Effects of tRNS on perception of static and dynamic displays of social-emotional communication.

Accurately decoding emotions from facial and vocal cues is essential to successful social interaction. The human mirror neuron system (hMNS) is thought to support this through sensorimotor simulation of observed emotional expressions. While prior studies linked hMNS activity-indexed by mu rhythm desynchronization (mu-ERD)-to emotional action perception, causal evidence with dynamic, multimodal social stimuli remains limited. We investigated whether transcranial random noise stimulation (tRNS) to the inferior frontal cortex (IFC), a key node of the hMNS, enhances perception of static and dynamic emotional displays. Fifty-two participants received active or sham tRNS over the IFC. Consistent with pre-registered predictions, active tRNS led to better performance on static emotion perception tasks compared to sham, with no group difference on a static identity-matching control task-validating stimulation specificity. Extending prior work, active tRNS led to faster response times and greater mu-ERD measured by EEG during dynamic audio-visual emotion perception tasks, consistent with predictions relating to enhanced sensorimotor simulation. These findings suggest that tRNS to the IFC can augment rapid, embodied emotion perception-particularly when stimuli more closely approximate real-world social communication-and contribute to the causal mapping of the hMNS, opening new avenues for studying social-emotional function in neurotypical and clinical populations.