Language Learning under Working Memory Constraints Correlates with Microstructural Differences in the Ventral Language Pathway

Abstract

The present study combined behavioral measures and diffusion tensor imaging to investigate the neuroanatomical basis of language learning in relation to phonological working memory (WM). Participants were exposed to simplified artificial languages under WM constraints. The results underscore the role of the rehearsal subcomponent of WM in successful speech segmentation and rule learning. Moreover, when rehearsal was blocked task performance was correlated to the white matter microstructure of the left ventral pathway connecting frontal and temporal language-related cortical areas through the extreme/external capsule. This ventral pathway may therefore play an important additional role in language learning when the main dorsal pathway-dependent rehearsal mechanisms are not available.

Word learning is mediated by the left arcuate fasciculus

“…Similar lesions after the age of 5 y (56) lead to preserved oral language, although with poor performance in nonword repetition, verbal working memory, and reading. In healthy adults, the use of articulatory suppression to block the use of the dorsal pathway interferes with word learning as well, and performance under this condition correlates with individual differences in the microstructural properties of the ventral pathway (9). Taken together, the above studies indicate that lesions to the AF induce language-learning difficulties.…”

“…Moreover, stimulation of the premotor cortex with repetitive transcranial magnetic stimulation disrupts the capacity to discriminate between phonemes (8). Similarly, learning new words is impaired if participants are engaged in the articulation of irrelevant sounds while they try to learn new ones (9). These studies are supportive of a link between auditory and motor processes in word learning.…”

Corticostriatal Contributions to Musical Expectancy Perception

“…Interactions between IFG and the STG are consistent with studies of congenital amusia that find decreased gray matter in both regions along with decreased white matter in the tracts connecting the two regions (Hyde, Zatorre, & Peretz, 2011;Peretz, Brattico, Järvenpää, & Tervaniemi, 2009). In addition, white matter connectivity in this pathway is associated with the ability to learn new syntactic structures in the auditory domain (Lopez-Barroso et al, 2011;Loui, Li, & Schlaug, 2011) and increased white matter connectivity is found in these tracts after intensive melodic intonation therapy for nonfluent aphasia (Schlaug, Marchina, & Norton, 2009).…”

Neurology of foreign language aptitude

“…A few studies have addressed the problem of morphosyntactic attainment in late-onset learners (Lopez-Barroso et al, 2011;Wong, MorganShort, Ettlinger, & Zheng, 2012;Wood Bowden, Steinhauer, Sanz, & Ullman, 2013). Lopez-Barroso et al (2011) provided evidence that the phonological component of WM, that is, articulatory rehearsal, influences the learning of syntax. By blocking rehearsal, segmentation and rule learning in an L2 are significantly impaired as compared with a learning condition without interference or interference with the phonological store.…”

“…Nauchi and Sakai (2009) Inferior frontal gyrus proposed as the grammar center. Lopez- Barroso et al (2011) Articulatory rehearsal in WM influences the learning of syntax. Wong et al (2012) Subjects with an increased impact of dopamine are better at grammar learning.…”