The dorsal medial frontal cortex mediates automatic motor inhibition in uncertain contexts: evidence from combined fMRI and EEG studies.
Response inhibition is commonly thought to rely on voluntary, reactive, selective, and relatively slow prefrontal mechanisms. In contrast, we suggest here that response inhibition is achieved automatically, nonselectively, within very short delays in uncertain environments. We modified a classical go/nogo protocol to probe context-dependent inhibitory mechanisms. Because no single neuroimaging method can definitely disentangle neural excitation and inhibition, we combined fMRI and EEG recordings in healthy humans. Any stimulus (go or nogo) presented in an uncertain context requiring action restraint was found to evoke activity changes in the supplementary motor complex (SMC) with respect to a control condition in which no response inhibition was required. These changes included: (1) An increase in event-related BOLD activity, (2) an attenuation of the early (170 ms) event related potential generated by a single, consistent source isolated by advanced blind source separation, and (3) an increase in the evoked-EEG Alpha power of this source. Considered together, these results suggest that the BOLD signal evoked by any stimulus in the SMC when the situation is unpredictable can be driven by automatic, nonselective, context-dependent inhibitory activities. This finding reveals the paradoxical mechanisms by which voluntary control of action may be achieved. The ability to provide controlled responses in unpredictable environments would require setting-up the automatic self-inhibitory circuitry within the SMC. Conversely, enabling automatic behavior when the environment becomes predictable would require top-down control to deactivate anticipatorily and temporarily the inhibitory set.
['Albares|Marion|M|', 'Lio|Guillaume|G|', 'Criaud|Marion|M|', 'Anton|Jean-Luc|JL|', 'Desmurget|Michel|M|', 'Boulinguez|Philippe|P|']
D000328:Adult D001931:Brain Mapping D002755:Choice Behavior D004569:Electroencephalography D005071:Evoked Potentials D005260:Female D005625:Frontal Lobe D006801:Humans D007091:Image Processing, Computer-Assisted D007266:Inhibition, Psychological D008279:Magnetic Resonance Imaging D008297:Male D009068:Movement D010100:Oxygen D011930:Reaction Time D055815:Young Adult
automaticity fMRI EEG response inhibition go/nogo Alpha oscillations executive control task setting