Oh surprise! fast ripples on scalp EEG

When I heard of the work of Anatol Bragin (Bragin et al., 1999), the recording of ripples (low amplitude brief oscillations at 80 to 250 Hz) and fast ripples (oscillations at 250 to 600 Hz) with extracellular microelectrodes in experimental epileptic rats and in epileptic patients, I thought that we should look in the human intracerebral EEG to see if such high frequencies and such events could be recorded without the complexity and limitations of microelectrodes. I was not optimistic because I thought that the difference in scale between a microelectrode of 40 micrometers in diameter and a clinical intracerebral EEG electrode having a surface of 1 or 2 mm2, 500 to 1000 times larger, was such that an event as local as the High Frequency Oscillations (HFOs) recorded by Bragin would be not be picked up by the much larger clinical electrodes.

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