title: Similarity of fMRI activity patterns in left perirhinal cortex reflects semantic similarity between words.
abstract: How verbal and nonverbal visuoperceptual input connects to semantic knowledge is a core question in visual and cognitive neuroscience, with significant clinical ramifications. In an event-related functional magnetic resonance imaging (fMRI) experiment we determined how cosine similarity between fMRI response patterns to concrete words and pictures reflects semantic clustering and semantic distances between the represented entities within a single category. Semantic clustering and semantic distances between 24 animate entities were derived from a concept-feature matrix based on feature generation by >1000 subjects. In the main fMRI study, 19 human subjects performed a property verification task with written words and pictures and a low-level control task. The univariate contrast between the semantic and the control task yielded extensive bilateral occipitotemporal activation from posterior cingulate to anteromedial temporal cortex. Entities belonging to a same semantic cluster elicited more similar fMRI activity patterns in left occipitotemporal cortex. When words and pictures were analyzed separately, the effect reached significance only for words. The semantic similarity effect for words was localized to left perirhinal cortex. According to a representational similarity analysis of left perirhinal responses, semantic distances between entities correlated inversely with cosine similarities between fMRI response patterns to written words. An independent replication study in 16 novel subjects confirmed these novel findings. Semantic similarity is reflected by similarity of functional topography at a fine-grained level in left perirhinal cortex. The word specificity excludes perceptually driven confounds as an explanation and is likely to be task dependent.
authors.affiliation: Laboratory for Cognitive Neurology, Department of Neurosciences, Neurology Department, and Radiology Department, University Hospitals Leuven, 3000 Leuven, Belgium, and Laboratory of Experimental Psychology, Humanities and Social Sciences Group, University of Leuven, 3000 Leuven, Belgium.
authors.forename: Rose
authors.initials: R
authors.lastname: Bruffaerts
authors.forename: Patrick
authors.initials: P
authors.lastname: Dupont
authors.forename: Ronald
authors.initials: R
authors.lastname: Peeters
authors.forename: Simon
authors.initials: S
authors.lastname: De Deyne
authors.forename: Gerrit
authors.initials: G
authors.lastname: Storms
authors.forename: Rik
authors.initials: R
authors.lastname: Vandenberghe
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D004192:Discrimination, Psychological; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009778:Occipital Lobe / Q000098:blood supply*; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D012660:Semantics; D013702:Temporal Lobe / Q000098:blood supply*; D014825:Vocabulary; D055815:Young Adult
chemical_list: D010100:Oxygen