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Lily M. Solomon-Harris, Jennifer K.E. Steeves; Consecutive TMS–fMRI: Remote effects of OFA disruption on the face perception network . Journal of Vision 2014;14(10):124. doi: 10.1167/14.10.124.
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The face perception system is comprised of a network of connected regions including the middle fusiform gyrus ("fusiform face area" or FFA), the inferior occipital gyrus ("occipital face area" or OFA), and the posterior part of the superior temporal sulcus. These regions are typically active bilaterally but may show right hemisphere dominance. The functional magnetic resonance imaging (fMRI) response of the right FFA is normally attenuated for face stimuli of the same compared to different identities, called fMR adaptation. Patients with prosopagnosia who are unable to visually recognize faces and who show right OFA damage, nonetheless show face-selective activation at the right FFA (Rossion et al., 2003; Steeves et al., 2006). However, the sensitivity to face identity is abnormal in the right FFA and does not show the typical release from adaptation for different face identities (Steeves et al., 2009). This indicates that in these patients, the FFA is not differentiating face identity and suggests that an intact right OFA is integral for face identity coding. We used offline repetitive transcranial magnetic stimulation (TMS) to temporarily disrupt processing in the right OFA in healthy controls. We then immediately performed fMRI to observe changes in BOLD signal across the face network using a face adaptation paradigm. We found that release from adaptation persisted despite right OFA disruption. Furthermore, we observed increased activity in remote face-selective regions. These results demonstrate remote effects of TMS in the face perception network where TMS disruption at the target site may permit connected regions in the network to utilize more of the available processing power. Unlike patients with OFA damage, TMS disruption of the OFA in one hemisphere appears to leave FFA response properties intact.
Meeting abstract presented at VSS 2014
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