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Nakajima T, Tazoe T, Sakamoto M, Endoh T, Shibuya S, Elias LA, Mezzarane RA, Komiyama T, Ohki Y. Reassessment of Non-Monosynaptic Excitation from the Motor Cortex to Motoneurons in Single Motor Units of the Human Biceps Brachii. Front Hum Neurosci 2017; 11:19. [PMID: 28194103 PMCID: PMC5276998 DOI: 10.3389/fnhum.2017.00019] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 01/10/2017] [Indexed: 12/05/2022] Open
Abstract
Corticospinal excitation is mediated by polysynaptic pathways in several vertebrates, including dexterous monkeys. However, indirect non-monosynaptic excitation has not been clearly observed following transcranial electrical stimulation (TES) or cervicomedullary stimulation (CMS) in humans. The present study evaluated indirect motor pathways in normal human subjects by recording the activities of single motor units (MUs) in the biceps brachii (BB) muscle. The pyramidal tract was stimulated with weak TES, CMS, and transcranial magnetic stimulation (TMS) contralateral to the recording side. During tasks involving weak co-contraction of the BB and hand muscles, all stimulation methods activated MUs with short latencies. Peristimulus time histograms (PSTHs) showed that responses with similar durations were induced by TES (1.9 ± 1.4 ms) and CMS (2.0 ± 1.4 ms), and these responses often showed multiple peaks with the PSTH peak having a long duration (65.3% and 44.9%, respectively). Such long-duration excitatory responses with multiple peaks were rarely observed in the finger muscles following TES or in the BB following stimulation of the Ia fibers. The responses obtained with TES were compared in the same 14 BB MUs during the co-contraction and isolated BB contraction tasks. Eleven and three units, respectively, exhibited activation with multiple peaks during the two tasks. In order to determine the dispersion effects on the axon conduction velocities (CVs) and synaptic noise, a simulation study that was comparable to the TES experiments was performed with a biologically plausible neuromuscular model. When the model included the monosynaptic-pyramidal tract, multiple peaks were obtained in about 34.5% of the motoneurons (MNs). The experimental and simulation results indicated the existence of task-dependent disparate inputs from the pyramidal tract to the MNs of the upper limb. These results suggested that intercalated interneurons are present in the spinal cord and that these interneurons might be equivalent to those identified in animal experiments.
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Affiliation(s)
- Tsuyoshi Nakajima
- Division of Sports and Health Science, Chiba UniversityChiba, Japan; Department of Integrative Physiology, Kyorin University School of MedicineTokyo, Japan
| | - Toshiki Tazoe
- Division of Sports and Health Science, Chiba UniversityChiba, Japan; Department of Physical Medicine and Rehabilitation, Center for the Neural Basis of Cognition, Systems Neuroscience Institute, University of PittsburghPittsburgh, PA, USA
| | - Masanori Sakamoto
- Division of Sports and Health Science, Chiba UniversityChiba, Japan; Faculty of Education, Department of Physical Education, Kumamoto UniversityKumamoto, Japan
| | - Takashi Endoh
- Division of Sports and Health Science, Chiba UniversityChiba, Japan; Faculty of Child Development and Education, Uekusa Gakuen UniversityChiba, Japan
| | - Satoshi Shibuya
- Department of Integrative Physiology, Kyorin University School of Medicine Tokyo, Japan
| | - Leonardo A Elias
- Neural Engineering Research Laboratory, Department of Biomedical Engineering, School of Electrical and Computer Engineering, University of CampinasCampinas, Brazil; Biomedical Engineering Laboratory, Escola Politecnica, Departamento de Engenharia de Telecomunicações e Controle (PTC), University of Sao PauloSao Paulo, Brazil
| | - Rinaldo A Mezzarane
- Division of Sports and Health Science, Chiba UniversityChiba, Japan; Biomedical Engineering Laboratory, Escola Politecnica, Departamento de Engenharia de Telecomunicações e Controle (PTC), University of Sao PauloSao Paulo, Brazil; Laboratory of Signal Processing and Motor Control, College of Physical Education, University of BrasíliaBrasília, Brazil
| | | | - Yukari Ohki
- Department of Integrative Physiology, Kyorin University School of Medicine Tokyo, Japan
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Beretta Piccoli M, Rainoldi A, Heitz C, Wüthrich M, Boccia G, Tomasoni E, Spirolazzi C, Egloff M, Barbero M. Innervation zone locations in 43 superficial muscles: Toward a standardization of electrode positioning. Muscle Nerve 2013; 49:413-21. [DOI: 10.1002/mus.23934] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Matteo Beretta Piccoli
- Department of Health Sciences; University of Applied Sciences and Arts of Southern Switzerland, SUPSI; Manno Switzerland
| | - Alberto Rainoldi
- Motor Science Research Center, School of Exercise and Sport Science, S.U.I.S.M., Department of Medical Sciences; University of Turin; Turin Italy
| | - Carolin Heitz
- Department of Health Sciences; University of Applied Sciences and Arts of Southern Switzerland, SUPSI; Landquart Switzerland
| | - Marianne Wüthrich
- Department of Health Sciences; University of Applied Sciences and Arts of Southern Switzerland, SUPSI; Landquart Switzerland
| | - Gennaro Boccia
- Motor Science Research Center, School of Exercise and Sport Science, S.U.I.S.M., Department of Medical Sciences; University of Turin; Turin Italy
| | - Enrico Tomasoni
- Motor Science Research Center, School of Exercise and Sport Science, S.U.I.S.M., Department of Medical Sciences; University of Turin; Turin Italy
| | - Carlo Spirolazzi
- School of Physiotherapy; Vita-Salute San Raffaele University; Milan Italy
| | - Michele Egloff
- Department of Health Sciences; University of Applied Sciences and Arts of Southern Switzerland, SUPSI; Manno Switzerland
| | - Marco Barbero
- Department of Health Sciences; University of Applied Sciences and Arts of Southern Switzerland, SUPSI; Manno Switzerland
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Özdemirkiran T, Ertekin C. Cremaster muscle motor unit action potentials. Clin Neurophysiol 2011; 122:1679-85. [DOI: 10.1016/j.clinph.2010.12.057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 12/24/2010] [Accepted: 12/27/2010] [Indexed: 10/18/2022]
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Lateva ZC, McGill KC, Johanson ME. The innervation and organization of motor units in a series-fibered human muscle: the brachioradialis. J Appl Physiol (1985) 2010; 108:1530-41. [PMID: 20360433 DOI: 10.1152/japplphysiol.01163.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We studied the innervation and organization of motor units in the brachioradialis muscle of 25 normal human subjects. We recorded intramuscular EMG signals at points separated by 15 mm along the proximodistal muscle axis during moderate isometric contractions, identified from 27 to 61 (mean 39) individual motor units per subject using EMG decomposition, and estimated the locations of the endplates and distal muscle/tendon junctions from the motor-unit action potential (MUAP) propagation patterns and terminal standing waves. In three subjects all the motor units were innervated in a single endplate zone. In the other 22 subjects, the motor units were innervated in 3-6 (mean 4) distinct endplate zones separated by 15-55 mm along the proximodistal axis. One-third of the motor units had fibers innervated in more than one zone. The more distally innervated motor units had distinct terminal waves indicating tendonous termination, while the more proximal motor units lacked terminal waves, indicating intrafascicular termination. Analysis of blocked MUAP components revealed that 19% of the motor units had at least one doubly innervated fiber, i.e., a fiber innervated in two different endplate zones by two different motoneurons, and thus belonging to two different motor units. These results are consistent with the brachioradialis muscle having a series-fibered architecture consisting of multiple, overlapping bands of muscle fibers in most individuals and a simple parallel-fibered architecture in some individuals.
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Affiliation(s)
- Zoia C Lateva
- Rehabilitation Research and Development Center, Department of Veterans Affairs Palo Alto Health Care System, 3801 Miranda Ave., Palo Alto, CA 94304, USA
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Kayalioglu G, Altay B, Uyaroglu FG, Bademkiran F, Uludag B, Ertekin C. Morphology and innervation of the human cremaster muscle in relation to its function. Anat Rec (Hoboken) 2008; 291:790-6. [PMID: 18449892 DOI: 10.1002/ar.20711] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The electromyographic properties of the cremaster muscle (CM) are quite different from other skeletal muscles. It shows excessive spontaneous discharges, and the motor unit shape and firing frequency of the CM muscle differ from that of limb muscles. In this study, CM of six adult cadavers and six orchiectomy specimens were used to reveal the detailed histology of the muscle and provide an anatomophysiological explanation for these unusual electromyographic properties. Routine histochemical stains revealed the CM was composed of several distinct bundles of smooth and striated muscle fibers within connective tissue. The smooth muscle fibers that were more profuse than previously known and were not arranged in layers, but widely dispersed between striated muscle fibers. Bielschowsky silver staining technique, anti-neurofilament and anti-synaptophysin immunostaining showed the presence of multiple motor end-plates observed as a series of small dots or lines running along the striated muscle fibers and several nerve endings on a single muscle fiber. Myosin immunostaining confirmed the CM is a slow-twitch muscle, and alpha-actin smooth muscle immunostaining confirmed the presence of a large number of smooth muscle fibers. There were also small multipolar neurons forming nerve plexuses between smooth muscle fibers. Anti-GFAP immunostaining confirmed the presence of glial cells similar to astrocytes. In conclusion, the findings of this detailed anatomical study showed the CM, widely known as a striated muscle, contains a large number of smooth muscle fibers, and the spontaneous electromyographic discharges are due to the presence of multiple motor end-plates and dense innervation.
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Lateva ZC, McGill KC. Electrophysiological evidence of doubly innervated branched muscle fibers in the human brachioradialis muscle. Clin Neurophysiol 2007; 118:2612-9. [PMID: 17977064 DOI: 10.1016/j.clinph.2007.09.058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Revised: 08/06/2007] [Accepted: 09/07/2007] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Motor-unit action potentials (MUAPs) with unstable satellite (late-latency) components are found in EMG signals from the brachioradialis muscles of normal subjects. We analyzed the morphology and blocking behavior of these MUAPs to determine their anatomical origin. METHODS EMG signals were recorded from the brachioradialis muscles of 5 normal subjects during moderate-level isometric contractions. MUAP waveforms, discharge patterns, and blocking were determined using computer-aided EMG decomposition. RESULTS Twelve MUAPs with unstable satellite potentials were detected, always two together in the same signal. Each MUAP also had a second unstable component associated with its main spike. The blocking behavior of the unstable components depended on how close together the two MUAPs were when they discharged. CONCLUSIONS The latencies and blocking behavior indicate that the unstable components came from branched muscle fibers innervated by two different motoneurons. The satellite potentials were due to action potentials that traveled to the branching point along one branch and back along the other. The blockings were due to action-potential collisions when both motoneurons discharged close together in time. SIGNIFICANCE Animal studies suggest that branched muscle fibers may be a normal characteristic of series-fibered muscles. This study adds to our understanding of these muscles in humans.
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Affiliation(s)
- Zoia C Lateva
- Rehabilitation Research and Development Center, VA Palo Alto Health Care System, Palo Alto, CA 94304, USA.
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Lapatki BG, Oostenveld R, Van Dijk JP, Jonas IE, Zwarts MJ, Stegeman DF. Topographical Characteristics of Motor Units of the Lower Facial Musculature Revealed by Means of High-Density Surface EMG. J Neurophysiol 2006; 95:342-54. [PMID: 16000526 DOI: 10.1152/jn.00265.2005] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The objective of this study was to systematically characterize motor units (MUs) of the musculature of the lower face. MU endplate positions and principal muscle fiber orientations relative to facial landmarks were identified. This was done by the analysis of motor unit action potentials (MUAPs) in the surface electromyogram. Thirteen specially trained, healthy subjects performed selective contractions of the depressor anguli oris, depressor labii inferioris, mentalis, and orbicularis oris inferior muscles. Signals were recorded using recently developed, 0.3-mm thin and flexible high-density surface electromyography (sEMG) grids (120 channels). For each subject and each muscle and for different low contraction levels, representative MUAPs ("MU fingerprints") were extracted from the raw sEMG data according to their spatiotemporal amplitude characteristics. We then topographically characterized the lower facial MUs' endplate zones and main muscle fiber orientations on the individual faces of the subjects. These topographical MU parameters were spatially warped to correct for the different sizes and shapes of the faces of individual subjects. This electrophysiological study revealed a distribution of the lower facial MU endplates in more or less restricted, distinct clusters on the muscle often with eccentric locations. The results add substantially to the basic neurophysiologic and anatomical knowledge of the complex facial muscle system. They can also be used to establish objective guidelines for placement of conventional (surface or needle) EMG electrodes as well as for clinical investigations on neuromuscular diseases affecting the facial musculature. The localized endplate positions may also indicate optimal locations for botulinum toxin injection in the face.
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Affiliation(s)
- Bernd G Lapatki
- Department of Orthodontics, School of Dental Medicine, University of Freiburg im Breisgau, Hugstetter Str. 55, D-79106 Freiburg i.Br., Germany.
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McGill KC, Lateva ZC, Marateb HR. EMGLAB: An interactive EMG decomposition program. J Neurosci Methods 2005; 149:121-33. [PMID: 16026846 DOI: 10.1016/j.jneumeth.2005.05.015] [Citation(s) in RCA: 196] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Revised: 04/22/2005] [Accepted: 04/22/2005] [Indexed: 11/23/2022]
Abstract
This paper describes an interactive computer program for decomposing EMG signals into their component motor-unit potential (MUP) trains and for averaging MUP waveforms. The program is able to handle single- or multi-channel signals recorded by needle or fine-wire electrodes during low and moderate levels of muscular contraction. It includes advanced algorithms for template matching, resolving superimpositions, and waveform averaging, as well as a convenient user interface for manually editing and verifying the results. The program also provides the ability to inspect the discharges of individual motor units more closely by subtracting out interfering activity from other MUP trains. Decomposition accuracy was assessed by cross-checking pairs of signals recorded by nearby electrodes during the same contraction. The results show that 100% accuracy can be achieved for MUPs with peak-to-peak amplitudes greater than 2.5 times the rms signal amplitude. Examples are presented to show how decomposition can be used to investigate motor-unit recruitment and discharge behavior, to study motor-unit architecture, and to detect action potential blocking in doubly innervated muscle fibers.
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Affiliation(s)
- Kevin C McGill
- Rehabilitation R&D Center, VA Palo Alto Health Care System, 3801 Miranda Ave, Palo Alto, CA 94304, USA.
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