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Task- and Intensity-Dependent Modulation of Arm-Trunk Neural Interactions in the Corticospinal Pathway in Humans. eNeuro 2021; 8:ENEURO.0111-21.2021. [PMID: 34503966 PMCID: PMC8482852 DOI: 10.1523/eneuro.0111-21.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 08/16/2021] [Accepted: 08/19/2021] [Indexed: 12/02/2022] Open
Abstract
Most human movements require coordinated activation of multiple muscles. Although many studies reported associations between arm, leg, and trunk muscles during functional tasks, their neural interaction mechanisms still remain unclear. Therefore, the aim of our study was to investigate arm-trunk or arm-leg neural interactions in the corticospinal tract during different arm muscle contractions. Specifically, we examined corticospinal excitability of the erector spinae (ES; trunk extensor), rectus abdominis (RA; trunk flexor), and tibialis anterior (TA; leg) muscles while participants exerted: (1) wrist flexion and (2) wrist extension isometric contraction at various contraction intensity levels ranging from rest to 50% of maximal voluntary contraction (MVC) effort. Corticospinal excitability was assessed using motor evoked potentials (MEPs) elicited through motor cortex transcranial magnetic stimulation (TMS). Results showed that ES MEPs were facilitated even at low contractions (>5% MVC) during wrist flexion and extension, while stronger contractions (>25% MVC) were required to facilitate RA MEPs. The extent of facilitation of ES MEPs depended on contraction intensity of wrist extension, but not flexion. Moreover, TA MEPs were facilitated at low contractions (>5% MVC) during wrist flexion and extension, but contraction intensity dependence was only shown during stronger wrist extension contractions (>25% MVC). In conclusion, trunk extensor corticospinal excitability seems to depend on the task and the intensity of arm contraction, while this is not true for trunk flexor and leg muscles. Our study therefore demonstrated task- and intensity-dependent neural interactions of arm-trunk connections, which may underlie anatomic and/or functional substrates of these muscle pairs.
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Cortical and Subcortical Neural Interactions Between Trunk and Upper-limb Muscles in Humans. Neuroscience 2020; 451:126-136. [PMID: 33075460 DOI: 10.1016/j.neuroscience.2020.10.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Revised: 10/01/2020] [Accepted: 10/05/2020] [Indexed: 12/28/2022]
Abstract
Activities of daily living require simultaneous and coordinated activation of trunk and upper-limb segments, which involves complex interlimb interaction within the central nervous system. Although many studies have reported associations between activity of trunk and limb muscles during functional tasks, evidence on cortical and subcortical contributions to trunk-limb neural interactions is still not fully clear. Therefore, the aim of this study was to examine interactions between trunk and upper-limb muscles in the: (i) corticospinal circuits by using motor evoked potential (MEP) elicited through transcranial magnetic stimulation; and (ii) subcortical circuits by using cervicomedullary motor evoked potential (CMEP) elicited through cervicomedullary junction magnetic stimulation. Responses were evoked in the erector spinae (trunk) and flexor carpi radialis (upper-limb) muscles in twelve able-bodied individuals: (1) while participants were relaxed; (2) during trunk muscle contractions while arms were at rest; and (3) during upper-limb muscle contractions while the trunk was at rest. Our results showed that trunk muscle CMEP responses were not affected by upper-limb muscle contractions, while MEP responses were modulated. This indicates that at least the subcortical circuits may not attribute to facilitation of the trunk muscles during upper-limb contractions. On the other hand, in the upper-limb muscles, both CMEP and MEP responses were modulated during trunk contractions. These results indicate that cortical and subcortical mechanisms attributed to facilitation of upper-limb muscles during trunk contractions. In conclusion, our study demonstrated evidence that trunk-limb neural interactions may be attributed to cortical and/or subcortical mechanisms depending on the contracted muscle.
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Sasaki A, Kaneko N, Masugi Y, Milosevic M, Nakazawa K. Interlimb neural interactions in corticospinal and spinal reflex circuits during preparation and execution of isometric elbow flexion. J Neurophysiol 2020; 124:652-667. [DOI: 10.1152/jn.00705.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
We found that upper limb muscle contractions facilitated corticospinal circuits controlling lower limb muscles even during motor preparation, whereas motor execution of the task was required to facilitate spinal circuits. We also found that facilitation did not depend on whether contralateral or ipsilateral hands were contracted or if they were contracted bilaterally. Overall, these findings suggest that training of unaffected upper limbs may be useful to enhance facilitation of affected lower limbs in paraplegic individuals.
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Affiliation(s)
- Atsushi Sasaki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
- Japan Society for the Promotion of Science, Chiyoda, Tokyo, Japan
| | - Naotsugu Kaneko
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
- Japan Society for the Promotion of Science, Chiyoda, Tokyo, Japan
| | - Yohei Masugi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
- Institute of Sports Medicine and Science, Tokyo International University, Kawagoe, Saitama, Japan
| | - Matija Milosevic
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
| | - Kimitaka Nakazawa
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro, Tokyo, Japan
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Effects of sustained unilateral handgrip on corticomotor excitability in both knee extensor muscles. Eur J Appl Physiol 2020; 120:1865-1879. [PMID: 32533244 DOI: 10.1007/s00421-020-04414-5] [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: 12/16/2019] [Accepted: 06/03/2020] [Indexed: 10/24/2022]
Abstract
PURPOSE Repetitive or sustained simple muscle contractions have been shown to alter corticomotor excitability. The present study investigated the effects of a sustained handgrip contraction with the right hand on motor-evoked potentials (MEPs) in task-unrelated knee extensor muscles and determined whether the effects are influenced by intensity of the handgrip contraction. METHODS Subjects performed a 120-s sustained handgrip contraction at 10% or 50% maximal voluntary contraction (MVC) using the right hand. MEPs in vastus lateral (VL) muscles elicited by transcranial magnetic stimulation were measured before, during, and after the handgrip contraction. RESULTS Both the handgrip contractions at 10 and 50% MVC induced significant greater MEPs in the left VL muscle (121.5 ± 25.7%) than in the right VL muscle (97.9 ± 17.4%) from 10 min after the handgrip contraction (P < 0.05). MEPs in both the right and left VL muscles were significantly increased by the handgrip contractions at 10% MVC (124.8 ± 45.2%, P < 0.05), but were not increased by the handgrip contractions at 50% MVC. CONCLUSION The results of the present study indicate that a unilateral sustained handgrip contraction can differentially alter corticomotor excitability in knee extensor muscles ipsilateral and contralateral to the exercised hand after the handgrip and that the intensity of the handgrip contraction influences corticomotor excitability in both knee extensor muscles after the handgrip.
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Cabibel V, Hordacre B, Perrey S. Implication of the ipsilateral motor network in unilateral voluntary muscle contraction: the cross-activation phenomenon. J Neurophysiol 2020; 123:2090-2098. [DOI: 10.1152/jn.00064.2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Voluntary force production requires that the brain produces and transmits a motor command to the muscles. It is widely acknowledged that motor commands are executed from the primary motor cortex (M1) located in the contralateral hemisphere. However, involvement of M1 located in the ipsilateral hemisphere during moderate to high levels of unilateral muscle contractions (>30% of the maximum) has been disclosed in recent years. This phenomenon has been termed cross-activation. The activation of the ipsilateral M1 relies on complex inhibitory and excitatory interhemispheric interactions mediated via the corpus callosum and modulated according to the contraction level. The regulatory mechanisms underlying these interhemispheric interactions, especially excitatory ones, remain vague, and contradictions exist in the literature. In addition, very little is known regarding the possibility that other pathways could also mediate the cross-activation. In the present review, we will therefore summarize the concept of cross-activation during unilateral voluntary muscle contraction and explore the associated mechanisms and other nervous system pathways underpinning this response. A broader knowledge of these mechanisms would consequently allow a better comprehension of the motor system as a whole, as distant brain networks working together to produce the motor command.
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Affiliation(s)
- Vincent Cabibel
- EuroMov Digital Health in Motion, University of Montpellier, IMT Mines Ales, Montpellier, France
| | - Brenton Hordacre
- Innovation, IMPlementation and Clinical Translation (IIMPACT) in Health, University of South Australia, Adelaide, Australia
| | - Stéphane Perrey
- EuroMov Digital Health in Motion, University of Montpellier, IMT Mines Ales, Montpellier, France
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Akınoğlu B, Kocahan T. Comparison of muscular strength and balance in athletes with visual impairment and hearing impairment. J Exerc Rehabil 2018; 14:765-770. [PMID: 30443521 PMCID: PMC6222145 DOI: 10.12965/jer.1836304.152] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 08/10/2018] [Indexed: 11/22/2022] Open
Abstract
This study was conducted to compare muscular strength and balance of athletes with visual and hearing impairment. The study was carried out with 20 athletes of national Olympic level sports goalball team and 20 athletes of national Olympic level sports hearing-impaired karate team. Isokinetic muscular strength was assessed by IsoMed 2000 device as concentric-concentric at 60°/sec and 240°/sec. Balance assessment was carried out with the Human Body Equilibrium 360 device. There was no significant difference between groups regarding age, height, weight and body mass index (P>0.05). There were no differences between the dominant and nondominant knee flexion and extension peak torque (PT), % of flexion/extension PT ratio, % of dominant/nondominant PT differences at 60°/sec and 240°/sec velocities (P>0.05). There was no difference between the groups regarding of both leg static balance (P>0.05). However, single leg standing balance was significantly different between groups in favor of athletes with hearing impairment (P<0.001). As a result of our study it was determined that muscular strength and static balance of athletes with visual and hearing impairment were similar, but athletes with visual problems are likely to have lower levels of single leg balance. Strategies to promote single leg balance in athletes with visual impairments are warranted.
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Affiliation(s)
- Bihter Akınoğlu
- Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Ankara Yıldırım Beyazıt University, Ankara, Turkey
| | - Tuğba Kocahan
- Department of Health Services, Sports General Directorship, The Ministry of Youth and Sports, Center of Athlete Training and Health Research, Ankara, Turkey
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Leung H, Latella C, Lamon S, Hendy AM. The Reliability of Neurological Measurement in the Vastus Medialis: Implications for Research and Practice. Front Psychol 2018; 9:1857. [PMID: 30327634 PMCID: PMC6174212 DOI: 10.3389/fpsyg.2018.01857] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 09/11/2018] [Indexed: 11/21/2022] Open
Abstract
The integrity of the corticomotor pathway is paramount in the optimal functioning of skeletal muscle. However, variability of neurophysiological assessment via peripheral nerve and transcranial magnetic stimulation can render interpretation difficult. Seldom evidence exists regarding the reliability of such measurements in the leg extensors, which have important locomotive and functional roles. This study aimed to assess the test-retest reliability of peripheral, corticospinal and intracortical responses in the vastus medialis. Transcranial magnetic and direct current electrical nerve stimulation were delivered to sixteen healthy young adults (8M and 8F) on two separate occasions. The Hoffmann reflex, maximal compound wave, motor evoked potential, corticospinal silent period, intracortical facilitation, and short-interval intracortical inhibition were recorded from the vastus medialis at rest, and during controlled submaximal voluntary contraction. Relative reliability was quantified using intra-class correlation coefficient (ICC2,1). Absolute reliability was quantified using standard error of measurement (SEm) and minimal detectable change (MDC). Corticospinal silent period, corticospinal silent period/motor evoked potential ratio, active motor evoked potential, maximal Hoffman reflex, and passive short-interval intracortical inhibition demonstrated “good to excellent” relative reliability (ICC ≥ 0.643). Intracortical facilitation demonstrated the lowest relative reliability (ICC = 0.420–0.908). Corticospinal silent period displayed the lowest absolute reliability (SEm ≤ 18.68%). Good reliability of the maximal compound wave, Hoffman reflex, motor evoked potential, and corticospinal silent period allow for reliable neurological evaluation of peripheral and corticospinal pathways in the vastus medialis. Future research should investigate reliability of the intracortical (short-interval intracortical inhibition and intracortical facilitation) measures by using different paired-pulse stimulus parameters. These findings hold important implications for neurophysiological assessment conducted in the leg extensor group.
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Affiliation(s)
- Hans Leung
- School of Exercise and Nutrition Sciences, Institute for Physical Activity and Nutrition (IPAN), Deakin University, Geelong, VIC, Australia
| | - Christopher Latella
- School of Exercise and Nutrition Sciences, Institute for Physical Activity and Nutrition (IPAN), Deakin University, Geelong, VIC, Australia
| | - Séverine Lamon
- School of Exercise and Nutrition Sciences, Institute for Physical Activity and Nutrition (IPAN), Deakin University, Geelong, VIC, Australia
| | - Ashlee M Hendy
- School of Exercise and Nutrition Sciences, Institute for Physical Activity and Nutrition (IPAN), Deakin University, Geelong, VIC, Australia
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Sasaki A, Milosevic M, Sekiguchi H, Nakazawa K. Evidence for existence of trunk-limb neural interaction in the corticospinal pathway. Neurosci Lett 2018; 668:31-36. [PMID: 29309857 DOI: 10.1016/j.neulet.2018.01.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 12/23/2017] [Accepted: 01/04/2018] [Indexed: 10/18/2022]
Abstract
In humans, trunk muscles have an essential role in postural control as well as walking. However, little is known about the mechanisms of interaction with different muscles, especially related to how trunk muscles interact with the limbs. Contraction of muscles can modulate the corticospinal excitability not only of the contracted muscle, but also of other muscles even in the remote segments of the body. However, "remote effect" mechanism has only been examined for inter-limb interactions. The aim of our current study was to test if there are trunk-limb interactions in the corticospinal pathways. We examined corticospinal excitability of: (a) trunk muscles at rest when hands, legs and jaw muscles were contracted and; (b) hand, leg, and jaw muscles at rest when trunk muscles were contracted. We measured motor evoked potentials elicited using transcranial magnetic stimulation in the rectus abdominis, flexor digitorum superficialis, masseter, tibialis anterior muscles under the following experimental conditions: (1) participants remained relaxed (Rest); (2) during trunk contraction (Trunk); (3) during bilateral hand clenching (Hands); (4) during jaw clenching (Jaw); and (5) during bilateral ankle dorsiflexion (Legs). Each condition was performed at three different stimulation intensities and conditions were randomized between participants. We found that voluntary contraction of trunk muscle facilitated the corticospinal excitability of upper-limb and lower-limb muscles during rest state. Furthermore, voluntary contraction of upper-limb muscle also facilitated the corticospinal excitability of trunk muscles during rest state. Overall, these results suggest the existence of trunk-limb interaction in the corticospinal pathway, which is likely depended on proximity of the trunk and limb representation in the motor cortex.
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Affiliation(s)
- Atsushi Sasaki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan
| | - Matija Milosevic
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
| | - Hirofumi Sekiguchi
- Sports & Health Management Program, Faculty of Business and Information Sciences, Jobu University, 634-1 Toyazukamachi, Isesaki, Gunma, 372-8588, Japan
| | - Kimitaka Nakazawa
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo, 153-8902, Japan
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Maudrich T, Kenville R, Lepsien J, Villringer A, Ragert P, Steele CJ. Mirror Electromyografic Activity in the Upper and Lower Extremity: A Comparison between Endurance Athletes and Non-Athletes. Front Hum Neurosci 2017; 11:485. [PMID: 29085288 PMCID: PMC5649197 DOI: 10.3389/fnhum.2017.00485] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 09/20/2017] [Indexed: 11/13/2022] Open
Abstract
During unimanual motor tasks, muscle activity may not be restricted to the contracting muscle, but rather occurs involuntarily in the contralateral resting limb, even in healthy individuals. This phenomenon has been referred to as mirror electromyographic activity (MEMG). To date, the physiological (non-pathological) form of MEMG has been observed predominately in upper extremities (UE), while remaining sparsely described in lower extremities (LE). Accordingly, evidence regarding the underlying mechanisms and modulation capability of MEMG, i.e., the extent of MEMG in dependency of exerted force during unilateral isometric contractions are insufficiently investigated in terms of LE. Furthermore, it still remains elusive if and how MEMG is affected by long-term exercise training. Here, we provide novel quantitative evidence for physiological MEMG in homologous muscles of LE (tibialis anterior (TA), rectus femoris (RF)) during submaximal unilateral dorsiflexion in healthy young adults. Furthermore, endurance athletes (EA, n = 11) show a higher extent of MEMG in LE compared to non-athletes (NA, n = 11) at high force demands (80% MVC, maximum voluntary contraction). While the underlying neurophysiological mechanisms of MEMG still remain elusive, our study indicates, at least indirectly, that sport-related long-term training might affect the amount of MEMG during strong isometric contractions specifically in trained limbs. To support this assumption of exercise-induced limb-specific MEMG modulation, future studies including different sports disciplines with contrasting movement patterns and parameters should additionally be performed.
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Affiliation(s)
- Tom Maudrich
- Institute for General Kinesiology and Exercise Science, Faculty of Sport Science, University of Leipzig, Leipzig, Germany.,Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Rouven Kenville
- Institute for General Kinesiology and Exercise Science, Faculty of Sport Science, University of Leipzig, Leipzig, Germany.,Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Jöran Lepsien
- Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Arno Villringer
- Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.,Clinic for Cognitive Neurology, University of Leipzig, Leipzig, Germany
| | - Patrick Ragert
- Institute for General Kinesiology and Exercise Science, Faculty of Sport Science, University of Leipzig, Leipzig, Germany.,Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Christopher J Steele
- Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.,Douglas Mental Health University Institute, McGill University, Montreal, QC, Canada
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Hendy AM, Chye L, Teo WP. Cross-Activation of the Motor Cortex during Unilateral Contractions of the Quadriceps. Front Hum Neurosci 2017; 11:397. [PMID: 28824401 PMCID: PMC5541022 DOI: 10.3389/fnhum.2017.00397] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 07/18/2017] [Indexed: 01/24/2023] Open
Abstract
Transcranial magnetic stimulation (TMS) studies have demonstrated that unilateral muscle contractions in the upper limb produce motor cortical activity in both the contralateral and ipsilateral motor cortices. The increase in excitability of the corticomotor pathway activating the resting limb has been termed “cross-activation”, and is of importance due to its involvement in cross-education and rehabilitation. To date, very few studies have investigated cross-activation in the lower limb. Sixteen healthy participants (mean age 29 ± 9 years) took part in this study. To determine the effect of varying contraction intensities in the lower limb, we investigated corticomotor excitability and intracortical inhibition of the right rectus femoris (RF) while the left leg performed isometric extension at 0%, 25%, 50%, 75% and 100% of maximum force output. Contraction intensities of 50% maximal force output and greater produced significant cross-activation of the corticomotor pathway. A reduction in silent period duration was observed during 75% and 100% contractions, while the release of short-interval intracortical inhibition (SICI) was only observed during maximal (100%) contractions. We conclude that increasing isometric contraction intensities produce a monotonic increase in cross-activation, which was greatest during 100% force output. Unilateral training programs designed to induce cross-education of strength in the lower limb should therefore be prescribed at the maximal intensity tolerable.
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Affiliation(s)
- Ashlee M Hendy
- Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Science, Deakin UniversityBurwood, VIC, Australia
| | - Lilian Chye
- Frailty Research Programme, Geriatric Education and Research InstituteYishun Central, Singapore
| | - Wei-Peng Teo
- Institute for Physical Activity and Nutrition (IPAN), School of Exercise and Nutrition Science, Deakin UniversityBurwood, VIC, Australia
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11
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Preparation and execution of teeth clenching and foot muscle contraction influence on corticospinal hand-muscle excitability. Sci Rep 2017; 7:41249. [PMID: 28117368 PMCID: PMC5259748 DOI: 10.1038/srep41249] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 12/20/2016] [Indexed: 11/30/2022] Open
Abstract
Contraction of a muscle modulates not only the corticospinal excitability (CSE) of the contracting muscle but also that of different muscles. We investigated to what extent the CSE of a hand muscle is modulated during preparation and execution of teeth clenching and ipsilateral foot dorsiflexion either separately or in combination. Hand-muscle CSE was estimated based on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) and recorded from the first dorsal interosseous (FDI) muscle. We found higher excitability during both preparation and execution of all the motor tasks than during mere observation of a fixation cross. As expected, the excitability was greater during the execution phase than the preparation one. Furthermore, both execution and preparation of combined motor tasks led to higher excitability than individual tasks. These results extend our current understanding of the neural interactions underlying simultaneous contraction of muscles in different body parts.
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12
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Smith MC, Stinear JW, Alan Barber P, Stinear CM. Effects of non-target leg activation, TMS coil orientation, and limb dominance on lower limb motor cortex excitability. Brain Res 2016; 1655:10-16. [PMID: 27840187 DOI: 10.1016/j.brainres.2016.11.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 09/15/2016] [Accepted: 11/07/2016] [Indexed: 11/25/2022]
Abstract
Transcranial magnetic stimulation (TMS) is used to examine corticospinal tract integrity after stroke, however, generating motor-evoked potentials (MEPs) in the lower limb (LL) can be difficult. Previous studies have used activation of the target leg to facilitate MEPs in the LL but this may not be possible after stroke due to hemiplegia. The dominance of the target limb may also be important, however the neurophysiological effects of LL dominance are not known. We investigated whether voluntary activation of the non-target leg combined with optimal TMS coil orientation increases corticomotor excitability in healthy adults, and whether limb dominance influences these results. TMS was delivered to induce a posterior-anterior (PA) and a medial-lateral (ML) cortical current in 22 healthy adults. MEPs were recorded in tibialis anterior (TA) with the participant at rest and when activating the non-target leg. We found that non-target leg activation increased corticomotor excitability in the target leg (reduced rest motor threshold (RMT) and MEP latency, and increased recruitment curve slope). ML cortical current also reduced RMT and MEP latency. The degree of footedness correlated with the degree of RMT asymmetry, with a PA but not ML cortical current direction. In summary, cross-facilitation by activating the non-target leg in a task requiring postural stabilisation and inducing ML current increase corticomotor excitability regardless of limb dominance. This protocol may have practical application in testing CST integrity after stroke when paretic limb thresholds are high, by increasing the likelihood of eliciting a MEP.
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Affiliation(s)
- Marie-Claire Smith
- Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - James W Stinear
- Department of Exercise Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - P Alan Barber
- Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; Centre for Brain Research, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Cathy M Stinear
- Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand; Centre for Brain Research, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
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13
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Fractional anisotropy in corpus callosum is associated with facilitation of motor representation during ipsilateral hand movements. PLoS One 2014; 9:e104218. [PMID: 25118828 PMCID: PMC4131905 DOI: 10.1371/journal.pone.0104218] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 07/10/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Coactivation of primary motor cortex ipsilateral to a unilateral movement (M1(ipsilateral)) has been observed, and the magnitude of activation is influenced by the contracting muscles. It has been suggested that the microstructural integrity of the callosal motor fibers (CMFs) connecting M1 regions may reflect the observed response. However, the association between the structural connectivity of CMFs and functional changes in M1(ipsilateral) remains unclear. The purpose of this study was to investigate the relationship between functional changes within M1(ipsilateral) during unilateral arm or leg movements and the microstructure of the CMFs connecting both homotopic representations (arm or leg). METHODS Transcranial magnetic stimulation was used to assess changes in motor evoked potentials (MEP) in an arm muscle during unilateral movements compared to rest in fifteen healthy adults. Functional magnetic resonance imaging was then used to identify regions of M1 associated with either arm or leg movements. Diffusion-weighted imaging data was acquired to generate CMFs for arm and leg areas using the areas of activation from the functional imaging as seed masks. Individual values of regional fractional anisotropy (FA) of arm and leg CMFs was then calculated by examining the overlap between CMFs and a standard atlas of corpus callosum. RESULTS The change in the MEP was significantly larger in the arm movement compared to the leg movement. Additionally, regression analysis revealed that FA in the arm CMFs was positively correlated with the change in MEP during arm movement, whereas a negative correlation was observed during the leg movement. However, there was no significant relationship between FA in the leg CMF and the change in MEP during the movements. CONCLUSIONS These findings suggest that individual differences in interhemispheric structural connectivity may be used to explain a homologous muscle-dominant effect within M1(ipsilateral) hand representation during unilateral movement with topographical specificity.
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14
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Tazoe T, Komiyama T. Interlimb neural interactions in the corticospinal pathways. JOURNAL OF PHYSICAL FITNESS AND SPORTS MEDICINE 2014. [DOI: 10.7600/jpfsm.3.181] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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