However, a broader EEG bandwidth has undergone examination by clinical neurophysiologists and researchers and has been found to be clinically significant in certain conditions. Elimination of the lower (infra-slow) or higher (ultra-fast) bands of the EEG frequency spectrum in routine EEG results in loss of several important physiological and pathological meaningful features of brain activity. A full bandwidth EEG (FbEEG) looks at the full, physiologically and clinically relevant waveforms without any trade-off that would favor one frequency band at the expense of another. This analysis occurs through the use of bandpass filtering of the EEG recordings. The conventional bandwidth of clinical EEG focuses on the analysis of waveforms ranging from 0.5Hz to 70Hz. In addition, there are other waveforms such as infra slow oscillations (ISO) (less than 0.5Hz) and high-frequency oscillations (HFOs) (greater than 30Hz) which are outside the conventional bandwidth of clinical EEG but have recently found clinical importance with the advent of digital signal processing. The most commonly studied waveforms include delta (0.5 to 4Hz) theta (4 to 7Hz) alpha (8 to 12Hz) sigma (12 to 16Hz) and beta (13 to 30Hz). However, the most frequently used method to classify EEG waveforms is by the frequency, so much so, that EEG waves are named based on their frequency range using Greek numerals. EEG waveforms may be characterized based on their location, amplitude, frequency, morphology, continuity (rhythmic, intermittent or continuous), synchrony, symmetry, and reactivity.
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