Establishing task- and modality-dependent dissociations between the semantic and default mode networks
Proceedings of the National Academy of Sciences June 8, 2015 Gina F. Humphreys, Paul Hoffman, Maya Visser et al. 219 citations
The default mode network (DMN) and semantic network (SN) are thought to overlap in brain regions like the anterior temporal lobe (ATL) and angular gyrus (AG), but their relationship is rarely tested directly. Using fMRI data from 69 participants performing semantic and nonsemantic tasks, the authors found that both networks split into subparts depending on task demands, stimulus type, and difficulty. The left ATL was active for semantic tasks and deactivated for nonsemantic ones, while the left AG was deactivated for all tasks, with deactivation linked to difficulty. Thus, ATL and AG do not share a common role in semantic processing; instead, both are inactive during nonsemantic tasks. These findings challenge the idea that both regions are semantic hubs and have implications for understanding DMN variability and resting-state fMRI.