EARLY EVIDENCE ON THE EFFECTS OF AN ACCELERATED TDCS PROTOCOL TARGETING THE RIGHT INFERIOR FRONTAL GYRUS ON INHIBITORY CONTROL, METACOGNITIVE SENSITIVITY, AND DELAY DISCOUNTING

Although the clinical application of accelerated transcranial direct current stimulation (tDCS) protocols has become increasingly frequent in recent years, their use for investigating human cognitive functioning remains limited. Concurrently, the right inferior frontal gyrus (rIFG) has emerged as a key target for neuromodulation due to its involvement in cognitive processes consistently impaired in psychiatric populations. Thus, the aim of this work was to test the short- and early long-term effects of an accelerated tDCS protocol targeting the rIFG on three transdiagnostic higher-order functions, namely inhibitory control, delay discounting, and metacognitive sensitivity. Fifteen subjects underwent two accelerated tDCS sessions, each consisting of three daily stimulations that were either real or sham, followed by a 24 hours post-stimulation follow-up assessment. Participants were assessed at multiple timepoints using a monetary intertemporal choice task, a two-alternative forced choice task with confidence judgments, and a stop-signal task. Linear mixed effects models showed a significant cumulative effect of anodal stimulation on inhibitory control within the first day of intensive treatment (p = 0.030), but not at 24 hours post-stimulation. At 24 hours post-stimulation, a trend toward reduced delay discounting and enhanced metacognitive sensitivity was also observed under real stimulation compared to sham. These preliminary results suggest that accelerated tDCS targeting the rIFG consistently enhances response inhibition, although additional sessions might be required to sustain this effect. If confirmed, such protocols could be applied to clinical populations with impaired inhibitory control, delay discounting, and metacognitive sensitivity, such as individuals with Tourette syndrome, obsessive-compulsive disorder, or substance addiction.