Human jaw movement in mastication and speech.

Area of Science:

• Biomechanics
• Neuroscience
• Human motor control

Background:

• Jaw movement analysis provides insights into voluntary and primitive motor functions.
• Understanding the geometric properties of jaw movement velocity is crucial for motor control studies.

Purpose of the Study:

• To analyze and compare the geometric form of human jaw movement velocity functions during mastication and speech.
• To identify similarities and differences in normalized velocity, acceleration, and deceleration patterns between these two activities.

Main Methods:

• Utilized a linear voltage displacement transducer to measure jaw movement velocity.
• Focused on the geometric shape of normalized velocity functions for jaw opening and closing movements.
• Compared movement amplitudes, maximum velocities, durations, and acceleration/deceleration profiles.

Main Results:

• Mastication exhibited greater movement amplitudes, velocities, and durations than speech.
• Normalized velocity functions showed detailed similarities in shape for both jaw closing and opening movements, irrespective of amplitude or bolus compliance.
• Opening movements differed in normalized function shape between fast and slow instances.
• Deceleration duration exceeded acceleration duration in slower movements, while they were equal in rapid movements.

Conclusions:

• Despite quantitative differences, human jaw movements in mastication and speech share fundamental kinematic similarities in their normalized velocity profiles.
• The findings suggest a common underlying motor control strategy for voluntary jaw actions.
• The study highlights how movement speed influences acceleration and deceleration dynamics in slower jaw movements.