Speech sequencing in the human precentral gyrus

Area of Science:

• Neuroscience
• Speech Science
• Motor Control

Background:

• Fluent speech relies on precise motor planning and sequencing of speech sounds.
• The neural mechanisms underlying speech-motor sequencing are not fully understood.
• Identifying the specific brain regions involved is key to understanding speech production.

Purpose of the Study:

• To investigate the neural basis of speech-motor sequencing.
• To identify brain regions involved in preparing and executing sequential speech motor plans.
• To explore the role of the middle precentral gyrus (mPrCG) in speech sequencing.

Main Methods:

• High-density direct cortical recordings were performed in 14 participants during speech tasks.
• Participants produced utterances with varying phonemic and syllabic sequence complexity.
• Electrocortical stimulation of the middle precentral gyrus (mPrCG) was used to assess its function.

Main Results:

• Sustained neural activity was observed throughout speech production, delay, and target presentation phases.
• Activity in the middle precentral gyrus (mPrCG) correlated with sequence complexity and reaction time.
• Electrocortical stimulation of the mPrCG induced speech disfluencies similar to apraxia of speech.

Conclusions:

• Speech-motor sequencing involves a distributed cortical network.
• The middle precentral gyrus (mPrCG) plays a critical role in speech-motor sequencing.
• The mPrCG is essential for preparing and executing complex speech sound sequences.