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Normal EEG in Wakefulness and Sleep: Adults and Elderly 

Normal EEG in Wakefulness and Sleep: Adults and Elderly
Chapter:
Normal EEG in Wakefulness and Sleep: Adults and Elderly
Author(s):

Vaishnav Krishnan

, Bernard S. Chang

, and Donald L. Schomer

DOI:
10.1093/med/9780190228484.003.0008
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date: 19 October 2019

The normal adult electroencephalogram (EEG) is not a singular entity, and recognizing and appreciating the various expressions of a normal EEG is vital for any electroencephalographer. During wakefulness, the posterior dominant rhythm (PDR) must display a frequency within the alpha band, although an absent PDR is not abnormal. A symmetrically slowed PDR, excessive theta activity, or any delta activity during wakefulness is abnormal and a biomarker of encephalopathy. Low-voltage EEGs have been associated with a variety of neuropathological states but are themselves not abnormal. During non-rapid eye movement sleep, a normal EEG will display progressively greater degrees of background slowing and amplitude enhancement, which may or may not be associated with specific sleep-related transients. In contrast, the EEG during rapid eye movement sleep more closely resembles a waking EEG (“desynchronized”) in amplitude and background frequencies. Across both wakefulness and sleep, significant asymmetries in background frequencies and amplitude are abnormal.

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