Opposing cortical forces: Alpha slowing and sensorimotor mu acceleration during motor-related BCI training
Fig 4
(a) Scatter plots of estimated initial versus final alpha/mu frequency for all participants across the four datasets (Schalk2004, Dreyer2023, Schwarz2020, and Pulferer2022) and (b) PSDs from representative participants and channels, comparing the first and last 5 minutes of the BCI session.
In (a) initial and final frequencies were derived from the fitted robust linear regression of EKF-estimated frequency trajectories by evaluating the regression model at the beginning and at the end of each recording, rather than using instantaneous frequency estimates. For visualization, channels were grouped into anatomically defined regions of interest (ROIs: frontal, sensorimotor, and posterior; with the sensorimotor ROI comprising central and centroparietal electrodes). The identity line is shown for reference; points above the line indicate an increase in alpha/mu frequency over the session, whereas points below indicate a decrease. In (b) the top row illustrates cases where both mu peak frequency and magnitude increase over time, while the bottom row shows a decrease in mu peak frequency accompanied by a magnitude increase. Gray shaded regions indicate the dataset-specific alpha/mu frequency bands used for bandpass filtering.