Non-invasive characterization of motor unit behaviour in pathological tremor

This paper presents the fully automatic identification of motor unit spike trains from high-density surface electromyograms (EMG) in pathological tremor. First, a mathematical derivation is provided to theoretically prove the possibility of decomposing noise-free high-density surface EMG signals into motor unit spike trains with high correlation, which are typical of tremor contractions. Further, the proposed decomposition method is tested on simulated signals with different levels of noise and on experimental signals from 14 tremor-affected patients. In the case of simulated tremor with central frequency ranging from 5 Hz to 11 Hz and signal-to-noise ratio of 20 dB, the method identified ∼8 motor units per contraction with sensitivity in spike timing identification ≥ 95% and false alarm and miss rates ≤ 5%. In experimental signals, the number of identified motor units varied substantially (range 0-21) across patients and contraction types, as expected. The behaviour of the identified motor units was consistent with previous data obtained by intramuscular EMG decomposition. These results demonstrate for the first time the possibility of a fully non-invasive investigation of motor unit behaviour in tremor-affected patients. The method provides a new means for physiological investigations of pathological tremor.

[1]  A. Das Gupta,et al.  Paired response of motor units during voluntary contraction in Parkinsonism , 1963 .

[2]  Damjan Zazula,et al.  Gradient Convolution Kernel Compensation Applied to Surface Electromyograms , 2007, ICA.

[3]  R. Enoka,et al.  Influence of amplitude cancellation on the simulated surface electromyogram. , 2005, Journal of applied physiology.

[4]  M. Brin,et al.  Consensus Statement of the Movement Disorder Society on Tremor , 2008, Movement disorders : official journal of the Movement Disorder Society.

[5]  R. Dengler,et al.  Parameters of human motor unit twitches obtained by intramuscular microstimulation , 1992, Neuromuscular Disorders.

[6]  D. Farina,et al.  Linear transmission of cortical oscillations to the neural drive to muscles is mediated by common projections to populations of motoneurons in humans , 2011, The Journal of physiology.

[7]  Dario Farina,et al.  A Model of the Surface Electromyogram in Pathological Tremor , 2011, IEEE Transactions on Biomedical Engineering.

[8]  F. Richmond,et al.  Compartmentalization of motor units in the cat neck muscle, biventer cervicis. , 1988, Journal of neurophysiology.

[9]  W Wolf,et al.  Discharge pattern of single motor units in basal ganglia disorders , 1986, Neurology.

[10]  Damjan Zazula,et al.  Multichannel Blind Source Separation Using Convolution Kernel Compensation , 2007, IEEE Transactions on Signal Processing.

[11]  C. Christakos,et al.  Tremor‐related motor unit firing in Parkinson's disease: implications for tremor genesis , 2009, The Journal of physiology.

[12]  Dario Farina,et al.  A novel approach for precise simulation of the EMG signal detected by surface electrodes , 2001, IEEE Trans. Biomed. Eng..

[13]  R. Elble.  Origins of tremor , 2000, The Lancet.

[14]  V. Dietz,et al.  Correlation between tremor, voluntary contraction, and firing pattern of motor units in Parkinson's disease , 1974, Journal of neurology, neurosurgery, and psychiatry.

[15]  Dario Farina,et al.  Amplitude cancellation reduces the size of motor unit potentials averaged from the surface EMG. , 2006, Journal of applied physiology.

[16]  S Hesse,et al.  Mechanical implications of paired motor unit discharges in pathological and voluntary tremor. , 1991, Electroencephalography and clinical neurophysiology.

[17]  William J Tyler,et al.  A quantitative overview of biophysical forces impinging on neural function , 2013, Physical biology.

[18]  Bert U Kleine,et al.  Using two-dimensional spatial information in decomposition of surface EMG signals. , 2007, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[19]  C. D. De Luca,et al.  High-yield decomposition of surface EMG signals , 2010, Clinical Neurophysiology.

[20]  D. Farina,et al.  Estimating motor unit discharge patterns from high-density surface electromyogram , 2009, Clinical Neurophysiology.

[21]  D. Farina,et al.  Characterization of Pathological Tremor from Motor Unit Spike Trains , 2011 .

[22]  A. Prochazka,et al.  Attenuation of pathological tremors by functional electrical stimulation I: Method , 2006, Annals of Biomedical Engineering.

[23]  R. Elble.  Tremor: clinical features, pathophysiology, and treatment. , 2009, Neurologic clinics.

[24]  Dario Farina,et al.  A new method for the extraction and classification of single motor unit action potentials from surface EMG signals , 2004, Journal of Neuroscience Methods.

[25]  D. Farina,et al.  Experimental Analysis of Accuracy in the Identification of Motor Unit Spike Trains From High-Density Surface EMG , 2010, IEEE Transactions on Neural Systems and Rehabilitation Engineering.

[26]  E. Henneman.  Relation between size of neurons and their susceptibility to discharge. , 1957, Science.

[27]  J. Benito-León,et al.  Essential tremor: emerging views of a common disorder , 2006, Nature Clinical Practice Neurology.

[28]  J. Hogrel,et al.  Use of surface EMG for studying motor unit recruitment during isometric linear force ramp. , 2003, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[29]  C. Marsden,et al.  Physiological and pathological tremors and rhythmic central motor control. , 2000, Brain : a journal of neurology.

[30]  Naoichi Chino,et al.  Synchronization of single motor units during voluntary contractions in the upper and lower extremities , 2001, Clinical Neurophysiology.