Language processing within the striatum: evidence from a PET correlation study in Huntington's disease

Area of Science:

• Neuroscience
• Psycholinguistics
• Cognitive Neurology

Background:

• The role of sub-cortical structures, particularly the striatum, in language processing is debated.
• Existing models propose striatal involvement in either lexical recovery or rule application, but not both.
• Conflicting views necessitate a study to clarify the striatum's comprehensive function in language.

Purpose of the Study:

• To investigate the dual role of the striatum in both lexical and rule-based language processing.
• To identify distinct sub-regions within the striatum responsible for different linguistic functions.
• To explore these functions in the context of a neurodegenerative disorder affecting striatal circuits.

Main Methods:

• Utilized Positron Emission Tomography (PET) scanning to assess metabolic activity in striatal sub-regions.
• Correlated metabolic data with behavioral scores from rule/lexicon tasks in 31 early-stage Huntington's disease (HD) patients.
• Included tasks from word morphology, syntax, and a non-linguistic arithmetic domain.

Main Results:

• Behavioral assessments revealed impairments in both lexical and rule-based processing in HD patients.
• Deficits were more pronounced in rule application compared to lexical recovery.
• Both processing types correlated with the left striatum, but engaged distinct sub-regions.

Conclusions:

• The left striatum supports both linguistic and arithmetic processing through distinct circuits.
• Ventral striatal regions are implicated in rule computations.
• Dorsal striatal regions are associated with lexical processing mechanisms.