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Meigal A, Gerasimova-Meigal L, Kuzmina A, Antonen E, Peskova A, Burkin M. Electromyographic Characteristics of Postactivation Effect in Dopamine-Dependent Spectrum Models Observed in Parkinson's Disease and Schizophrenia. Biomedicines 2024; 12:1338. [PMID: 38927545 PMCID: PMC11202052 DOI: 10.3390/biomedicines12061338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2024] [Revised: 06/14/2024] [Accepted: 06/16/2024] [Indexed: 06/28/2024] Open
Abstract
This study aimed to test the hypothesis that the postactivation effect (PAE, involuntary normal muscle tone) is modified by dopaminergic mechanisms. The PAE was tested with surface electromyography (sEMG) in the "off medication" phase in participants with Parkinson's disease (PDoff) and in the "on medication" state in participants with schizophrenia (SZon), which modeled hypodopaminegic conditions, and in participants with PD "on medication" (PDon) and in participants with SZ "off medication" (SZoff) state which modeled the hyperdopaminergic conditions. Healthy age-matched participants constituted the control group (HC, n = 11). In hyperdopaminergic models, PAE was triggered in 71.3% of participants in SZoff and in 35.7% in PDon conditions. In the hypodopaminergic models, PAE was triggered in 12% in SZon and in 21.4% in PDoff conditions. In the HC group, PAE was present in 91% of participants. In the HC and PD groups, the mean frequency and correlation dimension of sEMG at PAE was higher than that during voluntary isometric contraction. In conclusion, in hypodopaminergic models, PAE triggering was inhibited. The manifestations and EMG characteristics of PAE in people with PD or SZ may indicate dopaminergic dysfunction.
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Affiliation(s)
- Alexander Meigal
- Department of Physiology and Pathophysiology, Petrozavodsk State University, 33, Lenina Pr., 185910 Petrozavodsk, Russia; (L.G.-M.)
| | - Liudmila Gerasimova-Meigal
- Department of Physiology and Pathophysiology, Petrozavodsk State University, 33, Lenina Pr., 185910 Petrozavodsk, Russia; (L.G.-M.)
| | - Anna Kuzmina
- Department of Neurology, Psychiatry and Microbiology, Petrozavodsk State University, 33, Lenina Pr., 185910 Petrozavodsk, Russia
- Republican Psychiatric Hospital, 4, Bol’nichnyy Gorodok, 186131 Matrosy, Russia
| | - Elena Antonen
- Department of Neurology, Psychiatry and Microbiology, Petrozavodsk State University, 33, Lenina Pr., 185910 Petrozavodsk, Russia
| | - Alexandra Peskova
- Department of Physiology and Pathophysiology, Petrozavodsk State University, 33, Lenina Pr., 185910 Petrozavodsk, Russia; (L.G.-M.)
| | - Mark Burkin
- Department of Neurology, Psychiatry and Microbiology, Petrozavodsk State University, 33, Lenina Pr., 185910 Petrozavodsk, Russia
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Yokoyama H, Kaneko N, Sasaki A, Saito A, Nakazawa K. Firing behavior of single motor units of the tibialis anterior in human walking as non-invasively revealed by HDsEMG decomposition. J Neural Eng 2022; 19. [PMID: 36541453 DOI: 10.1088/1741-2552/aca71b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 11/29/2022] [Indexed: 12/02/2022]
Abstract
Objective.Investigation of the firing behavior of motor units (MUs) provides essential neuromuscular control information because MUs are the smallest organizational component of the neuromuscular system. The MUs activated during human infants' leg movements and rodent locomotion, mainly controlled by the spinal central pattern generator (CPG), show highly synchronous firing. In addition to spinal CPGs, the cerebral cortex is involved in neuromuscular control during walking in human adults. Based on the difference in the neural control mechanisms of locomotion between rodent, human infants and adults, MU firing behavior during adult walking probably has some different features from the other populations. However, so far, the firing activity of MUs in human adult walking has been largely unknown due to technical issues.Approach.Recent technical advances allow noninvasive investigation of MU firing by high-density surface electromyogram (HDsEMG) decomposition. We investigated the MU firing behavior of the tibialis anterior (TA) muscle during walking at a slow speed by HDsEMG decomposition.Main results.We found recruitment threshold modulation of MU between walking and steady isometric contractions. Doublet firings, and gait phase-specific firings were also observed during walking. We also found high MU synchronization during walking over a wide range of frequencies, probably including cortical and spinal CPG-related components. The amount of MU synchronization was modulated between the gait phases and motor tasks. These results suggest that the central nervous system flexibly controls MU firing to generate appropriate force of TA during human walking.Significance.This study revealed the MU behavior during walking at a slow speed and demonstrated the feasibility of noninvasive investigation of MUs during dynamic locomotor tasks, which will open new frontiers for the study of neuromuscular systems in the fields of neuroscience and biomedical engineering.
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Affiliation(s)
- Hikaru Yokoyama
- Institute of Engineering, Tokyo University of Agriculture and Technology, Tokyo 184-8588, Japan.,Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan
| | - Naotsugu Kaneko
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan.,Japan Society for the Promotion of Science, Tokyo 102-0083, Japan.,Department of Neuropsychiatry, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Atsushi Sasaki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan.,Japan Society for the Promotion of Science, Tokyo 102-0083, Japan.,Graduate School of Engineering Science, Department of Mechanical Science and Bioengineering, Osaka University, Osaka 560-8531, Japan
| | - Akira Saito
- Center for Health and Sports Science, Kyushu Sangyo University, Fukuoka 813-8503, Japan
| | - Kimitaka Nakazawa
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan
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Anastasopoulos D. Tremor in Parkinson's Disease May Arise from Interactions of Central Rhythms with Spinal Reflex Loop Oscillations. JOURNAL OF PARKINSONS DISEASE 2020; 10:383-392. [PMID: 31929120 PMCID: PMC7242831 DOI: 10.3233/jpd-191715] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
It is commonly believed that tremor, one of the cardinal signs of Parkinson’s disease, is associated with cerebello-thalamo-cortical oscillations set off by the dopamine-depleted basal ganglia networks. The triggering mechanism has been, however, not entirely delineated. Several reports have pointed to the relevance of interactions with peripheral/spinal mechanisms to tremor generation. Investigations of motor unit synchronization and discharge patterns suggested that exaggerated beta-band oscillations may intermittently reach alpha-motoneurons and modulate low-amplitude membrane oscillations due to spinal loop transmission delays. As a result, the spinal reflex loop will oscillate more vigorously and at a lower frequency and, in turn, entrain larger transcortical loops. Motoneurons may thus represent the specific generator “node” in a tremor network encompassing both cerebral and peripheral/spinal recurrent circuits.
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Affiliation(s)
- Dimitri Anastasopoulos
- Department of Neurology, University of Ioannina, Ioannina, Greece.,Akutnahe Rehabilitation, Kantonsspital Baden, Baden/Bad Zurzach, Switzerland
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Miroshnichenko GG, Meigal AY, Saenko IV, Gerasimova-Meigal LI, Chernikova LA, Subbotina NS, Rissanen SM, Karjalainen PA. Parameters of Surface Electromyogram Suggest That Dry Immersion Relieves Motor Symptoms in Patients With Parkinsonism. Front Neurosci 2018; 12:667. [PMID: 30319343 PMCID: PMC6168649 DOI: 10.3389/fnins.2018.00667] [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: 03/13/2017] [Accepted: 09/05/2018] [Indexed: 11/13/2022] Open
Abstract
Dry immersion (DI) is acknowledged as a reliable space flight analog condition. At DI, subject is immersed in water being wrapped in a waterproof film to imitate microgravity (μG). Microgravity is known to decrease muscle tone due to deprivation of the sensory stimuli that activate the reflexes that keep up the muscle tone. In contrary, parkinsonian patients are characterized by elevated muscle tone, or rigidity, along with rest tremor and akinesia. We hypothesized that DI can diminish the elevated muscle tone and/or the tremor in parkinsonian patients. Fourteen patients with Parkinson's disease (PD, 10 males, 4 females, 47-73 years) and 5 patients with vascular parkinsonism (VP, 1 male, 4 females, 65-72 years) participated in the study. To evaluate the effect of DI on muscles' functioning, we compared parameters of surface electromyogram (sEMG) measured before and after a single 45-min long immersion session. The sEMG recordings were made from the biceps brachii muscle, bilaterally. Each recording was repeated with the following loading conditions: with arms hanging freely down, and with 0, 1, and 2 kg loading on each hand with elbows flexed to 90°. The sEMG parameters comprised of amplitude, median frequency, time of decay of mutual information, sample entropy, correlation dimension, recurrence rate, and determinism of sEMG. These parameters have earlier been proved to be sensitive to PD severity. We used the Wilcoxon test to decide which parameters were statistically significantly different before and after the dry immersion. Accepting the p < 0.05 significance level, amplitude, time of decay of mutual information, recurrence rate, and determinism tended to decrease, while median frequency and sample entropy of sEMG tended to increase after the DI. The most statistically significant change was for the determinism of sEMG from the left biceps with 1 kg loading, which decreased for 84% of the patients. The results suggest that DI can promptly relieve motor symptoms of parkinsonism. We conclude that DI has strong potential as a rehabilitation method for parkinsonian patients.
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Affiliation(s)
- German G Miroshnichenko
- Biosignal Analysis and Medical Imaging Group, Department of Applied Physics, Faculty of Science and Forestry, University of Eastern Finland, Kuopio, Finland
| | - Alexander Yu Meigal
- Laboratory for Novel Methods in Physiology, Institute of High-Tech Biomedical Solutions, Petrozavodsk State University, Petrozavodsk, Russia
| | - Irina V Saenko
- Laboratory of Gravitational Physiology of Sensorimotor System, Department of Sensorimotor Physiology and Countermeasure, Institute of BioMedical Problems, Russian Academy of Sciences, Moscow, Russia
| | - Liudmila I Gerasimova-Meigal
- Department of Human and Animal Physiology, Physiopathology, Histology, Petrozavodsk State University, Petrozavodsk, Russia
| | - Liudmila A Chernikova
- Department of Neurorehabilitation and Physiotherapy, Research Center of Neurology, Russian Academy of Medical Sciences, Moscow, Russia
| | - Natalia S Subbotina
- Department of Neurology, Psychiatry, and Microbiology, Petrozavodsk State University, Petrozavodsk, Russia
| | - Saara M Rissanen
- Biosignal Analysis and Medical Imaging Group, Department of Applied Physics, Faculty of Science and Forestry, University of Eastern Finland, Kuopio, Finland
| | - Pasi A Karjalainen
- Biosignal Analysis and Medical Imaging Group, Department of Applied Physics, Faculty of Science and Forestry, University of Eastern Finland, Kuopio, Finland
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Castronovo AM, Negro F, Farina D. Theoretical Model and Experimental Validation of the estimated proportions of common and independent input to motor neurons. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2016; 2015:254-7. [PMID: 26736248 DOI: 10.1109/embc.2015.7318348] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Motor neurons in the spinal cord receive synaptic input that comprises common and independent components. The part of synaptic input that is common to all motor neurons is the one regulating the production of force. Therefore, its quantification is important to assess the strategy used by Central Nervous System (CNS) to control and regulate movements, especially in physiological conditions such as fatigue. In this study we present and validate a method to estimate the ratio between strengths of common and independent inputs to motor neurons and we apply this method to investigate its changes during fatigue. By means of coherence analysis we estimated the level of correlation between motor unit spike trains at the beginning and at the end of fatiguing contractions of the Tibialis Anterior muscle at three different force targets. Combining theoretical modeling and experimental data we estimated the strength of the common synaptic input with respect to the independent one. We observed a consistent increase in the proportion of the shared input to motor neurons during fatigue. This may be interpreted as a strategy used by the CNS to counteract the occurrence of fatigue and the concurrent decrease of generated force.
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Kline JC, De Luca CJ. Synchronization of motor unit firings: an epiphenomenon of firing rate characteristics not common inputs. J Neurophysiol 2015; 115:178-92. [PMID: 26490288 DOI: 10.1152/jn.00452.2015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 10/16/2015] [Indexed: 01/21/2023] Open
Abstract
Synchronous motor unit firing instances have been attributed to anatomical inputs shared by motoneurons. Yet, there is a lack of empirical evidence confirming the notion that common inputs elicit synchronization under voluntary conditions. We tested this notion by measuring synchronization between motor unit action potential trains (MUAPTs) as their firing rates progressed within a contraction from a relatively low force level to a higher one. On average, the degree of synchronization decreased as the force increased. The common input notion provides no empirically supported explanation for the observed synchronization behavior. Therefore, we investigated a more probable explanation for synchronization. Our data set of 17,546 paired MUAPTs revealed that the degree of synchronization varies as a function of two characteristics of the motor unit firing rate: the similarity and the slope as a function of force. Both are measures of the excitation of the motoneurons. As the force generated by the muscle increases, the firing rate slope decreases, and the synchronization correspondingly decreases. Different muscles have motor units with different firing rate characteristics and display different amounts of synchronization. Although this association is not proof of causality, it consistently explains our observations and strongly suggests further investigation. So viewed, synchronization is likely an epiphenomenon, subject to countless unknown neural interactions. As such, synchronous firing instances may not be the product of a specific design and may not serve a specific physiological purpose. Our explanation for synchronization has the advantage of being supported by empirical evidence, whereas the common input does not.
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Affiliation(s)
- Joshua C Kline
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts; and Delsys Incorporated, Natick, Massachusetts
| | - Carlo J De Luca
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts; and Delsys Incorporated, Natick, Massachusetts
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Castronovo AM, Negro F, Conforto S, Farina D. The proportion of common synaptic input to motor neurons increases with an increase in net excitatory input. J Appl Physiol (1985) 2015; 119:1337-46. [PMID: 26404614 DOI: 10.1152/japplphysiol.00255.2015] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 09/22/2015] [Indexed: 11/22/2022] Open
Abstract
α-Motor neurons receive synaptic inputs from spinal and supraspinal centers that comprise components either common to the motor neuron pool or independent. The input shared by motor neurons--common input--determines force control. The aim of the study was to investigate the changes in the strength of common synaptic input delivered to motor neurons with changes in force and with fatigue, two conditions that underlie an increase in the net excitatory drive to the motor neurons. High-density surface electromyogram (EMG) signals were recorded from the tibialis anterior muscle during contractions at 20, 50, and 75% of the maximal voluntary contraction force (in 3 sessions separated by at least 2 days), all sustained until task failure. EMG signal decomposition identified the activity of a total of 1,245 motor units. The coherence values between cumulative motor unit spike trains increased with increasing force, especially for low frequencies. This increase in coherence was not observed when comparing two subsets of motor units having different recruitment thresholds, but detected at the same force level. Moreover, the coherence values for frequencies <5 Hz increased at task failure with respect to the beginning of the contractions for all force levels. In conclusion, the results indicated that the relative strength of common synaptic input to motor neurons increases with respect to independent input when the net excitatory drive to motor neurons increases as a consequence of a change in force and fatigue.
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Affiliation(s)
- Anna Margherita Castronovo
- Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany; and BioLab, Biomedical Engineering Laboratory, Department of Engineering, University Roma TRE, Rome, Italy
| | - Francesco Negro
- Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany; and
| | - Silvia Conforto
- BioLab, Biomedical Engineering Laboratory, Department of Engineering, University Roma TRE, Rome, Italy
| | - Dario Farina
- Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany; and
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The phase difference between neural drives to antagonist muscles in essential tremor is associated with the relative strength of supraspinal and afferent input. J Neurosci 2015; 35:8925-37. [PMID: 26063924 DOI: 10.1523/jneurosci.0106-15.2015] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The pathophysiology of essential tremor (ET), the most common movement disorder, is not fully understood. We investigated which factors determine the variability in the phase difference between neural drives to antagonist muscles, a long-standing observation yet unexplained. We used a computational model to simulate the effects of different levels of voluntary and tremulous synaptic input to antagonistic motoneuron pools on the tremor. We compared these simulations to data from 11 human ET patients. In both analyses, the neural drive to muscle was represented as the pooled spike trains of several motor units, which provides an accurate representation of the common synaptic input to motoneurons. The simulations showed that, for each voluntary input level, the phase difference between neural drives to antagonist muscles is determined by the relative strength of the supraspinal tremor input to the motoneuron pools. In addition, when the supraspinal tremor input to one muscle was weak or absent, Ia afferents provided significant common tremor input due to passive stretch. The simulations predicted that without a voluntary drive (rest tremor) the neural drives would be more likely in phase, while a concurrent voluntary input (postural tremor) would lead more frequently to an out-of-phase pattern. The experimental results matched these predictions, showing a significant change in phase difference between postural and rest tremor. They also indicated that the common tremor input is always shared by the antagonistic motoneuron pools, in agreement with the simulations. Our results highlight that the interplay between supraspinal input and spinal afferents is relevant for tremor generation.
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Gallego JA, Dideriksen JL, Holobar A, Ibáñez J, Pons JL, Louis ED, Rocon E, Farina D. Influence of common synaptic input to motor neurons on the neural drive to muscle in essential tremor. J Neurophysiol 2014; 113:182-91. [PMID: 25274343 DOI: 10.1152/jn.00531.2014] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Tremor in essential tremor (ET) is generated by pathological oscillations at 4-12 Hz, likely originating at cerebello-thalamo-cortical pathways. However, the way in which tremor is represented in the output of the spinal cord circuitries is largely unknown because of the difficulties in identifying the behavior of individual motor units from tremulous muscles. By using novel methods for the decomposition of multichannel surface EMG, we provide a systematic analysis of the discharge properties of motor units in nine ET patients, with concurrent recordings of EEG activity. This analysis allowed us to infer the contribution of common synaptic inputs to motor neurons in ET. Motor unit short-term synchronization was significantly greater in ET patients than in healthy subjects. Furthermore, the strong association between the degree of synchronization and the peak in coherence between motor unit spike trains at the tremor frequency indicated that the high synchronization levels were generated mainly by common synaptic inputs specifically at the tremor frequency. The coherence between EEG and motor unit spike trains demonstrated the presence of common cortical input to the motor neurons at the tremor frequency. Nonetheless, the strength of this input was uncorrelated to the net common synaptic input at the tremor frequency, suggesting a contribution of spinal afferents or secondary supraspinal pathways in projecting common input at the tremor frequency. These results provide the first systematic analysis of the neural drive to the muscle in ET and elucidate some of its characteristics that determine pathological tremulous muscle activity.
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Affiliation(s)
- Juan A Gallego
- Neuroengineering and Cognitive Science Group, Centre for Automation and Robotics, Consejo Superior de Investigaciones Científicas, Arganda del Rey, Spain
| | - Jakob L Dideriksen
- Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
| | - Ales Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Jaime Ibáñez
- Neural Rehabilitation Group, Cajal Institute, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - José L Pons
- Neural Rehabilitation Group, Cajal Institute, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Elan D Louis
- Department of Neurology, College of Physicians and Surgeons, and Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York; and
| | - Eduardo Rocon
- Neuroengineering and Cognitive Science Group, Centre for Automation and Robotics, Consejo Superior de Investigaciones Científicas, Arganda del Rey, Spain; Postgraduate Program, Universidade Federal do Espírito Santo, Vitória, Brazil
| | - Dario Farina
- Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany;
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Schmied A, Descarreaux M. Influence of contraction strength on single motor unit synchronous activity. Clin Neurophysiol 2010; 121:1624-32. [PMID: 20462788 DOI: 10.1016/j.clinph.2010.02.165] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 02/12/2010] [Accepted: 02/17/2010] [Indexed: 10/19/2022]
Abstract
OBJECTIVE The influence of contraction strength on motoneurone (MN) synchrony is poorly documented. With stronger contraction, more common and/or synchronized inputs might contribute to greater MN drive and generate more synchronous firings. This effect might be counterbalanced, however, by a negative impact of MN faster firing rates on synaptic effectiveness. METHODS Pairs of motor units (MUs) were tested at various force levels, in 2-s sequences. MN synchrony was assessed using the index k', the synchronous impulse probability (SIP), and the synchronous impulse frequency (SIF) in cross-correlograms. MU inter-spike interval duration and variability, surface EMG activity and force output were evaluated concurrently. RESULTS Both SIP and SIF increased with contraction strength, whereas k' remained unaffected. Faster firing rates and stronger contraction had the greatest effects on SIF. CONCLUSIONS By testing the same MUs at different force levels, we showed that contraction strength does influence MN synchrony. The enhancement of MU synchrony with stronger contraction suggests an efficient contribution of more common and/or synchronized inputs. SIGNIFICANCE Force output must be controlled when assessing MN synchrony. Normalizing MU synchronous activity per reference spike is preferable to minimize the influence of firing rate. This is particularly relevant for clinical research, in conditions of poorer neuromuscular control.
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Affiliation(s)
- Annie Schmied
- Plasticity and Physiopathology of Movement, UMR 6196 CNRS 31, Chemin Joseph Aiguier, Marseilles 13402 Cedex 20, France.
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Christakos CN, Erimaki S, Anagnostou E, Anastasopoulos D. Tremor-related motor unit firing in Parkinson's disease: implications for tremor genesis. J Physiol 2009; 587:4811-27. [PMID: 19703960 DOI: 10.1113/jphysiol.2009.173989] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Muscle tremors reflect rhythmical motor unit (MU) activities. Therefore, the MU firing patterns and synchrony determine the properties of the parkinsonian force tremor (FT) and the neurogenic components of associated limb tremors. They may also be indicative of the neural mechanisms of tremor genesis which to date remain uncertain. We examined these MU behaviours during isometric contractions of a finger muscle in 19 parkinsonian subjects. Our results reveal that the parkinsonian FT is abnormally large. Like the physiological FT, it is accompanied by in-phase rhythms in all MU activities. However, there exist two important differences. Firstly, the synchrony during the parkinsonian FT is stronger than the normal one and therefore contributes to the FT enhancement. Secondly, the synchronous MU components partly represent rhythmical sequences of spike doublets and triplets whose incidences directly reflect the differences of the MU firing rates to the FT frequency. According to our analyses, the latter frequency coincides with the MU recruitment rate. Consequently, the numerous medium- and small-sized active MUs contribute rhythmical twitch doublets and triplets, i.e. large force pulses, to the parkinsonian FT. The impact of this effect on the FT amplitude is found to predominate over the impact of the augmented synchrony. Importantly, apart from the rule governing the occurrence of doublets/triplets, the mean interspike intervals within such spike events are fairly fixed around 50 ms. Such regularities in MU activities may reflect properties of the neural input underlying the FT, and thus represent a basis for more focused studies of the generator(s) of parkinsonian tremors.
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Affiliation(s)
- C N Christakos
- Laboratory of Systems Physiology, Division of Basic Sciences, Medical School, University of Crete, 71003 Heraklion, Greece.
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Meigal A, Lupandin Y. “Thermoregulation-dependent component” in pathophysiology of motor disorders in Parkinson's disease? PATHOPHYSIOLOGY 2005; 11:187-196. [PMID: 15837163 DOI: 10.1016/j.pathophys.2005.02.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2005] [Revised: 02/11/2005] [Accepted: 02/11/2005] [Indexed: 11/17/2022] Open
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder characterised by motor symptoms (resting tremor, brady- or akinesia and muscle rigidity), and also by postural problems gait disorder and fatigue as well as behavioural and autonomic symptoms, including thermoregulatory impairment. These symptoms are strikingly similar with some motor phenomena, evoked by the whole body cooling, though the primary cause of PD and cold-induced symptoms are apparently different. The review is focused on the hypothesis that thermoregulatory mechanisms are involved in pathophysiology of motor disorders in PD. The comparative analysis provides some examples of analogy between PD and the state of cooling in respect with tremor, muscle hypertonus, postural reactions and impairment of gross and fine muscle performance. This analogy cannot be considered as specific, because in some normal conditions the motor system utilises identical strategy to compensate for motor deterioration, e.g. at fatigue and ageing. However, such motor phenomena, as neuroleptic malignant syndrome and paired discharges of motor units indicate that the "thermoregulation-dependent component" exists in the pathophysiology of PD. Data on the influence of the whole body cooling and heating on muscle performance, rigidity and tremor in PD patients also provide evidence for the involvement of thermoregulatory mechanisms in PD.
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Affiliation(s)
- Alexander Meigal
- Department of Human and Animal Physiology, Petrozavodsk State University, Lenin Street, 33, Petrozavodsk 185002, Republic of Karelia, Russia
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Morita H, Shindo M, Ikeda SI. Paradoxical modulation of tendon tap reflex during voluntary contraction in Parkinson's disease. Clin Neurophysiol 2005; 116:769-74. [PMID: 15792885 DOI: 10.1016/j.clinph.2004.11.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2004] [Revised: 10/19/2004] [Accepted: 11/03/2004] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Inadequate supraspinal modulation of spinal motor control mechanisms such as alpha-gamma coactivation is supposed to cause difficulty in maintaining proper voluntary contraction in Parkinson's disease (PD). METHODS Subjects were 42 patients with PD and 20 normal volunteers. Soleus H-reflex and tendon tap reflex (T-reflex) were recorded. The maximal reflexes (H(max) and T(max)) at rest were recorded first. Next, the stimulus intensities were fixed to obtain a reflex size of around 25% of M(max) at rest for both H- and T-reflexes, and the reflexes were recorded at rest, during tonic plantarflexion (TPF), and at the onset of plantarflexion. RESULTS H(max) at rest was 55% and T(max) 30% in normal subjects, while they were 36 and 31%, respectively, in PD. The size ratio of T(max) and H(max) at rest in PD was larger than normal. In PD, the size of H-reflex increased with TPF as in normal subjects, but T-reflex decreased. These changes in T-reflex were correlated with the grade of rigidity, bradykinesia, and time for 10 m gait. H-reflex had no such correlations. CONCLUSIONS T-reflex was abnormally modulated in PD especially during tonic contraction. SIGNIFICANCE Inappropriate supraspinal modulation of the spinal reflex pathways disturbs motor performance in PD.
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Affiliation(s)
- Hiroshi Morita
- The Third Department of Medicine, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto 390-8621, Japan.
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14
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Piotrkiewicz M, Kudina L, Mierzejewska J. Recurrent inhibition of human firing motoneurons (experimental and modeling study). BIOLOGICAL CYBERNETICS 2004; 91:243-257. [PMID: 15378374 DOI: 10.1007/s00422-004-0507-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2004] [Accepted: 07/08/2004] [Indexed: 05/24/2023]
Abstract
Recurrent inhibition between tonically activated single human motoneurons was studied experimentally and by means of a computer simulation. Motor unit activity was recorded during weak isometric constant-force muscle contractions of brachial biceps (BB) and soleus (SOL) muscles. Three techniques (cross correlogram, frequencygram, and interspike interval analysis) were used to gauge the relations between single motor unit potential trains. Pure inhibition was detected in 5.6% of 54 BB motoneuron pairs and in 5.2% of 43 SOL motoneuron pairs. In 27.8% (BB) and 23.7% (SOL) presumed inhibition symptoms were accompanied by a synchrony peak; 37% (BB) and 48.8% (SOL) exhibited synchrony alone. The demonstrated inhibition was very weak, at the edge of detectability. Computer simulations were based on the threshold-crossing model of a tonically firing motoneuron. The model included synaptic noise as well as threshold and postsynaptic potential (PSP) amplitude change within interspike interval. Inhibition efficiency of the model neurons increased with IPSP amplitude and duration, and with increasing source firing rate. The efficiency depended on target motoneuron interspike interval in a manner similar to standard deviation of ISI. The minimum detectable amplitude estimated in the simulations was about 50 microV, which, compared with the experimental results, suggests that amplitudes of detectable recurrent IPSPs in human motoneurons during weak muscle contractions do not exceed this magnitude. Since recurrent inhibition is known to be progressively depressed with an increase in the force of voluntary contraction, it is concluded that the recurrent inhibition hardly plays any important role in the isometric muscle contractions of constant force.
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Affiliation(s)
- Maria Piotrkiewicz
- Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, 4 Trojdena Str., 02-109 Warsaw, Poland.
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15
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Firing properties of spinal interneurons during voluntary movement. II. Interactions between spinal neurons. J Neurosci 2003. [PMID: 14573541 DOI: 10.1523/jneurosci.23-29-09611.2003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The relationship between the activity of pairs of simultaneously recorded spinal interneurons (INs) in the cervical enlargement was studied in five monkeys performing voluntary wrist movements. The tendency for INs to exhibit similar response properties and synchronized firing was tested as a function of physical distance between the cells and their correlational linkages with forearm muscles. Nearby INs tended to have more similar torque and direction turning (signal correlation) and more similar response profiles (e.g., tonic vs phasic firing) than INs that were far apart. This suggests that nearby cells receive common synaptic input. In contrast, the trial-to-trial covariation of rate around the mean rate for all trials (noise correlation) was independent of the distance between the neurons. Furthermore, signal and noise correlation were independent, suggesting different underlying mechanisms. Surprisingly, spike-to-spike correlation between INs was relatively infrequent and weak, as measured by cross-correlation histograms. In contrast, single motor units (SMUs) in forearm muscles fired more synchronously, particularly for SMUs in single extensor muscles. Either common drive to INs is too weak to induce synchronized firing, or there is an active decorrelation mechanism within IN networks.
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Thomas CK, Butler JE, Zijdewind I. Patterns of pathological firing in human motor units. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 508:237-44. [PMID: 12171117 DOI: 10.1007/978-1-4615-0713-0_29] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
Modulation of motor unit firing rates can change muscle force production. Motor unit firing rates are often reduced during voluntary contractions of muscles influenced by disorders such as stroke or multiple sclerosis, while higher firing rates are typical of muscles innervated by a reduced number of motoneurones. An expanded range of motor unit firing rates is characteristic of disorders in which damage to various systems and neurons occur. Most neuromuscular disorders result in an increase in motor unit discharge variability, in part due to a higher incidence of doublets. In spinal cord injured subjects, long lasting involuntary contractions are common. This activity may reflect persistent inward currents that are revealed due to a lack of (voluntary) inhibition. Some of these changes in motor unit behaviour may actually work to enhance muscle force rather than to reduce it.
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Affiliation(s)
- Christine K Thomas
- The Miami Project to Cure Paralysis and Department of Neurological Surgery, University of Miami School of Medicine, FL 33101, USA.
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17
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Türker KS, Powers RK. Effects of common excitatory and inhibitory inputs on motoneuron synchronization. J Neurophysiol 2001; 86:2807-22. [PMID: 11731538 DOI: 10.1152/jn.2001.86.6.2807] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We compared the effects of common excitatory and inhibitory inputs on motoneuron synchronization by simulating synaptic inputs with injected current transients. We elicited repetitive discharge in hypoglossal motoneurons recorded in slices of rat brain stem using a combination of a suprathreshold injected current step with superimposed noise to mimic the synaptic drive likely to occur during physiological activation. The effects of common inputs to motoneurons were simulated by the addition of a waveform composed of from 6 to 300 trains of current transients designed to mimic excitatory and/or inhibitory synaptic currents. We compared the discharge records obtained in several trials in which the same "common input" waveform was applied repeatedly in the presence of different background noise waveforms. The effects of the common input on motoneuron discharge probability and discharge rate were determined by compiling a cross-correlation histogram (CCHist) and a perispike frequencygram (PSFreq) between the discharges of the same cell at different times. Both excitatory and inhibitory common inputs induced synchronous discharge that was evident by a large central peak in the CCHist. The CCHists produced by common excitatory inputs were characterized by larger and narrower central peaks than those generated by common inhibitory inputs. The PSFreqs produced by common excitatory inputs indicated an increase in the discharge rate of motoneurons around time 0 that coincided with the narrow and large central peak in the CCHist. On the other hand, inhibitory inputs often generated very little, if any, change in the discharge rate around time 0 corresponding with the small and wide central peak in the CCHist. These results suggest that the CCHist indicates the effective strength of the net common input but not its sign. Although correlated changes in discharge rate are often quite different for net excitatory and inhibitory common input, except in some restricted conditions, the PSFreq analysis also cannot be used to unambiguously distinguish net excitation from net inhibition.
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Affiliation(s)
- K S Türker
- Department of Physiology, University of Adelaide, SA 5005, Australia.
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18
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Kleine BU, Blok JH, Oostenveld R, Praamstra P, Stegeman DF. Magnetic stimulation-induced modulations of motor unit firings extracted from multi-channel surface EMG. Muscle Nerve 2000; 23:1005-15. [PMID: 10882994 DOI: 10.1002/1097-4598(200007)23:7<1005::aid-mus2>3.0.co;2-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The noninvasive assessment of motor unit (MU) firing patterns on the basis of topographical information from 128-channel high-density surface electromyography (SEMG) is reported. First, multi-channel MU action potential (MUAP) templates are obtained by clustering detected firing events according to the surface topography of the MUAP. Second, a template-matching algorithm is used to find all firings of a MU, including the superimpositions of MUAPs. From a single recording, the firing pattern of up to five MUs could be derived. The modulation of MU firing by transcranial magnetic stimulation was analyzed in peri-stimulus time histograms. The results are similar to previous results of transcranial magnetic stimulation (TMS) obtained by needle electromyographic (EMG) recordings. The method can be used to investigate MU firing patterns in patients with central motor disorders. An additional advantage of the technique, apart from its noninvasiveness, is the structural and functional information that it provides on the MUs, which is not obtained by needle EMG.
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Affiliation(s)
- B U Kleine
- Department of Clinical Neurophysiology, Institute of Neurology, University Hospital Nijmegen St. Radboud, P.O. Box 9101, NL-6500 HB Nijmegen, The Netherlands
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Kirkwood PA, Munson JB. The incidence of initial doublets in the discharges of motoneurones of two different inspiratory muscles in the cat. J Physiol 1996; 493 ( Pt 2):577-87. [PMID: 8782118 PMCID: PMC1158939 DOI: 10.1113/jphysiol.1996.sp021405] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
1. Trains of action potentials in motoneurones frequently commence with an initial doublet; i.e. a uniquely short interspike interval. Previous authors have speculated on the functional importance of initial doublets. Here we test the hypotheses that these doublets are associated with particular classes of motoneurones or particular physiological conditions. 2. Discharges of inspiratory motoneurones were recorded extracellularly in the thoracic ventral horn of anaesthetized, paralysed cats. Seventy units (35 each with axons in the internal and external intercostal nerves) were classified on the basis of their maximum firing rates, start times in the respiratory cycle and axonal destination. 3. Initial doublets were defined by an interspike interval < 14 ms. Of seventeen units firing initial doublets, fifteen had axons in the external intercostal nerve and two had axons in the internal intercostal nerve. Neither maximum firing rate nor start time during the respiratory cycle predicted the occurrence of doublets. 4. The chemical drive to breathe was manipulated by altering the CO2 content of the inspired gas or by briefly stopping the respiratory pump. Varying the chemical drive to breathe had no consistent effect on the occurrence of initial doublets. 5. These results support the view that initial doublets are part of the normal pattern of discharge of motoneurones. However, because the incidence of doublets does not consistently support previous functional hypotheses, we argue that the occurrence of doublets may not necessarily be dictated by the CNS, but in some circumstances it is an epiphenomenon dependent on the state of the motoneurone, in particular on the statistical properties of its synaptic inputs.
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Affiliation(s)
- P A Kirkwood
- Sobell Department of Neurophysiology, Institute of Neurology, London, UK. P. A. Kirkwood:
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Yue G, Fuglevand AJ, Nordstrom MA, Enoka RM. Limitations of the surface electromyography technique for estimating motor unit synchronization. BIOLOGICAL CYBERNETICS 1995; 73:223-233. [PMID: 7548311 DOI: 10.1007/bf00201424] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Motor unit synchronization was estimated from the surface electromyograms (EMG) of the first dorsal interosseus muscle of human volunteers by a simplified surface-EMG technique (Milner-Brown et al. 1973, 1975). Single motor units were identified from intramuscular recordings and were used to obtain a spike-triggered average of the surface-EMG. The discharge rate of a reference motor unit was controlled at two levels (high and low), and the effect of motor unit activity on the surface-EMG estimate of synchronization was studied in 56 motor units. The surface-EMG estimate of motor unit synchronization was significantly higher when the reference motor unit discharged at the high rate than when it discharged at the low rate. A regression analysis indicated that the synchronization ratio calculated from the surface EMG was significantly correlated with the level of EMG activity in the muscle. Motor unit synchronization was also estimated from surface-EMG measurements that were derived by computer simulation. The simulation permitted manipulation of motor unit activity (discharge rate and recruitment) with a complete absence of synchrony among the units in the pool. The stimulated surface-EMG index was influenced by an artifact associated with signal rectification, and this effect changed non-monotonically with motor unit activity. Furthermore, the increase in the motor unit activity reduced the signal-to-noise ratio of the spike-triggered surface EMG average, and consequently decreased the sensitivity of the surface-EMG index as an estimate of motor unit synchronization. We conclude that the simplified surface-EMG method (Milner-Brown et al. 1973, 1975) does not provide a useful index of motor unit synchronization due to its inability to accurately distinguish the synchronization from methodological effects related to a rectification artifact and variation in the signal-to-noise ratio.
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Affiliation(s)
- G Yue
- Department of Exercise & Sport Sciences, University of Arizona, USA
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Ellaway PH, Davey NJ, Maskill DW, Dick JP. The relation between bradykinesia and excitability of the motor cortex assessed using transcranial magnetic stimulation in normal and parkinsonian subjects. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1995; 97:169-78. [PMID: 7607106 DOI: 10.1016/0924-980x(94)00336-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The response of single motor units in the first dorsal interosseus (FDI) muscle to transcranial magnetic stimulation (TMS) of the motor cortex has been assessed using the post-stimulus time histogram during weak voluntary contraction in patients with parkinsonian symptoms and in age-matched, normal subjects. Patients and subjects were required to maintain the discharge of a motor unit at a steady rate during TMS. Responses were evident in post-stimulus time histograms of motor unit discharges as single or double peaks at mean (+/- S.E.) latencies of 23.4 msec (+/- 0.7) for normal subjects and 24.9 msec (+/- 0.9) for parkinsonian patients. There were no significant differences in latency or tendency to double peaks in the responses of motor units when normal subjects and parkinsonian patients were compared. The group data showed no significant difference between the threshold TMS for modulation of the discharge of single motor units in patients and normal subjects. However, 7 of the 15 parkinsonian patients, but only 1 of 15 normal subjects, had thresholds to TMS greater than or equal to 45% of the maximum output of the magnetic stimulator. Speed of movement was measured by 3 tasks: (1) timed stand/walk/sit, (2) timed peg-board test, (3) frequency of 2-point table taps. In the parkinsonian group there was a positive linear correlation between threshold to TMS and degree of bradykinesia for each individual score and the average score on the tests of speed of movement. This was not evident for the normal group. The results are discussed in the light of current views on the mode of action of TMS. The findings are consistent with the conclusion that parkinsonian patients exhibiting pronounced bradykinesia have a lowered excitability of the motor cortex.
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Affiliation(s)
- P H Ellaway
- Department of Physiology, Charing Cross and Westminster Medical School, London, UK
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22
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Schmied A, Ivarsson C, Fetz EE. Short-term synchronization of motor units in human extensor digitorum communis muscle: relation to contractile properties and voluntary control. Exp Brain Res 1993; 97:159-72. [PMID: 8131826 DOI: 10.1007/bf00228826] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Synchronous activity was studied in relation to the contractile properties of pairs of motor units (MUs) recorded with independent microelectrodes in the right extensor digitorum communis muscle (EDC) of human subjects during isometric finger extension. MU contractile properties were characterized in terms of the rise time and amplitude of twitch tensions extracted by spike-triggered averages of the extension force. Synchronization of MU discharges appeared in the form of narrow central peaks in the cross-correlograms of 35 of 50 pairs of MUs, suggesting the contribution of common last-order neurons. Synchronization peaks tended to be briefer and higher among pairs of MUs with slower and smaller twitches than among pairs of MUs with faster and larger twitches. The higher peaks of slow-contracting MUs suggest a greater effectiveness of the common synaptic inputs. The broader peaks of fast-contracting MUs might reflect an additional synchronization of the inputs to fast MUs at high force levels. The areas of the cross-correlogram peaks were similar for both groups and suggest that under our conditions, about three motoneurons would discharge synchronously for a given motoneuron spike. To test whether the amount of MU synchronization could be altered voluntarily, four subjects attempted to increase or decrease synchrony, using as feedback clicks triggered by coincident firings of the recorded MUs. In nine of 15 conditioning sessions, the magnitudes of the synchronization peaks showed significant changes in the intended direction. These results imply that supraspinal centers can control the relative amount of inputs that contribute to the synchronization of motoneuron discharges during voluntary contraction of EDC.
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Affiliation(s)
- A Schmied
- Department of Physiology and Biophysics, University of Washington, Seattle 98195
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