Effect of Oral Proprioceptive Stimuli on Auditory–Visual Integration

Proprioception contributes to body position, balance, movement control, sensory spatial localization and multisensory integration. Interactions between the stomatognathic and visual systems through trigeminal afferents have been demonstrated. This exploratory study investigated whether oral proprioceptive stimulation influences visual perception and modulates sound-induced visual changes under binocular dissociation. Thirty-eight healthy adults participated. The Vertical Maddox Test (VM), which induces binocular dissociation and increases reliance on ocular proprioception, assessed visual perception during four experimental phases: baseline without stimulation, sound stimulation, simultaneous sound and oral proprioceptive stimulation, and oral proprioceptive stimulation alone. Oral proprioceptive stimuli (OPS) comprised combined oral stimuli (COS), involving tongue and lip positions, and dental stimuli (DS), consisting of controlled pressure or traction applied to the incisors. None of the participants reported visual pseudo-scotomas (VS; i.e., small, transient visual losses) at baseline, whereas 89.5% (95% CI [75.9, 95.8]) reported VS under at least one experimental condition. VS was reported by 60.5% (95% CI [44.7, 74.4]) during sound stimulation and by 81.6% (95% CI [66.6, 90.8]) under at least one oral proprioceptive condition. Among participants with sound-induced VS, 78.3% (95% CI [58.1, 90.3]) achieved VS elimination with at least one oral proprioceptive stimulus while sound continued. Elimination was achieved with DS only in 21.7% (95% CI [9.7, 41.9]), with COS only in 8.7% (95% CI [2.4, 26.8]), and with both in 47.8% (95% CI [29.2, 67.0]). Among participants who responded to both stimulus types, complete, partial, and no concordance between anatomically equivalent stimulations were observed in 45.5% (95% CI [21.3, 72.0]), 45.5% (95% CI [21.3, 72.0]), and 9.1% (95% CI [1.6, 37.7]), respectively. These exploratory findings support functional sensory interactions between the visual and stomatognathic systems and suggest that oral proprioception may influence visual perception and modulate sound-induced visual changes. They also suggest broader oral sensory contributions to central sensory processing.