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Voluntary control of human jaw stiffness
Douglas M Shiller1, Guillaume Houle, David J Ostry
1Department of Psychology, McGill University, 1205 Dr. Penfield Ave., Montreal, Quebec, Canada H3A 1B1.
Journal of Neurophysiology
|June 24, 2005
Summary
Humans can voluntarily control jaw stiffness to stabilize the jaw and improve speech precision. This study demonstrates adjustable postural stiffness in the jaw for enhanced motor control and accuracy.
Area of Science:
- Biomechanics
- Motor Control
- Speech Science
Background:
- Human arm movement studies highlight the role of stiffness control in stability and movement accuracy.
- Previous research linked jaw kinematic variability in speech to jaw stiffness patterns.
Purpose of the Study:
- To investigate voluntary control of postural stiffness in three dimensions (3D) in the human jaw.
- To determine the role of jaw stiffness control in stabilizing the jaw and meeting precision requirements for speech sounds.
Main Methods:
- A robotic device applied force pulses to the jaw to measure changes in stiffness resisting displacement.
- Experiments tested three orthogonal directions and three magnitudes of applied forces.
- Subjects' ability to voluntarily modify jaw stiffness was assessed.
Main Results:
- Subjects consistently increased jaw stiffness to resist applied forces across all tested conditions.
- Larger forces generally elicited greater increases in jaw stiffness, except in the horizontal direction.
- Jaw stiffness was differentially increased along the vertical axis to counteract disturbances.
Conclusions:
- Evidence suggests that jaw stiffness can be voluntarily adjusted by individuals.
- This voluntary control of jaw stiffness may contribute to jaw stabilization.
- Adjustable jaw stiffness likely plays a role in regulating movement variation within the orofacial system during speech.
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