Cognitive Control Is Enhanced by Single Pulse TMS Over the Left Frontal and Parietal Areas

This study investigates the relationship between cognitive control and neural activity in the left prefrontal, premotor, and parietal cortices to elucidate how these areas contribute to cognitive control processes. Thus, we used transcranial magnetic stimulation (TMS)-electroencephalogram co-registration to investigate if and how TMS applied over these areas (compared to a sham TMS condition), at 180 ms after the stimulus onset, modulates cognitive control and underlying neural activity during the performance of a Simon task, in which participants have to inhibit the bias to react towards the stimulus location. The behavioral results showed that TMS over prefrontal and premotor areas reduced the interference in incongruent trials preceded by congruent trials, which are the most demanding trials because they require inhibiting the response towards the stimulus location and switching the stimulus-response binding. Also, TMS applied over premotor and parietal areas improved accuracy in incongruent trials. The electrophysiological results showed that TMS over prefrontal and premotor areas increased the fronto-central P300 amplitude, an event-related potential (ERP) component linked to conflict monitoring. Also, TMS over the left parietal area was related to earlier latency of the contralateral posterior negativity, an ERP linked to visuospatial attention. Importantly, the present study shows that TMS over prefrontal and premotor areas enhanced performance in the higher demanding trials by increasing neural processes underlying conflict monitoring (i.e., fronto-central P300 amplitude). Also, although further research is required, TMS over premotor and parietal areas might have strengthened cognitive control to withhold the response towards the stimulus location by modulating the parietal-premotor (or visuomotor) pathway.