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Direct Current Shift Recordings 

Direct Current Shift Recordings
Chapter:
Direct Current Shift Recordings
Author(s):

Shasha Wu

, Vernon L. Towle

, Jonathan P. Miller

, and Hans O. Lüders

DOI:
10.1093/med/9780198714668.003.0012
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date: 23 October 2019

Direct current (DC) shift, also called infraslow activity (IFA), refers to brain activity slower than 0.5 Hz. DC shifts have been shown to have a close temporal and spatial relationship with the conventional seizure onset zone and a smaller field than the conventional ictal electroencephalogram (EEG); therefore, they may have potential value in identifying the epileptogenic zone. Studies have shown that DC shifts can be reliably recorded intracranially from chronic subdural grids or depth electrodes using AC amplifiers with a long time constant (e.g. 10 s) in a compressed viewing window. Although the mechanism remains under debate, most investigators agree that DC shifts are generated by neuroglial cells or neuroglial cells together with pyramidal neurons. With the widespread use of digital EEG recording, DC shifts, together with high-frequency oscillations should be routinely analysed in invasive EEG recordings to provide complementary information in presurgical evaluation of epilepsy.

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