Intracranial EEG evaluation of relationship within a resting state network Dominique Duncan a,⇑ , Robert B. Duckrow b,c , Steven M. Pincus d , Irina Goncharova b , Lawrence J. Hirsch b , Dennis D. Spencer c , Ronald R. Coifman e , Hitten P. Zaveri b a Department of Electrical Engineering, Yale University, New Haven, CT 06511, USA b Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA c Department of Neurosurgery, Yale University School of Medicine, New Haven, CT 06520, USA d Guilford, CT, USA e Department of Mathematics, Yale University, New Haven, CT 06511, USA article info Article history: Accepted 30 March 2013 Available online xxxx Keywords: Epilepsy Resting state networks Coherence Mutual information Cross-approximate entropy Gamma power highlights  We tested if a relationship between distant parts of the default mode network (DMN), a resting state network defined by fMRI studies, could be observed in the intracranial EEG.  Relationship was measured with linear and non-linear relationship measures of the intracranial EEG and an evaluation of the gamma power envelope.  The relationship within the DMN was not greater than the relationship from DMN locations to a con- trol location outside it, suggesting a lack of intracranial EEG support for the fMRI defined DMN. abstract Objective: We tested if a relationship between distant parts of the default mode network (DMN), a resting state network defined by fMRI studies, can be observed with intracranial EEG recorded from patients with localization-related epilepsy. Methods: Magnitude squared coherence, mutual information, cross-approximate entropy, and the coher- ence of the gamma power time-series were estimated, for one hour intracranial EEG recordings of back- ground activity from 9 patients, to evaluate the relationship between two test areas which were within the DMN (anterior cingulate and orbital frontal, denoted as T1 and posterior cingulate and mesial pari- etal, denoted as T2), and one control area (denoted as C), which was outside the DMN. We tested if the relationship between T1 and T2 was stronger than the relationship between each of these areas and C. Results: A low level of relationship was observed among the 3 areas tested. The relationships among T1, T2 and C did not demonstrate support for the DMN. Conclusions: This study suggests a lack of intracranial EEG support for the fMRI defined default mode net- work. Significance: The results obtained underscore the considerable difference between electrophysiological and hemodynamic measurements of brain activity and possibly suggest a lack of neuronal involvement in the DMN. Ó 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. 1. Introduction FMRI studies have described a number of resting state networks (RSNs), which are comprised of distant brain areas with relatively high correlation in the BOLD signal while the subject is in a resting state (Biswal et al., 1995). A particular RSN which has received con- siderable attention is the default mode network (DMN) comprised of the medial prefrontal cortex (MPFC), posterior cingulate cortex (PCC), and retrosplenial cortex (RCC) (Raichle et al., 2001). The correlated hemodynamic activity within the DMN has been considered to underlie cognitive processes which are important during rest (Raichle et al., 2001). In spite of considerable research activity in this area, skepticism still persists regarding the fMRI 1388-2457/$36.00 Ó 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.clinph.2013.03.028 ⇑ Corresponding author. Address: Department of Electrical Engineering, 51 Prospect St., AKW 101, Yale University, New Haven, CT 06511, USA. Tel.: +1 203 737 5407; fax: +1 203 785 5694. E-mail address: dominique.duncan@yale.edu (D. Duncan). Clinical Neurophysiology xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph Please cite this article in press as: Duncan D et al. Intracranial EEG evaluation of relationship within a resting state network. Clin Neurophysiol (2013), http://dx.doi.org/10.1016/j.clinph.2013.03.028