Dissociation of working memory processing associated with native and second languages: PET investigation

Area of Science:

• Neuroscience
• Cognitive Science
• Psycholinguistics

Background:

• Verbal working memory is crucial for language comprehension and problem-solving.
• The prefrontal cortex is a key area for working memory, with potential domain-specific divisions.
• While brain differences exist between native and second languages, verbal working memory dissociation remains unclear.

Purpose of the Study:

• To identify neural correlates of verbal working memory for native (Korean) and second (English) languages.
• To investigate functional divisions within verbal working memory processing based on language proficiency.

Main Methods:

• Used H2(15)O positron emission tomography in 14 subjects.
• Administered a two-back task with visual stimuli: simple pictures, English words, and Korean words.
• Subjects were highly proficient in Korean and poorly proficient in English.

Main Results:

• Native language working memory activated the anterior right dorsolateral prefrontal cortex and left superior temporal gyrus.
• Second language working memory activated the posterior right dorsolateral prefrontal cortex and left inferior temporal gyrus.
• Distinct neural patterns suggest language-specific functional systems within the brain.

Conclusions:

• The right dorsolateral prefrontal cortex and left temporal lobe form distinct, language-related functional systems.
• Native language working memory relies on phonological processing, while second language working memory involves higher-order visual control.