Excitatory repetitive transcranial magnetic stimulation over the dorsolateral prefrontal cortex does not affect perceptual filling-in in healthy volunteers.

Collinear flankers increase the reports of the target present, an effect attributed to excitatory activation induced by the flankers on the target location, which consequently induces the filling-in effect (Polat & Sagi, 2007). Repetitive transcranial magnetic stimulation (rTMS) is a powerful tool for non-invasive investigation of neural processing in the human brain. We explored how rTMS over the left dorsolateral prefrontal cortex (LDLPFC) affects filling-in perception in normal controls. Active and Sham rTMS were used over the DLPFC (90% of the subjects' motor threshold (MT)) using 10-Hz pulses for 5- and 20-s intertrain intervals. We used the filling-in paradigm to probe hit rates (pHit) and false-positive reports (false alarm, pFA). We found that the changes in the filling-in effect (pHit, pFA) were not significantly different between the groups. However, the reaction time (RT) was significantly reduced in the rTMS group but not in the Sham group. Our results suggest that neural processing in this area is not critical in the processing of the filling-in effect, probably because this process is mediated by lower-level visual processing.