Figure 2.

Experimental approaches for estimating motor neuron and muscle synergies. A, Extraction of motor neuron discharges from HD-sEMG used for computing motor neuron synergies. Muscle synergies were computed using the interference EMG signals (in figure represented for three muscles, respectively, red, blue, and violet). Motor neuron synergy weights represent the contribution of motor neurons into each synergy. Muscle synergy weights represent the contribution of individual muscles. B, The diagram shows how individual excitatory (EXC) and inhibitory (INH) PreM-INs synapse onto multiple motor neurons (MNs) innervating different muscles. Motor neuron pools are denoted by different colors. The computation of motor neuron synergies estimates how the discharges of concurrently active motor neurons can be grouped based on the spatial and temporal spiking patterns (dashed line box). In contrast, muscle synergies are computed based on the spatial and temporal coordination of interference EMG activity patterns (dotted line box).