Proprioceptive ability at the lips and jaw measured using the same psychophysical discrimination task

Area of Science:

• Neuroscience
• Biomechanics
• Human Physiology

Background:

• Orofacial muscles and temporomandibular joint (TMJ) possess distinct biomechanical properties.
• Facial musculature lacks typical muscle spindle proprioceptors, unlike conventional joints.

Purpose of the Study:

• To compare proprioceptive abilities between orofacial muscles (lips) and the temporomandibular joint (jaw).
• To investigate the correlation of proprioception between different facial structures.

Main Methods:

• A novel psychophysical task was used to assess proprioception in 21 neuro-typical adults (18-65 years).
• The task involved precise measurement of closure accuracy onto stimuli of varying diameters after a fixed starting separation.

Main Results:

• Lip proprioception (mean score 0.84) was significantly more accurate than jaw proprioception (mean score 0.79).
• Response error was lower for lip movements (0.1 mm less).
• Proprioceptive scores for lips and jaw were significantly correlated (r=0.5, p=0.018).

Conclusions:

• The orbicularis oris muscle exhibits a highly effective proprioceptive mechanism, distinct from the TMJ.
• Correlated proprioception between facial structures suggests coordinated use and has implications for clinical assessment.
• Findings support potential for coordinated rehabilitation strategies and predicting premorbid function in orofacial injuries.