Postural modulation of prepulse inhibition and its link to postural control: Insights from healthy subjects

An unexpected loud sound typically triggers a reflex eye-blink. A reliable pre-warning attenuates reflex blinking, a phenomenon known as ‘pre-pulse inhibition’ (PPI). PPI is enhanced when standing, suggesting that PPI might contribute to adaptive postural control. Here, we tested whether PPI is modulated under different postural conditions and identifies the determinants of this modulation. Forty-five participants’ PPI and postural sway were tested while supine, standing on a hard surface, soft surface, and in tandem stance. The effect of visual feedback, auditory (aPPI) and somatosensory (sPPI) prepulse modalities, and different interstimulus-intervals were tested. Compared to hard-surface, PPI is attenuated by soft-surface and tandem standing (p < 0.0125). sPPI correlates with sway area during hard surface standing (ρ=+0.321; p = 0.032) and sway velocity on tandem standing (ρ=+0.344; p = 0.021). While both sPPI and aPPI are modulated, sPPI shows greater inhibition. Abolishing the visual feedback by closing the eyes only minimally reduces sPPI. PPI changes depending on postural demands, with less inhibition during tasks requiring enhanced balance control. This suggests that PPI network adjusts to regulate sensory inputs, enhancing inhibition to prevent sensory overflow when postural control is less demanding and reducing inhibition to increase sensory feedback as task difficulty increases. This study establishes a link between PPI and postural control, which opens the possibility to test PPI as a marker of postural control network activity under specific circumstances.