Semantic Features Reveal Different Networks During Word Processing: An EEG Source Localization Study

• Published in: Frontiers in human neuroscience Vol. 12; p. 503
• Main Authors: Fahimi Hnazaee, Mansoureh, Khachatryan, Elvira, Van Hulle, Marc M
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Research Foundation 13.12.2018; Frontiers Media S.A
• Subjects: Coding theory; Cognition & reasoning; Cognitive ability; Conduction; EEG; Emotions; high-density EEG; Information processing; linear mixed effect model; Localization; Medical imaging; Neuroimaging; Neuroscience; semantic category representation; Semantics; single word processing; source localization; Spatial discrimination; Studies; single word processing; source localization; high-density EEG; semantic category representation; linear mixed effect model
• ISSN: 1662-5161; 1662-5161
• DOI: 10.3389/fnhum.2018.00503

The neural principles behind semantic category representation are still under debate. Dominant theories mostly focus on distinguishing concrete from abstract concepts but, in such theories, divisions into categories of concrete concepts are more developed than for their abstract counterparts. An encompassing theory on semantic category representation could be within reach when charting the semantic attributes that are capable of describing both concept types. A good candidate are the three semantic dimensions defined by Osgood (potency, valence, arousal). However, to show to what extent they affect semantic processing, specific neuroimaging tools are required. Electroencephalography (EEG) is on par with the temporal resolution of cognitive behavior and source reconstruction. Using high-density set-ups, it is able to yield a spatial resolution in the scale of millimeters, sufficient to identify anatomical brain parcellations that could differentially contribute to semantic category representation. Cognitive neuroscientists traditionally focus on scalp domain analysis and turn to source reconstruction when an effect in the scalp domain has been detected. Traditional methods will potentially miss out on the fine-grained effects of semantic features as they are possibly obscured by the mixing of source activity due to volume conduction. For this reason, we have developed a mass-univariate analysis in the source domain using a mixed linear effect model. Our analyses reveal distinct networks of sources for different semantic features that are active during different stages of lexico-semantic processing of single words. With our method we identified differences in the spatio-temporal activation patterns of abstract and concrete words, high and low potency words, high and low valence words, and high and low arousal words, and in this way shed light on how word categories are represented in the brain.