Neurological Sciences

, Volume 37, Issue 1, pp 37–43 | Cite as

Motor unit firing pattern: evidence for motoneuronal or axonal discharge origin?

  • Lydia P. KudinaEmail author
  • Regina E. Andreeva
Original Article


In neuromuscular diseases, a fasciculation origin is disputed. In some reports, it was suggested that motor unit firing pattern alone is evidence for motoneuronal or axonal fasciculations; namely interspike intervals of approximately 5 ms (doublet intervals) provide evidence for the axonal firing. To clarify the reliability of the suggestion, we compared doublet intervals originated in motoneurons and their axons in healthy humans. For this aim, the H-reflex and M-response of single motor units were elicited during gentle voluntary muscle contractions. Peri-stimulus time histograms allowed reliable judgment about a doublet origin: motoneuronal (at the H-reflex latency) or axonal (at the M-response latency). Significant difference between motoneuronal and axonal doublet intervals was absent. It was concluded that doublet interval alone cannot be the reliable criterion for an axonal firing origin; additional evidences are needed for this conclusion, for example, the appearance of the F-wave. The approach may be used as an additional estimation of mechanisms underlying motor unit diseases.


Human firing motor units Axonal and motoneuronal double discharges Fasciculation potentials Interspike interval analysis 



The authors thank Dr. M. Piotrkiewicz (Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw) who has kindly provided the analysis software.

Compliance with ethical standards

Conflict of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.


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Copyright information

© Springer-Verlag Italia 2015

Authors and Affiliations

  1. 1.Institute for Information Transmission Problems (Kharkevich Institute)Russian Academy of SciencesMoscowRussia

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