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Anatomical variability in the cortical representation of first and second language
S Dehaene1, E Dupoux, J Mehler
1Laboratoire de Sciences Cognitives et Psycholinguistique, EHESS/CNRS URA 1198, Paris, France.
Neuroreport
|January 14, 1998
Summary
First language comprehension consistently activates the left temporal lobe. Second language comprehension shows significant variability in brain activation patterns across individuals, challenging the idea of a fixed neural substrate.
Area of Science:
- Neuroscience
- Cognitive Science
- Linguistics
Background:
- Understanding the neural basis of language comprehension is crucial.
- Investigating how the brain processes native (L1) versus second (L2) languages reveals insights into neural plasticity and specialization.
- Previous research suggests distinct neural networks for L1 and L2, but inter-subject variability in L2 processing remains an area of active investigation.
Purpose of the Study:
- To examine inter-subject variability in the cortical representation of language comprehension.
- To compare brain activation patterns during L1 (French) and L2 (English) listening comprehension in bilingual individuals.
- To test the hypothesis of a dedicated left-hemispheric network for L1 versus a variable network for L2.
Main Methods:
- Functional magnetic resonance imaging (fMRI) was employed to measure brain activity.
- Participants included moderately fluent French-English bilinguals who learned English as a second language after age seven.
- fMRI data were collected while participants listened to stories in both their native French (L1) and second language (L2).
Main Results:
- Listening to L1 consistently activated a similar network of left temporal lobe areas, primarily along the left superior temporal sulcus.
- Listening to L2 elicited highly variable patterns of brain activation across individuals, involving left and right temporal and frontal regions.
- Some subjects showed predominantly right-hemispheric activation for L2 comprehension, while others displayed left-lateralized patterns, similar to L1.
Conclusions:
- First language comprehension appears to rely on a stable, left-hemispheric cerebral network.
- Late second language acquisition does not demonstrate a consistent, reproducible biological substrate in terms of brain activation.
- The involvement of the right hemisphere in L2 comprehension is an average trend, with significant individual differences in lateralization observed.