High-frequency oscillations (HFOs) occurring at the same time as spikes (a, c, e, and possibly f) and outside of spikes (b and d). The black trace is the original EEG. The red and blue traces result from high-pass filtering at 80 and 250 Hz, respectively. The amplitude of these traces has been multiplied by 10 to facilitate viewing (Source: http://www.mni.mcgill.ca/, permission obtained from author).
