Does the visual word form area split in bilingual readers? A millimeter-scale 7-T fMRI study

Area of Science:

• Neuroscience
• Cognitive Science
• Linguistics

Background:

• The visual word form area (VWFA) is a brain region sensitive to written words in expert readers.
• A posterior-to-anterior gradient of sensitivity to orthographic stimuli exists within the VWFA.
• It remains unclear if distinct cortical patches specialize for different languages in bilingual individuals.

Purpose of the Study:

• To investigate the neural organization of reading in bilingual individuals.
• To determine if the visual word form area (VWFA) contains language-specific patches in bilingual readers.
• To examine how learning multiple writing systems influences visual cortex specialization.

Main Methods:

• High-resolution 7-tesla functional magnetic resonance imaging (fMRI) was employed.
• Unsmoothed 1.2-millimeter fMRI data were analyzed in English-French and English-Chinese bilinguals.
• Cortical activity patterns during reading tasks were compared across languages.

Main Results:

• In English-French bilinguals, the VWFA showed near-complete overlap for both languages, with a consistent posterior-to-anterior word-similarity gradient.
• In English-Chinese bilinguals, most word-specific patches overlapped, but additional patches responded specifically to Chinese writing and faces.
• These findings indicate that the visual cortex can be differentially tuned by acquiring multiple writing systems.

Conclusions:

• The visual word form area (VWFA) is not a monolithic region but comprises distinct, highly selective cortical patches.
• While some language overlap exists, the acquisition of diverse writing systems, like Chinese, can lead to the emergence of language-specific cortical patches.
• This suggests plasticity in the visual cortex, allowing for specialization based on linguistic experience.