Rapid rTPJ-driven cortical interactions encode malicious intentions during implicit moral evaluation: a TMS-EEG study

Understanding how we attribute blame when witnessing harm provides insights into moral cognition. People judge harmful actions more harshly when they are intentional rather than accidental, emphasizing intentions over outcomes. Yet, the neural dynamics underlying this asymmetry remain debated. The right temporo-parietal junction (rTPJ) plays a key role in integrating beliefs about others' intentions with observed outcomes, including moral appraisal. However, its interactions with other brain regions during moral evaluation are not fully understood. To address this gap, we employed concurrent transcranial magnetic stimulation and electroencephalography (TMS-EEG) to probe the causal impact of rTPJ stimulation on downstream cortical activity with millisecond resolution. Sixty-six adults viewed videoclips depicting intentional harm (IHS), accidental harm (AHS), or neutral actions (NAS) while engaged in a non-moral attentional task. During the task, single-pulse TMS targeted rTPJ, left TPJ (lTPJ), or the right primary somatosensory cortex (rS1, control), and TMS-evoked potentials (TEPs) were recorded to track cortical dynamics. rTPJ stimulation selectively enhanced early frontal TEPs (∼20-65 ms) during IHS compared to AHS, indicating a rapid neural encoding of malicious intent detection. Source analyses linked this effect to dorsomedial prefrontal cortex (dmPFC) engagement, suggesting a fast rTPJ-to-dmPFC communication pathway for processing intentional harm. No comparable effects were observed for lTPJ or rS1 stimulation, highlighting anatomical and functional specificity. Moreover, stronger rTPJ TEPs amplitude in IHS trials correlated with harsher moral judgments. These findings provide time-resolved evidence that the rTPJ rapidly detects harmful intent and engages prefrontal evaluative circuits, informing the neural architecture of intent-based moral judgment.