PM501. Acute Effects of Nicotine and Nabilone on the Mismatch Negativity: A Combined Time-Frequency and Event-Related Potential Study

Objective: Quantitative electroencephalography (QEEG) is a well established method for evaluating brain functioning. Abnormal oscillatory activity measured with QEEG during resting state has been consistently reported in patients with schizophrenia. We aimed to examine whether resting state EEG is associated with 1 year outcome in patients with first episode psychosis (FEP). Method: Twenty five FEP patients participated in resting state EEG recording with their eyes closed. Clinical symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS) at the time of EEG recording, and then were reassessed after 1 year of follow-up period. In addition, neurocognitive function test was performed twice with same 1 year interval. Resting state continuous EEG data were analyzed quantitatively and frequency band power at each electrode site were extracted. Multiple regressive analysis with backward method was used to identify factors significantly predictive of symptomatic improvement in subjects. Delta and alpha band activity, age, sex, education years, use of medication, baseline clinical scale scores were considered as independent variables. Result: We found that delta band activity at Oz electrode site significantly predicted improvement in the PANSS positive subscale score (β=-0.238, p=0.019) during 1 year of follow-up period. In addition, alpha band activity at CP4 electrode site was associated with later improvement in the working memory which was measured with the perseverative response of Wisconsin Card Sorting Test (β=0.244, p=0.033) Conclusion: QEEG parameters effectively predicted improvement in both positive symptom and neurocognitive functioning in FEP patients during 1 year of follow-up period. Our results suggest that QEEG analysis would be a possible predictor of prognosis in patients with FEP.