Abstracts

Rationale: We tested if a resting state network (RSN) empirically defined by fMRI studies can be observed with intracranial EEG (icEEG) recorded from patients with localization-related epilepsy.Methods: This study was performed on 9 patients being evaluated for possible epilepsy surgery. Intracranial EEG recordings, one hour in duration, were collected from multiple electrode contacts in three areas: (1) T1: anterior cingulate and frontal orbital, (2) T2: posterior cingulate and mesial parietal, and (3) C: superior temporal and/or lateral frontal. The first two areas, T1 and T2, were part of the RSN being tested, whereas the third area, C, was a control area outside the RSN. A total of 176 electrode contacts were studied in the 9 patients, 46 in T1, 38 in T2 and 37 in C. Three time-series relationship measures: coherence (measured for delta, theta, alpha, beta, and gamma frequency bands), mutual information, and cross-approximate entropy (cross-ApEn), were estimated for the icEEG recordings from the two test areas within the RSN (T1, T2) and one control area (C). We tested if the relationship between T1 and T2 was stronger than the relationship between each of these areas and C.Results: Very low relationship values were observed between T1 and T2, T1 and C and T2 and C with coherence, mutual information, and cross-ApEn. The relationship between the two test areas T1 and T2, which were part of the studied RSN, was not stronger than the relationship between each of the two test areas and the control area.Conclusions: We did not observe support for an fMRI defined RSN using icEEG measurements. There are three possible explanations for this outcome: (1) the setting and measurement of the icEEG interferes with the observation of the RSN, (2) that this RSN does not exist in patients with localization-related epilepsy, or (3) the difference in activities measured by fMRI and icEEG precludes the observation of this relationship with icEEG.