EEGs and ERPs in bipolar disorders

McAllister-Williams, RH

doi:10.1017/CBO9781107477278.013

EEGs and ERPs in bipolar disorders

Lookup NU author(s): Professor Hamish McAllister-Williams ORCiD

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Abstract

© Cambridge University Press 2016. In the 2006 edition of this book, I noted that, while electroencephalographic (EEG) recordings have been possible for more than one century, there was a relatively small literature regarding their use in bipolar disorder. However, this has changed to some extent over the last few years with the publication of a number of important EEG studies in bipolar disorder. Much of this is driven by the current emphasis on identification of biomarkers and the notion that EEG may offer a number of possibilities in this regard. In addition there is an increasing recognition of the importance of cortical neuronal oscillatory behavior in how the brain functions. EEG offers the opportunity to study this activity in health and disease.This chapter is a selective review of EEG studies in bipolar disorder. It focuses on awake EEG, and sleep EEG research, for example, is not covered. After reviewing the nature of the EEG for the non-specialist, it will consider two issues of relevance to EEGs obtained clinically and then consider some recent key research findings and directions in bipolar disorder. The normal EEG The EEG (together with magnetoencephalography: MEG) has a great strength above any other form of functional imaging, such as functional magnetic resonance imaging (fMRI) or positron emission tomography (PET), in that it records signals that are the direct result of electrical activity of neurons, rather than some “downstream” consequence such as changes in oxygen utilization or blood flow. Partly as a result of this, EEG and MEG have temporal resolutions that are generally an order of magnitude better than fMRI or PET. EEG also has an advantage of being relatively inexpensive, easy to conduct, and well tolerated compared to both fMRI and PET and does not require the use of radioligands as in PET. This facilitates multiple recordings in subjects, such as in cross-over or longitudinal studies. However, the EEG does have some downsides, most notably problems of spatial resolution. This relates to how and what EEG electrodes record. The EEG is generated by inhibitory and excitatory postsynaptic potentials at cortical neuronal synapses. These postsynaptic potentials summate in the cortex and can be recorded at the scalp as EEG.