The tDCS effect on alpha brain oscillation for correct vs. incorrect object use. The contribution of the left DLPFC

Representation of the instrumentally incorrect use of an object was explored in the present research taking into account the role of the dorsolateral prefrontal cortex (DLPFC). Specifically the "inhibitory" effect performed by tDCS (transcranial Direct Current Stimulation) on DLPFC was analyzed by measuring alpha frequency band modulation when subjects processed congruous/incongruous object-related action. Thirty-four subjects performed the congruence detection task within a dynamic context (a sequence of four action frames), where the final one could be congruous or incongruous. The stimulation effect (cathode applied on the DLPFC and anode on the control site) was analyzed comparing the RTs (response times) and alpha modifications before and after the stimulation. A significant alpha increasing was found for incongruous actions in case of cathodic stimulation of DLPFC compared with the pre-stimulation condition. Moreover, RTs showed a significant reduction in response to incongruous condition after tDCS stimulation. It was suggested that the inhibition of DLPFC may limit the "incongruence effect" induced by the semantic anomaly. Secondly, the contribution of the frontal area for the semantic processing of action was demonstrated. Finally, tDCS influence on cortical oscillations was largely supported, showing alpha modulation induced by DLPFC inhibition.