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Poster A34, Tuesday, August 20, 2019, 10:15 am – 12:00 pm, Restaurant Hall

Overlapping patterns during semantic processing of abstract and concrete concepts revealed with Granger Causality analysis

Mansoureh Fahimi Hnazaee1, Elvira Khachatryan1, Sahar Chehrazad2, Miet De Letter3, Marc M. Van Hulle1;1Laboratory for Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven, 2Numerical Analysis and Applied Mathematics Section, Department of Computer Science, KU Leuven, 3Department of Speech, Language and Hearing Sciences, Ghent University

Abstract nouns reflect the invisible world of qualities which cannot be touched or sensed, unlike concrete nouns that refer to notions and things. Even though linguistic theories about concrete and abstract words are rather indecisive, neuroscience has found clear evidence of a “concreteness” effect, arising from a superior perceptive ability for one category over the other in patients with language impairments due to brain injury or developmental disorders. Neuroimaging studies of healthy subjects have also given a spatial and temporal account of processing differences, but the results are inconclusive. A description of the neural pathways during abstract word reading, how the pattern of information flow develops over the different stages of lexical and semantic processing, and how this dynamic connectivity pattern compares to that of concrete word processing still needs to be laid out. We conducted a high-density EEG study of 24 healthy young volunteers using a categorization task where the evaluation of the concreteness of the words is implicit, meaning that subjects were not aware of the purpose of the task. An implicit task has shown to have reduced effects of concreteness, nevertheless, it is closer to the natural state of understanding concepts in real life. The word dataset in this task was controlled for word frequency and the number of letters, and also additionally for the three dimensions of affective meaning as defined by Osgood (valence, arousal, potency). Using source reconstruction, we obtained high spatiotemporal resolution data, and at the same time, reduced the effect of signal mixing that occurs on the scalp level. Next, we employed two different techniques of statistical analysis to identify regions on the cortical surface that exhibited both common, and differential activity between the two types of concepts. A multivariate, time-varying and directional method of analyzing connectivity based on the concept of Granger Causality (Partial Directed Coherence) revealed a dynamic network that transfers information from the right superior occipital lobe along the ventral and dorsal stream, toward the anterior temporal and orbitofrontal lobes on both hemispheres. Some regions along these pathways were primarily involved in the receiving or sending of information. A clear difference in information transfer between abstract and concrete word processing was observed during the time window of semantic processing, specifically for information transferred towards the left anterior temporal lobe. Further exploratory analysis confirmed a generally stronger connectivity pattern for the processing of concrete concepts. We believe our study lays the experimental groundwork necessary for the future development of a refined theory on the processing of abstract concepts.

Themes: Meaning: Lexical Semantics, Methods
Method: Electrophysiology (MEG/EEG/ECOG)

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