Intermuscular Coherence is a measure to quantify correlations between the activity of two muscles, which is often assessed using electromyography. The correlations in muscle activity are quantified in frequency domain,[1] and therefore referred to as intermuscular coherence.[2]
History
The synchronisation of motor units of a single muscle in animals and humans are known for decades. The early studies that investigated the relationship of EMG activity used time-domain cross-correlation to quantify common input.[3][4] The explicit notion of presence of synchrony between motor units of two different muscles was reported at a later time.[5] In the 1990s, coherence analysis was introduced to examine in frequency content of common input.[2]
Physiology
Intermuscular coherence can be used to investigate the neural circuitry involved in motor control. Correlated muscle activity indicates common input to the motor unit pools of both muscles[6][7] and reflects shared neural pathways (including cortical, subcortical and spinal) that contribute to muscle activity and movement.[8] The strength of intermuscular coherence is dependent on the relationship between muscles and is generally stronger between muscle pairs that are anatomically and functionally closely related.[9][10] Intermuscular coherence can therefore be used to identify impairments in motor pathways.[11][12]
^Rosenberg, J. R., Amjad, A. M., Breeze, P., Brillinger, D. R., & Halliday, D. M. (1989). The Fourier approach to the identification of functional coupling between neuronal spike trains. Progress in Biophysics and Molecular Biology, 53(1), 1–31.
^ abFarmer, S. F., Bremner, F. D., Halliday, D. M., Rosenberg, J. R., & Stephens, J. A. (1993). The frequency content of common synaptic inputs to motoneurones studied during voluntary isometric contraction in man. The Journal of Physiology, 470(1), 127–155
^Person, R. S.; Kudina, L. P. (1968). "Cross-correlation of electromyograms showing interference patterns". Electroencephalography and Clinical Neurophysiology. 25 (1): 58–68. doi:10.1016/0013-4694(68)90087-4. ISSN0013-4694. PMID4174784.
^Bremner, F. D., Baker, J. R., & Stephens, J. A. (1991). Correlation between the discharges of motor units recorded from the same and from different finger muscles in man. The Journal of Physiology, 432(1), 355–380. http://doi.org/10.1113/jphysiol.1991.sp018389
