The vestibular system plays a central role in maintaining upright balance by encoding head motion and integrating this information with visual and somatosensory cues. When the relationship between self-motion and vestibular input becomes unreliable, the central nervous system (CNS) adapts to preserve postural stability. Previous studies demonstrated that adaptation occurs when altered vestibular input remains coherently linked to head movement; however, it remains unclear whether recalibration persists when this motion--afference relationship is degraded by non-coherent noise (\cite{Heroux2015, Chen2020}).

This report investigates vestibular recalibration under two forms of galvanic vestibular stimulation: a coherent, head-coupled stimulus derived from a validated motion-to-current conversion model, and the same stimulus combined with high-amplitude non-coherent noise. Fourteen participants completed standing-balance trials assessing baseline sway, externally replayed vestibular perturbations, and short-term learning during a brief eyes-open calibration period. Postural stability was quantified using T1 lateral displacement, and adaptation was assessed by comparing sway variability before and after calibration.

Under coherent stimulation, participants exhibited clear recalibration: sway variability increased immediately after stimulation onset but decreased during calibration, returning toward baseline levels. In contrast, non-coherent stimulation produced substantially greater sway and reduced adaptive improvement, indicating that noise limits the CNS’s ability to reinterpret vestibular input. Nonetheless, some recalibration was still observed, although highly variable across individuals. Additional findings revealed transient post-stimulation after-effects and modest order-dependent influences, though these did not reach statistical significance.

Overall, the results indicate that vestibular recalibration depends critically on the coherence and reliability of motion-linked vestibular input. When the motion–afference mapping is degraded by an external noise source, the CNS down-weights vestibular cues and exhibits limited adaptive learning.