Anterior insula activity and the effect of agency on the Stimulus-Preceding Negativity

If you know that you are the author of a freely chosen action and that you bear responsibility for its outcome, then you are said to have "a sense of agency." When there is a delay between action and outcome, this response must be remembered if you are to learn from the experience. Previous studies have shown that the Stimulus-Preceding Negativity (SPN) recorded during the delay interval is larger under conditions that foster a sense of agency. In an EEG experiment (N = 27), we confirmed that the SPN is larger when participants have a choice between two responses in a gambling task as compared to when there is only a single button and the computer determines the monetary outcome. This SPN agency effect was largest over right prefrontal cortex and it did not vary significantly between trial blocks in which only gains or only losses were possible. Participants in a second experiment (N = 26) performed the same task while activity in anterior insular cortex, a known SPN generator, was measured via functional magnetic resonance image (fMRI). An essentially identical pattern of results was obtained: Activity was greater on choice than no-choice trials, especially for the right hemisphere, and no effect of contextual valence was observed. Although parallel observations such as these cannot warrant causal inference, our findings are consistent with the assumption that anterior insular cortex contributes to the effect of agency on the SPN.