Figure 1.

Schematic overview of the experimental paradigms used in both experiments. A, Experimental flowchart for experiments 1 and 2. Both experiments start with estimating the MVC. In experiment 1, subjects are asked to repeat two blocks of ramp-and-hold force task at 10% MVC separated by a rest period. Experiment 2 continues with two initialization steps in which the online decomposition (“Initialization online decomposition”) and the neurofeedback parameters (“Initialization phase”) are initialized. In “Familiarization phase,” subjects are exposed to the neurofeedback paradigm used during the “Neurofeedback task.” A single block of the “Neurofeedback task” consisted of three trails: β down, β up, and control. The trials were presented in randomized order and separated by a rest period. A minimum of six and a maximum of nine blocks were presented to each subject separated by a rest period while only the last three blocks were used for the analysis. B, Schematic overview of experiment 2. HDsEMG of the tibialis anterior muscle was decomposed into the underlying neural activity while, concurrently, the force because of ankle dorsiflexion and the EEG were recorded. Subjects were asked to navigate a cursor inside a target rectangle by performing ankle dorsiflexion at 10 ± 0.5% MVC. Color of the cursor changed based on the β power in the MU pool. Subjects were asked to keep the cursor inside the force target and change the cursor color to either blue (down-modulation of the β activity) or red (up-modulation of the β activity). In a control condition, no feedback on the β feature was provided and, instead, the cursor turned white when placed inside the target.