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Chapter 6 - Frequencies and Rhythms

from Part I - Basics

Published online by Cambridge University Press:  24 June 2021

Neville M. Jadeja
Neville M. Jadeja
Affiliation:
University of Massachusetts Medical School
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Summary

Frequency is the number of times a waveform occurs per second (one big square). Rhythms in addition to frequency have characteristic features of location, morphology, reactivity, and state dependence. Frequencies are descriptive; rhythms are diagnostic. Clinically relevant frequency bands include delta (0.5-4 Hz), theta (5-7 Hz), alpha (8-13 Hz), and beta (14-30 Hz).The alpha rhythm is an obligate feature of normal wakefulness, and it has considerable variations. Abnormal alpha rhythm may be slow, asymmetric, or unreactive (Bancaud’s phenomena). Excessive beta is associated with sedative medications. In most normal adults, theta and delta rhythms are limited to drowsiness or sleep; their occurrence during wakefulness may be abnormal.

Keywords

frequencyrhythmslocationmorphologyreactivity and state dependencealphabetadeltatheta
Type
Chapter
Information
How to Read an EEG , pp. 32 - 39
Publisher: Cambridge University Press
Print publication year: 2021

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References

Nayak, CS, Anilkumar, AC. EEG normal waveforms. InStatPearls [Internet] 2020 Jun 28.Google Scholar
Tatum, WO IV, Husain, AM, Benbadis, SR, Kaplan, PW. Normal adult EEG and patterns of uncertain significance. Journal of Clinical Neurophysiology. 2006 Jun 1;23(3):194–207.CrossRefGoogle ScholarPubMed

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