What is an EEG?
Electroencephalogram (EEG) is a test used to record electrical activity from the brain’s cortex. Through electrodes placed on different regions of the scalp, it records changes in voltage as ions spontaneously move across the membrane of the neurons.Similar to EEG, evoked potentials are also recordings of the brain’s electrical activity. However, evoked potentials are produced by a stimulus (e.g. visual or auditory stimuli) instead of the spontaneous recording obtained through EEG.
Event related potentials (ERP) hold some promise in neuropsychiatric research but have little clinical relevance. These recordings, even smaller than EEG and evoked potential waveforms, are time-locked waveforms following a stimulus and its corresponding neurobehavioral response.
Can an EEG Test Find Depression?
In general, all of these waveforms offer non-specific findings as it relates to psychological conditions. For example, a depressed patient quite frankly will have normal EEG, evoked potentials, and event related potentials if no confounding structural lesion exists.In contrast, there is anecdotal evidence that patients with depression can have certain timed recordings with lower amplitude (i.e. P300 waveform). Emotions originate from deeper, more primitive areas of the brain, such as the limbic system.
However, they reach our conscious through the cortex. Therefore, theoretically, scalp electrodes can record waveforms related to feelings.
But since these recordings are generated through signal averaging, electrodes placed closer to the structures where emotions are generated may be offer more sensitive and specific recordings.
