Spatio-Temporal Dynamics of Human Intention Understanding in Temporo-Parietal Cortex: A Combined EEG/fMRI Repetition Suppression Paradigm

Inferring the intentions of other people from their actions recruits an inferior fronto-parietal action observation network as well as a putative social network that includes the posterior superior temporal sulcus (STS). However, the functional dynamics within and among these networks remains unclear. Here we used functional magnetic resonance imaging (fMRI) and high-density electroencephalogram (EEG), with a repetition suppression design, to assess the spatio-temporal dynamics of decoding intentions. Suppression of fMRI activity to the repetition of the same intention was observed in inferior frontal lobe, anterior intraparietal sulcus (aIPS), and right STS. EEG global field power was reduced with repeated intentions at an early (starting at 60 ms) and a later (similar to 330 ms) period after the onset of a hand-on-object encounter. Source localization during these two intervals involved right STS and aIPS regions highly consistent with RS effects observed with fMRI. These results reveal the dynamic involvement of temporal and parietal networks at multiple stages during the intention decoding and without a strict segregation of intention decoding between these networks.