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Piotrkiewicz M. The role of computer simulations in the investigation of mechanisms underlying rhythmic firing of human motoneuron. Biocybern Biomed Eng 2021. [DOI: 10.1016/j.bbe.2021.04.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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2
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Williams SE, Koch KC, Disselhorst-Klug C. Non-invasive assessment of motor unit activation in relation to motor neuron level and lesion location in stroke and spinal muscular atrophy. Clin Biomech (Bristol, Avon) 2020; 78:105053. [PMID: 32563725 DOI: 10.1016/j.clinbiomech.2020.105053] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 05/06/2020] [Accepted: 05/19/2020] [Indexed: 02/07/2023]
Abstract
BACKGROUND Neuromuscular disorders e.g. spinal muscular atrophy and stroke have a negative impact on functional movement capability. These disorders affect lower and upper motor neurons respectively. METHODS In this study high spatial resolution electromyography was used to record the motor unit activity in 3 groups: healthy subjects, a spinal muscular atrophy group and a stroke group. 7 clinically sensitive parameters were used to analyze the activation patterns of a few motor units. FINDINGS In the case of spinal muscular atrophy there was no effect on motor unit activation but on their number. Stroke was characterized by fewer active motor units and a significantly reduced firing rate with low variability. INTERPRETATION The results suggest, that for stroke, information from the brain is modified thereby resulting in motor units firing at their natural frequency. Thus, high spatial resolution electromyography and the chosen parameters facilitate non-invasive, objective differentiation and analysis of the activation patterns of motor units in neuromuscular disorders.
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Affiliation(s)
- Sybele E Williams
- Department of Rehabilitation and Prevention Engineering, Institute of Applied Medical Engineering, RWTH Aachen University, 52074 Aachen, Germany.
| | - Kathrin C Koch
- Department of Rehabilitation and Prevention Engineering, Institute of Applied Medical Engineering, RWTH Aachen University, 52074 Aachen, Germany
| | - Catherine Disselhorst-Klug
- Department of Rehabilitation and Prevention Engineering, Institute of Applied Medical Engineering, RWTH Aachen University, 52074 Aachen, Germany
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3
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Son J, Hu X, Suresh NL, Rymer WZ. Prolonged time course of population excitatory postsynaptic potentials in motoneurons of chronic stroke survivors. J Neurophysiol 2019; 122:176-183. [PMID: 31017842 DOI: 10.1152/jn.00288.2018] [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: 11/22/2022] Open
Abstract
Hyperexcitability of spinal motoneurons may contribute to muscular hypertonia after hemispheric stroke. The origins of this hyperexcitability are not clear, but we hypothesized that prolongation of the Ia excitatory postsynaptic potential (EPSP) in spastic motoneurons may be one potential mechanism, by enabling more effective temporal summation of Ia EPSPs, making action potential initiation easier. Thus, the purpose of this study is to quantify the time course of putative EPSPs in spinal motoneurons of chronic stroke survivors. To estimate the EPSP time course, a pair of low-intensity electrical stimuli was delivered sequentially to the median nerve in seven hemispheric stroke survivors and in six intact individuals, to induce an H-reflex response from the flexor carpi radialis muscle. H-reflex response probability was then used to quantify the time course of the underlying EPSPs in the motoneuron pool. A population EPSP estimate was then derived, based on the probability of evoking an H-reflex from the second test stimulus in the absence of a reflex response to the first conditioning stimulus. Our experimental results showed that in six of seven hemispheric stroke survivors, the apparent rate of decay of the population EPSP was markedly slower in spastic compared with contralateral (stroke) and intact motoneuron pools. There was no significant difference in EPSP time course between the contralateral side of stroke survivors and control subject muscles. We propose that one potential mechanism for hyperexcitability of spastic motoneurons in chronic stroke survivors may be associated with this prolongation of the Ia EPSP time course. Our subthreshold double-stimulation approach could provide a noninvasive tool for quantifying the time course of EPSPs in both healthy and pathological conditions. NEW & NOTEWORTHY Spastic motoneurons in stroke survivors showed a prolonged Ia excitatory postsynaptic potential (EPSP) time course compared with contralateral and intact motoneurons, suggesting that one potential mechanism for hyperexcitability of spastic motoneurons in chronic stroke survivors may be associated with this prolongation of the Ia EPSP time course.
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Affiliation(s)
- Jongsang Son
- Shirley Ryan AbilityLab (formerly the Rehabilitation Institute of Chicago) , Chicago, Illinois.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University , Chicago, Illinois
| | - Xiaogang Hu
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University , Raleigh, North Carolina
| | - Nina L Suresh
- Shirley Ryan AbilityLab (formerly the Rehabilitation Institute of Chicago) , Chicago, Illinois.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University , Chicago, Illinois
| | - William Z Rymer
- Shirley Ryan AbilityLab (formerly the Rehabilitation Institute of Chicago) , Chicago, Illinois.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University , Chicago, Illinois
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4
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Schambra HM, Xu J, Branscheidt M, Lindquist M, Uddin J, Steiner L, Hertler B, Kim N, Berard J, Harran MD, Cortes JC, Kitago T, Luft A, Krakauer JW, Celnik PA. Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials. Neurorehabil Neural Repair 2019; 33:568-580. [PMID: 31170880 DOI: 10.1177/1545968319850138] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Background. After stroke, recovery of movement in proximal and distal upper extremity (UE) muscles appears to follow different time courses, suggesting differences in their neural substrates. Objective. We sought to determine if presence or absence of motor evoked potentials (MEPs) differentially influences recovery of volitional contraction and strength in an arm muscle versus an intrinsic hand muscle. We also related MEP status to recovery of proximal and distal interjoint coordination and movement fractionation, as measured by the Fugl-Meyer Assessment (FMA). Methods. In 45 subjects in the year following ischemic stroke, we tracked the relationship between corticospinal tract (CST) integrity and behavioral recovery in the biceps (BIC) and first dorsal interosseous (FDI) muscle. We used transcranial magnetic stimulation to probe CST integrity, indicated by MEPs, in BIC and FDI. We used electromyography, dynamometry, and UE FMA subscores to assess muscle-specific contraction, strength, and inter-joint coordination, respectively. Results. Presence of MEPs resulted in higher likelihood of muscle contraction, greater strength, and higher FMA scores. Without MEPs, BICs could more often volitionally contract, were less weak, and had steeper strength recovery curves than FDIs; in contrast, FMA recovery curves plateaued below normal levels for both the arm and hand. Conclusions. There are shared and separate substrates for paretic UE recovery. CST integrity is necessary for interjoint coordination in both segments and for overall recovery. In its absence, alternative pathways may assist recovery of volitional contraction and strength, particularly in BIC. These findings suggest that more targeted approaches might be needed to optimize UE recovery.
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Affiliation(s)
- Heidi M Schambra
- 1 New York University School of Medicine, New York, NY, USA.,2 Columbia University, New York, NY, USA
| | - Jing Xu
- 3 Johns Hopkins University, Baltimore, MD, USA
| | - Meret Branscheidt
- 3 Johns Hopkins University, Baltimore, MD, USA.,4 University Hospital of Zurich, Zurich, Switzerland
| | | | | | - Levke Steiner
- 4 University Hospital of Zurich, Zurich, Switzerland
| | | | - Nathan Kim
- 3 Johns Hopkins University, Baltimore, MD, USA
| | | | - Michelle D Harran
- 2 Columbia University, New York, NY, USA.,3 Johns Hopkins University, Baltimore, MD, USA
| | - Juan C Cortes
- 2 Columbia University, New York, NY, USA.,3 Johns Hopkins University, Baltimore, MD, USA
| | | | - Andreas Luft
- 4 University Hospital of Zurich, Zurich, Switzerland.,5 cereneo Center for Neurology and Rehabilitation, Vitznau, Switzerland
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5
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Manuel M, Chardon M, Tysseling V, Heckman CJ. Scaling of Motor Output, From Mouse to Humans. Physiology (Bethesda) 2019; 34:5-13. [PMID: 30540233 DOI: 10.1152/physiol.00021.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Appropriate scaling of motor output from mouse to humans is essential. The motoneurons that generate all motor output are, however, very different in rodents compared with humans, being smaller and much more excitable. In contrast, feline motoneurons are more similar to those in humans. These scaling differences need to be taken into account for the use of rodents for translational studies of motor output.
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Affiliation(s)
- Marin Manuel
- Centre de Neurophysique, Physiologie, et Pathologie, UMR 8119 CNRS/Université Paris Descartes , Paris , France
| | - Matthieu Chardon
- Physiology, Northwestern University Feinberg School of Medicine , Chicago, Illinois
| | - Vicki Tysseling
- Physical Therapy and Human Movement Sciences, Physiology, Northwestern University Feinberg School of Medicine , Chicago, Illinois
| | - C J Heckman
- Physiology, Physical Medicine and Rehabilitation, Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine , Chicago, Illinois
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6
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Thompson CK, Negro F, Johnson MD, Holmes MR, McPherson LM, Powers RK, Farina D, Heckman CJ. Robust and accurate decoding of motoneuron behaviour and prediction of the resulting force output. J Physiol 2018; 596:2643-2659. [PMID: 29726002 DOI: 10.1113/jp276153] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 04/30/2018] [Indexed: 01/16/2023] Open
Abstract
KEY POINTS The spinal alpha motoneuron is the only cell in the human CNS whose discharge can be routinely recorded in humans. We have reengineered motor unit collection and decomposition approaches, originally developed in humans, to measure the neural drive to muscle and estimate muscle force generation in the in vivo cat model. Experimental, computational, and predictive approaches are used to demonstrate the validity of this approach across a wide range of modes to activate the motor pool. The utility of this approach is shown through the ability to track individual motor units across trials, allowing for better predictions of muscle force than the electromyography signal, and providing insights in to the stereotypical discharge characteristics in response to synaptic activation of the motor pool. This approach now allows for a direct link between the intracellular data of single motoneurons, the discharge properties of motoneuron populations, and muscle force generation in the same preparation. ABSTRACT The discharge of a spinal alpha motoneuron and the resulting contraction of its muscle fibres represents the functional quantum of the motor system. Recent advances in the recording and decomposition of the electromyographic signal allow for the identification of several tens of concurrently active motor units. These detailed population data provide the potential to achieve deep insights into the synaptic organization of motor commands. Yet most of our understanding of the synaptic input to motoneurons is derived from intracellular recordings in animal preparations. Thus, it is necessary to extend the new electrode and decomposition methods to recording of motor unit populations in these same preparations. To achieve this goal, we use high-density electrode arrays and decomposition techniques, analogous to those developed for humans, to record and decompose the activity of tens of concurrently active motor units in a hindlimb muscle in the in vivo cat. Our results showed that the decomposition method in this animal preparation was highly accurate, with conventional two-source validation providing rates of agreement equal to or superior to those found in humans. Multidimensional reconstruction of the motor unit action potential provides the ability to accurately track the same motor unit across multiple contractions. Additionally, correlational analyses demonstrate that the composite spike train provides better estimates of whole muscle force than conventional estimates obtained from the electromyographic signal. Lastly, stark differences are observed between the modes of activation, in particular tendon vibration produced quantal interspike intervals at integer multiples of the vibration period.
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Affiliation(s)
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Chicago, IL, USA
| | | | - Matthew R Holmes
- Department of Physiology, Northwestern University, Chicago, IL, USA
| | | | - Randall K Powers
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, USA
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, UK
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7
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Kuraszkiewicz B, Chen JJJ, Goszczyńska H, Wang YL, Piotrkiewicz M. Bilateral changes in afterhyperpolarization duration of spinal motoneurones in post-stroke patients. PLoS One 2018; 13:e0189845. [PMID: 29338007 PMCID: PMC5770035 DOI: 10.1371/journal.pone.0189845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 12/04/2017] [Indexed: 11/18/2022] Open
Abstract
This paper extends the observations presented in the previously published work on the afterhyperpolarization (AHP) duration changes in motoneurones (MNs) on the paretic (more affected) side of 11 post-stroke patients by the same analysis on the non-paretic (less-affected) side. The estimated AHP duration for patients’ MNs supplying more-affected muscles was significantly longer than control values and the elongation decreased with patient age and disorder duration. For MNs supplying less-affected muscles, dependency of AHP duration on age was closer to the control data, but the scatter was substantially bigger. However, the AHP duration estimate of less-affected MNs tended to be longer than that of controls in the short time elapsed since the stroke, and shorter than controls in the long time. Our results thus suggest that the spinal MNs on both sides respond to the cerebral stroke rapidly with prolongation of AHP duration, which tends to normalize with time, in line with functional recovery. This suggestion is in concert with the published research on post-stroke changes in brain hemispheres. To our knowledge, these dependencies have never been investigated before. Since the number of our data was limited, the observed trends should be verified in a larger sample of patients and such a verification could take into account the suggestions for data analysis that we provide in this paper. Our data are in line with the earlier published research on MN firing characteristics post-stroke and support the conclusion that the MUs of the muscles at the non-paretic side are also affected and cannot be considered a suitable control for the MUs on the paretic side.
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Affiliation(s)
- Bożenna Kuraszkiewicz
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland
| | - Jia-Jin Jason Chen
- Institute of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Hanna Goszczyńska
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland
| | - Yu-Lin Wang
- Department of Rehabilitation, Chi Mei Medical Center, Tainan, Taiwan
- Center for General Education, Southern Taiwan University of Science and Technology, Tainan, Taiwan
| | - Maria Piotrkiewicz
- Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland
- * E-mail:
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Johnson MD, Thompson CK, Tysseling VM, Powers RK, Heckman CJ. The potential for understanding the synaptic organization of human motor commands via the firing patterns of motoneurons. J Neurophysiol 2017; 118:520-531. [PMID: 28356467 DOI: 10.1152/jn.00018.2017] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 03/07/2017] [Accepted: 03/21/2017] [Indexed: 12/19/2022] Open
Abstract
Motoneurons are unique in being the only neurons in the CNS whose firing patterns can be easily recorded in human subjects. This is because of the one-to-one relationship between the motoneuron and muscle cell behavior. It has long been appreciated that the connection of motoneurons to their muscle fibers allows their action potentials to be amplified and recorded, but only recently has it become possible to simultaneously record the firing pattern of many motoneurons via array electrodes placed on the skin. These firing patterns contain detailed information about the synaptic organization of motor commands to the motoneurons. This review focuses on parameters in these firing patterns that are directly linked to specific features of this organization. It is now well established that motor commands consist of three components, excitation, inhibition, and neuromodulation; the importance of the third component has become increasingly evident. Firing parameters linked to each of the three components are discussed, along with consideration of potential limitations in their utility for understanding the underlying organization of motor commands. Future work based on realistic computer simulations of motoneurons may allow quantitative "reverse engineering" of human motoneuron firing patterns to provide good estimates of the relative amplitudes and temporal patterns of all three components of motor commands.
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Affiliation(s)
- Michael D Johnson
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois;
| | | | - Vicki M Tysseling
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Randall K Powers
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington
| | - Charles J Heckman
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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9
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Piotrkiewicz M, Türker KS. Onion Skin or Common Drive? Front Cell Neurosci 2017; 11:2. [PMID: 28154526 PMCID: PMC5243795 DOI: 10.3389/fncel.2017.00002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 01/05/2017] [Indexed: 11/13/2022] Open
Affiliation(s)
- Maria Piotrkiewicz
- Department of Engineering of Nervous and Muscular System, Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences Warsaw, Poland
| | - Kemal S Türker
- Laboratory of Neuromuscular Research, Koç University School of Medicine Istanbul, Turkey
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10
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Hu X, Suresh AK, Rymer WZ, Suresh NL. Altered motor unit discharge patterns in paretic muscles of stroke survivors assessed using surface electromyography. J Neural Eng 2016; 13:046025. [PMID: 27432656 DOI: 10.1088/1741-2560/13/4/046025] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Hemispheric stroke survivors often show impairments in voluntary muscle activation. One potential source of these impairments could come from altered control of muscle, via disrupted motor unit (MU) firing patterns. In this study, we sought to determine whether MU firing patterns are modified on the affected side of stroke survivors, as compared with the analogous contralateral muscle. APPROACH Using a novel surface electromyogram (EMG) sensor array, coupled with advanced template recognition software (dEMG) we recorded surface EMG signals over the first dorsal interosseous (FDI) muscle on both paretic and contralateral sides. Recordings were made as stroke survivors produced isometric index finger abductions over a large force range (20%-60% of maximum). Utilizing the dEMG algorithm, MU firing rates, recruitment thresholds, and action potential amplitudes were estimated for concurrently active MUs in each trial. MAIN RESULTS Our results reveal significant changes in the firing rate patterns in paretic FDI muscle, in that the discharge rates, characterized in relation to recruitment force threshold and to MU size, were less clearly correlated with recruitment force than in contralateral FDI muscles. Firing rates in the affected muscle also did not modulate systematically with the level of voluntary muscle contraction, as would be expected in intact muscles. These disturbances in firing properties also correlated closely with the impairment of muscle force generation. SIGNIFICANCE Our results provide strong evidence of disruptions in MU firing behavior in paretic muscles after a hemispheric stroke, suggesting that modified control of the spinal motoneuron pool could be a contributing factor to muscular weakness in stroke survivors.
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Affiliation(s)
- Xiaogang Hu
- Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, USA. Department of Biomedical Engineering, University of North Carolina at Chapel Hill and NC State University at Raleigh, USA
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11
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Does the Length of Elbow Flexors and Visual Feedback Have Effect on Accuracy of Isometric Muscle Contraction in Men after Stroke? BIOMED RESEARCH INTERNATIONAL 2016; 2016:7641705. [PMID: 27042670 PMCID: PMC4793147 DOI: 10.1155/2016/7641705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 12/28/2015] [Accepted: 01/26/2016] [Indexed: 11/17/2022]
Abstract
UNLABELLED The aim of the study was to determine the effect of different muscle length and visual feedback information (VFI) on accuracy of isometric contraction of elbow flexors in men after an ischemic stroke (IS). MATERIALS AND METHODS Maximum voluntary muscle contraction force (MVMCF) and accurate determinate muscle force (20% of MVMCF) developed during an isometric contraction of elbow flexors in 90° and 60° of elbow flexion were measured by an isokinetic dynamometer in healthy subjects (MH, n = 20) and subjects after an IS during their postrehabilitation period (MS, n = 20). RESULTS In order to evaluate the accuracy of the isometric contraction of the elbow flexors absolute errors were calculated. The absolute errors provided information about the difference between determinate and achieved muscle force. CONCLUSIONS There is a tendency that greater absolute errors generating determinate force are made by MH and MS subjects in case of a greater elbow flexors length despite presence of VFI. Absolute errors also increase in both groups in case of a greater elbow flexors length without VFI. MS subjects make greater absolute errors generating determinate force without VFI in comparison with MH in shorter elbow flexors length.
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Herda TJ, Siedlik JA, Trevino MA, Cooper MA, Weir JP. Motor unit control strategies of endurance- versus resistance-trained individuals. Muscle Nerve 2015; 52:832-43. [DOI: 10.1002/mus.24597] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 01/29/2015] [Accepted: 02/03/2015] [Indexed: 11/05/2022]
Affiliation(s)
- Trent J. Herda
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
| | - Jacob A. Siedlik
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
| | - Michael A. Trevino
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
| | - Michael A. Cooper
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
| | - Joseph P. Weir
- Neuromechanics Laboratory; Department of Health; Sport; and Exercise Sciences; University of Kansas; 1301 Sunnyside Avenue, Room 101BE Lawrence Kansas 66045 USA
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Klein CS, Zhou P, Marciniak C. Excitability properties of motor axons in adults with cerebral palsy. Front Hum Neurosci 2015; 9:329. [PMID: 26089791 PMCID: PMC4452826 DOI: 10.3389/fnhum.2015.00329] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 05/22/2015] [Indexed: 01/09/2023] Open
Abstract
Cerebral palsy (CP) is a permanent disorder caused by a lesion to the developing brain that significantly impairs motor function. The neurophysiological mechanisms underlying motor impairment are not well understood. Specifically, few have addressed whether motoneuron or peripheral axon properties are altered in CP, even though disruption of descending inputs to the spinal cord may cause them to change. In the present study, we have compared nerve excitability properties in seven adults with CP and fourteen healthy controls using threshold tracking techniques by stimulating the median nerve at the wrist and recording the compound muscle action potential over the abductor pollicis brevis. The excitability properties in the CP subjects were found to be abnormal. Early and late depolarizing and hyperpolarizing threshold electrotonus was significantly larger (i.e., fanning out), and resting current-threshold (I/V) slope was smaller, in CP compared to control. In addition resting threshold and rheobase tended to be larger in CP. According to a modeling analysis of the data, an increase in leakage current under or through the myelin sheath, i.e., the Barrett-Barrett conductance, combined with a slight hyperpolarization of the resting membrane potential, best explained the group differences in excitability properties. There was a trend for those with greater impairment in gross motor function to have more abnormal axon properties. The findings indicate plasticity of motor axon properties far removed from the site of the lesion. We suspect that this plasticity is caused by disruption of descending inputs to the motoneurons at an early age around the time of their injury.
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Affiliation(s)
- Cliff S Klein
- Guangdong Provincial Work Injury Rehabilitation Center, Guangzhou China ; Sensory Motor Performance Program, Rehabilitation Institute of Chicago Chicago, IL, USA ; Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL USA
| | - Ping Zhou
- Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center at Houston and TIRR Memorial Hermann Research Center, Houston, TX USA ; Biomedical Engineering Program, University of Science and Technology of China, Hefei China
| | - Christina Marciniak
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago Chicago, IL, USA ; Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL USA
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14
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Hu X, Suresh NL, Rymer WZ. Estimating the time course of population excitatory postsynaptic potentials in motoneurons of spastic stroke survivors. J Neurophysiol 2015; 113:1952-7. [PMID: 25540228 DOI: 10.1152/jn.00946.2014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hyperexcitable motoneurons are likely to contribute to muscle hypertonia after a stroke injury; however, the origins of this hyperexcitability are not clear. One possibility is that the effective duration of the Ia excitatory postsynaptic potential (EPSP) is prolonged, increasing the potential for temporal summation of EPSPs, making action potential initiation easier. Accordingly, the purpose of this study was to quantify the time course of EPSPs in motoneurons of stroke survivors. The experimental protocol, which was based on parameters derived from simulation, involved sequential subthreshold electrical stimuli delivered to the median nerve of hemispheric stroke survivors. The resulting H-reflex responses were recorded in the flexor carpi radialis muscle. H-reflex response probability was then used to quantify the time course of the underlying EPSPs in the motoneuron pool. A population EPSP was estimated based on the probability of evoking an H reflex from the second electrical stimulus in the absence of a reflex response to the first stimulus. The accuracy of this time-course estimate was quantified using a computer simulation that explored a range of feasible EPSP parameters. Our experimental results showed that in all five hemispheric stroke survivors the rate of decay of the population EPSP was consistently slower in spastic compared with the contralateral motoneuron pools. We propose that one potential mechanism for hyperexcitability of motoneurons in spastic stroke survivors may be linked to this prolongation of the Ia EPSP time course. Our subthreshold double-stimulation approach also provides a noninvasive tool for quantifying the time course of EPSPs in both healthy and pathological conditions.
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Affiliation(s)
- Xiaogang Hu
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois; and
| | - Nina L Suresh
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois; and
| | - William Z Rymer
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois; and Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
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15
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Li X, Holobar A, Gazzoni M, Merletti R, Rymer WZ, Zhou P. Examination of Poststroke Alteration in Motor Unit Firing Behavior Using High-Density Surface EMG Decomposition. IEEE Trans Biomed Eng 2014; 62:1242-52. [PMID: 25389239 DOI: 10.1109/tbme.2014.2368514] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Recent advances in high-density surface electromyogram (EMG) decomposition have made it a feasible task to discriminate single motor unit activity from surface EMG interference patterns, thus providing a noninvasive approach for examination of motor unit control properties. In the current study, we applied high-density surface EMG recording and decomposition techniques to assess motor unit firing behavior alterations poststroke. Surface EMG signals were collected using a 64-channel 2-D electrode array from the paretic and contralateral first dorsal interosseous (FDI) muscles of nine hemiparetic stroke subjects at different isometric discrete contraction levels between 2 to 10 N with a 2 N increment step. Motor unit firing rates were extracted through decomposition of the high-density surface EMG signals and compared between paretic and contralateral muscles. Across the nine tested subjects, paretic FDI muscles showed decreased motor unit firing rates compared with contralateral muscles at different contraction levels. Regression analysis indicated a linear relation between the mean motor unit firing rate and the muscle contraction level for both paretic and contralateral muscles (p < 0.001), with the former demonstrating a lower increment rate (0.32 pulses per second (pps)/N) compared with the latter (0.67 pps/N). The coefficient of variation (averaged over the contraction levels) of the motor unit firing rates for the paretic muscles (0.21 ± 0.012) was significantly higher than for the contralateral muscles (0.17 ± 0.014) (p < 0.05). This study provides direct evidence of motor unit firing behavior alterations poststroke using surface EMG, which can be an important factor contributing to hemiparetic muscle weakness.
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Garland SJ, Pollock CL, Ivanova TD. Could motor unit control strategies be partially preserved after stroke? Front Hum Neurosci 2014; 8:864. [PMID: 25400568 PMCID: PMC4215611 DOI: 10.3389/fnhum.2014.00864] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 10/07/2014] [Indexed: 11/13/2022] Open
Affiliation(s)
- S Jayne Garland
- Department of Physical Therapy, University of British Columbia Vancouver, BC, Canada
| | - Courtney L Pollock
- Graduate Program in Rehabilitation Sciences, Department of Physical Therapy, University of British Columbia Vancouver, BC, Canada
| | - Tanya D Ivanova
- Department of Physical Therapy, University of British Columbia Vancouver, BC, Canada
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