Regional and network relationship in the intracranial EEG second spectrum.
OBJECTIVE
We examined low-frequency amplitude modulations of band power time-series, i.e. the second spectrum, of the intracranial EEG (icEEG) for evidence of support for spatial relationships between different parts of the brain and within the default mode network (DMN).


METHODS
We estimated magnitude-squared coherence (MSC) of the running power in the delta, theta, alpha, beta, and gamma frequency bands for one-hour background icEEG epochs recorded from 9 patients. We isolated two test areas within the DMN and one control area outside it. We tested if the relationship between DMN areas was stronger than the relationship between each of these areas and the control location, and between all intrahemispheric contact pairs with similar intercontact distance.


RESULTS
We observed very low values of second spectrum relationship between different parts of the brain, except at very short distances. These relationships are strongest in the delta band and decrease with increasing frequency, with gamma band relationships being the weakest. Our DMN-specific analysis showed no enhanced connectivity in the second spectrum in DMN locations in any frequency band.


CONCLUSIONS
Though we observed significantly nonzero relationships in lower frequency bands, second spectrum relationships are consistently very low across the entire brain in every frequency band.


CONCLUSIONS
This study suggests a lack of support for the DMN in the icEEG second spectrum.
Department of Neurology, Yale University, New Haven, CT 06520, USA.
Rasesh B
RB
Joshi
Department of Neurology, Yale University, New Haven, CT 06520, USA.
Nicolas
N
Gaspard
Department of Neurology, Yale University, New Haven, CT 06520, USA.
Irina I
II
Goncharova
Department of Neurology, Yale University, New Haven, CT 06520, USA.
Robert B
RB
Duckrow
Laboratory of Neuro Imaging, USC Stevens Neuroimaging and Informatics Institute, University of Southern California, Los Angeles, CA 90032, USA.
Dominique
D
Duncan
Department of Neurosurgery, Yale University, Yale University School of Medicine, New Haven, CT 06520, USA.
Jason L
JL
Gerrard
Department of Neurosurgery, Yale University, Yale University School of Medicine, New Haven, CT 06520, USA.
Dennis D
DD
Spencer
Department of Neurology, Yale University, New Haven, CT 06520, USA.
Lawrence J
LJ
Hirsch
Department of Neurology, Yale University, New Haven, CT 06520, USA. Electronic address: hitten.zaveri@yale.edu.
Hitten P
HP
Zaveri
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002648:Child; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D011897:Random Allocation; D055815:Young Adult
Coherence; Epilepsy; Intracranial EEG; Resting state networks