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Shih Y, Powers CM, Fisher BE. Reliability of a method to assess corticomotor excitability of lower limb muscles using a normalized EMG motor thresholding procedure. Sci Rep 2024; 14:2052. [PMID: 38267437 PMCID: PMC10808104 DOI: 10.1038/s41598-024-51622-6] [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: 07/11/2023] [Accepted: 01/08/2024] [Indexed: 01/26/2024] Open
Abstract
Given the importance of determining intervention-induced neuroplastic changes with lower extremity functional tasks, a reliable transcranial magnetic stimulation (TMS) methodology for proximal lower extremity muscles is needed. A pre-set fixed voltage value is typically used as the criterion for identifying a motor evoked potential (MEP) during the motor thresholding procedure. However, the fixed voltage value becomes problematic when the procedure is applied to proximal lower extremity muscles where active contractions are required. We sought to establish the reliability of a method measuring corticomotor excitability of gluteus maximus and vastus lateralis using normalized electromyography (EMG) as the criterion for identifying MEPs during the motor thresholding procedure. The active motor threshold for each muscle was determined using the lowest stimulator intensity required to elicit 5 MEPs that exceeded 20% maximal voluntary isometric contraction from 10 stimulations. TMS data were obtained from 10 participants on 2 separate days and compared using random-effect intra-class correlation coefficients (ICCs). Slopes from two input-output curve fitting methods as well as the maximum MEP of gluteus maximus and vastus lateralis were found to exhibit good to excellent reliability (ICCs ranging from 0.75 to 0.99). The described TMS method using EMG-normalized criteria for motor thresholding produced reliable results utilizing a relatively low number of TMS pulses.
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Affiliation(s)
- Yo Shih
- Department of Rehabilitation Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
| | - Christopher M Powers
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, USA
| | - Beth E Fisher
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, USA
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2
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Woldeamanuel GG, Frazer AK, Lee A, Avela J, Tallent J, Ahtiainen JP, Pearce AJ, Kidgell DJ. Determining the Corticospinal Responses and Cross-Transfer of Ballistic Motor Performance in Young and Older Adults: A Systematic Review and Meta-Analysis. J Mot Behav 2022; 54:763-786. [PMID: 35437124 DOI: 10.1080/00222895.2022.2061409] [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: 10/18/2022]
Abstract
Ballistic motor training induces plasticity changes and imparts a cross-transfer effect. However, whether there are age-related differences in these changes remain unclear. Thus, the purpose of this study was to perform a meta-analysis to determine the corticospinal responses and cross-transfer of motor performance following ballistic motor training in young and older adults. Meta-analysis was performed using a random-effects model. A best evidence synthesis was performed for variables that had insufficient data for meta-analysis. There was strong evidence to suggest that young participants exhibited greater cross-transfer of ballistic motor performance than their older counterparts. This meta-analysis showed no significant age-related differences in motor-evoked potentials (MEPs), short-interval intracortical inhibition (SICI) and surface electromyography (sEMG) for both hands following ballistic motor training.
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Affiliation(s)
- Gashaw Garedew Woldeamanuel
- Faculty of Medicine, Nursing and Health Science, Department of Physiotherapy, School of Primary and Allied Health Care, Monash University, Melbourne, Australia
| | - Ashlyn K Frazer
- Faculty of Medicine, Nursing and Health Science, Department of Physiotherapy, School of Primary and Allied Health Care, Monash University, Melbourne, Australia
| | - Annemarie Lee
- Faculty of Medicine, Nursing and Health Science, Department of Physiotherapy, School of Primary and Allied Health Care, Monash University, Melbourne, Australia
| | - Janne Avela
- Faculty of Sport and Health Sciences, NeuroMuscular Research Center, University of Jyväskylä, Finland
| | - Jamie Tallent
- Faculty of Medicine, Nursing and Health Science, Department of Physiotherapy, School of Primary and Allied Health Care, Monash University, Melbourne, Australia.,Faculty of Sport, Health and Applied Sciences, St Mary's University, Twickenham, UK
| | - Juha P Ahtiainen
- Faculty of Sport and Health Sciences, NeuroMuscular Research Center, University of Jyväskylä, Finland
| | - Alan J Pearce
- College of Science, Health and Engineering, La Trobe University, Melbourne, Australia
| | - Dawson J Kidgell
- Faculty of Medicine, Nursing and Health Science, Department of Physiotherapy, School of Primary and Allied Health Care, Monash University, Melbourne, Australia
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Chiou SY, Strutton PH. Crossed Corticospinal Facilitation Between Arm and Trunk Muscles Correlates With Trunk Control After Spinal Cord Injury. Front Hum Neurosci 2020; 14:583579. [PMID: 33192418 PMCID: PMC7645046 DOI: 10.3389/fnhum.2020.583579] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 09/22/2020] [Indexed: 11/13/2022] Open
Abstract
Objective: To investigate whether crossed corticospinal facilitation between arm and trunk muscles is preserved following spinal cord injury (SCI) and to elucidate these neural interactions for postural control during functional arm movements. Methods: Using transcranial magnetic stimulation (TMS) in 22 subjects with incomplete SCI motor evoked potentials (MEPs) in the erector spinae (ES) muscle were examined when the contralateral arm was at rest or performed 20% of maximal voluntary contraction (MVC) of biceps brachii (BB) or triceps brachii (TB). Trunk function was assessed with rapid shoulder flexion and forward-reaching tasks. Results: MEP amplitudes in ES were increased during elbow flexion in some subjects and this facilitatory effect was more prominent in subjects with thoracic SCI than in the subjects with cervical SCI. Those who showed the increased MEPs during elbow flexion had faster reaction times and quicker anticipatory postural adjustments of the trunk in the rapid shoulder flexion task. The onset of EMG activity in ES during the rapid shoulder flexion task correlated with the trunk excursion in forward-reaching. Conclusions: Our findings demonstrate that crossed corticospinal facilitation in the trunk muscles can be preserved after SCI and is reflected in trunk control during functional arm movements.
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Affiliation(s)
- Shin-Yi Chiou
- Sport, Exercise, and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom.,The Nick Davey Laboratory, Division of Surgery, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Paul H Strutton
- The Nick Davey Laboratory, Division of Surgery, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom
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Monjo F, Zory R, Forestier N. Fatiguing Neuromuscular Electrical Stimulation Decreases the Sense of Effort During Subsequent Voluntary Contractions in Men. Neuroscience 2020; 446:113-123. [PMID: 32891703 DOI: 10.1016/j.neuroscience.2020.08.036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 08/26/2020] [Accepted: 08/27/2020] [Indexed: 12/14/2022]
Abstract
As voluntary muscle fatigue increases, the perception of the effort required to produce a particular level of force also increases. This occurs because we produce greater neural outputs from the brain to compensate for the fatigue-induced loss of force. Muscle fatigue can also be generated following bouts of neuromuscular electrical stimulation (NMES), a technique widely used for rehabilitation and training purposes. Yet the effects of NMES-induced fatigue on the perception of effort have never been tested. In this study, we thus evaluated how electrically evoked fatigue would affect the sense of effort. For this purpose, we used two psychophysical tasks intended to assess effort perception: (i) a bilateral matching task in which subjects were asked to contract the elbow flexors of their reference and indicator arms with similar amounts of effort and (ii) a unilateral matching task in which they produced controlled levels of isometric force with their indicator arm and rated their perceived effort using the Borg CR10 scale. These tasks were performed before and after the biceps brachii of the indicator arm was submitted to a fatiguing NMES program that generated maximal force losses of 10-15%. Contrary to voluntary muscle fatigue, the sense of effort decreased post-NMES in both tasks despite increased neural outputs to the elbow flexors of the fatigued indicator arm. This shows that the relationship between motor command magnitude and effort perception was completely modified by NMES. It is proposed that NMES alters the sensory structures responsible for effort signal integration.
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Affiliation(s)
| | | | - Nicolas Forestier
- Université Savoie Mont Blanc, Laboratoire Interuniversitaire de Biologie de la Motricité, Chambéry, France
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Freely Chosen Cadence During Cycling Attenuates Intracortical Inhibition and Increases Intracortical Facilitation Compared to a Similar Fixed Cadence. Neuroscience 2020; 441:93-101. [PMID: 32590040 DOI: 10.1016/j.neuroscience.2020.06.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 06/15/2020] [Accepted: 06/16/2020] [Indexed: 11/20/2022]
Abstract
In contrast to other rhythmic tasks such as running, the preferred movement rate in cycling does not minimize energy consumption. It is possible that neurophysiological mechanisms contribute to the choice of cadence, however this phenomenon is not well understood. Eleven participants cycled at a fixed workload of 125 W and different cadences including a freely chosen cadence (FCC, ∼72), and fixed cadences of 70, 80, 90 and 100 revolutions per minute (rpm) during which transcranial magnetic stimulation (TMS) was used to measure short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). There was a significant increase in SICI at 70 (P = 0.004), 80 (P = 0.008) and 100 rpm (P = 0.041) compared to FCC. ICF was significantly reduced at 70 rpm compared to FCC (P = 0.04). Inhibition-excitation ratio (SICI divided by ICF) declined (P = 0.014) with an increase in cadence. The results demonstrate that SICI is attenuated during FCC compared to fixed cadences. The outcomes suggest that the attenuation of intracortical inhibition and augmentation of ICF may be a contributing factor for FCC.
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Gomez-Tames J, Hirata A, Tamura M, Muragaki Y. Corticomotoneuronal Model for Intraoperative Neurophysiological Monitoring During Direct Brain Stimulation. Int J Neural Syst 2019; 29:1850026. [DOI: 10.1142/s0129065718500260] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Intraoperative neurophysiological monitoring during brain surgery uses direct cortical stimulation to map the motor cortex by recording muscle activity induced by the excitation of alpha motor neurons (MNs). Computational models have been used to understand local brain stimulation. However, a computational model revealing the stimulation process from the cortex to MNs has not yet been proposed. Thus, the aim of the current study was to develop a corticomotoneuronal (CMN) model to investigate intraoperative stimulation during surgery. The CMN combined the following three processes into one system for the first time: (1) induction of an electric field in the brain based on a volume conductor model; (2) activation of pyramidal neuron (PNs) with a compartment model; and (3) formation of presynaptic connections of the PNs to MNs using a conductance-based synaptic model coupled with a spiking model. The implemented volume conductor model coupled with the axon model agreed with experimental strength-duration curves. Additionally, temporal/spatial and facilitation effects of CMN synapses were implemented and verified. Finally, the integrated CMN model was verified with experimental data. The results demonstrated that our model was necessary to describe the interaction between frequency and pulses to assess the difference between low-frequency and multi-pulse high-frequency stimulation in cortical stimulation. The proposed model can be used to investigate the effect of stimulation parameters on the cortex to optimize intraoperative monitoring.
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Affiliation(s)
- Jose Gomez-Tames
- Department of Electromechanical Engineering, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
| | - Akimasa Hirata
- Department of Electromechanical Engineering, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan
| | - Manabu Tamura
- Faculty of Advanced Techno-Surgery, Institute of Advanced Biomedical Engineering and Science, Tokyo Women’s Medical University, Shinjuku-ku, Tokyo 162-8666, Japan
- Department of Neurosurgery, Neurological Institute, Tokyo Women’s Medical University, Shinjuku-ku, Tokyo 162-8666, Japan
| | - Yoshihiro Muragaki
- Faculty of Advanced Techno-Surgery, Institute of Advanced Biomedical Engineering and Science, Tokyo Women’s Medical University, Shinjuku-ku, Tokyo 162-8666, Japan
- Department of Neurosurgery, Neurological Institute, Tokyo Women’s Medical University, Shinjuku-ku, Tokyo 162-8666, Japan
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Potentiating paired corticospinal-motoneuronal plasticity after spinal cord injury. Brain Stimul 2018; 11:1083-1092. [PMID: 29848448 DOI: 10.1016/j.brs.2018.05.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 05/04/2018] [Accepted: 05/07/2018] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Paired corticospinal-motoneuronal stimulation (PCMS) increases corticospinal transmission in humans with chronic incomplete spinal cord injury (SCI). OBJECTIVE/HYPOTHESIS Here, we examine whether increases in the excitability of spinal motoneurons, by performing voluntary activity, could potentiate PCMS effects on corticospinal transmission. METHODS During PCMS, we used 100 pairs of stimuli where corticospinal volleys evoked by transcranial magnetic stimulation (TMS) over the hand representation of the primary motor cortex were timed to arrive at corticospinal-motoneuronal synapses of the first dorsal interosseous (FDI) muscle ∼1-2 ms before antidromic potentials were elicited in motoneurons by electrical stimulation of the ulnar nerve. PCMS was applied at rest (PCMSrest) and during a small level of isometric index finger abduction (PCMSactive) on separate days. Motor evoked potentials (MEPs) elicited by TMS and electrical stimulation were measured in the FDI muscle before and after each protocol in humans with and without (controls) chronic cervical SCI. RESULTS We found in control participants that MEPs elicited by TMS and electrical stimulation increased to a similar extent after both PCMS protocols for ∼30 min. Whereas, in humans with SCI, MEPs elicited by TMS and electrical stimulation increased to a larger extent after PCMSactive compared with PCMSrest. Importantly, SCI participants who did not respond to PCMSrest responded after PCMSactive and those who responded to both protocols showed larger increments in corticospinal transmission after PCMSactive. CONCLUSIONS Our findings suggest that muscle contraction during PCMS potentiates corticospinal transmission. PCMS applied during voluntary activity may represent a strategy to boost spinal plasticity after SCI.
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Christiansen L, Urbin MA, Mitchell GS, Perez MA. Acute intermittent hypoxia enhances corticospinal synaptic plasticity in humans. eLife 2018; 7:e34304. [PMID: 29688171 PMCID: PMC5915172 DOI: 10.7554/elife.34304] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 03/12/2018] [Indexed: 01/02/2023] Open
Abstract
Acute intermittent hypoxia (AIH) enhances voluntary motor output in humans with central nervous system damage. The neural mechanisms contributing to these beneficial effects are unknown. We examined corticospinal function by evaluating motor evoked potentials (MEPs) elicited by cortical and subcortical stimulation of corticospinal axons and the activity in intracortical circuits in a finger muscle before and after 30 min of AIH or sham AIH. We found that the amplitude of cortically and subcortically elicited MEPs increased for 75 min after AIH but not sham AIH while intracortical activity remained unchanged. To examine further these subcortical effects, we assessed spike-timing dependent plasticity (STDP) targeting spinal synapses and the excitability of spinal motoneurons. Notably, AIH increased STDP outcomes while spinal motoneuron excitability remained unchanged. Our results provide the first evidence that AIH changes corticospinal function in humans, likely by altering corticospinal-motoneuronal synaptic transmission. AIH may represent a novel noninvasive approach for inducing spinal plasticity in humans.
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Affiliation(s)
- Lasse Christiansen
- Department of Neurological Surgery, The Miami Project to Cure ParalysisUniversity of MiamiMiamiUnited States
| | - MA Urbin
- Department of Neurological Surgery, The Miami Project to Cure ParalysisUniversity of MiamiMiamiUnited States
| | - Gordon S Mitchell
- Center for Respiratory Research and RehabilitationUniversity of FloridaGainesvilleUnited States
- Department of Physical TherapyUniversity of FloridaGainesvilleUnited States
- McKnight Brain InstituteUniversity of FloridaGainesvilleUnited States
| | - Monica A Perez
- Department of Neurological Surgery, The Miami Project to Cure ParalysisUniversity of MiamiMiamiUnited States
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Muscle spindle thixotropy affects force perception through afferent-induced facilitation of the motor pathways as revealed by the Kohnstamm effect. Exp Brain Res 2018; 236:1193-1204. [PMID: 29468386 DOI: 10.1007/s00221-018-5207-5] [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: 10/10/2017] [Accepted: 02/16/2018] [Indexed: 10/18/2022]
Abstract
This study was designed to explore the effects of intrafusal thixotropy, a property affecting muscle spindle sensitivity, on the sense of force. For this purpose, psychophysical measurements of force perception were performed using an isometric force matching paradigm of elbow flexors consisting of matching different force magnitudes (5, 10 and 20% of subjects' maximal voluntary force). We investigated participants' capacity to match these forces after their indicator arm had undergone voluntary isometric conditioning contractions known to alter spindle thixotropy, i.e., contractions performed at long ('hold long') or short muscle lengths ('hold short'). In parallel, their reference arm was conditioned at the intermediate muscle length ('hold-test') at which the matchings were performed. The thixotropy hypothesis predicts that estimation errors should only be observed at low force levels (up to 10% of the maximal voluntary force) with overestimation of the forces produced following 'hold short' conditioning and underestimation following 'hold long' conditioning. We found the complete opposite, especially following 'hold-short' conditioning where subjects underestimated the force they generated with similar relative error magnitudes across force levels. In a second experiment, we tested the hypothesis that estimation errors depended on the degree of afferent-induced facilitation using the Kohnstamm phenomenon as a probe of motor pathway excitability. Because the stronger post-effects were observed following 'hold-short' conditioning, it appears that the conditioning-induced excitation of spindle afferents leads to force misjudgments by introducing a decoupling between the central effort and the cortical motor outputs.
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Kidgell DJ, Bonanno DR, Frazer AK, Howatson G, Pearce AJ. Corticospinal responses following strength training: a systematic review and meta-analysis. Eur J Neurosci 2017; 46:2648-2661. [DOI: 10.1111/ejn.13710] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 08/27/2017] [Accepted: 08/31/2017] [Indexed: 01/21/2023]
Affiliation(s)
- Dawson J. Kidgell
- Department of Physiotherapy; School of Primary and Allied Health Care; Faculty of Medicine, Nursing and Health Science; Monash University; Melbourne Vic. 3199 Australia
| | - Daniel R. Bonanno
- Discipline of Podiatry; School of Allied Health; La Trobe University; Melbourne Vic. Australia
- La Trobe Sport and Exercise Medicine Research Centre; School of Allied Health; La Trobe University; Melbourne Vic. Australia
| | - Ashlyn K. Frazer
- Department of Physiotherapy; School of Primary and Allied Health Care; Faculty of Medicine, Nursing and Health Science; Monash University; Melbourne Vic. 3199 Australia
| | - Glyn Howatson
- Faculty of Health and Life Sciences; Northumbria University; Newcastle-upon-Tyne UK
- Water Research Group; School of Environmental Sciences and Development; Northwest University; Potchefstroom South Africa
| | - Alan J. Pearce
- Discipline of Exercise Science; School of Allied Health; La Trobe University; Melbourne Vic. Australia
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Long J, Federico P, Perez MA. A novel cortical target to enhance hand motor output in humans with spinal cord injury. Brain 2017; 140:1619-1632. [PMID: 28549131 DOI: 10.1093/brain/awx102] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 03/04/2017] [Indexed: 01/01/2023] Open
Abstract
A main goal of rehabilitation strategies in humans with spinal cord injury is to strengthen transmission in spared neural networks. Although neuromodulatory strategies have targeted different sites within the central nervous system to restore motor function following spinal cord injury, the role of cortical targets remain poorly understood. Here, we use 180 pairs of transcranial magnetic stimulation for ∼30 min over the hand representation of the motor cortex at an interstimulus interval mimicking the rhythmicity of descending late indirect (I) waves in corticospinal neurons (4.3 ms; I-wave protocol) or at an interstimulus interval in-between I-waves (3.5 ms; control protocol) on separate days in a randomized order. Late I-waves are thought to arise from trans-synaptic cortical inputs and have a crucial role in the recruitment of spinal motor neurons following spinal cord injury. Motor evoked potentials elicited by transcranial magnetic stimulation, paired-pulse intracortical inhibition, spinal motor neuron excitability (F-waves), index finger abduction force and electromyographic activity as well as a hand dexterity task were measured before and after both protocols in 15 individuals with chronic incomplete cervical spinal cord injury and 17 uninjured participants. We found that motor evoked potentials size increased in spinal cord injury and uninjured participants after the I-wave but not the control protocol for ∼30 to 60 min after the stimulation. Intracortical inhibition decreased and F-wave amplitude and persistence increased after the I-wave but not the control protocol, suggesting that cortical and subcortical networks contributed to changes in corticospinal excitability. Importantly, hand motor output and hand dexterity increased in individuals with spinal cord injury after the I-wave protocol. These results provide the first evidence that late synaptic input to corticospinal neurons may represent a novel therapeutic target for improving motor function in humans with paralysis due to spinal cord injury.
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Affiliation(s)
- Jinyi Long
- Department of Neurological Surgery, The Miami Project to Cure Paralysis, University of Miami, Bruce W. Carter Department of Veterans Affairs Medical Center, Miami, FL, USA
| | - Paolo Federico
- Department of Neurological Surgery, The Miami Project to Cure Paralysis, University of Miami, Bruce W. Carter Department of Veterans Affairs Medical Center, Miami, FL, USA
| | - Monica A Perez
- Department of Neurological Surgery, The Miami Project to Cure Paralysis, University of Miami, Bruce W. Carter Department of Veterans Affairs Medical Center, Miami, FL, USA
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Luc-Harkey BA, Harkey MS, Pamukoff DN, Kim RH, Royal TK, Blackburn JT, Spang JT, Pietrosimone B. Greater intracortical inhibition associates with lower quadriceps voluntary activation in individuals with ACL reconstruction. Exp Brain Res 2017; 235:1129-1137. [DOI: 10.1007/s00221-017-4877-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 01/06/2017] [Indexed: 01/08/2023]
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Lepley AS, Bahhur NO, Murray AM, Pietrosimone BG. Quadriceps corticomotor excitability following an experimental knee joint effusion. Knee Surg Sports Traumatol Arthrosc 2015; 23:1010-7. [PMID: 24326780 DOI: 10.1007/s00167-013-2816-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 12/03/2013] [Indexed: 10/25/2022]
Abstract
PURPOSE Deficits in quadriceps strength and voluntary activation are common following knee injury. These deficits are hypothesized to generate from a neural level, however, it remains unclear how corticomotor pathways are affected following acute injury. The purpose of this investigation was to examine whether corticomotor alterations of the quadriceps were present following a simulated knee joint injury using an experimental effusion model. METHODS Participants completed two testing sessions, an experimental knee effusion and control session, separated by 7 days. The central activation ratio was used to assess change in quadriceps activation. Corticomotor excitability was assessed pre- and post-intervention via active motor thresholds (AMTs) and motor evoked potentials (MEPs) normalized to maximal muscle responses. MEPs were assessed at different percentages of AMT, and associated slopes between these percentages were analysed. Paired-sample t tests were performed on percentage change scores calculated from pre-intervention outcome measures to assess change in corticomotor excitability and changes in the slope of MEP values as percentage of AMT increased. RESULTS Quadriceps activation significantly decreased during the effusion session. AMT and MEP change scores were not different between effusion and control conditions. No substantial differences were found in slope between any percentages of AMT. CONCLUSIONS An experimental knee effusion did not induce changes in corticomotor excitability. Further research is needed to understand how corticomotor pathways are affected following joint injury. Corticomotor excitability alterations may not be the cause of acute changes in neuromuscular activation following joint effusion. Future research should determine whether clinically altering corticomotor excitability will improve physical function. LEVEL OF EVIDENCE II.
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Affiliation(s)
- Adam S Lepley
- Musculoskeletal Health and Movement Science Laboratory, Department of Kinesiology, University of Toledo, 2801 W. Bancroft Street, Toledo, OH, 43606-3390, USA,
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Abstract
The motor cortex and the corticospinal system contribute to the control of a precision grip between the thumb and index finger. The involvement of subcortical pathways during human precision grip remains unclear. Using noninvasive cortical and cervicomedullary stimulation, we examined motor evoked potentials (MEPs) and the activity in intracortical and subcortical pathways targeting an intrinsic hand muscle when grasping a small (6 mm) cylinder between the thumb and index finger and during index finger abduction in uninjured humans and in patients with subcortical damage due to incomplete cervical spinal cord injury (SCI). We demonstrate that cortical and cervicomedullary MEP size was reduced during precision grip compared with index finger abduction in uninjured humans, but was unchanged in SCI patients. Regardless of whether cortical and cervicomedullary stimulation was used, suppression of the MEP was only evident 1-3 ms after its onset. Long-term (∼5 years) use of the GABAb receptor agonist baclofen by SCI patients reduced MEP size during precision grip to similar levels as uninjured humans. Index finger sensory function correlated with MEP size during precision grip in SCI patients. Intracortical inhibition decreased during precision grip and spinal motoneuron excitability remained unchanged in all groups. Our results demonstrate that the control of precision grip in humans involves premotoneuronal subcortical mechanisms, likely disynaptic or polysynaptic spinal pathways that are lacking after SCI and restored by long-term use of baclofen. We propose that spinal GABAb-ergic interneuronal circuits, which are sensitive to baclofen, are part of the subcortical premotoneuronal network shaping corticospinal output during human precision grip.
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15
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Lepley AS, Ericksen HM, Sohn DH, Pietrosimone BG. Contributions of neural excitability and voluntary activation to quadriceps muscle strength following anterior cruciate ligament reconstruction. Knee 2014; 21:736-42. [PMID: 24618459 DOI: 10.1016/j.knee.2014.02.008] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 12/30/2013] [Accepted: 02/10/2014] [Indexed: 02/02/2023]
Abstract
BACKGROUND Persistent quadriceps weakness is common following anterior cruciate ligament reconstruction (ACLr). Alterations in spinal-reflexive excitability, corticospinal excitability and voluntary activation have been hypothesized as underlying mechanisms contributing to quadriceps weakness. The aim of this study was to evaluate the predictive capabilities of spinal-reflexive excitability, corticospinal excitability and voluntary activation on quadriceps strength in healthy and ACLr participants. METHODS Quadriceps strength was measured using maximal voluntary isometric contractions (MVIC). Voluntary activation was quantified via the central activation ratio (CAR). Corticospinal and spinal-reflexive excitability were measured using active motor thresholds (AMT) and Hoffmann reflexes normalized to maximal muscle responses (H:M), respectively. ACLr individuals were also split into high and low strength subsets based on MVIC. RESULTS CAR was the only significant predictor in the healthy group. In the ACLr group, CAR and H:M significantly predicted 47% of the variance in MVIC. ACLr individuals in the high strength subset demonstrated significantly higher CAR and H:M than those in the low strength subset. CONCLUSION Increased quadriceps voluntary activation, spinal-reflexive excitability and corticospinal excitability relates to increased quadriceps strength in participants following ACLr. CLINICAL RELEVANCE Rehabilitation strategies used to target neural alterations may be beneficial for the restoration of muscle strength following ACLr.
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Affiliation(s)
- Adam S Lepley
- Musculoskeletal Health and Movement Science Laboratory, Department of Kinesiology, University of Toledo, Toledo, OH, United States.
| | - Hayley M Ericksen
- Musculoskeletal Health and Movement Science Laboratory, Department of Kinesiology, University of Toledo, Toledo, OH, United States
| | - David H Sohn
- Department of Orthopedic Surgery, University of Toledo, Toledo, OH, United States
| | - Brian G Pietrosimone
- Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
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Williams PS, Hoffman RL, Clark BC. Cortical and spinal mechanisms of task failure of sustained submaximal fatiguing contractions. PLoS One 2014; 9:e93284. [PMID: 24667484 PMCID: PMC3965562 DOI: 10.1371/journal.pone.0093284] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 03/04/2014] [Indexed: 01/19/2023] Open
Abstract
In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF) of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks). On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS), paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2-3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5 ± 7.9 min) than the position-matching task (26.9 ± 15.11 min; p<0.01); however, both tasks caused the same amount of muscle fatigue (p = 0.59). There were no task-specific differences for the total amount or rate of change in the neurophysiologic outcome variables over time (p>0.05). Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p<0.02, ES = 0.35-0.52) coupled with a similar mean increase in measures of corticospinal excitability (p<0.03, ES = 0.30-0.41). Additionally, the amount of intracortical inhibition decreased (p<0.03, ES = 0.32) and the amount of intracortical facilitation (p>0.10) and an index of upstream excitation of the motor cortex remained constant (p>0.40). Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure.
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Affiliation(s)
- Petra S. Williams
- Ohio Musculoskeletal & Neurological Institute (OMNI), Ohio University, Athens, Ohio, United States of America
- Department of Physical Therapy and Athletic Training, Northern Arizona University, Flagstaff, Arizona, United States of America
| | - Richard L. Hoffman
- Ohio Musculoskeletal & Neurological Institute (OMNI), Ohio University, Athens, Ohio, United States of America
| | - Brian C. Clark
- Ohio Musculoskeletal & Neurological Institute (OMNI), Ohio University, Athens, Ohio, United States of America
- Department of Biomedical Sciences, Ohio University, Athens, Ohio, United States of America
- Department of Geriatric Medicine and Gerontology, Ohio University, Athens, Ohio, United States of America
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A novel model incorporating two variability sources for describing motor evoked potentials. Brain Stimul 2014; 7:541-52. [PMID: 24794287 DOI: 10.1016/j.brs.2014.03.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 02/04/2014] [Accepted: 03/03/2014] [Indexed: 11/21/2022] Open
Abstract
OBJECTIVE Motor evoked potentials (MEPs) play a pivotal role in transcranial magnetic stimulation (TMS), e.g., for determining the motor threshold and probing cortical excitability. Sampled across the range of stimulation strengths, MEPs outline an input-output (IO) curve, which is often used to characterize the corticospinal tract. More detailed understanding of the signal generation and variability of MEPs would provide insight into the underlying physiology and aid correct statistical treatment of MEP data. METHODS A novel regression model is tested using measured IO data of twelve subjects. The model splits MEP variability into two independent contributions, acting on both sides of a strong sigmoidal nonlinearity that represents neural recruitment. Traditional sigmoidal regression with a single variability source after the nonlinearity is used for comparison. RESULTS The distribution of MEP amplitudes varied across different stimulation strengths, violating statistical assumptions in traditional regression models. In contrast to the conventional regression model, the dual variability source model better described the IO characteristics including phenomena such as changing distribution spread and skewness along the IO curve. CONCLUSIONS MEP variability is best described by two sources that most likely separate variability in the initial excitation process from effects occurring later on. The new model enables more accurate and sensitive estimation of the IO curve characteristics, enhancing its power as a detection tool, and may apply to other brain stimulation modalities. Furthermore, it extracts new information from the IO data concerning the neural variability-information that has previously been treated as noise.
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Sidhu SK, Lauber B, Cresswell AG, Carroll TJ. Sustained cycling exercise increases intracortical inhibition. Med Sci Sports Exerc 2013. [PMID: 23190593 DOI: 10.1249/mss.0b013e31827b119c] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE In the current study, we measured EMG suppression induced by subthreshold transcranial magnetic stimulation (TMS) to investigate the effects of sustained cycling exercise on intracortical inhibition. METHODS Sixteen subjects cycled at 75% of their maximum workload (Wmax) for 30 min, during which subthreshold TMS was applied at a defined crank angle where vastus lateralis (VL) EMG amplitude was increasing and approximately 50% of its recorded maximum. Subthreshold TMS was also applied during nonfatiguing control cycling bouts at 75% and 37.5% of Wmaxbefore sustained cycling. RESULTS Although EMG in VL during control cycling at 37.5% Wmax was approximately half that during cycling at 75% Wmax (P ≤ 0.05), the amount of EMG suppression was not different between workloads (P > 0.05). EMG amplitude in VL recorded in the last 5 min of sustained cycling was not different from the first 5 min (P > 0.05), whereas the amount of EMG suppression at the end of the sustained cycling was significantly greater than that at the start (P ≤ 0.05). CONCLUSIONS The increase in TMS-evoked EMG suppression during sustained cycling implies an increase in the excitability of the intracortical inhibitory interneurons during the exercise. The observed increase in intracortical inhibition is similar to that observed during sustained single joint contractions, suggesting that changes in the responsiveness of intracortical inhibitory interneurons are similar during locomotor exercise and static single joint contractions.
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Affiliation(s)
- Simranjit K Sidhu
- School of Human Movement Studies, The University of Queensland, Brisbane, Queensland, Australia.
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19
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Specific interpretation of augmented feedback changes motor performance and cortical processing. Exp Brain Res 2013; 227:31-41. [PMID: 23525572 DOI: 10.1007/s00221-013-3482-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 03/10/2013] [Indexed: 10/27/2022]
Abstract
It is well established that the presence of external feedback, also termed augmented feedback, can be used to improve performance of a motor task. The present study aimed to elucidate whether differential interpretation of the external feedback signal influences the time to task failure of a sustained submaximal contraction and modulates motor cortical activity. In Experiment 1, subjects had to maintain a submaximal contraction (30% of maximum force) performed with their thumb and index finger. Half of the tested subjects were always provided with feedback about joint position (pF-group), whereas the other half of the subjects were always provided with feedback about force (fF-group). Subjects in the pF-group were led to belief in half of their trials that they would receive feedback about the applied force, and subjects in the fF-group to receive feedback about the position. In both groups (fF and pF), the time to task failure was increased when subjects thought to receive feedback about the force. In Experiment 2, subthreshold transcranial magnetic stimulation was applied over the right motor cortex and revealed an increased motor cortical activity when subjects thought to receive feedback about the joint position. The results showed that the interpretation of feedback influences motor behavior and alters motor cortical activity. The current results support previous studies suggesting a distinct neural control of force and position.
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Different current intensities of anodal transcranial direct current stimulation do not differentially modulate motor cortex plasticity. Neural Plast 2013; 2013:603502. [PMID: 23577272 PMCID: PMC3614037 DOI: 10.1155/2013/603502] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 02/16/2013] [Indexed: 11/17/2022] Open
Abstract
Transcranial direct current stimulation (tDCS) is a noninvasive technique that modulates the excitability of neurons within the motor cortex (M1). Although the aftereffects of anodal tDCS on modulating cortical excitability have been described, there is limited data describing the outcomes of different tDCS intensities on intracortical circuits. To further elucidate the mechanisms underlying the aftereffects of M1 excitability following anodal tDCS, we used transcranial magnetic stimulation (TMS) to examine the effect of different intensities on cortical excitability and short-interval intracortical inhibition (SICI). Using a randomized, counterbalanced, crossover design, with a one-week wash-out period, 14 participants (6 females and 8 males, 22–45 years) were exposed to 10 minutes of anodal tDCS at 0.8, 1.0, and 1.2 mA. TMS was used to measure M1 excitability and SICI of the contralateral wrist extensor muscle at baseline, immediately after and 15 and 30 minutes following cessation of anodal tDCS. Cortical excitability increased, whilst SICI was reduced at all time points following anodal tDCS. Interestingly, there were no differences between the three intensities of anodal tDCS on modulating cortical excitability or SICI. These results suggest that the aftereffect of anodal tDCS on facilitating cortical excitability is due to the modulation of synaptic mechanisms associated with long-term potentiation and is not influenced by different tDCS intensities.
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21
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Bunday KL, Perez MA. Motor recovery after spinal cord injury enhanced by strengthening corticospinal synaptic transmission. Curr Biol 2012. [PMID: 23200989 DOI: 10.1016/j.cub.2012.10.046] [Citation(s) in RCA: 152] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The corticospinal tract is an important target for motor recovery after spinal cord injury (SCI) in animals and humans. Voluntary motor output depends on the efficacy of synapses between corticospinal axons and spinal motoneurons, which can be modulated by the precise timing of neuronal spikes. Using noninvasive techniques, we developed tailored protocols for precise timing of the arrival of descending and peripheral volleys at corticospinal-motoneuronal synapses of an intrinsic finger muscle in humans with chronic incomplete SCI. We found that arrival of presynaptic volleys prior to motoneuron discharge enhanced corticospinal transmission and hand voluntary motor output. The reverse order of volley arrival and sham stimulation did not affect or decreased voluntary motor output and electrophysiological outcomes. These findings are the first demonstration that spike timing-dependent plasticity of residual corticospinal-motoneuronal synapses provides a mechanism to improve motor function after SCI. Modulation of residual corticospinal-motoneuronal synapses may present a novel therapeutic target for enhancing voluntary motor output in motor disorders affecting the corticospinal tract.
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Affiliation(s)
- Karen L Bunday
- Department of Physical Medicine and Rehabilitation, Center for the Neural Basis of Cognition, and Systems Neuroscience Institute, University of Pittsburgh, Pittsburgh, PA 15261, USA
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22
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Weier AT, Pearce AJ, Kidgell DJ. Strength training reduces intracortical inhibition. Acta Physiol (Oxf) 2012; 206:109-19. [PMID: 22642686 DOI: 10.1111/j.1748-1716.2012.02454.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 05/14/2012] [Accepted: 05/22/2012] [Indexed: 11/28/2022]
Abstract
AIM Paired-pulse transcranial magnetic stimulation was used to investigate the influence of 4 weeks of heavy load squat strength training on corticospinal excitability and short-interval intracortical inhibition (rectus femoris muscle). METHODS Participants (n = 12) were randomly allocated to a strength training or control group. The strength training group completed 4 weeks of heavy load squat strength training. Recruitment curves were constructed to determine values for the slope of the curve, V50 and peak height. Short-interval intracortical inhibition was assessed using a subthreshold (0.7 × active motor threshold) conditioning stimulus, followed 3 ms later by a supra-threshold (1.2 × active motor threshold) test stimulus. All motor evoked responses were taken during 10% of maximal voluntary isometric contraction (MVC) torque and normalized to the maximal M-wave. RESULTS The strength training group attained 87% increases in 1RM squat strength (P < 0.01), significant increases in measures of corticospinal excitability (1.2 × Motor threshold: 116%, P = 0.016; peak height of recruitment curve = 105%, P < 0.001), and a 32% reduction in short-interval intracortical inhibition (P < 0.01) following the 4-week intervention compared with control. There were no changes in any dependent variable (P > 0.05) detected in the control group. CONCLUSION Repeated high force voluntary muscle activation in the form of short-term strength training reduces short-interval intracortical inhibition. This is consistent with studies involving skilled/complex tasks or novel movement patterns and acute studies investigating acute voluntary contractions.
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Affiliation(s)
- A. T. Weier
- Centre for Physical Activity and Nutrition Research; Deakin University; Melbourne; Vic.; Australia
| | - A. J. Pearce
- Cognitive and Exercise Neuroscience Unit, School of Psychology; Deakin University; Melbourne; Vic.; Australia
| | - D. J. Kidgell
- Centre for Physical Activity and Nutrition Research; Deakin University; Melbourne; Vic.; Australia
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Tallus J, Lioumis P, Hämäläinen H, Kähkönen S, Tenovuo O. Long-lasting TMS motor threshold elevation in mild traumatic brain injury. Acta Neurol Scand 2012; 126:178-82. [PMID: 22103909 DOI: 10.1111/j.1600-0404.2011.01623.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES Mild traumatic brain injury (mTBI) is very common, and part of the patients experience persistent symptoms. These may be caused by diffuse neuronal damage and could therefore affect cortical excitability. The motor threshold (MT), measured by transcranial magnetic stimulation (TMS), is a measure of cortical excitability and cortico-spinal tract integrity. MATERIALS AND METHODS We used navigated TMS (nTMS) and electromyography to determine subjects' left hemisphere MTs. Nineteen subjects with mTBI (11 with persistent symptoms and eight fully recovered) and nine healthy controls were tested. The injuries had occurred on average 5 years earlier. All participants had normal brain MRIs, that is, no signs of injury. None used centrally acting medication. RESULTS The mean MT in controls was 43.0% (SD 2.5) of maximum stimulator output. The mTBI subjects mean MT was 53.4% (SD 9.7), being higher than the controls' threshold. Subjective recovery did not correlate with MT. CONCLUSIONS The results show chronic MT elevation in a sample of subjects with symptomatic or recovered mTBI. This suggests that mTBI may be compensated, although not fully recovered, years after the injury. While the cause for MT elevation cannot be concluded from these preliminary observations, possible explanations include decreased cortical excitability and impaired subcortical conduction.
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Affiliation(s)
- J Tallus
- Centre for Cognitive Neuroscience, Department of Psychology, University of Turku, Finland.
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Significance of adequate postural control in the appearance of habitual upright bipedal locomotion. Med Hypotheses 2012; 79:564-71. [PMID: 22883956 DOI: 10.1016/j.mehy.2012.07.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Revised: 06/07/2012] [Accepted: 07/16/2012] [Indexed: 11/21/2022]
Abstract
Analysis of qualitative indicators of stability of the body during different types of locomotion in primates suggests that bipedal locomotion is not variation of some other type of locomotion. Transition from quadrupedal to bipedal locomotion is accompanied by a qualitative difference in body stability. Because of assuming an upright bipedal posture, the center of mass is lifted, the surface of the base of support is reduced, and the body structure does not provide passive stability in relation to inertial moments of the body around Y-axis. Additional head movements, trunk rotations, forelimb manipulations with objects and surveying the surroundings are necessary for survival, but they increase the degree of freedom of movement and further complicate the task of maintaining balance in the case of a postural change from erect quadrupedal to erect bipedal. This article presents a hypothesis that the transition from quadrupedal to habitual upright bipedal locomotion was caused by qualitative changes in the nervous system that allowed controlling the more demanding type of locomotion. The ability to control a more demanding posture increases possibilities of interactions between the organism and the complex environment and consequently increases the survival rate, breeding possibilities, and chances for occupying a new environmental niche. Existing data show that ability to execute the more demanding type of locomotion was made possible because of changes in the frontal lobe and pyramidal system. Only after the more demanding posture was enabled by changes in the nervous system, could advantages of bipedal over quadrupedal locomotion be utilized, including better scanning of the environment, carrying food and infants, simultaneous upper extremity movements and observation of the environment, limitless manipulation of objects with upper extremities above the individual, and less space for rotating around the Z-axis. The aforementioned advantages of habitual bipedal over quadrupedal locomotion are present in physically complex environments, such as the forest, which is associated with the appearance of habitual bipedal locomotion.
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Affiliation(s)
- J Henriksson
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
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26
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Abstract
The corticospinal tract (CST) is a major descending pathway contributing to the control of voluntary movement in mammals. During the last decades anatomical and electrophysiological studies have demonstrated significant reorganization in the CST after spinal cord injury (SCI) in animals and humans. In animal models of SCI, anatomical evidence showed corticospinal sprouts rostral and caudal to the lesion and their integration into intraspinal axonal circuits. Electrophysiological data suggested that indirect connections from the primary motor cortex to forelimb motoneurons, via brainstem nuclei and spinal cord interneurons, or direct connections from slow uninjured corticospinal axons, might contribute to the control of movement after a CST injury. In humans with SCI, post mortem spinal cord tissue revealed anatomical changes in the CST some of which were similar but others markedly different from those found in animal models of SCI. Human electrophysiological studies have provided ample evidence for corticospinal reorganization after SCI that may contribute to functional recovery. Together these studies have revealed a large plastic capacity of the CST after SCI. There is also a limited understanding of the relationship between anatomical and electrophysiological changes in the CST and control of movement after SCI. Increasing our knowledge of the role of CST plasticity in functional restoration after SCI may support the development of more effective repair strategies.
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Affiliation(s)
- Martin Oudega
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh, 4074 BST3, 3501 Fifth Avenue, Pittsburgh, PA 15261, USA.
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27
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Pitcher JB, Schneider LA, Drysdale JL, Ridding MC, Owens JA. Motor system development of the preterm and low birthweight infant. Clin Perinatol 2011; 38:605-25. [PMID: 22107893 DOI: 10.1016/j.clp.2011.08.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Despite advances in knowledge and technology, accurate prediction of later neuromotor outcomes for infants born preterm remains somewhat elusive. Here we review some of the most recent findings regarding the differential effects of preterm birth and suboptimal fetal growth on neurodevelopment. Evidence from transcranial magnetic stimulation studies is presented that suggests neuromotor development may more directly influence cognitive outcomes than previously recognised. We discuss the role of neuroplasticity in both exacerbating and improving these postnatal outcomes, and possible therapeutic targets for manipulating this. Finally, some developmental care practices that might affect long-term outcomes for these children are discussed.
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Affiliation(s)
- Julia B Pitcher
- Neuromotor Plasticity and Development, Robinson Institute, Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, Australia.
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Abstract
More than 30 muscles drive the hand to perform a multitude of essential dextrous tasks. Here we consider new views on the evolution of hand structure and on peripheral and central constraints for independent control of the digits of the hand. The human hand is widely assumed to have evolved from hands like those of African apes, yet recent studies have shown that our hands and those of the earliest hominids are very similar and unlike those of living apes. Understanding the limits of hand function may come from investigation of our last common ancestor with the great apes, rather than the great apes themselves. In the periphery, movement across the full range of joint space can be limited by mechanical linkages among the extrinsic muscles. Further, peripheral limits occur when the hand adopts some positions in which the contraction of muscles fails to move the joints on which they usually act; there is muscle 'disengagement' and functional paralysis for some actions. Surprisingly, the central nervous system drives the hand seamlessly through this landscape of mechanical limits. Central constraints on control of the individual digits include the spillover of neural drive to neighbouring muscles and their 'compartments', and the inability to make maximal muscle forces when multiple digits contract strongly which produces a force deficit. The pattern of these latter constraints correlates with amounts of daily use of each digit and favours enslaved extension to lift fingers from an object but selective flexion of fingers to contact it.
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Affiliation(s)
- Hiske van Duinen
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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30
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Differential effects of low-intensity motor cortical stimulation on the inspiratory activity in scalene muscles during voluntary and involuntary breathing. Respir Physiol Neurobiol 2011; 175:265-71. [DOI: 10.1016/j.resp.2010.11.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Revised: 11/30/2010] [Accepted: 11/30/2010] [Indexed: 11/17/2022]
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Peljto M, Wichterle H. Programming embryonic stem cells to neuronal subtypes. Curr Opin Neurobiol 2010; 21:43-51. [PMID: 20970319 DOI: 10.1016/j.conb.2010.09.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 09/21/2010] [Accepted: 09/22/2010] [Indexed: 01/01/2023]
Abstract
Richness of neural circuits and specificity of neuronal connectivity depend on the diversification of nerve cells into functionally and molecularly distinct subtypes. Although efficient methods for directed differentiation of embryonic stem cells (ESCs) into multiple principal neuronal classes have been established, only a few studies systematically examined the subtype diversity of in vitro derived nerve cells. Here we review evidence based on molecular and in vivo transplantation studies that ESC-derived spinal motor neurons and cortical layer V pyramidal neurons acquire subtype specific functional properties. We discuss similarities and differences in the role of cell-intrinsic transcriptional programs, extrinsic signals and cell-cell interactions during subtype diversification of the two classes of nerve cells. We conclude that the high degree of fidelity with which differentiating ESCs recapitulate normal embryonic development provides a unique opportunity to explore developmental processes underlying specification of mammalian neuronal diversity in a simplified and experimentally accessible system.
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Affiliation(s)
- Mirza Peljto
- Dept. of Pathology and Cell Biology, Neurology, Neuroscience, Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, NY 10032, USA
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32
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Abstract
Recent work has not only defined the origin of the direct cortico-motoneuronal output to the upper limb but has also identified some of the cortical networks that engage the corticospinal output during movement. A surprising finding is that some corticospinal neurons show 'mirror-like' properties and are actively modulated not only during self-movement but also during action observation.
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Affiliation(s)
- Roger N Lemon
- UCL Institute of Neurology Queen Square, London WC1N 3BG UK
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33
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Seifert T, Petersen NC. Changes in presumed motor cortical activity during fatiguing muscle contraction in humans. Acta Physiol (Oxf) 2010; 199:317-26. [PMID: 20136794 DOI: 10.1111/j.1748-1716.2010.02098.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM Changes in sensory information from active muscles accompany fatiguing exercise and the force-generating capacity deteriorates. The central motor commands therefore must adjust depending on the task performed. Muscle potentials evoked by transcranial magnetic stimulation (TMS) change during the course of fatiguing muscle activity, which demonstrates activity changes in cortical or spinal networks during fatiguing exercise. Here, we investigate cortical mechanisms that are actively involved in driving the contracting muscles. METHODS During a sustained submaximal contraction (30% of maximal voluntary contraction) of the elbow flexor muscles we applied TMS over the motor cortex. At an intensity below motor threshold, TMS reduced the ongoing muscle activity in biceps brachii. This reduction appears as a suppression at short latency of the stimulus-triggered average of rectified electromyographic (EMG) activity. The magnitude of the suppression was evaluated relative to the mean EMG activity during the 50 ms prior to the cortical stimulus. RESULTS During the first 2 min of the fatiguing muscle contraction the suppression was 10 +/- 0.9% of the ongoing EMG activity. At 2 min prior to task failure the suppression had reached 16 +/- 2.1%. In control experiments without fatigue we did not find a similar increase in suppression with increasing levels of ongoing EMG activity. CONCLUSION Using a form of TMS which reduces cortical output to motor neurones (and disfacilitates them), this study suggests that neuromuscular fatigue increases this disfacilitatory effect. This finding is consistent with an increase in the excitability of inhibitory circuits controlling corticospinal output.
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Affiliation(s)
- T Seifert
- Department of Exercise and Sport Sciences, University of Copenhagen, Denmark
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