The human sensorimotor cortex fosters muscle synergies through cortico-synergy coherence.
In neuromotor control, the dimensionality of complex muscular activation patterns is effectively reduced through the emergence of muscle synergies. Muscle synergies are tailored to task-specific biomechanical needs. Traditionally, they are considered as low-dimensional neural output of the spinal cord and as such their coherent cortico-muscular pathways have remained underexplored in humans. We investigated whether muscle synergies have a higher-order origin, especially, whether they are manifest in the cortical motor network. We focused on cortical muscle synergy representations involved in balance control and examined changes in cortico-synergy coherence accompanying short-term balance training. We acquired electromyography and electro-encephalography and reconstructed cortical source activity using adaptive spatial filters. The latter were based on three muscle synergies decomposed from the activity of nine unilateral leg muscles using non-negative matrix factorization. The corresponding cortico-synergy coherence displayed phase-locked activity at the Piper rhythm, i.e., cortico-spinal synchronization around 40 Hz. Our study revealed the presence of muscle synergies in the motor cortex, in particular, in the paracentral lobule, known for the representation of lower extremities. We conclude that neural oscillations synchronize between the motor cortex and spinal motor neuron pools signifying muscle synergies. The corresponding cortico-synergy coherence around the Piper rhythm decreases with training-induced balance improvement.
['Zandvoort|Coen S|CS|', 'van Dieën|Jaap H|JH|', 'Dominici|Nadia|N|', 'Daffertshofer|Andreas|A|']
D000328:Adult D001696:Biomechanical Phenomena D058256:Brain Waves D058407:Electroencephalography Phase Synchronization D004576:Electromyography D005260:Female D006801:Humans D008137:Longitudinal Studies D008297:Male D009044:Motor Cortex D009046:Motor Neurons D018482:Muscle, Skeletal D013116:Spinal Cord D055815:Young Adult
Muscle synergies Electromyography Electro-encephalography Cortico-muscular connectivity Motor control Postural stability