Neurobiological signatures of L2 proficiency: Evidence from a bi-directional cross-linguistic study

Abstract

Recent evidence has shown that convergence of print and speech processing across a network of primarily left-hemisphere regions of the brain is a predictor of future reading skills in children, and a marker of fluent reading ability in adults. The present study extends these findings into the domain of second-language (L2) literacy, through brain imaging data of English and Hebrew L2 learners. Participants received an fMRI brain scan, while performing a semantic judgement task on spoken and written words and pseudowords in both their L1 and L2, alongside a battery of L1 and L2 behavioural measures. Imaging results show, overall, show a similar network of activation for reading across the two languages, alongside significant convergence of print and speech processing across a network of left-hemisphere regions in both L1 and L2 and in both cohorts. Importantly, convergence is greater for L1 in occipito-temporal regions tied to automatic skilled reading processes including the visual word-form area, but greater for L2 in frontal regions of the reading network, tied to more effortful, active processing. The main groupwise brain effects tell a similar story, with greater L2 than L1 activation across frontal, temporal and parietal regions, but greater L1 than L2 activation in parieto-occipital regions tied to automatic mapping processes in skilled reading. These results provide evidence for the shifting of the reading networks towards more automatic processing as reading proficiency rises and the mappings and statistics of the new orthography are learned and incorporated into the reading system.

The impact of second language immersion: Evidence from a bi-directional longitudinal cross-linguistic study

“…In speech fewer differences were seen for L1/L2, with L2 showing greater activation than L1 in the bilateral IFG, and in the left hemisphere anterior STG. This shows that the frontal regions more associated with effortful processing are engaged more for the less fluent L2, as was reported in the Ep1 paper (Brice et al, 2019). Table III.…”

“…Investigations of the neurobiological bases of second language (L2) processing have found, overall, that a very similar language network is activated for the processing of second languages (Brice et al, 2019;Das, Padakannaya, Pugh, & Singh, 2011;Perani & Abutalebi, 2005). Research has looked at how both proficiency and age of acquisition of the L2 affect reading processes (Perani et al, 1998), finding that more proficient L2s and those acquired at a younger age look more similar to the learner's L1 (although see Das et al, 2011, for a comparison with simultaneously acquired bilingulalism).…”

“…Another important metric that Brice et al (2019) reported on was the convergence of the neural networks of print and speech processing. Research by Preston and colleagues (2016) has probed this convergence in the context of L1 literacy acquisition, based on the understanding that efficient visual word processing must utilise pre-existing linguistic knowledge, leading to a functional convergence across modalities in order to achieve reading proficiency (Braze et al, 2011).…”

Functional plasticity associated with language learning in adults

“…In monolinguals, print-speech convergence has been found to be a reliable and universal indicator of reading-related skills, invariant across age and languages (Shankweiler et al 2008;Rueckl et al 2015;Preston et al 2016). In late bilingual-biliterates, participants displayed significantly more extensive print-speech convergence in frontal regions and less in parietal regions in L2 compared to L1, a finding considered to indicate more effortful reading in a new writing system (Brice et al 2019). In these previous studies, participants had learnt to speak before they learnt to read in the same language, and their reading circuits were integrated with previously-established spoken language networks commensurate with their reading proficiency.…”

“…Not limited to specific languages, this convergence between reading and speech comprehension networks has been found in adult native speakers of highly contrasting languages with different writing systems, levels of orthographic depth, and morphological properties, and is thus considered a universal signature of proficient reading (Rueckl et al 2015). A study with late bilingual-biliterates (bilinguals whose languages use different writing systems, e.g., English and Chinese; see Singh et al 2016) extended these results to L2, finding differences in the pattern of print-speech convergence between L1 and L2 that were indicative of the greater effort and lower automaticity of L2 reading in a new writing system (Brice et al 2019). However, monolinguals and many bilingual-biliterates learn to speak before they learn to read, which is not the case for late bilinguals whose L2 uses the same writing system as their L1.…”