duration, there was no relationship between SICF and SICI or ICF. Age appeared to have no influence on SICF, SICI, or ICF. Findings from the present work suggest that SICF appears to be mediated by I-wave facilitation.
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Affiliation(s)
| | - Parvathi Menon
- Westmead Clinical School, University of Sydney, Sydney, NSW, Australia
| | - James Howells
- Brain and Mind Center, University of Sydney, Sydney, NSW, Australia
| | | | | | - Steve Vucic
- Westmead Clinical School, University of Sydney, Sydney, NSW, Australia
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