26-08-2017, 04:02 PM
Electroencephalography (EEG) is a method of electrophysiological monitoring to record the electrical activity of the brain. It is typically non-invasive, with electrodes placed along the scalp, although sometimes invasive electrodes are used as in electrocorticography. The EEG measures voltage fluctuations resulting from the ionic current within brain neurons. In clinical settings, EEG refers to the recording of spontaneous electrical activity of the brain over a period of time, as recorded from multiple electrodes placed on the scalp. Diagnostic applications are generally focused on event-related potentials or spectral EEG content. The first investigates potential time-locked fluctuations to an event such as start stimulus or push button. The latter analyzes the type of neural oscillations (popularly called "brain waves") that can be observed in EEG signals in the frequency domain.
EEG is most commonly used to diagnose epilepsy, which causes abnormalities in EEG readings. It is also used to diagnose sleep disorders, depth of anesthesia, coma, encephalopathies and brain death. EEG used to be a first-line diagnostic method for tumors, strokes and other focal brain disorders, but this use has declined with the advent of high-resolution anatomical imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). Despite limited spatial resolution, EEG remains a valuable tool for research and diagnosis. It is one of the few available mobile techniques and offers a temporal resolution of milliseconds that is not possible with CT, PET or MRI.
Derivatives of the EEG technique include evoked potentials (PE), which implies the average EEG activity with time closed to the presentation of a stimulus of some type (visual, somatosensory or auditory). Event-related potentials (ERPs) refer to mediated EEG responses that are temporarily blocked for more complex stimulus processing; This technique is used in cognitive science, cognitive psychology and psychophysiological research.
EEG is most commonly used to diagnose epilepsy, which causes abnormalities in EEG readings. It is also used to diagnose sleep disorders, depth of anesthesia, coma, encephalopathies and brain death. EEG used to be a first-line diagnostic method for tumors, strokes and other focal brain disorders, but this use has declined with the advent of high-resolution anatomical imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). Despite limited spatial resolution, EEG remains a valuable tool for research and diagnosis. It is one of the few available mobile techniques and offers a temporal resolution of milliseconds that is not possible with CT, PET or MRI.
Derivatives of the EEG technique include evoked potentials (PE), which implies the average EEG activity with time closed to the presentation of a stimulus of some type (visual, somatosensory or auditory). Event-related potentials (ERPs) refer to mediated EEG responses that are temporarily blocked for more complex stimulus processing; This technique is used in cognitive science, cognitive psychology and psychophysiological research.