The Effects of rTMS on Criterion Shifting during Memory Recognition
Evan Layher1, Lukas Volz1, Tyler Santander1, Michael Miller1; 1University of California Santa Barbara
Previous recognition memory fMRI studies revealed that the successful retrieval effect (SRE) contrast (hits > correct rejections) is associated with increased activity across the inferior and middle frontal gyri (IFG and MFG) when people establish a cautious versus lax decision criterion. To expand on this finding, we used offline repetitive transcranial magnetic stimulation (rTMS) to inhibit cortical regions within the right IFG and MFG in an attempt to disrupt the maintenance of a cautious criterion. Participants (N=20) conducted memory recognition tasks during fMRI scanning, which included a cautious decision bias (only 30% of test images were studied). This provided us with subject-specific rTMS target sites based on peak activity within the right IFG and MFG from the SRE contrast. On 3 separate research visits, participants performed memory recognition tasks before and after rTMS. During a single visit, participants performed two study/test cycles that included studying 100 face images (300ms each) followed by two recognition tests with either 30% (cautious) or 70% (lax) of test items being previously studied. In between the study and test phases of the second cycle, participants underwent rTMS of the IFG, MFG, or occipital vertex (sham). Contrary to our predictions, we observed that participants established a more cautious decision criterion following rTMS of the right IFG (p<0.05), but no difference in criterion shifting following rTMS of the right MFG relative to sham stimulation. These results suggest that rTMS of the right IFG can causally manipulate a decision criterion (although in the opposite direction as predicted).
Topic Area: THINKING: Decision making