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Updated: Oct 3, 2025
Simultaneous Intracellular Recording of a Lumbar Motoneuron and the Force Produced by its Motor Unit in the Adult Mouse In vivo
Published on: December 5, 2012
Electrical cross-sectional imaging of human motor units in vivo
Stuart Maitland1, Enrique Escobedo-Cousin2, Ian Schofield1
1Translational and Clinical Research Institute, Henry Wellcome Building for Neuroecology, Newcastle University, NE2 4HH, UK.
Objectives:
In many neuromuscular diseases, weakness results from a disruption in muscle fibres' arrangement within a motor unit. Limitations in current techniques mean that the spatial distribution of fibres in human motor units remains unknown.
Methods:
A flexible multi-channel electrode was developed and bonded to a clinical electromyography (EMG) needle. Muscle fibre action potentials were localised using a novel deconvolution method. This was tested using simulated data, and in recordings collected from the tibialis anterior muscle of healthy subjects.
Results:
Simulated data indicated good localisation reliability across all sections of the electrode except the end sections. A corrected fibre density was estimated up to 1.4 fibres/mm2. Across five recordings from three individuals, between 4 and 14 motor units were detected. Between 1 and 20 muscle fibres were localised per motor unit within the electrode detection area, with up to 220 muscle fibres localised per recording, with overlapping motor unit territories.
Conclusions:
We provide the first direct evidence that human motor units spatially overlap, as well as data related to the spatial arrangement of muscle fibres within a motor unit.
Significance:
As well as providing insights into normal human motor physiology, this technology could lead to faster and more accurate diagnosis in patients with neuromuscular diseases.
