title: Phase-amplitude coupling and the BOLD signal: A simultaneous intracranial EEG (icEEG) - fMRI study in humans performing a finger-tapping task.
abstract: Although it has been consistently found that local blood-oxygen-level-dependent (BOLD) changes are better modelled by a combination of the power of multiple EEG frequency bands rather than by the power of a unique band alone, the local electro-haemodynamic coupling function is not yet fully characterised. Electrophysiological studies have revealed that the strength of the coupling between the phase of low- and the amplitude of high- frequency EEG activities (phase-amplitude coupling - PAC) has an important role in brain function in general, and in preparation and execution of movement in particular. Using electrocorticographic (ECoG) and functional magnetic resonance imaging (fMRI) data recorded simultaneously in humans performing a finger-tapping task, we investigated the single-trial relationship between the amplitude of the BOLD signal and the strength of PAC and the power of α, β, and γ bands, at a local level. In line with previous studies, we found a positive correlation for the γ band, and negative correlations for the PACβγstrength, and the α and β bands. More importantly, we found that the PACβγstrength explained variance of the amplitude of the BOLD signal that was not explained by a combination of the α, β, and γ band powers. Our main finding sheds further light on the distinct nature of PAC as a functionally relevant mechanism and suggests that the sensitivity of EEG-informed fMRI studies may increase by including the PAC strength in the BOLD signal model, in addition to the power of the low- and high- frequency EEG bands.
authors.affiliation: Dept. of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, United Kingdom; Institute for Systems and Robotics and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal. Electronic address: teresa.murta.11@ucl.ac.uk.
authors.forename: T
authors.initials: T
authors.lastname: Murta
authors.affiliation: Dept. of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, United Kingdom.
authors.forename: U J
authors.initials: UJ
authors.lastname: Chaudhary
authors.affiliation: UCL Institute of Child Health, London, United Kingdom.
authors.forename: Tim M
authors.initials: TM
authors.lastname: Tierney
authors.affiliation: Institute for Systems and Robotics and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Dias
authors.affiliation: Dept. of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, United Kingdom; Institute for Systems and Robotics and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Leite
authors.affiliation: UCL Institute of Child Health, London, United Kingdom.
authors.forename: D W
authors.initials: DW
authors.lastname: Carmichael
authors.affiliation: Institute for Systems and Robotics and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
authors.forename: P
authors.initials: P
authors.lastname: Figueiredo
authors.affiliation: Dept. of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, United Kingdom.
authors.forename: L
authors.initials: L
authors.lastname: Lemieux
mesh_terms: D001931:Brain Mapping / Q000379:methods*; D058256:Brain Waves; D000069280:Electrocorticography; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology; D005260:Female; D005385:Fingers; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009043:Motor Activity; D009044:Motor Cortex / Q000502:physiology* / Q000503:physiopathology; D011597:Psychomotor Performance; D012815:Signal Processing, Computer-Assisted
keywords: Electro-haemodynamic coupling; Intracranial EEG; Phase–amplitude coupling; fMRI