Poster E45, Thursday, August 22, 2019, 3:45 – 5:30 pm, Restaurant Hall
Arcuate fasciculus microstructure correlates with cross-linguistic measures of multilingual language experience and L1 skills
Jocelyn Caballero1, Nikola Vukovic1, Olga Kepinska1, Fumiko Hoeft1,2,3;1University of California, San Francisco, 2University of Connecticut, 3Haskins Laboratories
The complexity of a child’s phonemic inventory fundamentally depends on their linguistic environment such as the number and types of languages they are exposed to (Kuhl et al. 2003). Each of these languages is characterized by a set of discrete sounds, thus making up a unique phonemic inventory for each child. Over time, exposure to these sounds forms a crucial component of a child’s linguistic skills such as phonological awareness and impacts language developmental milestones. Such potent of an environmental influence must be represented in the child’s brain. The Arcuate fasciculus (AF), a white matter tract that has repeatedly been linked to phonological abilities is a likely candidate. The goal of the current study was to examine the AF as it relates to a behavioral index of phonological awareness and naturalistic language input. We tested a unique sample of L1-English kindergarteners that had been exposed to multiple languages during their preschool years (N = 29, mean age = 5.75 years, SD = 0.33; between 1 and 5 languages, median = 3, SD = 0.92). We measured their L1 phonological awareness and L1 receptive vocabulary scores - the former we hypothesize to be associated with the child’s phonemic inventory and the latter a standard metric for language skill. Leveraging these individual differences in exposure, using cross-linguistic data (obtained through https://phoible.org/), we calculated the richness of children’s phonemic inventories, representing a total number of distinct sound categories across all languages a given multilingual has been exposed to (mean = 79, SD = 22.0). We hypothesized that the anatomical development of the AF, would reflect the richness of children’s receptive vocabulary, phonemic inventories, and phonological awareness. We performed white matter tract segmentation using a novel convolutional neural network-based approach and probabilistic tractography based on multi-shell constrained spherical deconvolution. Mean fiber orientation distribution peaks were measured along the left and right AF - a measure which unlike fractional anisotropy can handle crossing fibers and thus provide a better proxy for white matter tissue integrity. We found that each of the scores representing children’s L1 skills (phonological awareness and receptive vocabulary) positively and significantly correlated with each other and with measures of left AF diffusivity (ps<0.001, FDR-corrected). On the other hand, an index describing the richness of their phonemic inventories showed positive associations with both left and right AF (ps<0.001, FDR-corrected), while not being correlated with the L1 phonological skills or receptive vocabulary. Further analyses are ongoing to establish the association between time-weighted measures of children’s multilingual exposure and white matter structure, reflecting the strength of their English phonological representations. In sum, our results demonstrate that the linguistic indices tested here differentially predict left and fight AF diffusivity measures, highlighting the importance of capturing not just L1 skills but also incorporating cross-linguistic information with regards to multilingual environment. Kuhl, et al. (2003). Foreign-language experience in infancy: Effects of short-term exposure and social interaction on phonetic learning. Proc. Natl. Acad. Sci. 100, 9096–9101.
Themes: Multilingualism, Phonology and Phonological Working Memory
Method: White Matter Imaging (dMRI, DSI, DKI)