The second example is the investigation into the genetic basis of an event-related potential, the P50. This is another endophenotype for schizophrenia, in which two stimuli are presented. At interstimulus intervals exceeding 8 s, two event-related potentials are detected. If the second stimulus occurs within 8 s of the first, normal subjects inhibit the response to the second stimulus. Schizophrenia subjects have a deficit in such inhibition, a finding supported by a recent meta-analysis (Bramon et al. 2005). The difference in inhibition is maximal when the second stimulus follows the first by 500 ms (Adler et al. 1982).
