Ultrafast EEG activities and their significance

Abstract

The true frequency range of the EEG is much broader than it has been assumed and taught for decades. The EEG apparatuses with inkwriting pens recording on paper are incapable of giving us trustworthy tracings beyond 80/sec. With the introduction of digital EEG machines, the exploration of the 60 to 1000 Hz range has already begun in the past few years (but, strangely enough, had been in use during the pioneer age when short photographic EEG recordings were made). The new wave of ultrafast recording began in the domain of somatosensory evoked potentials (SSEP). In the field of EEG (strictly speaking), research work started very recently. Ultrafast EEG activity promises new insights into the electrophysiological basis of epileptic phenomena. Activities from 150- to 500/sec have been noted in recent studies (including personal work). Faster frequencies (500-1000/sec) are likely to play a major role in the electrophysiology of neurocognition and motor initiation. Such EEG-based neurocognitive studies will provide us with in-real-time data and thus outperform PET scanning and functional MRI. Even ultrafast EEG activity has its limitation, which appears to lie around 1000/sec. Faster frequencies (1000-3000 Hz)--recorded mainly with cathode ray oscillography--are probably incompatible with the shortest duration of true field potentials and might be nothing but "neuronal chatter."