Comparison of natural frequencies using ERSP. TMS-evoked EEG responses for a representative stroke patient and one healthy control subject as butterfly plots. Red channels in the butterfly plots highlight the region of interest, i.e. prefrontal, motor, and parietal. The corresponding ERSP patterns (between 5 and 50 Hz) are shown below. Note that the red crosses indicate the region of interest for ERSP analysis and not the stimulation site, which was always the ipsilesional motor cortex. The greyscale graph plotted to the right of each ERSP reveals the power spectrum profile during 20–200 ms after TMS onset. The dotted lines indicate the frequency with maximum power, i.e. the natural frequency. The dashed line indicates the timing of the TMS pulse. The rightpanel shows a bar graph of averaged natural frequencies for each region analysed (*P < 0.05; error bars indicate the standard error).