Background: Brain’s alpha activity is one of major electrical signals that are related to sensory/cognitive signal processing. The present study aims to analyze the alpha activity in drug free euthymic bipolar patients.
Method: Fourteen DSM-IV euthymic bipolar I or II patients and fourteen healthy controls were included in the study. Patients needed to be euthymic at least for 4 weeks and psychotrop free for at least 2 weeks. Spontaneous EEG (4 min eyes closed, 4 min eyes open) and EEG upon application of simple visual stimuli were analyzed. EEG was recorded at 30 positions. The digital FFT-based power spectrum analysis was performed for spontaneous eyes closed and eyes open conditions and the response power spectrum was also analyzed for simple visual stimuli.
Results: The ANOVA on alpha responses revealed significant results for groups (F(1.26) = 7.581; p = 0.011). Post-hoc comparisons showed that spontaneous EEG alpha power of healthy subjects was significantly higher than the spontaneous EEG alpha power of euthymic patients. Furthermore, visual evoked alpha power of healthy subjects was significantly higher than Visual evoked EEG alpha power of euthymic patients (F(1.26) = 4,511; p = 0.043).
Conclusion: Decreased alpha activity in spontaneous EEG is an important pathological EEG finding in euthymic bipolar patients. Together with an evident decrease in evoked alpha responses, the findings may lead to a new pathway in search of biological correlates of cognitive impairment in bipolar disorder.