Functional MRI Investigation on Paradigmatic and Syntagmatic Lexical Semantic Processing

Abstract

The word embeddings related to paradigmatic and syntagmatic axes are applied in an fMRI encoding experiment to explore human brain's activity pattern during story listening. This study proposes the construction of paradigmatic and syntagmatic semantic embeddings respectively by transforming WordNet-alike knowledge bases and subtracting paradigmatic information from a statistical word embedding. It evaluates the semantic embeddings by leveraging word-pair proximity ranking tasks and contrasts voxel encoding models trained with the two types of semantic features to reveal the brain's spatial pattern for semantic processing. Results indicate that in listening comprehension, paradigmatic and syntagmatic semantic operations both recruit inferior (ITG) and middle temporal gyri (MTG), angular gyrus, superior parietal lobule (SPL), inferior frontal gyrus. A non-continuous voxel line is found in MTG with a predominance of paradigmatic processing. The ITG, middle occipital gyrus and the surrounding primary and associative visual areas are more engaged by syntagmatic processing. The comparison of two semantic axes' brain map does not suggest a neuroanatomical segregation for paradigmatic and syntagmatic processing. The complex yet regular contrast pattern starting from temporal pole, along MTG to SPL necessitates further investigation.