title: Directional patterns of cross frequency phase and amplitude coupling within the resting state mimic patterns of fMRI functional connectivity.
abstract: Functional imaging investigations into the brain's resting state interactions have yielded a wealth of insight into the intrinsic and dynamic neural architecture supporting cognition and behavior. Electrophysiological studies however have highlighted the fact that synchrony across large-scale cortical systems is composed of spontaneous interactions occurring at timescales beyond the traditional resolution of fMRI, a feature that limits the capacity of fMRI to draw inference on the true directional relationship between network nodes. To approach the question of directionality in resting state signals, we recorded resting state functional MRI (rsfMRI) and electrocorticography (ECoG) from four human subjects undergoing invasive epilepsy monitoring. Using a seed-point based approach, we employed phase-amplitude coupling (PAC) and biPhase Locking Values (bPLV), two measures of cross-frequency coupling (CFC) to explore both outgoing and incoming connections between the seed and all non-seed, site electrodes. We observed robust PAC between a wide range of low-frequency phase and high frequency amplitude estimates. However, significant bPLV, a CFC measure of phase-phase synchrony, was only observed at specific narrow low and high frequency bandwidths. Furthermore, the spatial patterns of outgoing PAC connectivity were most closely associated with the rsfMRI connectivity maps. Our results support the hypothesis that PAC is relatively ubiquitous phenomenon serving as a mechanism for coordinating high-frequency amplitudes across distant neuronal assemblies even in absence of overt task structure. Additionally, we demonstrate that the spatial distribution of a seed-point rsfMRI sensorimotor network is strikingly similar to specific patterns of directional PAC. Specifically, the high frequency activities of distal patches of cortex owning membership in a rsfMRI sensorimotor network were most likely to be entrained to the phase of a low frequency rhythm engendered from the neural populations at the seed-point, suggestive of greater directional coupling from the seed out to the site electrodes.
authors.affiliation: University of Washington, Department of Radiology, USA; University of Washington, Graduate Program in Neuroscience, USA; University of Washington, Integrated Brain Imaging Center, USA.
authors.forename: Kurt E
authors.initials: KE
authors.lastname: Weaver
authors.affiliation: University of Washington, Department of Bioengineering, USA.
authors.forename: Jeremiah D
authors.initials: JD
authors.lastname: Wander
authors.affiliation: University of Washington, Department of Neurological Surgery, USA.
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Ko
authors.affiliation: University of Washington, Graduate Program in Neuroscience, USA.
authors.forename: Kaitlyn
authors.initials: K
authors.lastname: Casimo
authors.affiliation: University of Washington, Department of Radiology, USA; University of Washington, Department of Neurology, USA; University of Washington, Graduate Program in Neuroscience, USA; University of Washington, Integrated Brain Imaging Center, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Grabowski
authors.affiliation: University of Washington, Department of Neurological Surgery, USA; University of Washington, Graduate Program in Neuroscience, USA; University of Washington, Integrated Brain Imaging Center, USA.
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Ojemann
authors.affiliation: University of Washington, Department of Neurological Surgery, USA.
authors.forename: Felix
authors.initials: F
authors.lastname: Darvas
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D000069279:Drug Resistant Epilepsy / Q000503:physiopathology; D000069280:Electrocorticography; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000502:physiology*; D012146:Rest / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D055815:Young Adult
keywords: Directionality; Electrocorticography; Functional connectivity; Phase amplitude coupling; Resting state; biPhase locking value; functional MRI