Lateralized neural mechanisms underlying the modulation of response inhibition processes.

Functional cerebral asymmetries (FCAs) are an important modulator of cognitive functions. Here, we investigated the temporal and spectral dynamics as well as the cortical networks underlying the lateralized modulation of executive functions related to response inhibition. To this end, we recorded event-related potentials (ERPs) during tachistoscopic presentation of verbal 'Go' and 'Nogo' stimuli in the left (LVF) and the right visual field (RVF). Participants committed fewer false alarms to verbal Nogo stimuli presented in the RVF than to stimuli presented in the LVF. This asymmetry was paralleled by neurophysiological data. The Nogo-N2 and related delta frequency band power were stronger when response inhibition was driven by stimuli presented in the LVF, implying a stronger response conflict. This effect was mediated by stronger activations in bilateral medial-prefrontal and especially left parietal networks. This shows that asymmetries in behavioural performance do not necessarily reflect differences in the overall capability of one hemisphere to solve a task. Even though information is initially confined to one hemisphere after tachistoscopic presentation, this does not primarily cause behavioural asymmetries. Instead, hemispheric dominances in information processing can induce differences in demands on cognitive processes operating via bilateral networks that ultimately drive behavioural asymmetries.