Brain structure is related to speech perception abilities in bilinguals

Area of Science:

• Neuroscience
• Psycholinguistics
• Cognitive Science

Background:

• Brain morphology influences learning new speech sounds in laboratory settings.
• Limited understanding exists regarding the neuroanatomy of second language (L2) speech perception in naturalistic learning environments.
• Individual differences in L2 sound discrimination are significant for proficient bilinguals.

Purpose of the Study:

• To investigate the neuroanatomical basis of individual differences in L2 speech perception among highly proficient bilinguals.
• To examine the association between cortical morphology (cortical thickness and surface area) and behavioral performance in distinguishing L2 speech sounds at lexical and prelexical levels.

Main Methods:

• Structural Magnetic Resonance Imaging (MRI) was used to measure vertex-wise cortical thickness (CT) and surface area (CSA).
• Two groups of highly proficient bilinguals were selected based on their ability to discriminate similar L2 sounds (prelexical vs. lexical tasks).
• Statistical analyses were performed to correlate cortical morphology with performance in L2 speech sound discrimination.

Main Results:

• Lexical task performance was negatively associated with increased cortical thickness in the left temporal cortex and angular gyrus.
• Poorer performance in the lexical task correlated with greater surface area in the left precuneus.
• These findings suggest a link between specific brain structure characteristics and phonological information processing in word recognition.

Conclusions:

• Cortical morphology in the left temporal cortex, angular gyrus, and left precuneus is relevant for word recognition involving phonological processing in a second language.
• The study proposes that increased cortical thickness and surface area in sound-to-meaning mapping regions among less proficient perceivers may be a result of plastic changes due to prolonged L2 exposure and functional activity.