Does Diglossia Impact Brain Structure? Data from Swiss German Early Diglossic Speakers.

(1) Background: Bilingualism has been reported to shape the brain by inducing cortical changes in cortical and subcortical language and executive networks. Similar yet different to bilingualism, diglossia is common in Switzerland, where the German-speaking population switches between an everyday spoken Swiss German (CH-GER) dialect and the standard German (stGER) used for reading and writing. However, no data are available for diglossia, defined as the use of different varieties or dialects of the same language, regarding brain structure. The aim of our study is to investigate if the presence of this type of diglossia has an impact on the brain structure, similar to the effects seen in bilingualism. (2) Methods: T1-weighted anatomical MRI scans of participants were used to compare the grey matter density and grey matter volume of 22 early diglossic CH-GER-speaking and 20 non-diglossic French-speaking right-handed university students, matched for age, linguistics and academic background. The images were processed with Statistical Parametric Mapping SPM12 and analyzed via voxel- and surface-based morphometry. (3) Results: A Bayesian ANCOVA on the whole brain revealed no differences between the groups. Also, for the five regions of interest (i.e., planum temporale, caudate nucleus, ACC, DLPFC and left interior parietal lobule), no differences in the cortical volume or thickness were found using the same statistical approach. (4) Conclusion: The results of this study may suggest that early diglossia does not shape the brain structure in the same manner as bilingualism.

Neural correlates of lexical stress processing in a foreign free-stress language.

INTRODUCTION: The paper examines the discrimination of lexical stress contrasts in a foreign language from a neural perspective. The aim of the study was to identify the areas associated with word stress processing (in comparison with vowel processing), when listeners of a fixed-stress language have to process stress in a foreign free-stress language. METHODS: We asked French-speaking participants to process stress and vowel contrasts in Spanish, a foreign language that the participants did not know. Participants performed a discrimination task on Spanish word pairs differing either with respect to word stress (penultimate or final stressed word) or with respect to the final vowel while functional magnetic resonance imaging data was acquired. RESULTS: Behavioral results showed lower accuracy and longer reaction times for discriminating stress contrasts than vowel contrasts. The contrast Stress > Vowel revealed an increased bilateral activation of regions shown to be associated with stress processing (i.e., supplementary motor area, insula, middle/superior temporal gyrus), as well as a stronger involvement of areas related to more domain-general cognitive control functions (i.e., bilateral inferior frontal gyrus). The contrast Vowel > Stress showed an increased activation in regions typically associated with the default mode network (known for decreasing its activity during attentionally more demanding tasks). CONCLUSION: When processing Spanish stress contrasts as compared to processing vowel contrasts, native listeners of French activated to a higher degree anterior networks including regions related to cognitive control. They also show a decrease in regions related to the default mode network. These findings, together with the behavioral results, reflect the higher cognitive demand, and therefore, the larger difficulties, for French-speaking listeners during stress processing as compared to vowel processing.

Predicting Reading From Behavioral and Neural Measures - A Longitudinal Event-Related Potential Study.

Fluent reading is characterized by fast and effortless decoding of visual and phonological information. Here we used event-related potentials (ERPs) and neuropsychological testing to probe the neurocognitive basis of reading in a sample of children with a wide range of reading skills. We report data of 51 children who were measured at two time points, i.e., at the end of first grade (mean age 7.6 years) and at the end of fourth grade (mean age 10.5 years). The aim of this study was to clarify whether next to behavioral measures also basic unimodal and bimodal neural measures help explaining the variance in the later reading outcome. Specifically, we addressed the question of whether next to the so far investigated unimodal measures of N1 print tuning and mismatch negativity (MMN), a bimodal measure of audiovisual integration (AV) contributes and possibly enhances prediction of the later reading outcome. We found that the largest variance in reading was explained by the behavioral measures of rapid automatized naming (RAN), block design and vocabulary (46%). Furthermore, we demonstrated that both unimodal measures of N1 print tuning (16%) and filtered MMN (7%) predicted reading, suggesting that N1 print tuning at the early stage of reading acquisition is a particularly good predictor of the later reading outcome. Beyond the behavioral measures, the two unimodal neural measures explained 7.2% additional variance in reading, indicating that basic neural measures can improve prediction of the later reading outcome over behavioral measures alone. In this study, the AV congruency effect did not significantly predict reading. It is therefore possible that audiovisual congruency effects reflect higher levels of multisensory integration that may be less important for reading acquisition in the first year of learning to read, and that they may potentially gain on relevance later on.

First and Second Language at Hand: A Chronometric Transcranial-Magnetic Stimulation Study on Semantic and Motor Resonance.

According to embodied theories, motor and language processing bidirectionally interact: Motor activation modulates behavior in lexico-semantic tasks (semantic resonance), and understanding motor-related words entails activation of the corresponding motor brain areas (motor resonance). Whereas many studies investigated such interaction in the first language (L1), only few did so in a second language (L2), focusing on motor resonance. Here, we directly compared L1 and a late L2, for the first time both in terms of semantic and motor resonance and both in terms of magnitude and timing, by taking advantage of single-pulse TMS. Twenty-five bilinguals judged, in each language, whether hand motor-related ("grasp") and non-motor-related verbs ("believe"), were physical or mental. Meanwhile, we applied TMS on the hand motor cortex at 125, 275, 350, and 500 msec post verb onset, and recorded behavioral responses and TMS-induced motor evoked potentials. TMS induced faster responses for L1 versus L2 motor and nonmotor verbs at 125 msec (three-way interaction ß = -0.0442, 95% CI [0.0814, -0.0070]), showing a semantic resonance effect at an early stage of word processing in L1 but not in L2. Concerning motor resonance, TMS-induced motor evoked potentials at 275 msec revealed higher motor cortex excitability for L2 versus L1 processing (two-way interaction ß = 0.095, 95% CI [0.017, 0.173]). These findings confirm action-language interaction at early stages of word recognition, provide further evidence that L1 and L2 are differently embodied, and call for an update of existing models of bilingualism and embodiment, concerning both language representations and processing.

Effects of Continuous Theta Burst Stimulation Over the Left Dlpfc on Mother Tongue and Second Language Production In Late Bilinguals: A Behavioral and ERP Study.

Clinical, neuroimaging, and non-invasive brain stimulation studies have associated the dorsolateral prefrontal cortex (DLPFC) with the multilingual language control system. Here, we investigated if this role is increased during the processing of the non-dominant language due to the higher cognitive/attentional demands. We used an inhibitory repetitive transcranial magnetic stimulation (rTMS) protocol over the left DLPFC and investigated the behavioral and electrophysiological effects on (i) picture naming in the mother tongue and second language, (ii) forward and backward translation and (iii) non-verbal inhibition. To this end, we compared the effects of inhibitory rTMS (cTBS) vs sham-rTMS using a single-blind within-subject design including 22 late bilinguals. Behaviorally, response times were longer after cTBS compared to sham-rTMS in the picture naming task independent of language, while response times were not affected for the word translation task. These results were mirrored on the electrophysiological level showing an effect of stimulation in the picture naming task starting at 547 ms post-stimulus onset, but not in the translation task. This late time range is likely associated with processes of conflict resolution and initiation of the articulation of the word rather than processes related to lexical selection or language switching. For the non-verbal inhibition task, behavioral outcome was not affected despite electrophysiological stimulation-induced changes. Overall, the results suggest that the DLPFC plays a role in top-down cognitive control in language production, but that this role is not increased with higher cognitive demand such as naming in a second language or in language switching during word translation.

Effects of theta burst stimulation over the dorsolateral prefrontal cortex on language switching - A behavioral and ERP study.

This study investigated the role of the left dorsolateral prefrontal cortex (DLPFC) in language switching using theta burst stimulation (TBS) and electroencephalography in late bilinguals. After a sham-controlled baseline, participants received either excitatory or inhibitory TBS over the left DLPFC before conducting picture naming tasks in pure language blocks and a language switching block, as well as a nonverbal switching task. On the behavioral level, we found no effect of TBS. However, the ERP-analysis revealed an effect of Stimulation for the picture naming tasks, characterized by alterations in the left DLPFC at 20-72 ms, and in networks associated with conflict resolution and self-monitoring at 533-600 ms. As we did not find an interaction between Stimulation and Block (switching vs non-switching), prefrontal stimulation did not specifically modulate interlanguage control. The left DLPFC might rather be involved in enhancingmaintenance of task demands and self-monitoring during language production in both mono- and bilingual contexts.

Embodied Semantics in a Second Language: Critical Review and Clinical Implications.

The role of the sensorimotor system in second language (L2) semantic processing as well as its clinical implications for bilingual patients has hitherto been neglected. We offer an overview of the issues at stake in this under-investigated field, presenting the theoretical and clinical relevance of studying L2 embodiment and reviewing the few studies on this topic. We highlight that (a) the sensorimotor network is involved in L2 processing, and that (b) in most studies, L2 is differently embodied than L1, reflected in a lower degree or in a different pattern of L2 embodiment. Importantly, we outline critical issues to be addressed in order to guide future research. We also delineate the subsequent steps needed to confirm or dismiss the value of language therapeutic approaches based on embodiment theories as a complement of speech and language therapies in adult bilinguals.

Effects of Prefrontal Transcranial Direct Current Stimulation on Lexical Access in Chronic Poststroke Aphasia.

BACKGROUND: A successful interplay between prefrontal and domain-specific language areas is critical for language processing. Previous studies involving people with aphasia have shown that executive control processes might act on lexical-semantic representations during retrieval. Modulating the prefrontal control network by means of noninvasive brain stimulation might, therefore, improve lexical access in people with aphasia. OBJECTIVE: The present study investigates the effects of prefrontal transcranial direct current stimulation (tDCS) on lexical access in chronic poststroke aphasia. METHODS: We report data of 14 participants with chronic poststroke aphasia. We used a sham-tDCS (S-tDCS) controlled and double-blind within-subjects design. Performances in picture naming, verbal fluency, and word repetition were assessed immediately after stimulation. RESULTS: As compared with S-tDCS, anodal tDCS (A-tDCS) improved verbal fluency as well as the speed of naming high frequency words, but not word repetition. CONCLUSION: The results of our study suggest that the brain network dedicated to lexical retrieval processing can be facilitated by A-tDCS over the left dorsolateral prefrontal cortex. This finding supports the notion that strengthening executive control functions after stroke could complement speech and language-focused therapy.

Behavioral and electrophysiological signatures of word translation processes.

Translation is a demanding process during which a message is analyzed, translated and communicated from one language to another. Despite numerous studies on translation mechanisms, the electrophysiological processes underlying translation with overt production remain largely unexplored. Here, we investigated how behavioral response patterns and spatial-temporal brain dynamics differ in a translation compared to a control within-language word-generation task. We also investigated how forward and backward translation differs on the behavioral and electrophysiological level. To address these questions, healthy late bilingual subjects performed a translation and a within-language control task while a 128-channel EEG was recorded. Behavioral data showed faster responses for translation compared to within-language word generation and faster responses for backward than forward translation. The ERP-analysis revealed stronger early ( < 200ms) preparatory and attentional processes for between than within word generation. Later (424-630ms) differences were characterized by distinct engagement of domain-general control networks, namely self-monitoring and lexical access interference. Language asymmetry effects occurred at a later stage (600ms), reflecting differences in conceptual processing characterized by a larger involvement of areas implicated in attention, arousal and awareness for forward versus backward translation.

Temporal dynamics of early visual word processing - Early versus late N1 sensitivity in children and adults.

In the course of reading development children become familiar with letter strings and learn to distinguish between lexical and non-lexical items. In previous studies, the N1 component of the ERP was shown to reflect print tuning but also to be sensitive to lexical effects. It remains unclear, however, whether these two aspects of orthographic processing occur at the same time or in different time windows during the lengthy N1 component. Moreover, it is unclear whether these processes develop late or occur already at early stages of literacy acquisition and whether this is similar for native languages and languages acquired later in life. To address these questions, 27 children were tested longitudinally, i.e. before (mean: 7.6 years) and after one year of classroom-based English instruction. Additionally, 22 adult speakers of English as a foreign language (mean: 25.1 years) were investigated. A 128-channel EEG was recorded while participants performed a one-back task with native German words, English words, pseudowords and false-font strings. The event-related EEG analysis of early and late N1 phases revealed early effects related to print tuning and late effects related to lexical processing in the native, but not in the second language of adult readers. In the absence of lexicality effects in children, print tuning effects were found across both early and late N1 segments. The temporally distinct N1 sensitivities to print and lexicality reflect temporal dynamics of visual word processing, which seem to depend on reading expertise or maturation.

Native and non-native speech sound processing and the neural mismatch responses: A longitudinal study on classroom-based foreign language learning.

Learning a foreign language in a natural immersion context with high exposure to the new language has been shown to change the way speech sounds of that language are processed at the neural level. It remains unclear, however, to what extent this is also the case for classroom-based foreign language learning, particularly in children. To this end, we presented a mismatch negativity (MMN) experiment during EEG recordings as part of a longitudinal developmental study: 38 monolingual (Swiss-) German speaking children (7.5 years) were tested shortly before they started to learn English at school and followed up one year later. Moreover, 22 (Swiss-) German adults were recorded. Instead of the originally found positive mismatch response in children, an MMN emerged when applying a high-pass filter of 3 Hz. The overlap of a slow-wave positivity with the MMN indicates that two concurrent mismatch processes were elicited in children. The children's MMN in response to the non-native speech contrast was smaller compared to the native speech contrast irrespective of foreign language learning, suggesting that no additional neural resources were committed to processing the foreign language speech sound after one year of classroom-based learning.

Neurocognitive mechanisms of learning to read: print tuning in beginning readers related to word-reading fluency and semantics but not phonology.

During reading acquisition children learn to recognize orthographic stimuli and link them to phonology and semantics. The present study investigated neurocognitive processes of learning to read after one year of schooling. We aimed to elucidate the cognitive processes underlying neural tuning for print that has been shown to play an important role for reading and dyslexia. A 128-channel EEG was recorded while 68 (Swiss-)German monolingual first grade children (mean age: 7.6) performed a one-back task with different types of letter and false-font strings. Print tuning was indexed by the N1 difference in the ERPs between German words and false-font strings, while the N1 lexicality effect was indexed by the difference between German words and pseudowords. In addition, we measured reading fluency, rapid automatized naming, phonological awareness, auditory memory span, and vocabulary. After one year of formal reading instruction N1 print tuning was clearly present at the group level, and could be detected at the individual level in almost 90% of the children. The N1 lexicality effect, however, could not be reliably found. On the cognitive level, next to word-reading fluency, vocabulary was also associated with N1 print tuning, but not measures reflecting phonological processing. These results demonstrate the presence of print tuning in the first year of reading acquisition and its development at the individual level. Moreover, individual differences in print tuning are not only related to word-reading fluency, but also to semantic knowledge, indicating that at early stages of learning to read the top-down modulation of print tuning is semantic rather than phonological in nature.

Integration of spoken and written words in beginning readers: a topographic ERP study.

Integrating visual and auditory language information is critical for reading. Suppression and congruency effects in audiovisual paradigms with letters and speech sounds have provided information about low-level mechanisms of grapheme-phoneme integration during reading. However, the central question about how such processes relate to reading entire words remains unexplored. Using ERPs, we investigated whether audiovisual integration occurs for words already in beginning readers, and if so, whether this integration is reflected by differences in map strength or topography (aim 1); and moreover, whether such integration is associated with reading fluency (aim 2). A 128-channel EEG was recorded while 69 monolingual (Swiss)-German speaking first-graders performed a detection task with rare targets. Stimuli were presented in blocks either auditorily (A), visually (V) or audiovisually (matching: AVM; nonmatching: AVN). Corresponding ERPs were computed, and unimodal ERPs summated (A + V = sumAV). We applied TANOVAs to identify time windows with significant integration effects: suppression (sumAV-AVM) and congruency (AVN-AVM). They were further characterized using GFP and 3D-centroid analyses, and significant effects were correlated with reading fluency. The results suggest that audiovisual suppression effects occur for familiar German and unfamiliar English words, whereas audiovisual congruency effects can be found only for familiar German words, probably due to lexical-semantic processes involved. Moreover, congruency effects were characterized by topographic differences, indicating that different sources are active during processing of congruent compared to incongruent audiovisual words. Furthermore, no clear associations between audiovisual integration and reading fluency were found. The degree to which such associations develop in beginning readers remains open to further investigation.