Association between CSF hypocretin-1 levels, vigilance regulation and intracortical EEG-frequency power in patients with major depressive disorder and healthy controls

Hypocretin-1 (hcrt-1) is responsible for sustained attention and sleep-wake regulation. Little is known about the impact of hcrt-1 cerebrospinal fluid (CSF) levels on cortical activity as assessed with electroencephalography (EEG). This study investigated hcrt-1 levels and intracortical EEG frequency band source power and markers of vigilance in patients suffering from major depression (MDD) and healthy controls. After a 15 minute resting EEG was recorded in 20 subjects (13 patients with MDD, 7 healthy controls), lumbar puncture was performed to determine CSF-hcrt-1 levels. EEG frequency band source power in 6239 intracortical grey matter voxels was calculated using eLORETA software. EEG-stages A and B and switch ratio between stages was determined using VIGALL software. Hcrt-1 levels were measured with a fluorescence immunoassay (FIA). For the whole study population, correlations between hcrt-1-CSF levels and EEG-theta power in the middle frontal gyrus (r = 0.79; p ≤ 0.05) and EEG-gamma power in the medial frontal gyrus were found (r = 0.81; p ≤ 0.05). In MDD, correlation with EEG-delta power in MDD in the inferior parietal lobule (r = 0.90; p ≤ 0.05) was found. No significant correlations between hcrt-1 and stages as well as switch rate were found. Findings point towards involvement of hcrt-1 in frontal neuronal activity that needs further investigation. On the opposite, hcrt-1 does not appear to have an impact on impaired vigilance regulation as detected with EEG.