Decomposition of Compound Muscle Action Potentials

Period: 1.7.2019―30.6.2022

The Partners

  • Science and Research Centre Koper
  • Faculty of Electrical Engineering and Computer Science
  • Faculty of Medicine

Problem description

Central nervous system modulates muscle force by controlling the number of active functional units of a muscle, so called motor units (MUs) and their firing rates. Every motor unit is innervated by a motor neuron that transmits the neural commands from the central nervous system. In many different healthy and pathological conditions, the neuromuscular junctions remain stable, thus, the activity of individual motor units reflects the neural codes sent down the motor neurons. Skeletal muscles spatially spread and amplify these neural codes, supporting their acqusition with needle and surface electrodes mounted at the skin above the investigated muscle. Recorded electrical activity of skeletal muscles is called electromyogram (EMG).

EMG is a highly interferential signal but can be decomposed by computer-aided techniques into contributions of individual motor units. This methodology provides a unique insight into the neural codes governing the human movements and has been under intense investigation in the fields of neurophysiology, neurology, rehabilitation, prosthetics, ergonomics and advanced human-machine interfaces. Information on the activity of motor units has also contributed to better understanding of pathologies such as stroke and pathological tremor and basic neurophysiologic research of reflexes and human aging.

Compound muscle action potential (CMAP) is sum of motor unit action potentials (MUAPs) in the muscle, elicited by electrical or mechanical stimulation of nerves and muscles or by transcranial magnetic (TMS) or electric stimulation (TES) of motor cortex. In the latter case, CMAP is also called motor evoked potential (MEP). CMAP analysis is routinely applied in clinical and neurophysiologic studies to non-invasively assess the functional status of a human motor system in vivo, to evaluate motor tract integrity and quantify responses of neuromuscular circuits to training, rehabilitation and degeneration due to various neuromuscular disorders, to study corticospinal excitability, to assess motor nerve conduction properties, fatigue and biomechanical responses in skeletal muscles.

Opis rešitev

In the project, we aim to develop new computer-aided and fully automated techniques for EMG-based CMAP decomposition to contributions of different motor unit types (type I, II) and to individual MUAPs. In particular, we will design and implement new methodologies for:

  • Analysis of conduction velocity distribution in supramaximal and submaximal CMAPs;
  • Quantification of muscle crosstalk contamination in CMAP, especially in areas with several nearby muscles;
  • Decomposition of supramaximal and submaximal CMAPs into contributions of slow and fast motor units
  • Decomposition of supramaximal and submaximal CMAPs into individual MUAPs;
  • Identification of motor unit firing patterns in CMAPs;
  • Comparison of individual motor unit behaviour in stimulated and voluntary contractions.