Figure 4

Spectral shapes and class-related variation at electrode ‘C4’. The spectra (dB) are averaged from 1 Hz resolution FFT of 500 ms windows with Hamming windowing and 250 ms overlap, and staggered (for readability) according to BCI performance with best performers at the top. Width of each line is proportional to mean class difference divided by pooled s.d. Dotted lines represent stagger in the y axis for each patient and 1/f2 spectral roll-off.