Transcranial magnetic stimulation of right inferior parietalcortex causally influences prefrontal activation for visualdetection

For effective interactions with the environment, the brain needs to form perceptual decisions based on noisy sensory evidence.Accumulating evidence suggests that perceptual decisions are formed by widespread interactions amongst sensory areas repre-senting the noisy sensory evidence and fronto-parietal areas integrating the evidence into a decision variable that is compared toa decisional threshold. This concurrent transcranial magnetic stimulation (TMS)-fMRI study applied 10 Hz bursts of four TMS (orSham) pulses to the intraparietal sulcus (IPS) to investigate the causal influence of IPS on the neural systems involved in percep-tual decision-making. Participants had to detect visual signals at threshold intensity that were presented in their left lower visualfield on 50% of the trials. Critically, we adjusted the signal strength such that participants failed to detect the visual stimulus onapproximately 30% of the trials allowing us to categorise trials into hits, misses and correct rejections (CR). Our results show thatIPS-relative to Sham-TMS attenuated activation increases for misses relative to CR in the left middle and superior frontal gyri.Critically, while IPS-TMS did not significantly affect participants’ performance accuracy, it affected how observers adjusted theirresponse times after making an error. We therefore suggest that activation increases in superior frontal gyri for misses relative tocorrect responses may not be critical for signal detection performance, but rather reflect post-decisional processing such asmetacognitive monitoring of choice accuracy or decisional confidence.