The goal of this observational study is to investigate how oral proprioceptive stimuli affect visual perception and auditory-visual integration in healthy young adults. The main questions it aims to answer are:

• Can Oral Proprioceptive Stimuli (OPS) induce Visual pseudo-Scotomas (VS) in the absence of other stimuli?
• Can Oral Proprioceptive Stimuli (OPS) modulate or eliminate Visual pseudo-Scotomas (VS) induced by auditory stimuli?

Researchers evaluated 38 healthy adults (aged 20-29) using the Vertical Maddox Test to detect functional visual alterations under different conditions. The study included four phases:

• Baseline assessment with no stimuli.
• Assessment with auditory stimuli alone.
• Assessment with simultaneous auditory and Oral Proprioceptive Stimuli (OPS), including tongue/lip positions (Combined Oral Stimuli) and dental pressure/traction stimuli (Dental Stimuli).
• Assessment with Oral Proprioceptive Stimuli (OPS) alone.

Visual pseudo-scotomas were recorded based on participant responses. The study was approved by the local ethics committee and all participants gave informed consent.

Proprioception plays a well-established role in postural control and motor coordination, but increasing evidence supports its involvement in higher-level sensory processing, including spatial localization and multisensory integration. Given the anatomical overlap of trigeminal afferents innervating both oculomotor and orofacial structures, this study focused on the potential interplay between the stomatognathic and visual systems.

This study is an observational investigation with an experimental within-subject design with repeated measures in healthy volunteers.

The aim is to investigate the influence of oral proprioceptive stimuli on visual perception and audiovisual integration in healthy young adults, and explore whether non-invasive oral stimuli could modulate the occurrence of transient visual distortions-specifically Visual pseudo-Scotomas (VS)-when binocular vision is altered, and whether these stimuli could counteract the effects induced by auditory input.

Participants have been screened to ensure normal hearing, vision, and dental status, and underwent testing using the Vertical Maddox Test, which induces a dissociation in binocular vision that relies heavily on proprioceptive cues.

The experimental protocol was composed of four phases:

1. Baseline evaluation with no stimuli.
2. Application of auditory stimuli (500 Hz tones delivered through headphones) to assess their influence on visual perception.
3. Application of simultaneous auditory and Oral Proprioceptive Stimuli (OPS), including both Combined Oral Stimuli (COS, such as specific tongue and lip positions) and Dental Stimuli (DS, consisting of gentle pressure/traction on central incisors using a calibrated probe).
4. Application of Oral Proprioceptive Stimuli (OPS) alone, without sound.

Participants were asked to report the occurrence and location of any Visual pseudo-Scotomas (VS) observed during each phase. These were defined as functional visual field losses detected via the Vertical Maddox Test, with no underlying ocular pathology.

This protocol was developed based on prior work investigating ocular and oral proprioception and its role in multisensory integration. No pharmacological agents, devices, or therapeutic interventions were used. The study is observational in nature, and no biospecimens were collected or retained.

EXCLUSION CRITERIA:

• General criteria:

  • Treatment with psychotropic drugs
  • Hearing loss in one or both ears

• Visual criteria:

  • Visual acuity worse than 20/20 in one or both eyes
  • Stereopsis (three-dimensional vision) less than 120 arc sec
  • Vertical phoria greater than 0.75 Δ
  • Strabismus operated on or not
  • Ongoing optometric rehabilitation
  • History of amblyopia

• Dental criteria:

  • Missing one or more incisors
  • Presence of conservative, prosthetic or orthodontic treatment on one or more incisors (fillings, root canal treatments, veneers, crowns, brackets, Invisalign type attachments...).

The participants of the study were healthy young adults recruited among the students of the Faculty of Medicine and Health Sciences of the University of Barcelona, who did not present any of the exclusion criteria listed above.

The individual participant data (IPD) that might be shared include anonymized data on age, sex, inclusion/exclusion criteria, and responses related to the presence or absence of visual pseudo-scotomas during each phase of the experimental protocol. Data would be fully de-identified and shared only upon request, under appropriate ethical and legal conditions. At present, no final decision has been made regarding IPD sharing.