Sequence of language acquisition as a factor determining language comprehension centre location in cerebral cortex in...

Area of Science:

• Neuroscience
• Cognitive Science
• Linguistics

Background:

• Multilingualism is common, yet the brain's representation of sequentially acquired languages is poorly understood.
• Lack of research hinders neurosurgical management guidelines for multilingual patients.

Purpose of the Study:

• Identify specific brain regions for speech comprehension in each language (L1-L4) of multilingual individuals.
• Investigate the link between the order of language acquisition and its cortical representation.

Main Methods:

• Recruited highly proficient multilinguals who learned languages after age three.
• Used passive listening with fMRI (T1-weighted and echo-planar imaging) to measure brain activity (BOLD signal).
• Compared brain activity for L2, L3, L4 against native language (L1) and an unknown language (LN) using SPM12.

Main Results:

• Observed a progressive decrease in left-hemisphere dominance from L1 to L4.
• L2 showed increased activation in right middle temporal gyrus; L3 in left fusiform gyrus compared to L1.
• L1 exhibited greater activation than later-acquired languages; L2/L3 showed increased right insula activity vs. LN.

Conclusions:

• Distinct cortical areas are involved in processing sequentially acquired languages.
• Recommend routine perioperative cortical mapping for L1, L2, and L3.
• Consider L4 mapping on a case-by-case basis; further research on speech production is needed.