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S086-3

Abnormal P300 in People with High Risk of Developing Psychosis

Elvira Bramon

King’s College London, UK

Background/Objective: Individuals with an "at-risk mental state" (or "prodromal" symptoms) have
a 20-40% chance of developing psychosis; however it is difficult to predict which of them will
become ill on the basis of their clinical symptoms alone. We examined whether neurophysiological
markers could help to identify those who are particularly vulnerable.

Method: 35 cases meeting PACE criteria for the at-risk mental state (ARMS) and 57 controls
performed an auditory oddball task whilst their electroencephalogram was recorded. The latency and
amplitude of the P300 and N100 waves were compared between groups using linear regression.

Result: The P300 amplitude was significantly reduced in the ARMS group [8.6+/-6.4 microvolt]
compared to controls [12.7+/-5.8 microvolt] (p<0.01). There were no group differences in P300
latency or in the amplitude and latency of the N100. Of the at-risk subjects that were followed up,
seven (21%) developed psychosis.

Conclusion: Striatal dopamine transporter levels and the P300 ERP are not altered in the early stages
of schizophrenia before medication is introduced, and the DAT availability does not influence the
P300 ERP amplitude or latency.