Corticomuscular and intermuscular coherence (CMC, IMC) reflect connectivity between neuronal activity in the motor cortex measured by electroencephalography (EEG) and muscular activity measured by electromyography (EMG), or between activity in different muscles, respectively. There is an ongoing debate on the appropriateness of EMG rectification prior to coherence estimation. This work examines the effects of EMG rectification in CMC and IMC estimation in 20 spinocerebellar ataxia type 2 (SCA2) patients, 16 prodromal SCA2 gene mutation carriers, and 26 healthy controls during a repetitive upper or lower limb motor task. Coherence estimations were performed using the non-rectified raw EMG signal vs. the rectified EMG signal. EMG rectification decreases the level of significance of lower beta-frequency band CMC and IMC values in SCA2 patients and prodromal SCA2 mutation carriers vs. healthy controls, and also results in overall lower coherence values. EMG rectification is detrimental for beta-frequency band CMC and IMC estimation. One likely reason for this effect is distortion of coherence estimation in high-frequency signals, where the level of amplitude cancelation is high.
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Giunti P, Sabbadini G, Sweeney MG, Davis MB, Veneziano L, Mantuano E, et al. The role of the SCA2 trinucleotide repeat expansion in 89 autosomal dominant cerebellar ataxia families. Frequency, clinical and genetic correlates. Brain. 1998;121(Pt 3):459–67.
Velazquez-Perez L, Rodriguez-Labrada R, Garcia-Rodriguez JC, Almaguer-Mederos LE, Cruz-Marino T, Laffita-Mesa JM. A comprehensive review of spinocerebellar ataxia type 2 in Cuba. Cerebellum. 2011;10:184–98.
Velazquez-Perez L, Seifried C, Abele M, Wirjatijasa F, Rodriguez-Labrada R, Santos-Falcon N, et al. Saccade velocity is reduced in presymptomatic spinocerebellar ataxia type 2. Clin Neurophysiol. 2009;120:632–5.
Rodriguez-Labrada R, Velazquez-Perez L, Seigfried C, Canales-Ochoa N, Auburger G, Medrano-Montero J, et al. Saccadic latency is prolonged in Spinocerebellar Ataxia type 2 and correlates with the frontal-executive dysfunctions. J Neurol Sci. 2011;306:103–7.
Rodriguez-Labrada R, Velazquez-Perez L, Ochoa NC, Polo LG, Valencia RH, Cruz GS, et al. Subtle rapid eye movement sleep abnormalities in presymptomatic spinocerebellar ataxia type 2 gene carriers. Mov Disord. 2011;26:347–50.
Velazquez-Perez L, Rodríguez-Labrada R, Torres-Vega R, Medrano Montero J, Vázquez-Mojena Y, Auburger G, et al. Abnormal corticospinal tract function and motor cortex excitability in non-ataxic SCA2 mutation carriers: a TMS study. Clin Neurophysiol. 2016;127:2713–9.
Linnemann C, Tezenas du Montcel S, Rakowicz M, Schmitz-Hubsch T, Szymanski S, Berciano J, et al. Peripheral neuropathy in spinocerebellar ataxia type 1, 2, 3, and 6. Cerebellum. 2016;15:165–73.
Velazquez-Perez L, Voss U, Rodriguez-Labrada R, Auburger G, Canales Ochoa N, Sanchez Cruz G, et al. Sleep disorders in spinocerebellar ataxia type 2 patients. Neurodegener Dis. 2011;8:447–54.
Velazquez-Perez L, Rodriguez-Labrada R, Cruz-Rivas EM, Fernandez-Ruiz J, Vaca-Palomares I, Lilia-Campins J, et al. Comprehensive study of early features in spinocerebellar ataxia 2: delineating the prodromal stage of the disease. Cerebellum. 2014;13:568–79.
Velazquez-Perez L, Tünnerhoff J, Rodriguez-Labrada R, Torres-Vega R, Ruiz-Gonzalez Y, Belardinelli P, et al. Early corticospinal tract damage in prodromal SCA2 revealed by EEG-EMG and EMG-EMG coherence. Clin Neurophysiol. 2017;128:2493–502.
Velazquez-Perez L, Rodriguez-Labrada R, Torres-Vega R, Montero JM, Vazquez-Mojena Y, Auburger G, et al. Central motor conduction time as prodromal biomarker in spinocerebellar ataxia type 2. Mov Disord. 2016;31:603–4.
Velazquez-Perez L, Rodriguez-Labrada R, Torres-Vega R, Ortega-Sanchez R, Medrano-Montero J, Gonzalez-Pina R, et al. Progression of corticospinal tract dysfunction in pre-ataxic spinocerebellar ataxia type 2: a two-years follow-up TMS study. Clin Neurophysiol. 2018;129:895–900.
Fisher KM, Zaaimi B, Williams TL, Baker SN, Baker MR. Beta-band intermuscular coherence: a novel biomarker of upper motor neuron dysfunction in motor neuron disease. Brain. 2012;135:2849–64.
Mima T, Toma K, Koshy B, Hallett M. Coherence between cortical and muscular activities after subcortical stroke. Stroke. 2001;32:2597–601.
Baker MR, Baker SN. The effect of diazepam on motor cortical oscillations and corticomuscular coherence studied in man. J Physiol. 2003;546:931–42.
Caviness JN, Shill HA, Sabbagh MN, Evidente VG, Hernandez JL, Adler CH. Corticomuscular coherence is increased in the small postural tremor of Parkinson’s disease. Mov Disord. 2006;21:492–9.
Jung KY, Cho JH, Ko D, Seok HY, Yoon HK, Lee HJ, et al. Increased corticomuscular coherence in idiopathic REM sleep behavior disorder. Front Neurol. 2012;3:60.
Velazquez-Perez L, Tünnerhoff J, Rodriguez-Labrada R, Torres-Vega R, Belardinelli P, Medrano-Montero J, et al. Corticomuscular coherence: a novel tool to assess the pyramidal tract dysfunction in spinocerebellar ataxia type 2. Cerebellum. 2017;16:602–6.
Farina D, Merletti R, Enoka RM. The extraction of neural strategies from the surface EMG. J Appl Physiol (1985). 2004;96:1486–95.
Farina D, Merletti R, Enoka RM. The extraction of neural strategies from the surface EMG: an update. J Appl Physiol (1985). 2014;117:1215–30.
Myers LJ, Lowery M, O’Malley M, Vaughan CL, Heneghan C, St Clair Gibson A, et al. Rectification and non-linear pre-processing of EMG signals for cortico-muscular analysis. J Neurosci Methods. 2003;124:157–65.
McClelland VM, Cvetkovic Z, Mills KR. Inconsistent effects of EMG rectification on coherence analysis. J Physiol. 2014;592:249–50.
Rosenberg JR, Amjad AM, Breeze P, Brillinger DR, Halliday DM. The Fourier approach to the identification of functional coupling between neuronal spike trains. Prog Biophys Mol Biol. 1989;53:1–31.
Negro F, Keenan K, Farina D. Power spectrum of the rectified EMG: when and why is rectification beneficial for identifying neural connectivity? J Neural Eng. 2015;12:036008.
Mima T, Hallett M. Electroencephalographic analysis of cortico-muscular coherence: reference effect, volume conduction and generator mechanism. Clin Neurophysiol. 1999;110:1892–9.
Farina D, Negro F, Jiang N. Identification of common synaptic inputs to motor neurons from the rectified electromyogram. J Physiol. 2013;591:2403–18.
Halliday DM, Farmer SF. On the need for rectification of surface EMG. J Neurophysiol. 2010;103:3547; author reply 8-9–3547; author reply 3549.
Yao B, Salenius S, Yue GH, Brown RW, Liu JZ. Effects of surface EMG rectification on power and coherence analyses: an EEG and MEG study. J Neurosci Methods. 2007;159:215–23.
Neto OP, Christou EA. Rectification of the EMG signal impairs the identification of oscillatory input to the muscle. J Neurophysiol. 2010;103:1093–103.
McClelland VM, Cvetkovic Z, Mills KR. Rectification of the EMG is an unnecessary and inappropriate step in the calculation of corticomuscular coherence. J Neurosci Methods. 2012;205:190–201.
Seeck M, Koessler L, Bast T, Leijten F, Michel C, Baumgartner C, et al. The standardized EEG electrode array of the IFCN. Clin Neurophysiol. 2017;128:2070–7.
Oostenveld R, Fries P, Maris E, Schoffelen JM. FieldTrip: open source software for advanced analysis of MEG, EEG, and invasive electrophysiological data. Comput Intell Neurosci. 2011;2011:156869.
Halliday DM, Rosenberg JR, Amjad AM, Breeze P, Conway BA, Farmer SF. A framework for the analysis of mixed time series/point process data-theory and application to the study of physiological tremor, single motor unit discharges and electromyograms. Prog Biophys Mol Biol. 1995;64:237–78.
Thomson DJ. Spectrum estimation and harmonic-analysis. Proc IEEE. 1982;70:1055–96.
Press WH, Teukolsky SA, Vetterling WT, Flannery BP. Numerical recipes: the art of scientific computing. New York: Cambridge University Press; 2007.
Maris E, Oostenveld R. Nonparametric statistical testing of EEG- and MEG-data. J Neurosci Methods. 2007;164:177–90.
A preliminary version of this manuscript has been published in a book representing the collection of lectures of the Iberoamerican Congress on Pattern Recognition (CIARP 2019, 28–31 October 2019, Havana, Cuba): Ruiz-Gonzalez Y, Velázquez-Pérez L, Rodríguez-Labrada R, Torres-Vega R, Ziemann U (2019) Role of EMG Rectification for Corticomuscular and Intermuscular Coherence Estimation of Spinocerebellar Ataxia Type 2 (SCA2). In: Nyström I, Hernández Heredia Y, Milián Núñez V (eds.) Progress in Pattern Recognition, Image Analysis, Computer Vision, and Applications. CIARP 2019. Lecture Notes in Computer Science, vol 11896. Springer, Cham. We are grateful to the SCA2 patients, prodromal SCA2 mutation carriers, and the healthy controls for their participation.
This work was carried out while Prof. Luis Velázquez-Pérez was the recipient of a Georg Forster Research Award from the Alexander von Humboldt Foundation (3.4 – KUB/1149891), which funded this research project together with the Cuban Ministry of Public Health. LVP is the Editor-in-Chief of Anales de la Academia de Ciencias de Cuba, Associate Editor of Cerebellum and Ataxias, and Associate Editor of Investigation en Discapacidad. He received grants from the Cuban Ministry of Public Health, and the German Ministry of Education and Research. UZ is the Editor-in-Chief of Clinical Neurophysiology, Deputy Editor of Brain Stimulation, and editorial board member of The Journal of Neuroscience, Experimental Brain Research, Neurological Research and Practice, Nervenarzt. He received grants from the European Research Council, German Research Foundation, German Ministry of Education and Research, Biogen Idec GmbH, Servier, and Janssen Pharmaceuticals NV, and consulting fees from Biogen Idec GmbH, Bayer Vital GmbH, Bristol Myers Squibb GmbH, Pfizer, CorTec GmbH, Medtronic GmbH, all not related to this work.
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Ruiz-Gonzalez, Y., Velázquez-Pérez, L., Rodríguez-Labrada, R. et al. EMG Rectification Is Detrimental for Identifying Abnormalities in Corticomuscular and Intermuscular Coherence in Spinocerebellar Ataxia Type 2. Cerebellum (2020). https://doi.org/10.1007/s12311-020-01149-z
- Corticomuscular coherence
- Intermuscular coherence
- EMG rectification
- Spinocerebellar ataxia type 2