Consecutive TBS-fMRI on scene-selective cortex reveals non-specific effects in high-level visual cortex
Edward Silson1, Iris Groen1, Chris Baker1; 1Laboratory of Brain & Cognition, NIMH, NIH
Human visual cortex contains multiple category-selective regions, including scene-selective regions that respond more strongly to visual scenes than to objects or faces. It is unclear, however, how these areas causally interact as a dedicated network to support the perception of visual scenes. Here, we used consecutive TBS-fMRI to examine how causal interference with neural activity in a posterior scene-selective region, the Occipital Place Area (OPA), affected visual responses in OPA itself, as well as the downstream Parahippocampal Place Area (PPA) and Medial Place Area (MPA). Healthy volunteers were scanned in three separate counterbalanced sessions while viewing pictures of scenes, faces, buildings, and objects. Midway in each session, participants received 60 seconds of TBS (30% max output, 50Hz, 900 pulses) to either OPA, or to a face-selective region (Occipital Face Area, OFA; active control), or no stimulation via a decoy coil (non-active control). Univariate analysis of fMRI response magnitudes revealed that active TBS induced a focal reduction in activity within OPA, as well as a remote effect in anterior PPA (but not MPA) that generalized across stimulus category. Surprisingly, however, TBS to face-selective OFA induced similar reductions in fMRI responses in PPA. This lack of site specificity might reflect strong inherent connectivity with high-level cortex, possibly due to shared retinotopy. Follow-up functional connectivity analyses indeed indicated the presence of substantial background connectivity between multiple face- and scene regions. These data suggest that TBS effects on fMRI responses are localized to specific regions but not necessarily restricted to a single category-selective network.
Topic Area: PERCEPTION & ACTION: Vision