1
|
Kukkar KK, Rao N, Huynh D, Shah S, Contreras-Vidal JL, Parikh PJ. Context-dependent reduction in corticomuscular coupling for balance control in chronic stroke survivors. Exp Brain Res 2024:10.1007/s00221-024-06884-x. [PMID: 38963559 DOI: 10.1007/s00221-024-06884-x] [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: 07/28/2023] [Accepted: 06/26/2024] [Indexed: 07/05/2024]
Abstract
Balance control is an important indicator of mobility and independence in activities of daily living. How the functional coupling between the cortex and the muscle for balance control is affected following stroke remains to be known. We investigated the changes in coupling between the cortex and leg muscles during a challenging balance task over multiple frequency bands in chronic stroke survivors. Fourteen participants with stroke and ten healthy controls performed a challenging balance task. They stood on a computerized support surface that was either fixed (low difficulty condition) or sway-referenced with varying gain (medium and high difficulty conditions). We computed corticomuscular coherence between electrodes placed over the sensorimotor area (electroencephalography) and leg muscles (electromyography) and assessed balance performance using clinical and laboratory-based tests. We found significantly lower delta frequency band coherence in stroke participants when compared with healthy controls under medium difficulty condition, but not during low and high difficulty conditions. These differences were found for most of the distal but not for proximal leg muscle groups. No differences were found at other frequency bands. Participants with stroke showed poor balance clinical scores when compared with healthy controls, but no differences were found for laboratory-based tests. The observation of effects at distal but not at proximal muscle groups suggests differences in the (re)organization of the descending connections across two muscle groups for balance control. We argue that the observed group difference in delta band coherence indicates balance context-dependent alteration in mechanisms for the detection of somatosensory modulation resulting from sway-referencing of the support surface for balance maintenance following stroke.
Collapse
Affiliation(s)
- Komal K Kukkar
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, 3875 Holman Street, suite 104R GAR, Houston, TX, 77204, USA
| | - Nishant Rao
- Yale Child Study Center, Yale University, New Haven, Connecticut, USA
| | - Diana Huynh
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, 3875 Holman Street, suite 104R GAR, Houston, TX, 77204, USA
| | - Sheel Shah
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, 3875 Holman Street, suite 104R GAR, Houston, TX, 77204, USA
| | - Jose L Contreras-Vidal
- Laboratory for Noninvasive Brain-Machine Interface Systems, Department of Electrical and Computer Engineering, University of Houston, Houston, TX, USA
| | - Pranav J Parikh
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, 3875 Holman Street, suite 104R GAR, Houston, TX, 77204, USA.
| |
Collapse
|
2
|
Wen L, Watanabe T, Iwamoto Y, Ishii Y, Miyoshi F, Shiraishi K, Date S, Siu KC, Kirimoto H, Takahashi M. Intramuscular and intermuscular coherence analysis while obstacle crossing during treadmill gait. Somatosens Mot Res 2023:1-11. [PMID: 38145411 DOI: 10.1080/08990220.2023.2296516] [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: 06/08/2022] [Accepted: 11/30/2023] [Indexed: 12/26/2023]
Abstract
PURPOSE This study aimed to identify the contribution of the common synaptic drives to motor units during obstacle avoidance, using coherence analysis between a-pair electromyography (EMG) signals (EMG-EMG coherence). MATERIALS AND METHODS Fourteen healthy volunteers walked on a treadmill with and without obstacle avoidance. During obstacle gait, subjects were instructed to step over an obstacle with their right leg while walking that would randomly and unpredictably appear. Surface EMG signals were recorded from the following muscles of the right leg: the proximal and distal ends of tibialis anterior (TAp and TAd), biceps femoris (BF), semitendinosus (ST), lateral gastrocnemius (LG), and medial gastrocnemius (MG). Beta-band (13-30 Hz) EMG-EMG coherence was analysed. RESULTS Beta-band EMG-EMG coherence of TAp-TAd during swing phase and BF-ST during pre and initial swing phase when stepping over an obstacle were significantly higher compared to normal gait (both p < 0.05). Beta-band EMG-EMG coherence of TAp-TAd, BF-ST, and LG-MG during stance phase were not significantly different between the two gait conditions (all p > 0.05). CONCLUSIONS The present findings suggest increased common synaptic drives to motor units in ankle dorsiflexor and knee flexor muscles during obstacle avoidance. It also may reflect an increased cortical contribution to modify the gait patterns to avoid an obstacle.
Collapse
Affiliation(s)
- Lin Wen
- Department of Biomechanics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Tatsunori Watanabe
- Department of Sensorimotor Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
- Department of Health Sciences, Aomori University of Health and Welfare, Aomori, Japan
| | - Yoshitaka Iwamoto
- Department of Biomechanics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Yosuke Ishii
- Department of Biomechanics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Fumiya Miyoshi
- Department of Biomechanics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Kanako Shiraishi
- Department of Biomechanics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Shota Date
- Department of Analysis and Control of Upper Extremity Function, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Ka-Chun Siu
- Physical Therapy Education, College of Allied Health Professions, University of Nebraska Medical Center, Omaha, NE, USA
| | - Hikari Kirimoto
- Department of Sensorimotor Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Makoto Takahashi
- Department of Biomechanics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| |
Collapse
|
3
|
Kukkar KK, Rao N, Huynh D, Shah S, Contreras-Vidal JL, Parikh PJ. Task-dependent Alteration in Delta Band Corticomuscular Coherence during Standing in Chronic Stroke Survivors. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.07.17.23292472. [PMID: 37503096 PMCID: PMC10371181 DOI: 10.1101/2023.07.17.23292472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
Balance control is an important indicator of mobility and independence in activities of daily living. How the changes in functional integrity of corticospinal tract due to stroke affects the maintenance of upright stance remains to be known. We investigated the changes in functional coupling between the cortex and lower limb muscles during a challenging balance task over multiple frequency bands in chronic stroke survivors. Eleven stroke patients and nine healthy controls performed a challenging balance task. They stood on a computerized platform with/without somatosensory input distortion created by sway-referencing the support surface, thereby varying the difficulty levels of the task. We computed corticomuscular coherence between Cz (electroencephalography) and leg muscles and assessed balance performance using Berg Balance scale (BBS), Timed-up and go (TUG) and center of pressure (COP) measures. We found lower delta frequency band coherence in stroke patients when compared with healthy controls under medium difficulty condition for distal but not proximal leg muscles. For both groups, we found similar coherence at other frequency bands. On BBS and TUG, stroke patients showed poor balance. However, similar group differences were not consistently observed across COP measures. The presence of distal versus proximal effect suggests differences in the (re)organization of the corticospinal connections across the two muscles groups for balance control. We argue that the observed group difference in the delta coherence might be due to altered mechanisms for the detection of somatosensory modulation resulting from sway-referencing of the support platform for balance control.
Collapse
Affiliation(s)
- Komal K Kukkar
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, Houston, Texas
| | - Nishant Rao
- Haskins Laboratories, Yale University, New Haven, Connecticut
| | - Diana Huynh
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, Houston, Texas
| | - Sheel Shah
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, Houston, Texas
| | - Jose L Contreras-Vidal
- Laboratory for Noninvasive Brain-Machine Interface Systems, Department of Electrical and Computer Engineering, University of Houston, Houston, Texas
| | - Pranav J Parikh
- Center for Neuromotor and Biomechanics Research, Department of Health and Human Performance, University of Houston, Houston, Texas
| |
Collapse
|
4
|
Sozzi S, Ghai S, Schieppati M. The 'Postural Rhythm' of the Ground Reaction Force during Upright Stance and Its Conversion to Body Sway-The Effect of Vision, Support Surface and Adaptation to Repeated Trials. Brain Sci 2023; 13:978. [PMID: 37508910 PMCID: PMC10377030 DOI: 10.3390/brainsci13070978] [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: 05/11/2023] [Revised: 06/12/2023] [Accepted: 06/18/2023] [Indexed: 07/30/2023] Open
Abstract
The ground reaction force (GRF) recorded by a platform when a person stands upright lies at the interface between the neural networks controlling stance and the body sway deduced from centre of pressure (CoP) displacement. It can be decomposed into vertical (VGRF) and horizontal (HGRF) vectors. Few studies have addressed the modulation of the GRFs by the sensory conditions and their relationship with body sway. We reconsidered the features of the GRFs oscillations in healthy young subjects (n = 24) standing for 90 s, with the aim of characterising the possible effects of vision, support surface and adaptation to repeated trials, and the correspondence between HGRF and CoP time-series. We compared the frequency spectra of these variables with eyes open or closed on solid support surface (EOS, ECS) and on foam (EOF, ECF). All stance trials were repeated in a sequence of eight. Conditions were randomised across different days. The oscillations of the VGRF, HGRF and CoP differed between each other, as per the dominant frequency of their spectra (around 4 Hz, 0.8 Hz and <0.4 Hz, respectively) featuring a low-pass filter effect from VGRF to HGRF to CoP. GRF frequencies hardly changed as a function of the experimental conditions, including adaptation. CoP frequencies diminished to <0.2 Hz when vision was available on hard support surface. Amplitudes of both GRFs and CoP oscillations decreased in the order ECF > EOF > ECS ≈ EOS. Adaptation had no effect except in ECF condition. Specific rhythms of the GRFs do not transfer to the CoP frequency, whereas the magnitude of the forces acting on the ground ultimately determines body sway. The discrepancies in the time-series of the HGRF and CoP oscillations confirm that the body's oscillation mode cannot be dictated by the inverted pendulum model in any experimental conditions. The findings emphasise the robustness of the VGRF "postural rhythm" and its correspondence with the cortical theta rhythm, shed new insight on current principles of balance control and on understanding of upright stance in healthy and elderly people as well as on injury prevention and rehabilitation.
Collapse
Affiliation(s)
| | - Shashank Ghai
- Department of Political, Historical, Religious and Cultural Studies, Karlstad University, 65188 Karlstad, Sweden
- Centre for Societal Risk Research, Karlstad University, 65188 Karlstad, Sweden
| | | |
Collapse
|
5
|
Stokkermans M, Solis-Escalante T, Cohen MX, Weerdesteyn V. Distinct cortico-muscular coupling between step and stance leg during reactive stepping responses. Front Neurol 2023; 14:1124773. [PMID: 36998772 PMCID: PMC10043329 DOI: 10.3389/fneur.2023.1124773] [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: 12/15/2022] [Accepted: 02/20/2023] [Indexed: 03/16/2023] Open
Abstract
Balance recovery often relies on successful stepping responses, which presumably require precise and rapid interactions between the cerebral cortex and the leg muscles. Yet, little is known about how cortico-muscular coupling (CMC) supports the execution of reactive stepping. We conducted an exploratory analysis investigating time-dependent CMC with specific leg muscles in a reactive stepping task. We analyzed high density EEG, EMG, and kinematics of 18 healthy young participants while exposing them to balance perturbations at different intensities, in the forward and backward directions. Participants were instructed to maintain their feet in place, unless stepping was unavoidable. Muscle-specific Granger causality analysis was conducted on single step- and stance-leg muscles over 13 EEG electrodes with a midfrontal scalp distribution. Time-frequency Granger causality analysis was used to identify CMC from cortex to muscles around perturbation onset, foot-off and foot strike events. We hypothesized that CMC would increase compared to baseline. In addition, we expected to observe different CMC between step and stance leg because of their functional role during the step response. In particular, we expected that CMC would be most evident for the agonist muscles while stepping, and that CMC would precede upregulation in EMG activity in these muscles. We observed distinct Granger gain dynamics over theta, alpha, beta, and low/high-gamma frequencies during the reactive balance response for all leg muscles in each step direction. Interestingly, between-leg differences in Granger gain were almost exclusively observed following the divergence of EMG activity. Our results demonstrate cortical involvement in the reactive balance response and provide insights into its temporal and spectral characteristics. Overall, our findings suggest that higher levels of CMC do not facilitate leg-specific EMG activity. Our work is relevant for clinical populations with impaired balance control, where CMC analysis may elucidate the underlying pathophysiological mechanisms.
Collapse
Affiliation(s)
- Mitchel Stokkermans
- Department of Rehabilitation, Radboud University Medical Center for Medical Neuroscience, Nijmegen, Netherlands
- Department of Synchronisation in Neural Systems, Donders Institute for Brain Cognition and Behavior, Nijmegen, Netherlands
| | - Teodoro Solis-Escalante
- Department of Rehabilitation, Radboud University Medical Center for Medical Neuroscience, Nijmegen, Netherlands
| | - Michael X. Cohen
- Department of Synchronisation in Neural Systems, Donders Institute for Brain Cognition and Behavior, Nijmegen, Netherlands
| | - Vivian Weerdesteyn
- Department of Rehabilitation, Radboud University Medical Center for Medical Neuroscience, Nijmegen, Netherlands
- Sint Maartenskliniek Research, Nijmegen, Netherlands
| |
Collapse
|
6
|
Sensorimotor recalibration of postural control strategies occurs after whole body vibration. Sci Rep 2023; 13:522. [PMID: 36627328 PMCID: PMC9831994 DOI: 10.1038/s41598-022-27117-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 12/26/2022] [Indexed: 01/11/2023] Open
Abstract
Efficient postural control results from an effective interplay between sensory feedbacks integration and muscle modulation and can be affected by ageing and neuromuscular injuries. With this study, we investigated the effect of whole-body vibratory stimulation on postural control strategies employed to maintain an upright posture. We explored both physiological and posturography metrics, through corticomuscular and intramuscular coherence, and muscle networks analyses. The stimulation disrupts balance in the short term, but leads to a greater contribution of cortical activity, necessary to modulate muscle activation via the formation of (new) synergies. We also observed a reconfiguration of muscle recruitment patterns that returned to pre-stimulation levels after few minutes, accompanied by a slight improvement of balance in the anterior-posterior direction. Our results suggest that, in the context of postural control, appropriate mechanical stimulation is capable of triggering a recalibration of the sensorimotor set and might offer new perspectives for motor re-education.
Collapse
|
7
|
Sozzi S, Do MC, Schieppati M. Vertical ground reaction force oscillation during standing on hard and compliant surfaces: The “postural rhythm”. Front Neurol 2022; 13:975752. [PMID: 36119676 PMCID: PMC9475112 DOI: 10.3389/fneur.2022.975752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 08/10/2022] [Indexed: 11/14/2022] Open
Abstract
When a person stands upright quietly, the position of the Centre of Mass (CoM), the vertical force acting on the ground and the geometrical configuration of body segments is accurately controlled around to the direction of gravity by multiple feedback mechanisms and by integrative brain centres that coordinate multi-joint movements. This is not always easy and the postural muscles continuously produce appropriate torques, recorded as ground reaction force by a force platform. We studied 23 young adults during a 90 s period, standing at ease on a hard (Solid) and on a compliant support (Foam) with eyes open (EO) and with eyes closed (EC), focusing on the vertical component of the ground reaction force (VGRF). Analysis of VGRF time series gave the amplitude of their rhythmic oscillations (the root mean square, RMS) and of their frequency spectrum. Sway Area and Path Length of the Centre of Pressure (CoP) were also calculated. VGRF RMS (as well as CoP sway measures) increased in the order EO Solid ≈ EC Solid < EO Foam < EC Foam. The VGRF frequency spectra featured prevailing frequencies around 4–5 Hz under all tested conditions, slightly higher on Solid than Foam support. Around that value, the VGRF frequencies varied in a larger range on hard than on compliant support. Sway Area and Path Length were inversely related to the prevailing VGRF frequency. Vision compared to no-vision decreased Sway Area and Path Length and VGRF RMS on Foam support. However, no significant effect of vision was found on VGRF mean frequency for either base of support condition. A description of the VGRF, at the interface between balance control mechanisms and sway of the CoP, can contribute information on how upright balance is maintained. Analysis of the frequency pattern of VGRF oscillations and its role in the maintenance of upright stance should complement the traditional measures of CoP excursions in the horizontal plane.
Collapse
Affiliation(s)
- Stefania Sozzi
- Istituti Clinici Scientifici Maugeri IRCCS, Centro Studi Attività Motorie (CSAM), Pavia, Italy
| | - Manh-Cuong Do
- Complexité, Innovation, Activités Motrices et Sportives (CIAMS), Université Paris-Saclay, Orsay, France
- Complexité, Innovation, Activités Motrices et Sportives (CIAMS), Université d'Orléans, Orléans, France
| | - Marco Schieppati
- Istituti Clinici Scientifici Maugeri IRCCS, Centro Studi Attività Motorie (CSAM), Pavia, Italy
- *Correspondence: Marco Schieppati ;
| |
Collapse
|
8
|
Liang T, Hong L, Xiao J, Wei L, Liu X, Wang H, Dong B, Liu X. Directed network analysis reveals changes in cortical and muscular connectivity caused by different standing balance tasks. J Neural Eng 2022; 19. [PMID: 35767971 DOI: 10.1088/1741-2552/ac7d0c] [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: 02/24/2022] [Accepted: 06/29/2022] [Indexed: 11/12/2022]
Abstract
Objective.Standing balance forms the basis of daily activities that require the integration of multi-sensory information and coordination of multi-muscle activation. Previous studies have confirmed that the cortex is directly involved in balance control, but little is known about the neural mechanisms of cortical integration and muscle coordination in maintaining standing balance.Approach.We used a direct directed transfer function (dDTF) to analyze the changes in the cortex and muscle connections of healthy subjects (15 subjects: 13 male and 2 female) corresponding to different standing balance tasks.Main results.The results show that the topology of the EEG brain network and muscle network changes significantly as the difficulty of the balancing tasks increases. For muscle networks, the connection analysis shows that the connection of antagonistic muscle pairs plays a major role in the task. For EEG brain networks, graph theory-based analysis shows that the clustering coefficient increases significantly, and the characteristic path length decreases significantly with increasing task difficulty. We also found that cortex-to-muscle connections increased with the difficulty of the task and were significantly stronger than the muscle-to-cortex connections.Significance.These results show that changes in the difficulty of balancing tasks alter EEG brain networks and muscle networks, and an analysis based on the directed network can provide rich information for exploring the neural mechanisms of balance control.
Collapse
Affiliation(s)
- Tie Liang
- Key Laboratory of Digital Medical Engineering of Hebei Province, Hebei University, Baoding 071002, People's Republic of China.,Institute of Electric Engineering, Yanshan University, Qinhuangdao, Hebei 066004, People's Republic of China
| | - Lei Hong
- Key Laboratory of Digital Medical Engineering of Hebei Province, Hebei University, Baoding 071002, People's Republic of China
| | - Jinzhuang Xiao
- Key Laboratory of Digital Medical Engineering of Hebei Province, Hebei University, Baoding 071002, People's Republic of China
| | - Lixin Wei
- Institute of Electric Engineering, Yanshan University, Qinhuangdao, Hebei 066004, People's Republic of China
| | - Xiaoguang Liu
- Key Laboratory of Digital Medical Engineering of Hebei Province, Hebei University, Baoding 071002, People's Republic of China
| | - Hongrui Wang
- Key Laboratory of Digital Medical Engineering of Hebei Province, Hebei University, Baoding 071002, People's Republic of China.,Institute of Electric Engineering, Yanshan University, Qinhuangdao, Hebei 066004, People's Republic of China
| | - Bin Dong
- Key Laboratory of Digital Medical Engineering of Hebei Province, Hebei University, Baoding 071002, People's Republic of China.,Development Planning Office, Affiliated Hospital of Hebei University, Baoding 071002, People's Republic of China
| | - Xiuling Liu
- Key Laboratory of Digital Medical Engineering of Hebei Province, Hebei University, Baoding 071002, People's Republic of China
| |
Collapse
|
9
|
Corticomuscular coherence dependence on body side and visual feedback. Neuroscience 2022; 490:144-154. [DOI: 10.1016/j.neuroscience.2022.02.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 02/02/2022] [Accepted: 02/17/2022] [Indexed: 12/26/2022]
|
10
|
Zaback M, Adkin AL, Chua R, Timothy Inglis J, Carpenter MG. Facilitation and habituation of cortical and subcortical control of standing balance following repeated exposure to a height-related postural threat. Neuroscience 2022; 487:8-25. [DOI: 10.1016/j.neuroscience.2022.01.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Revised: 12/23/2021] [Accepted: 01/17/2022] [Indexed: 01/21/2023]
|
11
|
Araújo-Silva F, Santinelli FB, Felipe I Imaizumi L, Silveira APB, Vieira LHP, Alcock L, Barbieri FA. Temporal dynamics of cortical activity and postural control in response to the first levodopa dose of the day in people with Parkinson's disease. Brain Res 2021; 1775:147727. [PMID: 34788638 DOI: 10.1016/j.brainres.2021.147727] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 11/02/2021] [Accepted: 11/10/2021] [Indexed: 11/02/2022]
Abstract
BACKGROUND Our understanding of how balance control responds to levodopa over the course of a single day in people with Parkinson's disease (PD) is limited with the majority of studies focused on isolated comparisons of ON vs. OFF levodopa medication. OBJECTIVE To evaluate the temporal dynamics of postural control following the first levodopa dose of the day during a challenging standing task in a group of people with PD. METHODS Changes in postural control were evaluated by monitoring cortical activity (covering frontal, motor, parietal and occipital areas), body sway parameters (force platform), and lower limb muscle activity (tibialis anterior and gastrocnemius medialis) in 15 individuals with PD during a semi-tandem standing task. Participants were assessed during two 60 second trials every 30 minutes (ON-30 ON-60 etc.) for 3 hours after the first matinal dose (ON-180). RESULTS Compared to when tested OFF-medication, cortical activity was increased across all four regions from ON-60 to ON-120 with early increases in alpha and beta band activity observed at ON-30. Levodopa was associated with increased gastrocnemius medialis activity (ON-30 to ON-120) and ankle co-contraction (ON-60 to ON-120). Changes in body sway outcomes (particularly in the anterior-posterior direction) were evident from ON-60 to ON-120. CONCLUSIONS Our results reveal a 60-minute window within which postural control outcomes may be obtained that are different compared to OFF-state and remain stable (from 60-minutes to 120-minutes after levodopa intake). Identifying a window of opportunity for measurement when individuals are optimally medicated is important for observations in a clinical and research setting.
Collapse
Affiliation(s)
- Fabiana Araújo-Silva
- São Paulo State University (UNESP), School of Sciences, Graduate Program in Movement Sciences, Department of Physical Education, Human Movement Research Laboratory (MOVI-LAB), Bauru, Brazil
| | - Felipe B Santinelli
- São Paulo State University (UNESP), School of Sciences, Graduate Program in Movement Sciences, Department of Physical Education, Human Movement Research Laboratory (MOVI-LAB), Bauru, Brazil; REVAL Rehabilitation Research Center, Faculty of Rehabilitation Sciences, Hasselt University, Hasselt, Belgium
| | - Luis Felipe I Imaizumi
- São Paulo State University (UNESP), School of Sciences, Graduate Program in Movement Sciences, Department of Physical Education, Human Movement Research Laboratory (MOVI-LAB), Bauru, Brazil
| | - Aline P B Silveira
- São Paulo State University (UNESP), School of Sciences, Graduate Program in Movement Sciences, Department of Physical Education, Human Movement Research Laboratory (MOVI-LAB), Bauru, Brazil
| | - Luiz H P Vieira
- São Paulo State University (UNESP), School of Sciences, Graduate Program in Movement Sciences, Department of Physical Education, Human Movement Research Laboratory (MOVI-LAB), Bauru, Brazil
| | - Lisa Alcock
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University Newcastle upon Tyne, UK
| | - Fabio A Barbieri
- São Paulo State University (UNESP), School of Sciences, Graduate Program in Movement Sciences, Department of Physical Education, Human Movement Research Laboratory (MOVI-LAB), Bauru, Brazil.
| |
Collapse
|
12
|
Chen YC, Huang CC, Zhao CG, Hwang IS. Visual Effect on Brain Connectome That Scales Feedforward and Feedback Processes of Aged Postural System During Unstable Stance. Front Aging Neurosci 2021; 13:679412. [PMID: 34366825 PMCID: PMC8339373 DOI: 10.3389/fnagi.2021.679412] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 06/29/2021] [Indexed: 12/04/2022] Open
Abstract
Older adults with degenerative declines in sensory systems depend strongly on visual input for postural control. By connecting advanced neural imaging and a postural control model, this study investigated the visual effect on the brain functional network that regulates feedback and feedforward processes of the postural system in older adults under somatosensory perturbations. Thirty-six older adults conducted bilateral stance on a foam surface in the eyes-open (EO) and eyes-closed (EC) conditions while their center of pressure (COP) and scalp EEG were recorded. The stochastic COP trajectory was modeled with non-linear stabilogram diffusion analysis (SDA) to characterize shifts in postural control in a continuum of feedback and feedforward processes. The EEG network was analyzed with the phase-lag index (PLI) and minimum spanning tree (MST). The results indicated that visual input rebalanced feedforward and feedback processes for postural sway, resulting in a greater critical point of displacement (CD), short-term effective diffusion coefficients (Ds) and short-term exponent (Hs), but the smaller critical point of time (CT) and long-term exponent (Hl) for the EC state. The EC network demonstrated stronger frontoparietal-occipital connectivity but weaker fronto-tempo-motor connectivity of the theta (4–7 Hz), alpha (8–12 Hz), and beta (13–35 Hz) bands than did the EO network. MST analysis revealed generally greater leaf fraction and maximal betweenness centrality (BCmax) and kappa of the EC network, as compared with those of the EO network. In contrast, the EC network exhibited a smaller diameter and average eccentricity than those of the EO network. The modulation of long-term negative feedback gain of the aged postural system with visual occlusion was positively correlated with leaf fraction, BCmax, and kappa, but negatively correlated with the diameter and average eccentricity for all EEG sub-bands. In conclusion, the aged brain functional network in older adults is tuned to visual information for modulating long-term negative feedback of the postural system under somatosensory perturbations.
Collapse
Affiliation(s)
- Yi-Ching Chen
- Department of Physical Therapy, College of Medical Science and Technology, Chung Shan Medical University, Taichung, Taiwan.,Physical Therapy Room, Chung Shan Medical University Hospital, Taichung, Taiwan
| | - Chien-Chun Huang
- Department of Environmental and Occupational Health, National Cheng Kung University, Tainan, Taiwan
| | - Chen-Guang Zhao
- Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Ing-Shiou Hwang
- Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| |
Collapse
|
13
|
Rubega M, Formaggio E, Di Marco R, Bertuccelli M, Tortora S, Menegatti E, Cattelan M, Bonato P, Masiero S, Del Felice A. Cortical correlates in upright dynamic and static balance in the elderly. Sci Rep 2021; 11:14132. [PMID: 34238987 PMCID: PMC8266885 DOI: 10.1038/s41598-021-93556-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 06/24/2021] [Indexed: 02/06/2023] Open
Abstract
Falls are the second most frequent cause of injury in the elderly. Physiological processes associated with aging affect the elderly's ability to respond to unexpected balance perturbations, leading to increased fall risk. Every year, approximately 30% of adults, 65 years and older, experiences at least one fall. Investigating the neurophysiological mechanisms underlying the control of static and dynamic balance in the elderly is an emerging research area. The study aimed to identify cortical and muscular correlates during static and dynamic balance tests in a cohort of young and old healthy adults. We recorded cortical and muscular activity in nine elderly and eight younger healthy participants during an upright stance task in static and dynamic (core board) conditions. To simulate real-life dual-task postural control conditions, the second set of experiments incorporated an oddball visual task. We observed higher electroencephalographic (EEG) delta rhythm over the anterior cortex in the elderly and more diffused fast rhythms (i.e., alpha, beta, gamma) in younger participants during the static balance tests. When adding a visual oddball, the elderly displayed an increase in theta activation over the sensorimotor and occipital cortices. During the dynamic balance tests, the elderly showed the recruitment of sensorimotor areas and increased muscle activity level, suggesting a preferential motor strategy for postural control. This strategy was even more prominent during the oddball task. Younger participants showed reduced cortical and muscular activity compared to the elderly, with the noteworthy difference of a preferential activation of occipital areas that increased during the oddball task. These results support the hypothesis that different strategies are used by the elderly compared to younger adults during postural tasks, particularly when postural and cognitive tasks are combined. The knowledge gained in this study could inform the development of age-specific rehabilitative and assistive interventions.
Collapse
Affiliation(s)
- Maria Rubega
- Department of Neuroscience, Section of Rehabilitation, University of Padua, Padova, 35128, Italy
| | - Emanuela Formaggio
- Department of Neuroscience, Section of Rehabilitation, University of Padua, Padova, 35128, Italy
| | - Roberto Di Marco
- Department of Neuroscience, Section of Rehabilitation, University of Padua, Padova, 35128, Italy
| | - Margherita Bertuccelli
- Department of Neuroscience, Section of Rehabilitation, University of Padua, Padova, 35128, Italy
| | - Stefano Tortora
- Department of Information Engineering, University of Padua, Padova, Italy, 35131
| | - Emanuele Menegatti
- Department of Information Engineering, University of Padua, Padova, Italy, 35131
| | - Manuela Cattelan
- Department of Statistical Sciences, University of Padua, Padova, 35121, Italy
| | - Paolo Bonato
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, Charlestown, Boston, MA, 02129, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, 02115, USA
| | - Stefano Masiero
- Department of Neuroscience, Section of Rehabilitation, University of Padua, Padova, 35128, Italy
- Padova Neuroscience Center, Padova, 35128, Italy
| | - Alessandra Del Felice
- Department of Neuroscience, Section of Rehabilitation, University of Padua, Padova, 35128, Italy.
- Padova Neuroscience Center, Padova, 35128, Italy.
| |
Collapse
|
14
|
Tun NN, Sanuki F, Iramina K. Electroencephalogram-Electromyogram Functional Coupling and Delay Time Change Based on Motor Task Performance. SENSORS 2021; 21:s21134380. [PMID: 34206753 PMCID: PMC8271984 DOI: 10.3390/s21134380] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 06/17/2021] [Accepted: 06/21/2021] [Indexed: 11/21/2022]
Abstract
Synchronous correlation brain and muscle oscillations during motor task execution is termed as functional coupling. Functional coupling between two signals appears with a delay time which can be used to infer the directionality of information flow. Functional coupling of brain and muscle depends on the type of muscle contraction and motor task performance. Although there have been many studies of functional coupling with types of muscle contraction and force level, there has been a lack of investigation with various motor task performances. Motor task types play an essential role that can reflect the amount of functional interaction. Thus, we examined functional coupling under four different motor tasks: real movement, intention, motor imagery and movement observation tasks. We explored interaction of two signals with linear and nonlinear information flow. The aim of this study is to investigate the synchronization between brain and muscle signals in terms of functional coupling and delay time. The results proved that brain–muscle functional coupling and delay time change according to motor tasks. Quick synchronization of localized cortical activity and motor unit firing causes good functional coupling and this can lead to short delay time to oscillate between signals. Signals can flow with bidirectionality between efferent and afferent pathways.
Collapse
Affiliation(s)
- Nyi Nyi Tun
- Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
- Correspondence: (N.N.T.); (K.I.); Tel.: +81-80-9392-9429 (N.N.T.); Fax: +81-92-802-3581 (N.N.T.)
| | - Fumiya Sanuki
- Graduate School of Systems Life Sciences, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan;
| | - Keiji Iramina
- Faulty of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
- Correspondence: (N.N.T.); (K.I.); Tel.: +81-80-9392-9429 (N.N.T.); Fax: +81-92-802-3581 (N.N.T.)
| |
Collapse
|
15
|
Liu J, Sheng Y, Liu H. Corticomuscular Coherence and Its Applications: A Review. Front Hum Neurosci 2019; 13:100. [PMID: 30949041 PMCID: PMC6435838 DOI: 10.3389/fnhum.2019.00100] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 03/04/2019] [Indexed: 12/11/2022] Open
Abstract
Corticomuscular coherence (CMC) is an index utilized to indicate coherence between brain motor cortex and associated body muscles, conventionally. As an index of functional connections between the cortex and muscles, CMC research is the focus of neurophysiology in recent years. Although CMC has been extensively studied in healthy subjects and sports disorders, the purpose of its applications is still ambiguous, and the magnitude of CMC varies among individuals. Here, we aim to investigate factors that modulate the variation of CMC amplitude and compare significant CMC between these factors to find a well-developed research prospect. In the present review, we discuss the mechanism of CMC and propose a general definition of CMC. Factors affecting CMC are also summarized as follows: experimental design, band frequencies and force levels, age correlation, and difference between healthy controls and patients. In addition, we provide a detailed overview of the current CMC applications for various motor disorders. Further recognition of the factors affecting CMC amplitude can clarify the physiological mechanism and is beneficial to the implementation of CMC clinical methods.
Collapse
Affiliation(s)
- Jinbiao Liu
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Yixuan Sheng
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Honghai Liu
- State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China
| |
Collapse
|
16
|
Mouchnino L, Lhomond O, Morant C, Chavet P. Plantar Sole Unweighting Alters the Sensory Transmission to the Cortical Areas. Front Hum Neurosci 2017; 11:220. [PMID: 28539876 PMCID: PMC5423901 DOI: 10.3389/fnhum.2017.00220] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 04/18/2017] [Indexed: 11/23/2022] Open
Abstract
It is well established that somatosensory inputs to the cortex undergo an early and a later stage of processing. The later has been shown to be enhanced when the earlier transmission decreased. In this framework, mechanical factors such as the mechanical stress to which sensors are subjected when wearing a loaded vest are associated with a decrease in sensory transmission. This decrease is in turn associated with an increase in the late sensory processes originating from cortical areas. We hypothesized that unweighting the plantar sole should lead to a facilitation of the sensory transmission. To test this hypothesis, we recorded cortical somatosensory evoked potentials (SEPs) of individuals following cutaneous stimulation (by mean of an electrical stimulation of the foot sole) in different conditions of unweighting when standing still with eyes closed. To this end, the effective bodyweight (BW) was reduced from 100% BW to 40% BW. Contrary to what was expected, we found an attenuation of sensory information when the BW was unweighted to 41% which was not compensated by an increase of the late SEP component. Overall these results suggested that the attenuation of sensory transmission observed in 40 BW condition was not solely due to the absence of forces acting on the sole of the feet but rather to the current relevance of the afferent signals related to the balance constraints of the task.
Collapse
Affiliation(s)
- Laurence Mouchnino
- Aix-Marseille Université, CNRS, Laboratoire de Neurosciences Cognitives, FR 3CMarseille, France
| | - Olivia Lhomond
- Aix-Marseille Université, CNRS, Laboratoire de Neurosciences Cognitives, FR 3CMarseille, France
| | - Clément Morant
- Aix-Marseille Université, CNRS, Laboratoire de Neurosciences Cognitives, FR 3CMarseille, France.,Aix-Marseille Université, CNRS, Institut des Sciences du MouvementMarseille, France
| | - Pascale Chavet
- Aix-Marseille Université, CNRS, Institut des Sciences du MouvementMarseille, France
| |
Collapse
|
17
|
Individual difference in β-band corticomuscular coherence and its relation to force steadiness during isometric voluntary ankle dorsiflexion in healthy humans. Clin Neurophysiol 2016; 128:303-311. [PMID: 28042996 DOI: 10.1016/j.clinph.2016.11.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 11/24/2016] [Accepted: 11/26/2016] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Magnitude of β-band coherent neural activities between the sensorimotor cortex and contracting muscle is known to vary across healthy individuals. To clarify how this variance affects actual motor function, this study examined associations between the corticomuscular coherence (CMC) and force steadiness. METHODS CMC was calculated between scalp electroencephalograms (EEGs) over the sensorimotor cortex and surface electromyograms (EMGs) from the tibialis anterior muscle during tonic isometric voluntary ankle dorsiflexion at 30% of maximal effort in 22 healthy individuals. We calculated the maximal peak of CMC (CMCmax), and examined its relations to some measures of force fluctuation, such as the coefficient of variation (ForceCV), the sum of the power spectral density within 1-4Hz (Forceδ-PSD), 5-14Hz (Forceα-PSD), and 15-35Hz (Forceβ-PSD) bands of force signal. RESULTS In all participants showing significant CMC, CMCmax was observed within the β-band. CMCmax was varied across participants (range, 0.084-0.451), and was correlated significantly and positively with ForceCV (r=0.602, p=0.003), Forceβ-PSD (r=0.637, p=0.001), Forceα-PSD (r=0.647, p=0.001), and Forceδ-PSD (r=0.518, p=0.014). CONCLUSION The magnitude of the CMC between EEG over the sensorimotor cortex and EMG of contracting muscle is associated with the amount of force fluctuation during tonic isometric voluntary ankle dorsiflexion in healthy humans. SIGNIFICANCE CMC may influence an individual's ability to stabilize their muscle force output.
Collapse
|
18
|
Cheron G. How to Measure the Psychological "Flow"? A Neuroscience Perspective. Front Psychol 2016; 7:1823. [PMID: 27999551 PMCID: PMC5138413 DOI: 10.3389/fpsyg.2016.01823] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 11/03/2016] [Indexed: 01/22/2023] Open
Affiliation(s)
- Guy Cheron
- Laboratory of Neurophysiology and Movement Biomechanics, ULB Neuroscience Institute, Université Libre de BruxellesBrussels, Belgium; Laboratory of Electrophysiology, Université de Mons-HainautMons, Belgium
| |
Collapse
|
19
|
Chang CJ, Yang TF, Yang SW, Chern JS. Cortical Modulation of Motor Control Biofeedback among the Elderly with High Fall Risk during a Posture Perturbation Task with Augmented Reality. Front Aging Neurosci 2016; 8:80. [PMID: 27199732 PMCID: PMC4848299 DOI: 10.3389/fnagi.2016.00080] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 03/29/2016] [Indexed: 12/29/2022] Open
Abstract
The cerebral cortex provides sensorimotor integration and coordination during motor control of daily functional activities. Power spectrum density based on electroencephalography (EEG) has been employed as an approach that allows an investigation of the spatial–temporal characteristics of neuromuscular modulation; however, the biofeedback mechanism associated with cortical activation during motor control remains unclear among elderly individuals. Thirty one community-dwelling elderly participants were divided into low fall-risk potential (LF) and high fall-risk potential (HF) groups based upon the results obtained from a receiver operating characteristic analysis of the ellipse area of the center of pressure. Electroencephalography (EEG) was performed while the participants stood on a 6-degree-of-freedom Stewart platform, which generated continuous perturbations and done either with or without the virtual reality scene. The present study showed that when there was visual stimulation and poor somatosensory coordination, a higher level of cortical response was activated in order to keep postural balance. The elderly participants in the LF group demonstrated a significant and strong correlation between postural-related cortical regions; however, the elderly individuals in the HF group did not show such a relationship. Moreover, we were able to clarify the roles of various brainwave bands functioning in motor control. Specifically, the gamma and beta bands in the parietal–occipital region facilitate the high-level cortical modulation and sensorimotor integration, whereas the theta band in the frontal–central region is responsible for mediating error detection during perceptual motor tasks. Finally, the alpha band is associated with processing visual challenges in the occipital lobe.With a variety of motor control demands, increment in brainwave band coordination is required to maintain postural stability. These investigations shed light on the cortical modulation of motor control among elderly participants with varying fall-risk potentials. The results suggest that, although elderly adults may be without neurological deficits, inefficient central modulation during challenging postural conditions could be an internal factor that contributes to the risk of fall. Furthermore, training that helps to improve coordinated sensorimotor integration may be a useful approach to reduce the risk of fall among elderly populations or when patients suffer from neurological deficits.
Collapse
Affiliation(s)
- Chun-Ju Chang
- Department of Biomedical Engineering, National Yang-Ming University Taipei, Taiwan
| | - Tsui-Fen Yang
- Department of Physical Medicine and Rehabilitation, Taipei Veterans General HospitalTaipei, Taiwan; Department of Physical Therapy and Assistive Technology, National Yang-Ming UniversityTaipei, Taiwan
| | - Sai-Wei Yang
- Department of Biomedical Engineering, National Yang-Ming University Taipei, Taiwan
| | - Jen-Suh Chern
- Graduate Institute of Rehabilitation Counseling, National Taiwan Normal University Taipei, Taiwan
| |
Collapse
|
20
|
Role of brain hemispheric dominance in anticipatory postural control strategies. Exp Brain Res 2016; 234:1997-2005. [DOI: 10.1007/s00221-016-4603-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2015] [Accepted: 02/18/2016] [Indexed: 11/26/2022]
|
21
|
Fast Oscillatory Commands from the Motor Cortex Can Be Decoded by the Spinal Cord for Force Control. J Neurosci 2016; 35:13687-97. [PMID: 26446221 DOI: 10.1523/jneurosci.1950-15.2015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Oscillations in the beta and gamma bands (13-30 Hz; 35-70 Hz) have often been observed in motor cortical outputs that reach the spinal cord, acting on motoneurons and interneurons. However, the frequencies of these oscillations are above the muscle force frequency range. A current view is that the transformation of the motoneuron pool inputs into force is linear. For this reason possible roles for these oscillations are unclear, since if this transformation is linear, the high frequencies in the motoneuron inputs (e.g., 20 Hz from pyramidal tract neurons) would be filtered out by the muscle and have no effect on force control. A biologically inspired mathematical model of the neuromuscular system was used to investigate the impact of high-frequency cortical oscillatory activity on force control. The model simulation results evidenced that a typical motoneuron pool has a nonlinear behavior that enables the decoding of a high-frequency oscillatory input. An input at a single frequency (e.g., beta band) leads to an increase in the steady-state force generated by the muscle. When the input oscillation was amplitude modulated at a given low frequency, the force oscillated at this frequency. In both cases, the mechanism relies on the recruitment and derecruitment of motor units in response to the oscillatory descending drive. Therefore, the results from this study suggest a potential role in force control for cortical oscillations at frequencies at or above the beta band, despite the low-pass behavior of the muscles. SIGNIFICANCE STATEMENT The role of cortical oscillations in motor control has been a long-standing question, one view being that they are an epiphenomenon. Fast oscillations are known to reach the spinal cord, and hence they have been thought to affect muscle behavior. However, experimental limitations have hampered further advances to explain how they could influence muscle force. An approach for such a challenge was adopted in the present research: to study the problem through computer simulations of an advanced biologically compatible mathematical model. Using such a model, we found that the well-known mechanism of recruitment and derecruitment of the spinal cord motoneurons can allow the muscle to respond to cortical oscillations, suggesting that these oscillations are not epiphenomena in motor control.
Collapse
|