Positive affect increases aperiodic brain activity.

Metacontrol refers to the capacity to effectively balance persistence and flexibility according to situational circumstances. Recent studies suggest a crucial role of cortical noise in metacontrol by showing that the aperiodic exponent, a measure of aperiodic neural activity, varies systematically with metacontrol requirements. Given the behavioral evidence that affect and metacontrol are related, we predicted that affect could also induce systematic changes of the aperiodic exponent. We thus analyzed aperiodic activity in response to affective facial expressions of negative, neutral, or positive valence in a 2-back task from two separate datasets. Our results showed that, at the whole-brain level, aperiodic activity was higher for positive faces than for both neutral and negative faces, but only if valence was blocked (i.e., was the same over consecutive trials). Subsequent analysis further showed that the difference was significant in electrodes widely spread across the frontal, parietal, temporal, and occipital lobes. In conclusion, the present study demonstrates that aperiodic activity changed with affective valence and was more pronounced when processing positive, as compared to neutral or negative stimuli.