Inhibition of the P50 cerebral evoked response to repeated auditory stimuli: results from the Consortium on Genetics of Schizophrenia.

Inhibition of the P50 evoked electroencephalographic response to the second of paired auditory stimuli has been frequently examined as a neurophysiological deficit in schizophrenia. The Consortium on the Genetics of Schizophrenia (COGS), a 7-site study funded by the National Institute of Mental Health, examined this endophenotype in recordings from 181 probands with schizophrenia, 429 of their first degree relatives, and 333 community comparison control subjects. Most probands were treated with second generation antipsychotic medications. Highly significant differences in P50 inhibition, measured as either the ratio of amplitudes or their difference in response to the two stimuli, were found between the probands and the community comparison sample. There were no differences between the COGS sites for these findings. For the ratio parameter, an admixture analysis found that nearly 40% of the relatives demonstrated deficiencies in P50 inhibition that are comparable to the deficit found in the probands. These results indicate that P50 auditory evoked potentials can be recorded across multiple sites and reliably demonstrate a physiological abnormality in schizophrenia. The appearance of the physiological abnormality in a substantial proportion of clinically unaffected first degree relatives is consistent with the hypothesis that deficits in cerebral inhibition are a familial neurobiological risk factor for the illness.