Brain structure is related to speech perception abilities in bilinguals (original) (raw)
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Brain and Language, 2016
Diffusion tensor imaging was used to compare white matter structure between American monolingual and Spanish-English bilingual adults living in the United States. In the bilingual group, relationships between white matter structure and naturalistic immersive experience in listening to and speaking English were additionally explored. White matter structural differences between groups were found to be bilateral and widespread. In the bilingual group, experience in listening to English was more robustly correlated with decreases in radial and mean diffusivity in anterior white matter regions of the left hemisphere, whereas experience in speaking English was more robustly correlated with increases in fractional anisotropy in more posterior left hemisphere white matter regions. The findings suggest that (a) foreign language immersion induces neuroplasticity in the adult brain, (b) the degree of alteration is proportional to language experience, and (c) the modes of immersive language experience have more robust effects on different brain regions and on different structural features.
Bilingualism: Language and Cognition, 2023
Structural and functional brain adaptations in bilingual speakers are well documented in the neurolinguistic literature. However, far less is known about neural changes evidenced in multilingual speakers. This study investigates brain plasticity in a group of highly proficient multilinguals, fluent in four or more languages, compared to a group of monolinguals. An ROI analysis used to evaluate differences in core linguistic regions and regions associated with language control revealed robust decreases for multilinguals in grey matter thickness of two brain regions within the parietal lobe (i.e., precuneus and angular gyrus), involved in lexico-semantic processing, memory retrieval, and control maintenance. We discuss our findings in the context of emerging models characterizing trajectorial changes in brain structures associated with language experience. We consider how the demands of optimal functioning within multi-linguistic environments may foster cortical changes that manifest as decreased GM thickness in highly proficient multilingual compared to monolinguals.
Neuroimaging of phonetic perception in bilinguals
This review addresses the cortical basis of phonetic processing in bilinguals and of phonetic learning, with a focus on functional magnetic resonance imaging studies of phonetic perception. Although results vary across studies depending on stimulus characteristics, task demands, and participants’ previous experience with the non-native/second-language sounds, taken together, the literature reveals involvement of overlapping brain regions during phonetic processing in the first and second language of bilinguals, with special involvement of regions of the dorsal audio-motor interface including frontal and posterior cortices during the processing of new, or ‘difficult’ speech sounds. These findings converge with the brain imaging literature on language processing in bilinguals more generally, during semantic and syntactic processing of words and of connected speech. More brain imaging work can serve to better elucidate the precise mechanisms underlying phonetic encoding and its interaction with articulatory processes, in particular where multiple phonetic repertoires have been or are being acquired.
International Journal of Bilingualism, 2014
In the domain of language and audition, studies have shown large individual differences, within the normal range (i.e. in healthy, non-expert individuals), in performance on tasks involving speech sound processing, vocabulary knowledge, and reading, these in both monolingual and bilingual participants and in native and non-native language contexts. These individual differences have often been related to individual differences in brain structure. Evidence for structural differences is especially striking since brain structure can be assumed to be more stable, or less malleable, than brain function. Brain function, on the other hand, can be expected to change, or be plastic, after only very short periods of training/learning. The present paper provides a review of studies that have investigated the brain structural correlates of normative individual differences in aspects of language-related performance, these spanning a hierarchy in terms of the underlying complexity of processing and brain networks involved. Specifically, the review is structured so as to describe work examining the following domains, which involve progressively increasing levels of complexity in terms of the posited perceptual/cognitive sub-functions involved: 1) lower-level acoustic processing; 2) phonetic processing, including non-native speech sound learning, learning to use pitch information linguistically, non-native speech sound articulation, and phonetic expertise; 3) working memory for verbal and for pitch information; 4) semantics, in the context of lexical knowledge and of semantic memory; 5) reading; 6) syntax, both natural and artificial; 7) bilingualism; and finally 8) executive control of language in the contexts of fluency and of speech-in-noise processing. Results are discussed and synthesized in the context of lower to higher-level brain regions thought to be functionally involved in these respective domains, which are very often, if not always, the very ones that structurally partly predict domain-specific performance.
NeuroImage, 2003
The objective of the study was to explore differences in regional fMRI activation topography and lateralization between semantic and phonological tasks performed in English and Spanish in bilingual individuals. Eight bilingual (primary Spanish and secondary Englishspeaking) individuals performed fMRI noun-verb association and rhyming tasks in both Spanish and English. Functional dataset analysis within Statistical Parametric Mapping (SPM99) with overlay on T1-weighted anatomic images was performed. Significantly higher laterality indices were noted in the semantic tasks as compared with the phonological tasks in the anterior regions of interest comprising the frontal and superior temporal lobes. A task subtraction analysis demonstrated right hemispheric (inferior frontal gyrus and supramarginal gyrus) foci of significantly increased activation in the combined language phonological tasks compared to the combined language semantic tasks; similarly prominent right hemispheric activation was seen in the English phonological-English semantic subtraction, but the analogous Spanish task subtraction revealed no task-related differences. This divergence in activation topography between semantic and phonological tasks performed in the nonnative language, but not in the primary language, suggests that neural networks utilized for phonological and semantic language processing in the nonnative language may not be as similar as those in the primary language.
Structural brain differences between Monolinguals and Bilinguals
2012
Two independent lines of research provide evidence that speaking more than one language may 1) contribute to increased grey matter in healthy younger and older adults and 2) delay cognitive symptoms in mild cognitive impairment (MCI) or Alzheimer disease (AD). We examined cortical thickness and tissue density in monolingual and multilingual MCI and AD patients matched (within Diagnosis Groups) on demographic and cognitive variables. In medial temporal disease-related (DR) areas, we found higher tissue density in multilingual MCIs versus monolingual MCIs, but similar or lower tissue density in multilingual AD versus monolingual AD, a pattern consistent with cognitive reserve in AD. In areas related to language and cognitive control (LCC), both multilingual MCI and AD patients had thicker cortex than the monolinguals. Results were largely replicated in our native-born Canadian MCI participants, ruling out immigration as a potential confound. Finally, multilingual patients showed a correlation between cortical thickness in LCC regions and performance on episodic memory tasks. Given that MULTILINGUALISM AND RESERVE 2 multilinguals and monolinguals were matched on memory functioning, this suggests that increased gray matter in these regions may provide support to memory functioning. Our results suggest that being multilingual may contribute to increased gray matter in LCC areas and may also delay the cognitive effects of disease-related atrophy.
Brain Structure Predicts the Learning of Foreign Speech Sounds
2007
Previous work has shown a relationship between parietal lobe anatomy and nonnative speech sound learning. We scanned a new group of phonetic learners using structural magnetic resonance imaging and diffusion tensor imaging. Voxel-based morphometry indicated higher white matter (WM) density in left Heschl's gyrus (HG) in faster compared with slower learners, and manual segmentation of this structure confirmed that the WM volume of left HG is larger in the former compared with the latter group. This finding was replicated in a reanalysis of the original groups tested in Golestani and others (2002, Anatomical correlates of learning novel speech sounds. Neuron 35:997--1010). We also found that faster learners have a greater asymmetry (left > right) in parietal lobe volumes than slower learners and that the right insula and HG are more superiorly located in slower compared with faster learners. These results suggest that left auditory cortex WM anatomy, which likely reflects auditory processing efficiency, partly predicts individual differences in an aspect of language learning that relies on rapid temporal processing. It also appears that a global displacement of components of a right hemispheric language network, possibly reflecting individual differences in the functional anatomy and lateralization of language processing, is predictive of speech sound learning.
The Influence of Language Experience on Cortical Activation in Bilinguals 1
2005
A recurrent question concerning the neural organization of language processing in bilinguals concerns the extent to which different languages engage brain regions involved in language processing. This question continues to result in new publications and fresh debate because activation topography can be influenced by task demands and language experience. In this presentation, we will review our own work as well as work by other functional imaging laboratories concerning the role of prior language experience on brain activation topography and magnitude.