P50

What is P50 event-related potential?

Some theories suggest that schizophrenia is associated with cognitive and perceptual deficits, which may be manifested as an inability to “gate” or inhibit irrelevant sensory information, ultimately leading to conscious information overload. The P50 event-related potential is interpreted as a physiological substrate for this deficit. In this paradigm, paired auditory clicks are presented, separated by a 500ms interval. A positive brain potential measured maximally over the vertex is observed using electroencephalogram (EEG) technology, with the vertex 50ms following the stimulus. The first click initiates or conditions the inhibition, while the second (test) click indexes the strength of the inhibition. P50 ratio is quantified as the amplitude of the response to the second click divided by the first. The absence of a reduced response to the second stimulus is interpreted as a failure of inhibitory mechanisms, postulated to represent a defect in sensory gating. Alterations in the P50 gating mechanism is proposed to have potential candidacy as an endophenotype (closer to genetic link than phenotype) for schizophrenia.

What is the evidence on P50 event-related potential?

Moderate to high quality evidence suggests a large effect of increased P50 ratio in people with schizophrenia, and in relatives of people with schizophrenia, when compared to people without schizophrenia. There is also a small effect of decreased S1 amplitude (initial response to stimuli), and a medium effect of increased S2 amplitude (response after repeated exposure to stimuli). Moderate quality evidence suggests P50 latency is not altered. High quality evidence suggests no differences in P50 ratios before versus after treatment with antipsychotics in Chinese people with schizophrenia.

March 2019
Last updated at: 1:18 am, 28th March 2019
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