We were interested in the association between the severity of motor impairment and activity within the beta band (13–30 Hz) and HFO range (150–400 Hz). As our results suggested differential modulations for low and high frequencies within the beta band, we decided to divide it into a range of low-beta and a range of high-beta frequencies and to consider them separately in subsequent analyses. The cut-off frequency between low- and high-beta frequencies was determined based on the histogram of all beta band peak and sub-peak frequencies of the power spectrum, which showed a clear bimodal pattern. A mixture of two normal distributions was fitted and the lowest point between the centre frequencies served as the cut-off frequency. As a result, the low-beta range comprised frequencies between 13 and 20.36 Hz, and the high-beta range between 20.36 and 30 Hz. Mean power and PAC values were obtained by averaging across all frequencies within the specified ranges for low/high-beta and/or HFO.
