Thalamic but Not Subthalamic Neuromodulation Simplifies Word Use in Spontaneous Language

Area of Science:

• Neuroscience
• Linguistics
• Neurology

Background:

• Deep Brain Stimulation (DBS) surgery for movement disorders can lead to language impairments.
• The effects of DBS stimulation on language vary significantly depending on the targeted brain region.

Purpose of the Study:

• To investigate the impact of thalamic versus subthalamic nucleus DBS on spontaneous language production.
• To analyze word frequency and open/closed class word usage in patients with essential tremor and Parkinson's disease undergoing DBS.

Main Methods:

• Speech samples were analyzed from participants with essential tremor (VIM DBS), Parkinson's disease (STN DBS), and healthy controls.
• Analysis focused on word frequency and the proportion of open (content) and closed (function) class words.

Main Results:

• Active thalamic (VIM) DBS increased word frequency, while subthalamic (STN) DBS did not.
• Both DBS groups used fewer open class words than controls.
• VIM DBS decreased open class words, whereas STN DBS increased them.

Conclusions:

• Thalamic DBS may induce lexical simplification, favoring common words in spontaneous speech.
• Subthalamic DBS effects on language differ, potentially indicating distinct roles of thalamus and basal ganglia in language processing.