Nonlinear Dynamics of MEG and EMG: Stability and Similarity Analysis
<b>Background:</b> Sensorimotor beta oscillations are critical for motor control and become synchronized with muscle activity during sustained contractions, forming corticomuscular coherence (CMC). Although beta activity manifests in transient bursts, suggesting nonlinear behavior, most...
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2025-06-01
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| author | Armin Hakkak Moghadam Torbati Christian Georgiev Daria Digileva Nicolas Yanguma Muñoz Pierre Cabaraux Narges Davoudi Harri Piitulainen Veikko Jousmäki Mathieu Bourguignon |
| author_facet | Armin Hakkak Moghadam Torbati Christian Georgiev Daria Digileva Nicolas Yanguma Muñoz Pierre Cabaraux Narges Davoudi Harri Piitulainen Veikko Jousmäki Mathieu Bourguignon |
| author_sort | Armin Hakkak Moghadam Torbati |
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| description | <b>Background:</b> Sensorimotor beta oscillations are critical for motor control and become synchronized with muscle activity during sustained contractions, forming corticomuscular coherence (CMC). Although beta activity manifests in transient bursts, suggesting nonlinear behavior, most studies rely on linear analyses, leaving the underlying dynamic structure of brain–muscle interactions underexplored. <b>Objectives:</b> To investigate the nonlinear dynamics underlying beta oscillations during isometric contraction. <b>Methods:</b> MEG and EMG were recorded from 17 right-handed healthy adults performing a 10 min isometric pinch task. Lyapunov exponent (LE), fractal dimension (FD), and correlation dimension (CD) were computed in 10 s windows to assess temporal stability. Signal similarity was assessed using Pearson correlation of amplitude envelopes and the nonlinear features. Burstiness was estimated using the coefficient of variation (CV) of the beta envelope to examine how transient fluctuations in signal amplitude relate to underlying nonlinear dynamics. Phase-randomized surrogate signals were used to validate the nonlinearity of the original data. <b>Results:</b> In contrast to FD, LE and CD revealed consistent, structured dynamics over time and significantly differed from surrogate signals, indicating sensitivity to non-random patterns. Both MEG and EMG signals demonstrated temporal stability in nonlinear features. However, MEG–EMG similarity was captured only by linear envelope correlation, not by nonlinear features. CD was strongly associated with beta burstiness in MEG, suggesting it reflects information similar to that captured by the amplitude envelope. In contrast, LE showed a weaker, inverse relationship, and FD was not significantly associated with burstiness. <b>Conclusions:</b> Nonlinear features capture intrinsic, stable dynamics in cortical and muscular beta activity, but do not reflect cross-modal similarity, highlighting a distinction from conventional linear analyses. |
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| institution | Kabale University |
| issn | 2076-3425 |
| language | English |
| publishDate | 2025-06-01 |
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| record_format | Article |
| series | Brain Sciences |
| spelling | doaj-art-ccdfbff591fa4eeea818d367f040de522025-08-20T03:58:30ZengMDPI AGBrain Sciences2076-34252025-06-0115768110.3390/brainsci15070681Nonlinear Dynamics of MEG and EMG: Stability and Similarity AnalysisArmin Hakkak Moghadam Torbati0Christian Georgiev1Daria Digileva2Nicolas Yanguma Muñoz3Pierre Cabaraux4Narges Davoudi5Harri Piitulainen6Veikko Jousmäki7Mathieu Bourguignon8Laboratory of Functional Anatomy, Faculty of Human Motor Sciences, Universite Libre de Bruxelles (ULB), 1070 Brussels, BelgiumLaboratory of Functional Anatomy, Faculty of Human Motor Sciences, Universite Libre de Bruxelles (ULB), 1070 Brussels, BelgiumLaboratory of Functional Anatomy, Faculty of Human Motor Sciences, Universite Libre de Bruxelles (ULB), 1070 Brussels, BelgiumLaboratory of Functional Anatomy, Faculty of Human Motor Sciences, Universite Libre de Bruxelles (ULB), 1070 Brussels, BelgiumLaboratory of Functional Anatomy, Faculty of Human Motor Sciences, Universite Libre de Bruxelles (ULB), 1070 Brussels, BelgiumDepartment of Physics “Ettore Pancini”, University of Naples Federico II, 80126 Naples, ItalyFaculty of Sport and Health Sciences, University of Jyväskylä, 40014 Jyväskylä, FinlandDepartment of Neuroscience and Biomedical Engineering, Aalto University School of Science, 02150 Espoo, FinlandLaboratory of Functional Anatomy, Faculty of Human Motor Sciences, Universite Libre de Bruxelles (ULB), 1070 Brussels, Belgium<b>Background:</b> Sensorimotor beta oscillations are critical for motor control and become synchronized with muscle activity during sustained contractions, forming corticomuscular coherence (CMC). Although beta activity manifests in transient bursts, suggesting nonlinear behavior, most studies rely on linear analyses, leaving the underlying dynamic structure of brain–muscle interactions underexplored. <b>Objectives:</b> To investigate the nonlinear dynamics underlying beta oscillations during isometric contraction. <b>Methods:</b> MEG and EMG were recorded from 17 right-handed healthy adults performing a 10 min isometric pinch task. Lyapunov exponent (LE), fractal dimension (FD), and correlation dimension (CD) were computed in 10 s windows to assess temporal stability. Signal similarity was assessed using Pearson correlation of amplitude envelopes and the nonlinear features. Burstiness was estimated using the coefficient of variation (CV) of the beta envelope to examine how transient fluctuations in signal amplitude relate to underlying nonlinear dynamics. Phase-randomized surrogate signals were used to validate the nonlinearity of the original data. <b>Results:</b> In contrast to FD, LE and CD revealed consistent, structured dynamics over time and significantly differed from surrogate signals, indicating sensitivity to non-random patterns. Both MEG and EMG signals demonstrated temporal stability in nonlinear features. However, MEG–EMG similarity was captured only by linear envelope correlation, not by nonlinear features. CD was strongly associated with beta burstiness in MEG, suggesting it reflects information similar to that captured by the amplitude envelope. In contrast, LE showed a weaker, inverse relationship, and FD was not significantly associated with burstiness. <b>Conclusions:</b> Nonlinear features capture intrinsic, stable dynamics in cortical and muscular beta activity, but do not reflect cross-modal similarity, highlighting a distinction from conventional linear analyses.https://www.mdpi.com/2076-3425/15/7/681beta powernonlinear dynamicsLyapunov exponentsfractal dimensioncorrelation dimensions |
| spellingShingle | Armin Hakkak Moghadam Torbati Christian Georgiev Daria Digileva Nicolas Yanguma Muñoz Pierre Cabaraux Narges Davoudi Harri Piitulainen Veikko Jousmäki Mathieu Bourguignon Nonlinear Dynamics of MEG and EMG: Stability and Similarity Analysis Brain Sciences beta power nonlinear dynamics Lyapunov exponents fractal dimension correlation dimensions |
| title | Nonlinear Dynamics of MEG and EMG: Stability and Similarity Analysis |
| title_full | Nonlinear Dynamics of MEG and EMG: Stability and Similarity Analysis |
| title_fullStr | Nonlinear Dynamics of MEG and EMG: Stability and Similarity Analysis |
| title_full_unstemmed | Nonlinear Dynamics of MEG and EMG: Stability and Similarity Analysis |
| title_short | Nonlinear Dynamics of MEG and EMG: Stability and Similarity Analysis |
| title_sort | nonlinear dynamics of meg and emg stability and similarity analysis |
| topic | beta power nonlinear dynamics Lyapunov exponents fractal dimension correlation dimensions |
| url | https://www.mdpi.com/2076-3425/15/7/681 |
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