Articulatory Gain Predicts Motor Cortex and Subthalamic Nucleus Activity During Speech

Area of Science:

• Neuroscience
• Speech Motor Control
• Auditory Neuroscience

Background:

• Precise speech relies on articulatory gain, a key aspect of speech motor control.
• The basal ganglia are implicated in regulating movement gain for limbs.
• The role of the basal ganglia in articulatory gain remains largely unexplored.

Purpose of the Study:

• To investigate the contribution of the basal ganglia to articulatory gain.
• To explore the relationship between basal ganglia activity and speech precision.

Main Methods:

• Recorded local field potentials (LFP) from the subthalamic nucleus (STN), precentral gyrus, and postcentral gyrus during deep brain stimulation surgery.
• Participants read aloud syllables while LFP data were collected.
• Assessed articulatory gain indirectly using the F2 Ratio, an acoustic measure of vowel acoustics.

Main Results:

• The F2 Ratio correlated with alpha and theta activity in the precentral gyrus and STN.
• No correlations were found with the postcentral gyrus.
• Higher beta activity synchrony between the STN and precentral gyrus correlated with lower F2 Ratios, indicating impaired articulatory precision.

Conclusions:

• Articulatory gain appears to be encoded within the basal ganglia-cortical loop.
• Basal ganglia-cortical network synchrony, particularly beta activity, influences speech precision.
• These findings offer insights into the neural mechanisms of speech motor control.