Event-related repetitive TMS reveals distinct, critical roles for right OFA and bilateral posterior STS in judging the sex and trustworthiness of faces.

Abstract

Judging the sex of faces relies on cues related to facial morphology and spatial relations between features, whereas judging the trustworthiness of faces relies on both structural and expressive cues that signal affective valence. Right occipital face area (OFA) processes structural cues and has been associated with sex judgments, whereas posterior superior temporal sulcus (STS) processes changeable facial cues related to muscle movements and is activated when observers judge trustworthiness. It is commonly supposed that STS receives inputs from OFA, yet it is unknown whether these regions have functionally dissociable, critical roles in sex and trustworthiness judgments. We addressed this issue using event-related, fMRI-guided repetitive transcranial magnetic stimulation (rTMS). Twelve healthy volunteers judged the sex of individually presented faces and, in a separate session, whether those same faces were trustworthy or not. Relative to sham stimulation, reaction times (RTs) were significantly longer for sex judgments when rTMS was delivered over right OFA but not right or left STS, and for trustworthiness judgments on male but not female faces when rTMS was delivered over right STS or left STS but not right OFA. Nonetheless, an analysis of the RT distributions revealed a possible critical role also for right OFA in trustworthiness judgments, limited to faces with longer RTs, perhaps reflecting the later, ancillary use of structural cues related to the sex of the face. On the whole, our findings provide evidence that evaluations of the trustworthiness and sex of faces rely on functionally dissociable cortical regions.