Dysfunctional brain circuitry in obsessive-compulsive disorder: Source and coherence analysis of EEG rhythms

Background: Morphological and functional studies suggested involvement of several cortical and subcortical circuitries in patients with obsessive-compulsive disorder (OCD). The aim of the present study was to investigate networks involved in OCD pathophysiology, using power (coupling of EEG bands, low-resolution electromagnetic tomography-LORETA) and coherence analysis in drug naïve patients. Method: EEG was obtained from 37 drug-naïve patients with OCD and 37 age- and sex-matched controls. Resting EEG was recorded from 29 scalp channels. Coupling (ratio and correlation) between low and high frequencies was analyzed on Fz. For each frequency band, LORETA current density distribution, intra-hemispheric and inter-hemispheric coherence analysis were computed. Results: OCD had increased current density for delta in the insula and for beta in frontal, parietal and limbic lobes. OCD also had decreased inter-hemispheric coherence and reduced coupling between delta and beta frequencies. Conclusions: In OCD, increased frontal beta is consistent with previous evidence of frontal dysfunction. Hyperactivity of insular delta sources, together with rhythms decoupling and reduced interhemispheric alpha coherence are consistent with additional involvement of cortico-subcortical functional connections. Combined use of power and coherence analysis may provide functional measures on different levels of involvement of cortico-subcortical circuits in neuropsychiatric disorders.