[P50 component of auditory evoked potentials in persons with schizophrenia and their first degree relatives].

UNLABELLED

A pair of auditory stimuli presented in a 0.5 second interval cause a reduction of the P50 auditory evoked potential (P50 AEP) amplitude after the second stimuli in the pair. In some, but not all studies, a clear deficit of such P50 AEP gating was observed in schizophrenic patients. It was present constantly irrespective of the clinical state. This deficit was also found in first degree relatives of schizophrenic patients. However the results of the studies, as well as their interpretation remain controversial.

AIM

To differentiate between P50 AEP in groups of schizophrenic patients, their healthy first degree relatives, as well as those in the control group.

METHOD

50 schizophrenic patients (ICD-10 criteria (DCR)) in early clinical improvement phase, 26 healthy first degree relatives, as well sa 46 healthy individuals with no psychiatric illness in the self-report and family history. All those studied were stimulated with 120 pairs of auditory stimuli (clicks), each of duration 2 mseconds and a sound intensity of 73 dB, with a 500 msecond interval between the stimuli in a pair (S1 and S2) every 8 seconds. A high-end filter of 70 Hz and low-end filter of 10 Hz were applied. Bio potentials were recorded from the head apex, relatively to the mastoid process (A1 + A2). Eyeball-movement artefacts were registered from the Fp1-A1 and Fp2-A2 potentials. The registered bio potentials were evened on-line.

RESULTS

Relative (i.e. evaluated in relation to the potential after S1) lowering of the P50 potential after S2 was the most significant in the healthy control group (75%), in the other groups usually there was an increase in the S2 potential--higher in the schizophrenic patient group (-45%) and lower in their first degree relatives (-11%).

CONCLUSIONS

(1) Healthy individuals suppressed the neurophysiologic response to the second pair of auditory stimuli much more than the schizophrenic patients and their healthy families. (2) No difference was seen in the suppression of the response between the schizophrenic patients and their first degree relatives. The results are coherent with the idea of the dysfunction of the P50 gating having endophenotypic traits as far as schizophrenia goes.