Examining the consistency in bilingualism and white matter research: A meta-analysis.

This study aimed to systematically investigate the relationship between bilingualism, age, L2 onset age of acquisition (AoA), and white matter integrity (operationalized as fractional anisotropy, FA), addressing inconsistencies in the literature. We conducted a meta-analysis of 23 studies and used meta-regression models to assess the influence of age and L2AoA on effect sizes in studies comparing monolinguals and bilinguals. Even though the overall between-group effect size across the whole brain was unreliable, bilingualism was associated with increased white matter integrity in specific tracts and in groups with a limited range of age and L2AoA. Age had a small, negative effect on white matter integrity, with differences between monolinguals and bilinguals more pronounced in younger adults, consistent with a view of an initial increase in white matter integrity, followed by remodeling for efficiency over time. In contrast, later L2AoA was associated with greater white matter integrity in bilinguals than monolinguals, again consistent with the remodeling for efficiency model. Our findings highlight the importance of considering age and L2AoA when examining the neural basis of bilingualism on white matter in the brain and how bilingualism contributes to structural changes that stave off cognitive decline in older age.

Special Education Representation Trends Vary by Language Status: Evidence of Underrepresentation in Tennessee.

Using state-level data, we report unadjusted and adjusted odds ratio of special education (SPED) trends in Tennessee from 2009 to 2019 for students in Grades 3 to 8 by three language groups: native English speakers (NES), English-proficient bilinguals (EPB), and Current English learners (Current EL). We report trends across all SPED disability categories and across five prevalent disability categories (specific learning disability, specific language impairment, intellectual disability, other health impairments, and autism). The cross-sectional analytic sample included 812,783 students from 28 districts that met the SPED risk ratio threshold set by the state. Results revealed that, compared with NES students, both EPB and Current EL students were generally less likely to receive SPED services, suggesting evidence of language status disparities in SPED representation. Furthermore, findings varied depending on whether adjustments were made to generate odds ratios, especially for higher-incidence disabilities (specific learning disability, specific language impairment, and intellectual disability). Finally, the most severe evidence of underrepresentation was in lower-incidence disabilities (other health impairments and autism). Our results underscore the need for further examination into low rates of SPED identification among learners whose first language is not English (EPB and Current EL). We discuss the contextualized research, practice, and policy implications of our findings.

Phonetic discrimination, phonological awareness, and pre-literacy skills in Spanish-English dual language preschoolers.

The current study explores variation in phonemic representation among Spanish-English dual language learners (DLLs, n = 60) who were dominant in English or in Spanish. Children were given a phonetic discrimination task with speech sounds that: 1) occur in English and Spanish, 2) are exclusive to English, and 3) are exclusive to Russian, during Fall (age m = 57 months) and Spring (age m = 62 months, n = 42). In Fall, English-dominant DLLs discriminated more accurately than Spanish-dominant DLLs between English-Spanish phones and English-exclusive phones. Both groups discriminated Russian phones at or close to chance. In Spring, however, groups no longer differed in discriminating English-exclusive phones and both groups discriminated Russian phones above chance. Additionally, joint English-Spanish and English-exclusive phonetic discrimination predicted children's phonological awareness in both groups. Results demonstrate plasticity in early childhood through diverse language exposure and suggest that phonemic representation begins to emerge driven by lexical restructuring.

Early Reading Comprehension Intervention for Preschoolers with Autism Spectrum Disorder and Hyperlexia.

Children with autism spectrum disorder (ASD) and hyperlexia (HPL) have both advanced word reading skills and a reading comprehension disorder, alongside impaired oral language. We developed a unique, parent-supported, tablet-based intervention aiming to improve oral and reading comprehension at the word-, phrase- and sentence-level, for preschoolers with ASD and hyperlexia (ASD + HPL). English-speaking preschoolers (N = 30) with ASD + HPL (N = 8), ASD without HPL (N = 7) and typical development (N = 15) underwent a 6-week no-intervention period followed by a 6-week intervention period. Findings revealed a significant increase in reading comprehension scores for the group with ASD + HPL as compared to the TD group (p = .023). Gains were also found for receptive but not expressive language for all groups. Implications for early intervention for preschoolers with ASD + HPL are discussed.

Early Word Reading of Preschoolers with ASD, Both With and Without Hyperlexia, Compared to Typically Developing Preschoolers.

A portion of children with Autism Spectrum Disorder (ASD) exhibit a strength in early word reading referred to as hyperlexia (HPL), yet it remains unclear what mechanisms underlie this strength. Typically developing children (TD) acquire phonological awareness, alphabet knowledge and language skills as precursors to word reading. We compared these skills across English-speaking preschoolers with ASD, both with and without hyperlexia, and TD preschoolers. Findings indicated that the group with both ASD and HPL (ASD + HPL) exhibited advanced word reading and letter naming skills as compared to the other two groups, but did not demonstrate commensurate phonological awareness, letter-sound correspondence, or language skills. Findings support an alternative, non-phonological approach to early word reading in preschoolers with ASD and hyperlexia.

The Case for Measuring and Reporting Bilingualism in Developmental Research.

Many children around the world grow up bilingual, learning and using two or more languages in everyday life. Currently, however, children's language backgrounds are not always reported in developmental studies. There is mounting evidence that bilingualism interacts with a wide array of processes including language, cognitive, perceptual, brain, and social development, as well as educational outcomes. As such, bilingualism may be a hidden moderator that obscures developmental patterns, and limits the replicability of developmental research and the efficacy of psychological and educational interventions. Here, we argue that bilingualism and language experience in general should be routinely documented in all studies of infant and child development regardless of the research questions pursued, and provide suggestions for measuring and reporting children's language exposure, proficiency, and use.

Eligibility for Special Education in Elementary School: The Role of Diverse Language Experiences.

Purpose: We examined the association between language experience and elementary students' eligibility for special education in Massachusetts. Method: A secondary descriptive data analysis was conducted on the anonymized demographic data obtained from the Massachusetts Department of Elementary and Secondary Education. Third, 4th, and 5th grade students were categorized into native English speakers, English-proficient bilinguals, and emerging bilinguals. Eligibility for free or reduced lunch was also considered. Proportions of students eligible for autism, communication disorders, and specific learning disabilities (including those with dyslexia) were calculated. Results: A strong association was observed between students' language background and whether they were eligible for free/reduced lunch. Children eligible for free/reduced lunch were more likely to be eligible for special education. Relative to native English speakers, English-proficient bilingual students were less likely to be considered eligible for special education. However, for emerging bilinguals, eligibility was lowest in 3rd grade and highest in 5th grade. This observation was most apparent in the category of specific learning disabilities. Conclusions: Students from diverse language and low-income backgrounds were disproportionately represented in special education. More substantial research-practice partnerships are warranted to understand how bilingual experience and socioeconomic status interact with eligibility for special education services in public school settings.

Language and cognitive control networks in bilinguals and monolinguals.

Neuroimaging studies have reported overlapping neural circuits for cognitive control when engaging in tasks that involve verbal and nonverbal stimuli in young adult bilinguals. However, no study to date has examined the neural basis of verbal and nonverbal task switching in both monolinguals and bilinguals due to the inherent challenge of testing verbal task switching with monolinguals. Therefore, it is not clear whether the finding for overlapping networks is unique to bilingualism or indicative of general cognitive control. To address this question, the current study compared functional neural activation for young adults who were bilingual speakers of English and French or monolingual English speakers who had limited French learning experience ("functional monolinguals") on verbal and nonverbal task switching. Analyses showed common variance explaining general cognitive control in task switching across verbal and nonverbal domains for both groups, in line with the explanation that task switching involves general cognitive control, as well as unique brain regions recruited by monolinguals and bilinguals. Specifically, beyond the processing common to the tasks, monolinguals also recruited distinct networks for each of verbal and nonverbal switching but bilinguals used a common shared network. Thus, the domain-general aspect of switching is different for monolinguals and bilinguals.

Does developmental timing of exposure to child maltreatment predict memory performance in adulthood? Results from a large, population-based sample.

Although maltreatment is a known risk factor for multiple adverse outcomes across the lifespan, its effects on cognitive development, especially memory, are poorly understood. Using data from a large, nationally representative sample of young adults (Add Health), we examined the effects of physical and sexual abuse on working and short-term memory in adulthood. We examined the association between exposure to maltreatment as well as its timing of first onset after adjusting for covariates. Of our sample, 16.50% of respondents were exposed to physical abuse and 4.36% to sexual abuse by age 17. An analysis comparing unexposed respondents to those exposed to physical or sexual abuse did not yield any significant differences in adult memory performance. However, two developmental time periods emerged as important for shaping memory following exposure to sexual abuse, but in opposite ways. Relative to non-exposed respondents, those exposed to sexual abuse during early childhood (ages 3-5), had better number recall and those first exposed during adolescence (ages 14-17) had worse number recall. However, other variables, including socioeconomic status, played a larger role (than maltreatment) on working and short-term memory. We conclude that a simple examination of "exposed" versus "unexposed" respondents may obscure potentially important within-group differences that are revealed by examining the effects of age at onset to maltreatment.

A meta-analysis of functional reading systems in typically developing and struggling readers across different alphabetic languages.

Functional neuroimaging research has identified multiple brain regions supporting reading-related activity in typical and atypical readers across different alphabetic languages. Previous meta-analyses performed on these functional magnetic resonance imaging findings typically report significant between-group contrasts comparing typical readers and readers with reading difficulty or a clinical diagnosis of developmental dyslexia. In order to advance our understanding of cross-linguistic convergence of reading-related brain activations for these reader groups, analyses using activation likelihood estimation were carried out separately for typical and atypical readers who ranged from children to adults. Contrasts were analyzed for tasks involving rhyming or reading of letter or word stimuli presented visually in English, Dutch, Italian, German, French, or Norwegian. Typical readers showed reliable activation in only left lateralized regions, including the inferior frontal area, precentral area and middle temporal gyrus. Atypical readers also showed activation in the left inferior frontal area and precentral region, in addition to significant activations in the right hemisphere, including the superior, medial and inferior frontal regions, lingual gyrus and the inferior occipital area. These results distinguish between typical and atypical reader group activations, showing common and distinct regions of activation when engaged in reading-related activities, extending previous meta-analyses on identifying brain regions relevant to reading to include cross-linguistic analyses for alphabetic scripts. Results support the universality of a signature pattern of brain activation in developmental dyslexia across alphabetic languages.

The effect of lifelong bilingualism on regional grey and white matter volume.

Lifelong bilingualism is associated with the delayed diagnosis of dementia, suggesting bilingual experience is relevant to brain health in aging. While the effects of bilingualism on cognitive functions across the lifespan are well documented, less is known about the neural substrates underlying differential behaviour. It is clear that bilingualism affects brain regions that mediate language abilities and that these regions are at least partially overlapping with those that exhibit age-related decline. Moreover, the behavioural advantages observed in bilingualism are generally found in executive function performance, suggesting that the frontal lobes may also be sensitive to bilingualism, which exhibit volume reductions with age. The current study investigated structural differences in the brain of lifelong bilingual older adults (n=14, mean age=70.4) compared with older monolinguals (n=14, mean age=70.6). We employed two analytic approaches: 1) we examined global differences in grey and white matter volumes; and, 2) we examined local differences in volume and cortical thickness of specific regions of interest previously implicated in bilingual/monolingual comparisons (temporal pole) or in aging (entorhinal cortex and hippocampus). We expected bilinguals would exhibit greater volume of the frontal lobe and temporal lobe (grey and white matter), given the importance of these regions in executive and language functions, respectively. We further hypothesized that regions in the medial temporal lobe, which demonstrate early changes in aging and exhibit neural pathology in dementia, would be more preserved in the bilingual group. As predicted, bilinguals exhibit greater frontal lobe white matter compared with monolinguals. Moreover, increasing age was related to decreasing temporal pole cortical thickness in the monolingual group, but no such relationship was observed for bilinguals. Finally, Stroop task performance was positively correlated with frontal lobe white matter, emphasizing the importance of preserved white matter in maintaining executive function in aging. These results underscore previous findings implicating an association between bilingualism and preserved frontal and temporal lobe function in aging. This article is part of a Special Issue entitled SI: Memory Å.

Proficiency and Control in Verbal Fluency Performance across the Lifespan for Monolinguals and Bilinguals.

The verbal fluency task is a widely used neuropsychological test of word retrieval efficiency. Both category fluency (e.g., list animals) and letter fluency (e.g., list words that begin with F) place demands on semantic memory and executive control functions. However letter fluency places greater demands on executive control than category fluency, making this task well-suited to investigating potential bilingual advantages in word retrieval. Here we report analyses on category and letter fluency for bilinguals and monolinguals at four ages, namely, 7-year-olds, 10-year-olds, young adults, and older adults. Three main findings emerged: 1) verbal fluency performance improved from childhood to young adulthood and remained relatively stable in late adulthood; 2) beginning at 10-years-old, the executive control requirements for letter fluency were less effortful for bilinguals than monolinguals, with a robust bilingual advantage on this task emerging in adulthood; 3) an interaction among factors showed that category fluency performance was influenced by both age and vocabulary knowledge but letter fluency performance was influenced by bilingual status.

Brain network activity in monolingual and bilingual older adults.

Bilingual older adults typically have better performance on tasks of executive control (EC) than do their monolingual peers, but differences in brain activity due to language experience are not well understood. Based on studies showing a relation between the dynamic range of brain network activity and performance on EC tasks, we hypothesized that life-long bilingual older adults would show increased functional connectivity relative to monolinguals in networks related to EC. We assessed intrinsic functional connectivity and modulation of activity in task vs. fixation periods in two brain networks that are active when EC is engaged, the frontoparietal control network (FPC) and the salience network (SLN). We also examined the default mode network (DMN), which influences behavior through reduced activity during tasks. We found stronger intrinsic functional connectivity in the FPC and DMN in bilinguals than in monolinguals. Although there were no group differences in the modulation of activity across tasks and fixation, bilinguals showed stronger correlations than monolinguals between intrinsic connectivity in the FPC and task-related increases of activity in prefrontal and parietal regions. This bilingual difference in network connectivity suggests that language experience begun in childhood and continued throughout adulthood influences brain networks in ways that may provide benefits in later life.

Bilingualism is not a categorical variable: Interaction between language proficiency and usage.

Bilingual experience is dynamic and poses a challenge for researchers to develop instruments that capture its relevant dimensions. The present study examined responses from a questionnaire administered to 110 heterogeneous bilingual young adults. These questions concern participants' language use, acquisition history and self-reported proficiency. The questionnaire responses and performances on standardized English proficiency measures were analyzed using factor analysis. In order to retain a realistic representation of bilingual experience, the factors were allowed to correlate with each other in the analysis. Two correlating factors were extracted, representing daily bilingual usage and English proficiency. These two factors were also related to self-rated proficiency in English and non-English language. Results were interpreted as supporting the notion that bilingual experience is composed of multiple related dimensions that will need to be considered in assessments of the consequences of bilingualism.

Bilingualism: consequences for mind and brain.

Building on earlier evidence showing a beneficial effect of bilingualism on children's cognitive development, we review recent studies using both behavioral and neuroimaging methods to examine the effects of bilingualism on cognition in adulthood and explore possible mechanisms for these effects. This research shows that bilingualism has a somewhat muted effect in adulthood but a larger role in older age, protecting against cognitive decline, a concept known as 'cognitive reserve'. We discuss recent evidence that bilingualism is associated with a delay in the onset of symptoms of dementia. Cognitive reserve is a crucial research area in the context of an aging population; the possibility that bilingualism contributes to cognitive reserve is therefore of growing importance as populations become increasingly diverse.

Lifelong bilingualism maintains white matter integrity in older adults.

Previous research has shown that bilingual speakers have higher levels of cognitive control than comparable monolinguals, especially at older ages. The present study investigates a possible neural correlate of this behavioral effect. Given that white matter (WM) integrity decreases with age in adulthood, we tested the hypothesis that bilingualism is associated with maintenance of WM in older people. Using diffusion tensor imaging, we found higher WM integrity in older people who were lifelong bilinguals than in monolinguals. This maintained integrity was measured by fractional anisotropy (FA) and was found in the corpus callosum extending to the superior and inferior longitudinal fasciculi. We also hypothesized that stronger WM connections would be associated with more widely distributed patterns of functional connectivity in bilinguals. We tested this by assessing the resting-state functional connectivity of frontal lobe regions adjacent to WM areas with group differences in FA. Bilinguals showed stronger anterior to posterior functional connectivity compared to monolinguals. These results are the first evidence that maintained WM integrity is related to lifelong naturally occurring experience; the resulting enhanced structural and functional connectivity may provide a neural basis for "brain reserve."

Cognitive control for language switching in bilinguals: A quantitative meta-analysis of functional neuroimaging studies.

In a quantitative meta-analysis, using the activation likelihood estimation method, we examined the neural regions involved in bilingual cognitive control, particularly when engaging in switching between languages. The purpose of this study was to evaluate the bilingual cognitive control model based on a qualitative analysis [Abutalebi, J., & Green, D. W. (2008). Control mechanisms in bilingual language production: Neural evidence from language switching studies. Language and Cognitive Processes, 23, 557-582.]. After reviewing 128 peer-reviewed articles, ten neuroimaging studies met our inclusion criteria and in each study, bilinguals switched between languages in response to cues. We isolated regions involved in voluntary language switching, by including reported contrasts between the switching conditions and high level baseline conditions involving similar tasks but requiring the use of only one language. Eight brain regions showed significant and reliable activation: left inferior frontal gyrus, left middle temporal gyrus, left middle frontal gyrus, right precentral gyrus, right superior temporal gyrus, midline pre-SMA and bilateral caudate nuclei. This quantitative result is consistent with bilingual aphasia studies that report switching deficits associated with lesions to the caudate nuclei or prefrontal cortex. It also extends the previously reported qualitative model. We discuss the implications of the findings for accounts of bilingual cognitive control.