Rectification and non-linear pre-processing of EMG signals for cortico-muscular analysis

Myers, Lance; Lowery, Madeleine M.; O’Malley, Mark; Vaughan, Christopher L.; Heneghan, Conor; Gibson, A. St Clair; Harley, Yolande X.R.; Sreenivasan, R.

doi:10.1016/s0165-0270(03)00004-9

Cited by 252 publications

(186 citation statements)

References 23 publications

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“…This corresponds to an estimate of the time-varying total power of the EMG signal. The demodulation results in a signal that is similar to full-wave rectification of the EMG signal (Myers et al, 2003). The post-TMS EMG signal was not demodulated, because it was used for determining the MEP.…”

Section: Methodsmentioning

confidence: 99%

Corticospinal Beta-Band Synchronization Entails Rhythmic Gain Modulation

Elswijk¹,

Maij²,

Schoffelen³

et al. 2010

J. Neurosci.

100

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Rhythmic synchronization of neurons in the beta or gamma band occurs almost ubiquitously, and this synchronization has been linked to numerous nervous system functions. Many respective studies make the implicit assumption that neuronal synchronization affects neuronal interactions. Indeed, when neurons synchronize, their output spikes reach postsynaptic neurons together, trigger coincidence detection mechanisms, and therefore have an enhanced impact. There is ample experimental evidence demonstrating this consequence of neuronal synchronization, but beyond this, beta/gamma-band synchronization within a group of neurons might also modulate the impact of synaptic input to that synchronized group. This would constitute a separate mechanism through which synchronization affects neuronal interactions, but direct in vivo evidence for this putative mechanism is lacking. Here, we demonstrate that synchronized beta-band activity of a neuronal group modulates the efficacy of synaptic input to that group in-phase with the beta rhythm. This response modulation was not an addition of rhythmic activity onto the average response but a rhythmic modulation of multiplicative input gain. Our results demonstrate that beta-rhythmic activity of a neuronal target group multiplexes input gain along the rhythm cycle. The actual gain of an input then depends on the precision and the phase of its rhythmic synchronization to this target, providing one mechanistic explanation for why synchronization modulates interactions.

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Section: Methodsmentioning

confidence: 99%

Corticospinal Beta-Band Synchronization Entails Rhythmic Gain Modulation

Elswijk¹,

Maij²,

Schoffelen³

et al. 2010

J. Neurosci.

100

View full text Add to dashboard Cite

show abstract

“…EMG onsets were derived with a generalized likelihood ratio estimator (Micera et al 1998;Stylianou et al 2003), using a test function based on the linear envelope of the EMGs. The EMG traces were full-wave rectified to obtain a linear envelope (Myers et al 2003). For each trial, these EMG traces were averaged over tap events to increase the signal-to-noise ratio.…”

Section: Discussionmentioning

confidence: 99%

Tapping with intentional drift

2008

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When tapping a desired frequency, subjects tend to drift away from this target frequency. This compromises the estimate of the correlation between inter-tap intervals (ITIs) as predicted by the two-level model of Wing and Kristofferson which consists of an internal timer ('clock') and motor delays. Whereas previous studies on the timing of rhythmic tapping attempted to eliminate drift, we compared the production of three constant frequencies (1.5, 2.0, and 2.5 Hz) to the production of tapping sequences with a linearly decreasing inter-tap interval (ITI) (corresponding to an increase in tapping frequency from 1.5 to 2.5 Hz). For all conditions a synchronization-continuation paradigm was used. Tapping forces and electromyograms of the index-finger flexor and extensor were recorded and ITIs were derived yielding interval variability and model parameters, i.e., clock and motor variances. Electromyographic recordings served to study the influence of tapping frequency on the peripheral part of the tap event. The condition with an increasing frequency was more difficult to perform, as evidenced by an increase in deviation from the intended ITIs. In general, tapping frequency affected force level, inter-tap variability, model parameters, and muscle co-activation. Parameters for the condition with a decreasing ITI were comparable to those found in the constant frequency conditions. That is, although tapping with an intentional drift is different from constant tapping and more difficult to perform, the timing properties of both forms of tapping are remarkably similar and described well by the Wing and Kristofferson model.

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“…The same EEG‐EMG filter and re‐referencing method used for JLBA were applied. Additionally, the EMG channels were rectified to enhance the firing rate information of the signal 30. The EEG‐EMG was segmented into nonoverlapping epochs of 1‐second based on the position of the JLBA markers.…”

Section: Methodsmentioning

confidence: 99%

The interrelation between clinical presentation and neurophysiology of posthypoxic myoclonus

Zijl

Beudel

Jong

et al. 2018

Ann Clin Transl Neurol

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ObjectivePosthypoxic myoclonus (PHM) in the first few days after resuscitation can be divided clinically into generalized and focal (uni‐ and multifocal) subtypes. The former is associated with a subcortical origin and poor prognosis in patients with postanoxic encephalopathy (PAE), and the latter with a cortical origin and better prognosis. However, use of PHM as prognosticator in PAE is hampered by the modest objectivity in its clinical assessment. Therefore, we aimed to obtain the anatomical origin of PHM with use of neurophysiological investigations, and relate these to its clinical presentation.MethodsThis study included 20 patients (56 ± 18 y/o, 68% M, 2 survived, 1 excluded) with EEG‐EMG‐video recording. Three neurologists classified PHM into generalized or focal PHM. Anatomical origin (cortical/subcortical) was assessed with basic and advanced neurophysiology (Jerk‐Locked Back Averaging, coherence analysis).ResultsClinically assessed origin of PHM did not match the result obtained with neurophysiology: cortical PHM was more likely present in generalized than in focal PHM. In addition, some cases demonstrated co‐occurrence of cortical and subcortical myoclonus. Patients that recovered from PAE had cortical myoclonus (1 generalized, 1 focal).InterpretationHypoxic damage to variable cortical and subcortical areas in the brain may lead to mixed and varying clinical manifestations of myoclonus that differ of those patients with myoclonus generally encountered in the outpatient clinic. The current clinical classification of PHM is not adequately refined to play a pivotal role in guiding treatment decisions to withdraw care. Our neurophysiological characterization of PHM provides specific parameters to be used in designing future comprehensive studies addressing the potential role of PHM as prognosticator in PAE.

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Rectification and non-linear pre-processing of EMG signals for cortico-muscular analysis

Cited by 252 publications

References 23 publications

Corticospinal Beta-Band Synchronization Entails Rhythmic Gain Modulation

Corticospinal Beta-Band Synchronization Entails Rhythmic Gain Modulation

Tapping with intentional drift

The interrelation between clinical presentation and neurophysiology of posthypoxic myoclonus

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