Reprinted from the German Journal of Psychiatry · http://www.gjpsy.uni-goettingen.de · ISSN 1433-1055 A High Resolution Quantitative EEG Power Analysis of Obsessive-Compulsive Disorder Pushpal Desarkar 1 , Vinod Kumar Sinha 2 , K. Jagadheesan 3 , S. Haque Nizamie 4 1 Senior Resident, Centre for Cognitive Neuroscience, Central Institute of Psychiatry, Ranchi 2 Associate Professor of Psychiatry, Central Institute of Psychiatry, Ranchi 3 Broadmeadows Adult Psychiatric Inpatient Unit, Melbourne, Victoria, Australia 4 Professor of Psychiatry & Director, Central Institute of Psychiatry, Ranchin Corresponding author: Pushpal Desarkar MD, DPM. Senior Resident, Centre for Cognitive Neuroscience, Central Institute of Psychiatry, Kanke (PO), Ranchi-834006, Jharkhand, India. E-mail: pushpalds@yahoo.com Abstract Introduction : The findings of the quantitative EEG power-spectral studies in obsessive-compulsive disorder (OCD) have so far been mostly inconsistent. Moreover, none of the studies has been a high resolution one. Aim : The aim of the study was to examine the band power of delta, theta, alpha, beta1 and beta2 bands with high resolution EEG data in patients with obsessive- compulsive disorder and compare it with that of normal controls. It was hypothesized that there will be no significant group difference of individual band power between patient and control group. Methods : Raw EEG data were acquired from 64 channels using a linked ear reference. We obtained EEG power values for 20 adult OCD patients (10 males; 10 females) and 19 appropriately matched healthy controls across the abovementioned bands. We used Advanced Source Analysis (ASA, ANT software b.v. Netherlands; version- 3.0.0.5.) program for analysis of power. Results: OCD patients had significantly higher power in comparison to controls which was widespread in the theta fre- quency, predominantly left sided fronto-temporo-parietal in delta and alpha and only left frontal in beta2 bands. Conclusion: Increased band power in obsessive-compulsive disorder patients in all these bands which have been shown to be associated with cognitive processing, may reflect increased processing load in this group of patients with recruitment of wide area of cerebral hemisphere (German J Psychiatry 2007; 10: 29-35). Keywords: Obsessive-compulsive disorder, quantitative EEG, band power, increased cognitive processing Received: 9.1.2006 Published: 19.6.2006 Published: 1.4.2007 Introduction n the past two decades, there has been a considerable advance in the understanding of the biological underpin- nings of obsessive-compulsive disorder (OCD) with emergence of various hypothetical models. Currently, there is little confusion over a significant neurobiological basis of OCD. Genetic, neurochemical, neuropsychological and neu- roimaging studies have shown certain consistent abnormali- ties in OCD. After repeated failures of structural neuroima- ging methods in finding consistent structural abnormalities in psychiatric disorders, evolving functional brain-imaging tech- niques nowadays represent the most powerful tools for cha- racterizing in vivo human anatomy, neurophysiology and neurochemistry at modest temporal and spatial resolution. Recent functional neuroimaging studies in OCD population have consistently found abnormalities the frontal cortex and basal ganglia structures (Saxena & Rauch, 2000). Quantitative EEG (QEEG) being a physiological imaging technique can be used to delineate abnormal functioning of brain regions with remarkable temporal precision. However, the findings of the quantitative EEG power-spectral studies in OCD population have so far been mostly inconsistent. In one of the first quantitative EEG studies using power- I