Jaw-muscle activity during speech with the mandible fixed

Area of Science:

• Neuroscience
• Speech Science
• Biomechanics

Background:

• Understanding the neural control of speech articulation is crucial for diagnosing and treating speech disorders.
• The role of jaw muscle activity during speech, particularly when jaw movement is restricted, remains an area of investigation.

Purpose of the Study:

• To investigate the electromyographic activity of jaw muscles during speech with and without jaw movement.
• To evaluate the consistency of findings with existing models of motor control for speech production.

Main Methods:

• Electromyographic recordings were obtained from four primary jaw muscles: anterior temporalis, masseter, medial pterygoid, and lateral pterygoid.
• Recordings were taken during speech tasks under two conditions: with the jaw freely moving and with jaw movement restricted by a bite block.

Main Results:

• Discrete bursts of activity were observed in the recorded jaw muscles even when the jaw was prevented from moving.
• The frequency, timing, and magnitude of this muscle activity were comparable to those observed when the jaw was free to move.
• These findings challenge the necessity of a central simulation process for coordinating jaw movements during speech.

Conclusions:

• The observed jaw muscle activity during fixed-jaw speech is more consistent with motor control systems utilizing lower-level neural mechanisms.
• This suggests that articulatory coordination may rely more on intrinsic neural feedback loops than on a predictive central command system.
• Further research into these lower-level neural mechanisms could inform therapeutic strategies for speech impairments.