Modulation of response inhibition through transcranial direct current stimulation (tDCS) on the right inferior frontal gyrus (RIFG)

Response inhibition is the inhibition or cancellation of an initiated, planned, or prepotent response and involves different interrelated inhibitory mechanisms. The Stop Signal Task (SST) measures the ability of individuals to cancel a planned or initiated response. Right inferior frontal gyrus (rIFG) is evaluated as the key structure of the response inhibition. Still, it is debated whether the function of the right inferior frontal gyrus is inhibition or response updating. The present study aimed to clarify the function of the rIFG under the effect of different tDCS modulations. We examined the effects of computational-modelled high-definition (HD-tDCS) and conventional tDCS on participants' stop signal (SST) and double-response task (DRT) performance compared to sham condition. 42 healthy and young participants underwent each one of the 20-minute tDCS conditions in three sessions, at least 72 hours apart, and then performed the SST and DRT tasks within 20 minutes. Bayesian paired-sample T-Test is conducted to compare stop-signal reaction time (SSRT) and double-response latency (DRT2) across conditions. For all measurements, results predicted moderate evidence against a difference between HD-tDCS, conventional tDCS, and sham stimulation. These findings suggest that neither HD-tDCS nor conventional tDCS significantly improved response inhibition or response selection performance. Further research is needed to clarify the role of rIFG modulation in response inhibition and the efficacy of different tDCS parameters. Keywords: right inferior frontal gyrus, stop signal task, tDCS, response inhibition, HD-tDCS