EEG

What is electroencephalography (EEG) and PTSD?

Electroencephalography (EEG) has been used to study changes in brain functioning in people with PTSD. It uses electrodes on the scalp to measure electrical activity from the brain. Quantitative spectral EEG investigates several waveforms so the activity can be measured. However, EEG also gives rise to event related potentials (ERP). These measure the EEG activity directly evoked by a stimulus, often using cognitive or perceptual stimuli.

P300, also referred to as P3, may be the ERP most suitable for the assessment of PTSD. This is because it is well documented, and with the appropriate stimulus can convey information about attention and working memory. P300 refers to a spike in activity approximately 300ms following presentation of a target stimulus. The target stimulus is alternated with standard stimuli to create an ‘oddball’ paradigm, which is most commonly auditory. In this paradigm, the subject must respond only to the infrequent target stimulus rather than the frequent standard stimulus. The amplitude of the P300 response is proportional to the amount of attentional resource devoted to the task and the degree of information processing required. The latency is considered a measure of stimulus classification speed, unrelated to behavioural response time.

What is the evidence for changes in electroencephalography (EEG) readings in people with PTSD?

Moderate quality evidence found large increases in P3a (involuntary attention) amplitude with trauma-related distractors in people with PTSD compared to trauma-exposed people without PTSD. Medium-sized effects showed P3b (voluntary attention) amplitude was also increased with trauma-related distractors in people with PTSD. This was found in frontal and central brain regions, but not in parietal brain regions.

There were medium-sized reductions in P3b amplitude with neutral distractors in people with PTSD compared to healthy controls. There were also small reductions in P3wm (working memory) amplitude with neutral distractors in parietal, but not in frontal and central regions of people with PTSD.

August 2021

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Last updated at: 6:09 pm, 9th December 2021
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