Chapter

Neuronal Synchronization and Thalamocortical Rhythms during Sleep, Wake, and Epilepsy

Igor Timofeev, Maxim Bazhenov, Josée Seigneur and Terrence Sejnowski

in Jasper's Basic Mechanisms of the Epilepsies

Fourth edition

Published on behalf of ©Jeffrey L. Noebels, Massimo Avoli, Michael A. Rogawski, Richard W. Olsen, and Antonio V. Delgado-Escueta

Published in print July 2012 | ISBN: 9780199746545
Published online April 2013 | e-ISBN: 9780199322817 | DOI: http://dx.doi.org/10.1093/med/9780199746545.003.0013

Series: Contemporary Neurology Series

Neuronal Synchronization and Thalamocortical Rhythms during Sleep, Wake, and Epilepsy

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Neuronal synchronization can be divided into long-range and local synchrony. Long-range synchrony is usually detected with two or more electrodes placed some distance apart. It leads to brain activity that is correlated at long distances and may be seen using both local field potential (LFP) and electroencephalogram (EEG) recordings. The first tool (i.e., the LFP) provides a microscopic measure of brain activity summarizing electrical activities of possibly thousands of neurons 1–4. The second type of recording (i.e., the EEG) is a result of changes in electrical activity of multiple sources and ultimately represents activity patterns of large populations of neurons and glial cells in the brain. Local or short-range synchrony can be detected either with one relatively large field potential electrode or with two or more small [intracellular or extracellular unit (action potential) recording] electrodes located at short (less than 1 mm) distances from each other. Synchronous activity of a few neurons does not necessarily lead to measurable EEG signals, but this can be seen using LFP recordings. Because of the low-pass filtering properties of the extracellular media,5 high-frequency electric fields associated with action potentials steeply attenuate and large-amplitude slow LFP and EEG potentials are mainly generated from nearly simultaneously occurring de- and hyperpolarizing events in a large number of neighboring cells with a major contribution from large pyramidal neurons.6

Chapter.  10788 words.  Illustrated.

Subjects: Neurology

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