Intracranial EEG evaluation of relationship within a resting state network.

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 coherence of the gamma power time-series were estimated, for one hour intracranial EEG recordings of background 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 parietal, 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 network. 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.