Only the fastest corticospinal fibers contribute to beta corticomuscular coherence
File(s)
Accepted version
Author(s)
Ibanez Pereda, Jaime
Alessandro, Del Vecchio
John C, Rothwell
Stuart, Baker
Dario, Farina
Type
Journal Article
Abstract
Human corticospinal transmission is commonly studied using brain stimulation. However, this approach is biased to activity in the fastest conducting axons. It is unclear whether conclusions obtained in this context are representative of volitional activity in mild-to-moderate contractions. An alternative to overcome this limitation may be to study the corticospinal transmission of endogenously generated brain activity. Here we investigate in humans (N=19; of either sex), the transmission speeds of cortical beta rhythms (∼20Hz) traveling to arm (first dorsal interosseous) and leg (tibialis anterior) muscles during tonic mild contractions. For this purpose, we propose two improvements for the estimation of cortico-muscular beta transmission delays. First, we show that the cumulant density (cross-covariance) is more accurate than the commonly-used directed coherence to estimate transmission delays in bidirectional systems transmitting band-limited signals. Second, we show that when spiking motor unit activity is used instead of interference electromyography, cortico-muscular transmission delay estimates are unaffected by the shapes of the motor unit action potentials. Applying these improvements, we show that descending cortico-muscular beta transmission is only 1-2ms slower than expected from the fastest corticospinal pathways. In the last part of our work, we show results from simulations using estimated distributions of the conduction velocities for descending axons projecting to lower motoneurons (from macaque histological measurements) to suggest two scenarios that can explain fast cortico-muscular transmission: either only the fastest corticospinal axons selectively transmit beta activity, or else the entire pool does. The implications of these two scenarios for our understanding of corticomuscular interactions are discussed.
Date Issued
2021-06-02
Date Acceptance
2021-03-14
Citation
The Journal of Neuroscience, 2021, 41 (22), pp.4867-4879
ISSN
0270-6474
Publisher
Society for Neuroscience
Start Page
4867
End Page
4879
Journal / Book Title
The Journal of Neuroscience
Volume
41
Issue
22
Copyright Statement
© 2021 The Authors. Published under a exclusive license by Society for Neuroscience.
Sponsor
Commission of the European Communities
Grant Number
810346
Subjects
corticomuscular coherence
corticospinal tract
electroencephalography
electromyography
motor units
β rhythm
Neurology & Neurosurgery
11 Medical and Health Sciences
17 Psychology and Cognitive Sciences
Publication Status
Published
Date Publish Online
2021-04-23