Transcranial ultrasound stimulation of the aMCC transiently improves performance, modulates N2 and conflict monitoring dynamics

Conflict monitoring and error processing are fundamental mechanisms underlying cognitive control and decision-making, and have been consistently associated with increased activity in the anterior midcingulate cortex (aMCC). Despite the extensive literature supporting this association, there remains a substantial gap in establishing a causal relationship between the aMCC and cognitive control processes. In the present study, we used low-intensity transcranial ultrasound stimulation (TUS), an emerging technique that enables non-invasive, deep, and focal neuromodulation, to investigate the causal role of the aMCC in behavioral and electrophysiological markers of cognitive control. Nineteen participants received 5Hz rTUS targeting the aMCC and the posterior cingulate cortex (PCC) on separate days, followed by performance of a Flanker task during EEG recording. Our findings demonstrate that TUS of aMCC modulated the relationship between conflict monitoring and the N2 component, but did not affect the coupling between error processing and the ERN, relative to the TUS of PCC, suggesting a dissociable contribution from both regions to cognitive control. These results were further supported by exploratory drift diffusion model (DDM) analyses, which revealed that, for most participants, TUS of aMCC enhanced suppression of flanker distractors. Importantly, after TUS of aMCC, but also PCC, we observed higher accuracy during early compared with later task blocks, corroborating previous findings suggesting that TUS effects are temporally dynamic and characterized by a limited post-stimulation window. HIGHLIGHTSO_LIaMCC-TUS selectively enhances response conflict sensitivity and modulates its coupling with the N2 compared with PCC-TUS. C_LIO_LIExploratory DDM analyses suggest that aMCC-TUS improves suppression of conflict-inducing distractors. C_LIO_LIaMCC-TUS and PCC-TUS both increase behavioral accuracy during the early stages of task performance. C_LIO_LITUS effects show a transient temporal profile, peaking 17-27 minutes after stimulation and declining after [~]37 minutes. C_LI