Demodulation of e.m.g.s. of pathological tremours. Development and testing of a demodulator for clinical use

  • H. L. Journée
  • J. van Manen
  • J. J. van der Meer


In clinical tremour recordings, e.m. g. signals allow highly localised recordings to be made. This is in contrast to mechanical recordings which have been used extensively in the past. E.m.g. recordings make it possible to distinguish between tremours in agonist and antagonist muscle groups. E.m.g. signals, however, have poor signal-to-noise characteristics. In this study the e.m.g. of pathological tremours is considered as amplitude-modulated noise. The design of a demodulator and some tests of its performance are described. The visual detectability of an undemodulated tremour e.m.g., when written on a polygraphic recorder, is expressed as a modulation depth, and is about 60%. This improves after demodulation to a level of 20%. The placement of the electrodes and filtering of the e.m.g. signal will influence the shape of the power spectrum of the e.m.g. itself. However, these factors do not critically influence the demodulated tremour e.m.g. For this reason also a demodulator is a useful instrument for recording clinical tremours.


Demodulator Electromyography Tremours 


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  1. Brumlik, J. andYap, C. B. (1969)Normal tremor: a comparative study. C. C. Thomas, Springfield, Illinois.Google Scholar
  2. Brumlik, J. andMeans, E. D. (1969) Tremorine-tremor, shivering and acute cerebellar ataxion in the adult and child. A comparative study.Brain,92, 157–190.Google Scholar
  3. Calne, D. B. andLader, M. H. (1969) Electromyographic studies of tremor using an averaging computer.Electroenc. Clin. Neurophysiol.,26, 86–92.CrossRefGoogle Scholar
  4. Hof, A. L. andvan den Berg, J. (1977) Linearity between the weighted sum of the human triceps surae and the total torque.J. Biomechanics,10, 529–539.CrossRefGoogle Scholar
  5. Hof, A. L. (1980) EMG to force processing. Thesis, Groningen Veenstra-Visser.Google Scholar
  6. Jung, R. (1941) Physiologische Untersuchungen über den Parkinsontremor und andere Zitterformen beim Menschen.Z. Ges. Neurol. Psychiatr.,173, 263–332.CrossRefGoogle Scholar
  7. Kreifeldt, J. G. (1969) An analysis of surface detected EMG as an amplitude modulated noise and its logarithmic detection. 8th ICMBE, Chicago.Google Scholar
  8. Kwatny, E., Thomas, D. H. andKwatny, H. G. (1970) An application of signal processing techniques to study myoelectric signals.IEEE Trans.,BME-17, (4).Google Scholar
  9. Lindström, L. (1970) On the frequency spectrum of EMG signals. Report, Depts. Appl. Electr. and Clin. Neurophysiol., Chalmers University, Götenburg, 7:70.Google Scholar
  10. Lindström, L. (1973) A model describing the power spectrum of myoelectric signals. Part 1. Single fibre signals., 5:73.Google Scholar
  11. Marshall, J. (1968) Tremor. In:Handbook of neurology, Vinken Bruin, North Holland, Amsterdam, Chap. 31.Google Scholar
  12. Morgan, M. H., Hewer, R. L. andCooper, R. (1975) Intention-tremor: a method of measurement.J. Neurol. Neurosurg. & Psychiatr.,38, 353–358.Google Scholar
  13. Pelnár, J. (1913)Das Zittern. Seine Erscheinungsformen, seine Pathogenese und Klinische Bedeutung. J. Springer, Berlin.Google Scholar
  14. Sältzer, M. (1975) Model zur beschreibung des Tremors.Europ. J. Appl. Physiol.,34, 19–31.CrossRefGoogle Scholar
  15. Sato, H. (1976a) Power spectral analysis of surface electromyograms during isometric contraction.J. Anthrop. Soc. Nippon.,84, 1–14.Google Scholar
  16. Sato, H. (1976b) Some factors affecting the power spectra of surface electromyograms in isometric contractions.,84, 105–113.Google Scholar
  17. Sato, H. (1977) Electromyographic study of muscular fatigue in sustained isometric contractions.,85, 83–94.Google Scholar
  18. Schwabb, R. S. andCobb, S. (1939) Simultaneous electromyograms and electroencephalograms in paralysis agitans.J. Neurophysiol.,2, 36–41.Google Scholar
  19. Shwedyk, E. R., Balashubramanian, R. andScott, R. N. (1977) A non stationary model for the electromyogram.IEEE Trans.,BME-24, 417–424.Google Scholar

Copyright information

© IFMBE 1983

Authors and Affiliations

  • H. L. Journée
    • 1
  • J. van Manen
    • 2
  • J. J. van der Meer
    • 3
  1. 1.Department of NeurosurgeryState UniversityGröningenThe Netherlands
  2. 2.Wilhelmina GasthuisAmsterdamThe Netherlands
  3. 3.Department of NeurosurgeryState UniversityGröningenThe Netherlands

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