In electroencephalography, the P50 is an event related potential occurring approximately 50 ms after the presentation of a stimulus, usually an auditory click.
Research has found an abnormal P50 suppression in people with schizophrenia, making it an example of a biological marker for the disorder.
[2][3] Besides schizophrenia, abnormal P50 suppression has been found in patients with traumatic brain injury, recreational drug use, and post-traumatic stress disorder.
The second sound is considered redundant, and so a typical control showing normal sensory gating will produce a reduced response (in wave amplitude) to the second click.
[1] Healthy infants as young as 1 to 4 months old were found to demonstrate a P50 suppression in a paired click task, suggesting that sensory gating is present early in development.