Vestibular modulation of face identity processing: Differential effects on self, familiar and unfamiliar faces

The vestibular system is increasingly recognized for its role in higher-order cognitive functions, including bodily self-representation. However, its involvement in self-face representation remains unexplored. In the present study, we investigated whether artificial modulation of the vestibular system via Galvanic Vestibular Stimulation (GVS) can influence the representation of one's own and others' faces. Fifty healthy individuals performed two face-recognition tasks (explicit and implicit) while receiving sinusoidal bipolar GVS or Sham stimulation. During tasks, images of faces belonging to Self (S), Familiar-Others (FO), and Stranger-Others (SO) were presented. Participants were randomly assigned to one of two groups according to GVS polarity: left-anodal/right-cathodal (L-GVS) or right-anodal/left-cathodal (R-GVS). In both tasks, a robust Self Advantage (SA) emerged, with faster reaction times (RTs) for self-faces than familiar-other and stranger-other faces. Interestingly, an interaction between Identity, Stimulation, and GVS polarity was observed only in the explicit task. Specifically, R-GVS slowed recognition of self-faces relative to Sham. In contrast, L-GVS slowed recognition of stranger-other faces while facilitating recognition of familiar-other faces. Notably, under L-GVS RTs for self-faces no longer differ from those of familiar-other faces, effectively shifting the SA toward a more general familiarity advantage. Galvanic Vestibular Stimulation modulates face recognition and self-other distinction, in a polarity-dependent manner, providing causal evidence for vestibular involvement in self-face representation and identity processing.