Chapter 7.Electrophysiological Assessment

Clinical electrophysiological techniques provide methods by which to study cerebral function and dysfunction after traumatic brain injury (TBI). Electroencephalography (EEG) was the first clinical diagnostic tool to provide evidence of abnormal brain function due to TBI (Glaser and Sjaardema 1940) and provided the platform on which sophisticated clinical and research electrophysiological techniques were based, including quantitative EEG (qEEG), topographical EEG (also known as brain electrical activity mapping, or BEAM), evoked and event-related potentials (EPs and ERPs, respectively), magnetoencephalography (MEG), and magnetic source imaging. These techniques permit noninvasive measurement of brain activity with temporal resolution superior to that of other functional neuroimaging methods, including positron emission tomography, single-photon emission computed tomography, and functional magnetic resonance imaging (fMRI) (Arciniegas 2011). Coregistering high-density EEG and/or MEG data with structural neuroimaging (e.g., magnetic resonance imaging [MRI]) enables electrophysiological techniques to “image” brain activity with spatial resolutions comparable to those of fMRI, particularly when interpretation of electrophysiological data is guided by fMRI-determined regions of interest for a particular brain state or function (Im 2007; Inuggi et al. 2010; Lei et al. 2011; Minati et al. 2008).