Simultaneously recorded subthalamic and cortical LFPs reveal different lexicality effects during reading aloud

Area of Science:

• Neuroscience
• Cognitive Science
• Neurolinguistics

Background:

• Language functions are primarily attributed to cortical areas.
• Subcortical structures' roles in language processing remain largely undefined.
• The subthalamic nucleus (STN) is explored for its potential contribution to lexical processing.

Purpose of the Study:

• To investigate the subthalamic nucleus's role in lexical processing, specifically reading aloud words and pseudowords.
• To compare neural activity in the STN with cortical regions during lexical tasks.
• To elucidate the differential involvement of STN and cortex in distinguishing lexical items.

Main Methods:

• Local field potentials were recorded from the STN and cortical areas (precentral, postcentral, superior temporal gyri).
• Data were collected from 13 individuals with Parkinson's disease undergoing awake deep brain stimulation.
• Lexicality-related neural activity was analyzed and compared between STN and cortical sites.

Main Results:

• Both STN and cortical activity showed significant task-related modulations.
• The STN exhibited increased gamma band activity (31-70 Hz) for pseudowords versus words during spoken responses.
• Cortical activity in the precentral gyrus showed a greater decrease in beta band activity (12-30 Hz) for pseudowords, with other cortical sites showing varied lexicality effects.

Conclusions:

• The subthalamic nucleus and sampled cortical regions exhibit distinct patterns of neural activity related to lexical processing.
• Findings suggest a differential involvement of the STN and cortex in processing lexical distinctions.
• This study highlights the subcortical nucleus's contribution to language functions previously thought to be exclusively cortical.