P124. QEEG and CSD power analysis in depression

Abstract

Introduction Major depressive disorder (MDD) is a chronic mood disorder with significant impairment of daily living. Neurophysiological studies have focused to identify endophenotypes of depression. Frontal asymmetry in EEG power within alpha band has been the most studied topic and a few results indicated the phenomenon of lower left and higher right frontal activity. However, some other studies failed to show homogeneous results. Our aims in this study are to extensively investigate the neurophysiogical pattern in depressive patients by using qEEG power value, transformed current source density (CSD) as well as the neural synchronization. Method 20 patients with MDD (mean age ± SD: 47 ± 12.57 years old, female: 13) were compared with 20 age matched healthy subjects (mean age ± SD: 51 ± 10.5; female: 12). All participants underwent a 10 min resting state EEG recording with closed eyes. 31 electrodes elastic cap (10/20 system) with additional ECG channel were applied to all participants. Impedances were kept below 5 k Ω . EEG raw data were manually cleaned from movement artefacts. ECG and ocular artefacts were excluded via independent component analysis. Filter settings were 0.5 Hz for high pass and 30 Hz for low pass and all channels average was set as reference. EEG power and asymmetry indices were calculated from 8 min of artefact free data for each frequency and pooled over 6 electrode sites. One minute of artefact free data in each participant were exported for CSD analysis. Voxelwise CSD power was calculated for each frequency with Low Resolution Electromagnetic Tomography (LORETA). Lagged phase synchronisation between mean CSD power time series was calculated for frontal and cingular regions. ANOVA with the inner subject factors “pooled electrode locations” and “hemisphere” (6 × 2) and between subjects grouping factor (patients versus controls) were calculated to analyze EEG power and asymmetry for each frequency band. Repetitive measure post hoc t-test was further applied to investigate variables that caused the differences in ANOVA interactions. Group differences of CSD power and synchronisation were analyzed by t-tests. Result We found a main effect of group in the alpha2 (p = .017), delta (p = .043), theta (p = .043) and beta band (p = .007), the MDD patients have higher overall power in these frequencies. For the beta frequency, the increased EEG power of the MDD patients was also significant when analysed separately in post hoc t-test for frontal, central and centroparietal regions (p.Post hoc t-test revealed that in particular the group differences of EEG power in the temporoparietal region (p = .05) was driving this interaction effect. CSD analysis showed no significant difference between groups. Conclusion Depressive patients have shown a non-regional specific higher global EEG power in slow and high EEG frequencies compared to healthy controls. Especially increased overall power in the beta band in frontal, central and centroparietal regions can be seen in relation to difficulty falling asleep, and inner restlessness which is often found in MDD patients. Our result did not show frontal alpha asymmetry in depressive patients as well as in healthy control.