To stop or not to stop: A high spatio-temporal resolution study of response inhibition using MEG

Event-related potential studies in healthy adults and children have shown that stimuli signaling the need to stop elicit a robust, right-frontal-maximal N2 that is strongly reduced in children with attention-deficit hyperactivity disorder. To further investigate the mechanisms of normal response inhibition, the Stop Signal Task was applied to 12 healthy young adults using whole-head magnetoencephalography. The evoked magnetic response to Successful Stops showed an earlier and greater amplitude N2-like peak (mean = 167 ms) relative to Failed Stops. Such success-related modulation had a scalp distribution over frontomedial scalp. Dipole source analysis using BESA and a five-dipole fMRI-constrained solution identified a dACC source as a major contributor to the success-related N2-like modulation, while right DLPFC appears to contribute to differences in early preparatory or orienting mechanisms.