title: Multimodal imaging of repetition priming: Using fMRI, MEG, and intracranial EEG to reveal spatiotemporal profiles of word processing.
abstract: Repetition priming is a core feature of memory processing whose anatomical correlates remain poorly understood. In this study, we use advanced multimodal imaging (functional magnetic resonance imaging (fMRI) and magnetoencephalography; MEG) to investigate the spatiotemporal profile of repetition priming. We use intracranial electroencephalography (iEEG) to validate our fMRI/MEG measurements. Twelve controls completed a semantic judgment task with fMRI and MEG that included words presented once (new, 'N') and words that repeated (old, 'O'). Six patients with epilepsy completed the same task during iEEG recordings. Blood-oxygen level dependent (BOLD) responses for N vs. O words were examined across the cortical surface and within regions of interest. MEG waveforms for N vs. O words were estimated using a noise-normalized minimum norm solution, and used to interpret the timecourse of fMRI. Spatial concordance was observed between fMRI and MEG repetition effects from 350 to 450 ms within bilateral occipitotemporal and medial temporal, left prefrontal, and left posterior temporal cortex. Additionally, MEG revealed widespread sources within left temporoparietal regions, whereas fMRI revealed bilateral reductions in occipitotemporal and left superior frontal, and increases in inferior parietal, precuneus, and dorsolateral prefrontal activity. BOLD suppression in left posterior temporal, left inferior prefrontal, and right occipitotemporal cortex correlated with MEG repetition-related reductions. IEEG responses from all three regions supported the timecourse of MEG and localization of fMRI. Furthermore, iEEG decreases to repeated words were associated with decreased gamma power in several regions, providing evidence that gamma oscillations are tightly coupled to cognitive phenomena and reflect regional activations seen in the BOLD signal.
authors.affiliation: Department of Psychiatry, University of California, San Diego, CA, USA. camcdonald@ucsd.edu
authors.forename: Carrie R
authors.initials: CR
authors.lastname: McDonald
authors.forename: Thomas
authors.initials: T
authors.lastname: Thesen
authors.forename: Chad
authors.initials: C
authors.lastname: Carlson
authors.forename: Mark
authors.initials: M
authors.lastname: Blumberg
authors.forename: Holly M
authors.initials: HM
authors.lastname: Girard
authors.forename: Amy
authors.initials: A
authors.lastname: Trongnetrpunya
authors.forename: Jason S
authors.initials: JS
authors.lastname: Sherfey
authors.forename: Orrin
authors.initials: O
authors.lastname: Devinsky
authors.forename: Rubin
authors.initials: R
authors.lastname: Kuzniecky
authors.forename: Werner K
authors.initials: WK
authors.lastname: Dolye
authors.forename: Sydney S
authors.initials: SS
authors.lastname: Cash
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Leonard
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Hagler
authors.forename: Anders M
authors.initials: AM
authors.lastname: Dale
authors.forename: Eric
authors.initials: E
authors.lastname: Halgren
mesh_terms: D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D003463:Cues; D003627:Data Interpretation, Statistical; D003657:Decision Making / Q000502:physiology; D004569:Electroencephalography; D004827:Epilepsy / Q000503:physiopathology / Q000601:surgery; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007802:Language; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D008606:Mental Processes / Q000502:physiology*; D008875:Middle Aged; D011932:Reading; D015203:Reproducibility of Results; D012660:Semantics; D055815:Young Adult