Vestibular Perturbation Disrupts Source and Reality Monitoring
The vestibular system has been implicated in several aspects of self-representation, including bodily self-location, yet its role in episodic source and reality monitoring remains unclear. Moreover, symptoms of depersonalisation and derealisation (DPDR) have been associated with both vestibular dysfunction and altered source and reality monitoring. We tested whether noisy galvanic vestibular stimulation (nGVS) modulates source and reality monitoring during a word-encoding paradigm and whether this increased symptoms of DPDR. Sixty young adults (N = 30 active nGVS, N = 30 sham) encoded words that varied by context (spoken vs. imagined), agentic source (self vs. other), and valence (positive vs. threat) before completing source/reality judgments. Active nGVS reduced overall accuracy relative to sham on both reality and source monitoring. Across conditions, self-referential items were remembered with greater sensitivity compared to other-referential items, and spoken items were recalled with greater sensitivity than imagined items. We additionally show an interaction effect whereby active nGVS reduced accuracy specifically for imagined and threat-valenced items. Trait DPDR did not moderate the effects of stimulation, although higher trait DPDR was associated with a more liberal reality-monitoring response criterion. Results indicate that transient vestibular perturbation via nGVS can impair source monitoring for internalised and threatening stimuli and impairs cognitive distinctions between internally and externally generated events in general, supporting a role for vestibular input in maintaining self-other and reality boundaries in episodic memory.