Differences in processing of taxonomic and sequential relations in semantic memory: an fMRI investigation

Conceptual knowledge of our world is represented in semantic memory in terms of concepts and semantic relations between concepts. We used functional magnetic resonance imaging (fMRI) to examine the cortical regions underlying the processing of sequential and taxonomic relations. Participants were presented verbal cues and performed three tasks: (1) a sequential relation judgement task judging the sequential relation between two script events, (2) a taxonomic relation judgement task judging the taxonomic relation between two objects, and (3) a grammatical judgement task (control condition) judging whether a presented word was a verb or a noun. We hypothesized that the processing of sequential and taxonomic relations were supported by dissociable cortical regions. The results showed that both semantic relation types activated large-scale neural networks including the left inferior and middle frontal gyrus. The activation in left inferior frontal gyrus correlated with higher processing demands during the sequential relation condition. The processing of sequential relations additionally activated left medial and middle frontal gyrus, whereas the processing of taxonomic relations activated the left superior temporal gyrus and posterior cingulate.