Advancing the understanding of performance monitoring with conventional and cutting-edge non-invasive brain stimulation techniques

monitoring is a fundamental cognitive function that enables individuals to evaluate and adjust their actions in pursuit of goals. Dysfunction in this system can lead to deficits in goal-directed behaviour, conflict resolution, and error processing, as observed in several clinical conditions. Moreover, growing evidence indicates that body representation may also play a role in performance monitoring. The present work adopts a multimodal approach combining behavioural, electrophysiological, and non-invasive brain stimulation (NIBS) methods to investigate the neural mechanisms underlying performance monitoring and embodiment. In the first study, theta transcranial alternating current stimulation was applied over fronto-parietal areas to entrain endogenous theta rhythms during a Flanker-like task. The stimulation led to improved conflict adaptation reflected by faster reactions times following conflict conditions, suggesting a state-dependent facilitation of fronto-parietal communication during high-conflict processing. The second study employed transcranial magnetic stimulation (TMS) over the left dorsolateral prefrontal cortex combined with electroencephalographic recording, during action observation of an embodied virtual avatar in an immersive virtual reality environment. High-embodiment conditions elicited an enhanced contralateral fronto-parietal activation and concurrent ipsilateral inhibition, consistent with neural embodiment processes and optimized motor control. Moreover, early modulations of TMS-evoked potentials likely reflected neurotransmitter fluctuations associated with error processing, and embodiment-related variations driven by action outcome. Finally, the third study tested an excitatory transcranial focused ultrasound stimulation protocol to evaluate its capability to modulate corticospinal excitability via motor-evoked potentials. Although preliminary, the results identified an effective control condition mitigating auditory confounds. Overall, this work highlights the complementary potential of standard and innovative NIBS techniques to elucidate the neural dynamics of performance monitoring.