title: Automatic semantic facilitation in anterior temporal cortex revealed through multimodal neuroimaging.
abstract: A core property of human semantic processing is the rapid, facilitatory influence of prior input on extracting the meaning of what comes next, even under conditions of minimal awareness. Previous work has shown a number of neurophysiological indices of this facilitation, but the mapping between time course and localization-critical for separating automatic semantic facilitation from other mechanisms-has thus far been unclear. In the current study, we used a multimodal imaging approach to isolate early, bottom-up effects of context on semantic memory, acquiring a combination of electroencephalography (EEG), magnetoencephalography (MEG), and functional magnetic resonance imaging (fMRI) measurements in the same individuals with a masked semantic priming paradigm. Across techniques, the results provide a strikingly convergent picture of early automatic semantic facilitation. Event-related potentials demonstrated early sensitivity to semantic association between 300 and 500 ms; MEG localized the differential neural response within this time window to the left anterior temporal cortex, and fMRI localized the effect more precisely to the left anterior superior temporal gyrus, a region previously implicated in semantic associative processing. However, fMRI diverged from early EEG/MEG measures in revealing semantic enhancement effects within frontal and parietal regions, perhaps reflecting downstream attempts to consciously access the semantic features of the masked prime. Together, these results provide strong evidence that automatic associative semantic facilitation is realized as reduced activity within the left anterior superior temporal cortex between 300 and 500 ms after a word is presented, and emphasize the importance of multimodal neuroimaging approaches in distinguishing the contributions of multiple regions to semantic processing.
authors.affiliation: Department of Psychiatry and Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology and Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Massachusetts General Hospital, Charlestown, Massachusetts 02129, Department of Linguistics, University of Maryland, College Park, Maryland, 20742, Department of Psychology, Tufts University, Medford, Massachusetts 02155, Institut Mines-Télécom, Télécom ParisTech, Centre National de la Recherche Scientifique Laboratoire Traitment et Communication de l'Information, 75013 Paris, France, and Division of Health Sciences and Technology, Harvard University and Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.
authors.forename: Ellen F
authors.initials: EF
authors.lastname: Lau
authors.forename: Alexandre
authors.initials: A
authors.lastname: Gramfort
authors.forename: Matti S
authors.initials: MS
authors.lastname: Hämäläinen
authors.forename: Gina R
authors.initials: GR
authors.lastname: Kuperberg
mesh_terms: D000293:Adolescent; D000328:Adult; D001244:Association; D001931:Brain Mapping; D005071:Evoked Potentials; D005260:Female; D005625:Frontal Lobe / Q000502:physiology; D006801:Humans; D008297:Male; D008568:Memory; D010296:Parietal Lobe / Q000502:physiology; D010470:Perceptual Masking; D012660:Semantics; D013702:Temporal Lobe / Q000502:physiology*; D014936:Word Association Tests