Subthalamic Nucleus and Sensorimotor Cortex Activity During Speech Production

Area of Science:

• Neuroscience
• Speech Science
• Motor Control

Background:

• The sensorimotor cortex's somatotopic organization for speech articulators is known.
• Subcortical encoding of speech and articulatory features remains largely unexplored.
• The subthalamic nucleus (STN), a basal ganglia node, is implicated in speech but its functional organization for articulators is unknown.

Purpose of the Study:

• To investigate how speech and articulatory features are encoded at the subcortical level, specifically within the STN.
• To compare the spatio-temporal organization of articulator-specific information in the STN and sensorimotor cortex.

Main Methods:

• Simultaneous local field potential (LFP) recordings from the STN and electrocorticography from the sensorimotor cortex in 11 Parkinson's disease patients during deep-brain stimulation (DBS) surgery.
• Analysis of high-gamma (60-150 Hz) power during the articulation of words with different primary articulators (tongue vs. lips).

Main Results:

• Increased high-gamma power was observed in both the STN and sensorimotor cortex before and during speech articulation.
• STN high-gamma activity demonstrated specificity for the primary articulator (tongue or lips), similar to the sensorimotor cortex, but without clear topography.
• Subthalamic high-gamma activity showed greater power in dorsal locations and often preceded sensorimotor cortex activity in discriminating articulators.

Conclusions:

• The STN contains articulator-specific speech information within its high-gamma activity.
• The spatial and temporal organization of this information in the STN differs from that in the sensorimotor cortex.
• These findings suggest the STN plays a significant, previously unmodeled, role in speech production at the level of vocal tract articulation.