Longitudinal evidence for subcortical learning systems involved during adult L2 acquisition
Helyne Adamson1, Tomás Goucha2, Alfred Anwander2, Matthias Schwendemann1, Martin Lišaník1, Angela Friederici2
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
Second language (L2) learning necessitates a reorganization of the brain. However, it remains unclear precisely how these plastic changes occur in individuals that did not acquire both languages simultaneously from a very early age and, moreover, which networks are involved (and to what degree) in successful L2 acquisition. Evidence suggests specific language skills (e.g. syntax comprehension, semantic knowledge) may have localized structural correlates within the language network (Friederici & Gierhan, 2013). Yet previous studies on bilingualism and L2 learning have also demonstrated an increased involvement of brain regions beyond the classical language network, recruiting structures associated with motor planning, conflict monitoring, and procedural and declarative memory. If there are characteristic structural and functional differences between monolinguals and late-bilinguals, as has been suggested (Li et al., 2014; Mechelli et al., 2004), one valuable method of study lies in following monolingual individuals as they learn another language
To explore this, we conducted a multi-modal longitudinal study of adult second language learners. A total of 59 Arabic native speakers (age 24 +/- 5 years) were taught German and split into either a syntax training group (n=31) or a semantic training group (n=28). Structural, functional, and behavioral measures were assessed over the course of 3-months during intensive L2 instruction. To assess structural network changes, high resolution diffusion MRI scans were acquired and fractional anisotropy (FA) was computed as a measure of white and grey matter microstructural organization. The participants took part in an L2 task-based fMRI session assessing their brain activations to both a semantic and a syntactic task. With this fMRI experiment, we also aimed to isolate areas demonstrating increased activation during L2 processing. To assess additional behavioral and language skills possibly associated with language learning, a battery of language aptitude tests was administered. Voxel-based statistics in SPM were applied to examine whole brain changes over time, along with differences in change over time between teaching groups. Extracted ROIs of significant changes over time and differences between groups were then correlated to language aptitude measures
Subcortical, medial temporal lobe, brain stem, internal capsule, and anterior corpus callosum regions showed an initial change during the first 3 months. A difference in areas of change between groups was found within the left internal capsule anterior to the putamen and thalamus and in the white matter connecting right anterior temporal lobe regions. In both the left internal capsule and right temporal lobe white matter, the semantic group showed a decrease in FA, while the syntactic group demonstrated an increase. Separating the groups, the syntactic group revealed multiple correlations of FA change to accuracy scores in the administered language tasks. Principally, a positive correlation was found in performance during the syntactic condition to structural changes in the left thalamus and bilateral internal capsule.
These results support a broad involvement of brain regions underlying adaptation of higher level cognitive functions, such as language. Adult language learning may fundamentally rely on more evolutionarily older learning systems involved in sensory integration, reward, and automation of response behavior. Controlled semantic retrieval, syntactic comprehension, phonemic perception and articulation, language conflict management and switching are all language skills necessary for learning a new language. Efficient use of lower level learning systems and interhemispheric information exchange, as opposed to an extensive recruitment and reshaping of the adult language network, may be the defining feature of succesful L2 acquisition during the early phases of learning.
Language Acquisition 1
Learning and Memory:
Learning and Memory Other 2
WHITE MATTER IMAGING - DTI, HARDI, DSI, ETC
1|2Indicates the priority used for review
My abstract is being submitted as a Software Demonstration.
Please indicate below if your study was a "resting state" or "task-activation” study.
Healthy subjects only or patients (note that patient studies may also involve healthy subjects):
Was any human subjects research approved by the relevant Institutional Review Board or ethics panel? NOTE: Any human subjects studies without IRB approval will be automatically rejected.
Was any animal research approved by the relevant IACUC or other animal research panel? NOTE: Any animal studies without IACUC approval will be automatically rejected.
Please indicate which methods were used in your research:
For human MRI, what field strength scanner do you use?
Which processing packages did you use for your study?
Provide references using author date format
Li, P. (2014). Neuroplasticity as a function of second language learning: Anatomical changes in the human brain. Cortex.
Mechelli, A. (2004). Structural plasticity in the bilingual brain: Proficiency in a second language and age at acquisition affect grey-matter density. Nature, 431(7010), 757.