Influence of posture on prepulse inhibition and its link to postural control in healthy subjects.

An unexpected loud sound typically elicits a reflexive eye-blink. This response is attenuated when preceded by a weaker non-startling stimulus, a phenomenon known as prepulse inhibition (PPI), which reflects sensory gating. PPI has been reported to differ between sitting and standing, suggesting a relationship with postural control. Sensory gating may dynamically suppress irrelevant inputs while preserving responsiveness to salient cues, a process likely supporting postural stability in complex environments. In this study, we investigated how PPI is modulated by postural demands and whether these changes relate to postural sway. Forty-five healthy participants underwent PPI testing while supine, standing on a hard surface, soft surface, and in tandem stance. We examined both auditory and somatosensory PPI, with and without visual input. Consistent with the hypothesis of dynamic gating, PPI was strongest during quiet standing on a firm surface, but weakened during more challenging postural conditions. While both somatosensory and auditory PPI were modulated, no significant modality-specific differences emerged. Removing visual input slightly reduced PPI but did not alter the overall pattern. These findings suggest that PPI reflects a flexible inhibitory mechanism tuned to postural context. While no causal relationship can be inferred, the results indicate a potential functional link between sensory gating and postural control, supporting future investigations into whether PPI could serve as a physiological marker of balance regulation.