Bilingual acquisition presents learning challenges beyond those found in monolingual environments, including the need to segment speech in two languages. Infants may use statistical cues, such as syllable-level transitional probabilities, to segment words from fluent speech. In the present study we assessed monolingual and bilingual 14-month-olds' abilities to segment two artificial languages using transitional probability cues. In Experiment 1, monolingual infants successfully segmented the speech streams when the languages were presented individually. However, monolinguals did not segment the same language stimuli when they were presented together in interleaved segments, mimicking the language switches inherent to bilingual speech. To assess the effect of real-world bilingual experience on dual language speech segmentation, Experiment 2 tested infants with regular exposure to two languages using the same interleaved language stimuli as Experiment 1. The bilingual infants in Experiment 2 successfully segmented the languages, indicating that early exposure to two languages supports infants' abilities to segment dual language speech using transitional probability cues. These findings support the notion that early bilingual exposure prepares infants to navigate challenging aspects of dual language environments as they begin to acquire two languages.
The aperiodic exponent of the electroencephalogram (EEG) power spectrum has received growing attention as a physiological marker of neurodevelopmental psychopathology, including attention-deficit/hyperactivity disorder (ADHD). However, its use as a marker of ADHD risk across development, and particularly in very young children, is limited by unknown reliability, difficulty in aligning canonical band-based measures across development periods, and unclear effects of treatment in later development. Here, we investigate the internal consistency of the aperiodic EEG power spectrum slope and its association with ADHD risk in both infants (n = 69, 1-monthold) and adolescents (n = 262, ages 11-17 years). Results confirm good to excellent internal consistency in infancy and adolescence. In infancy, a larger aperiodic exponent was associated with greater family history of ADHD. In contrast, in adolescence, ADHD diagnosis was associated with a smaller aperiodic exponent, but only in children with ADHD who had not received stimulant medication treatment. Results suggest that disruptions in cortical development associated with ADHD risk may be detectable shortly after birth via this approach. Together, findings imply a dynamic developmental shift in which the developmentally normative flattening of the EEG power spectrum is exaggerated in ADHD, potentially reflecting imbalances in cortical excitation and inhibition that could contribute to long-lasting differences in brain connectivity.
This research investigates the development of constraints in word learning. Previous experiments have shown that as infants gain more knowledge of native language structure, they become more selective about the forms that they accept as labels. However, the developmental pattern exhibited depends greatly on the way that infants are introduced to the labels and tested. In a series of experiments, we examined how providing referential context in the form of familiar objects and familiar object names affects how infants learn labels that they would otherwise reject, nonspeech sounds. We found evidence of the development of intersecting constraints: Younger infants (14-month-olds) were more open to learning nonspeech tone labels than older infants (19-month-olds), and younger infants were more open to the influence of referential context. These findings suggest that infants form expectations about labels and labeling contexts as they become more sophisticated learners.
Despite the prevalence of bilingualism (Crystal, 2004; Grosjean, 2010), there is limited work investigating how infants detect words in two languages. Infants with bilingual exposure may encounter conflicting prosodic, lexical, and co-occurrence cues to word boundaries across their languages, which in turn could disrupt word segmentation. For example, an infant learning both French and English would encounter opposing prosodic cues; the predominant stress pattern in English is trochaic (strong-weak), whereas French words tend to follow an iambic (weak-strong) pattern. Language-specific patterns that support segmentation within one language may interfere with segmentation in another (Polka, Orena, Sundara, & Worrall, 2017). However, effective separation of the languages' properties and efficient shifting between language contexts may support accurate word segmentation and allow infants to learn from the rich information present in dual speech streams. Early exposure to diverse regularities across languages may allow infants' language knowledge to self-organize into linguistic clusters over time (e.g. PRIMIR; Curtin, Byers-Heinlein, & Werker, 2011). This process would improve as infants learn core features that differentiate between languages (e.g. prosody, phonology, etc.; Byers-Heinlein, Burns, & Werker, 2010), allowing infants to monitor for language changes and to integrate new information by language, reducing cross-linguistic interference. This is critical, as the language in use in bilingual environments may change between, or even within, interactions and speakers, and failure to anticipate language switches can incur processing costs for both infants and adults (Byers-Heinlein, Morin-Lessard, & Lew-Williams, 2017), suggesting that change detection is important for efficient bilingual processing. Once bilinguals acquire tools to track information for each language separately, they can more effectively learn language-specific
Attention-deficit hyperactivity disorder (ADHD) is a common, chronic, and impairing disorder, yet presentations of ADHD and clinical course are highly heterogeneous. Despite substantial research efforts, both (a) the secondary co-occurrence of ADHD and complicating additional clinical problems and (b) the developmental pathways leading toward or away from recovery through adolescence remain poorly understood. Resolving these requires accounting for transactional influences of a large number of features across development. Here, we applied a longitudinal cross-lagged panel network model to a multimodal, multilevel dataset in a well-characterized sample of 488 children (nADHD = 296) to test Research Domain Criteria initiative-inspired hypotheses about transdiagnostic risk. Network features included Diagnostic and Statistical Manual of Mental Disorders symptoms, trait-based ratings of emotional functioning (temperament), and performance-based measures of cognition. Results confirmed that ADHD symptom domains, temperamental irritability, and working memory are independent transdiagnostic risk factors for psychopathology based on their direct associations with other features across time. ADHD symptoms and working memory each had direct, independent associations with depression. Results also demonstrated tightly linked co-development of ADHD symptoms and temperamental irritability, consistent with the possibility that this type of anger dysregulation is a core feature that is co-expressed as part of the ADHD phenotype for some children.
BackgroundThe clinical utility of MRI neuroimaging studies of psychopathology has been limited by a constellation of factors—small sample sizes, small effect sizes, and heterogeneity of methods and samples across studies—that hinder generalizability and specific replication. An analogy is early genomics studies of complex traits, wherein a move to large, multi-site samples and a focus on cumulative effects (polygenic scores) led to reproducible and clinically applicable effects from genome-wide association studies. A similar logic in MRI may provide a way to improve reproducibility, precision, and clinical utility for brain-wide MRI association studies.MethodsPolyneuro scores (PNS) represent the cumulative effect of brain-wide measures—in the present case, resting-state functional connectivity (rs-fcMRI) associated with ADHD symptoms. These scores were constructed and validated using baseline data from the Adolescent Brain Cognitive Development (ABCD, N=5666) study, with a reproducible matched subset as the discovery cohort (N=2801). Association between the PNS and ADHD symptoms was further tested in an independent case-control cohort, the Oregon-ADHD-1000 (N=533).ResultsThe ADHD PNS was significantly associated with ADHD symptoms in both the ABCD and Oregon cohorts after accounting for relevant covariates (p-values < 0.001). While the strongest effects contributing to the PNS were concentrated among connections involving the default mode and cingulo-opercular networks, the most predictive PNS involved connectivity across all brain networks. These findings were robust to stringent motion thresholds. In the longitudinal Oregon-ADHD-1000, non-ADHD comparison youth had significantly lower ADHD PNS (β=-0.309, p=0.00142) than children with persistent ADHD (met diagnostic criteria at two or more time points from age 7 to 19). The ADHD PNS, however, did not reliably mediate polygenic risk for ADHD. Instead, the PNS and an ADHD polygenic score were independently associated with ADHD symptoms.ConclusionsA polyneuro risk score representing cumulative ADHD-associated resting-state connectivity was robustly associated with ADHD symptoms in two independent cohorts using distinct sampling designs, yet was independent of polygenic liability for ADHD, suggesting the need to examine environmental influences. The polyneuro score approach holds promise for improving the reproducibility of neuroimaging studies, identifying their clinical utility, and unraveling the complex relationships between brain connectivity and the etiology of behavioral disorders.
Background attention‐deficit/hyperactivity disorder (ADHD) is associated with both polygenic liability and environmental exposures, both intrinsic to the family, such as family conflict, and extrinsic, such as air pollution. However, much less is known about the interplay between environmental and genetic risks relevant to ADHD—a better understanding of which could inform both mechanistic models and clinical prediction algorithms. Methods Two independent data sets, the population‐based Adolescent Brain Cognitive Development Study (ABCD) (N = 11,876) and the case‐control Oregon‐ADHD‐1000 (N = 1449), were used to examine additive (G + E) and interactive (GxE) effects of selected polygenic risk scores (PRS) and environmental factors in a cross‐sectional design. Genetic risk was measured using PRS for nine mental health disorders/traits. Exposures included family income, family conflict/negative sentiment, and geocoded measures of area deprivation, lead exposure risk, and air pollution exposure (nitrogen dioxide and fine particulate matter). Results ADHD PRS and family conflict jointly predicted concurrent ADHD symptoms in both cohorts. Additive‐effects models, including both genetic and environmental factors, explained significantly more variation in symptoms than any individual factor alone (joint R2 = .091 for total symptoms in ABCD; joint R2 = .173 in Oregon‐ADHD‐1000; all delta‐R2 p‐values <2e‐7). Significant effect size heterogeneity across ancestry groups was observed for genetic and environmental factors (e.g., Q = 9.01, p = .011 for major depressive disorder PRS; Q = 13.34, p = .001 for area deprivation). GxE interactions observed in the full ABCD cohort suggested stronger environmental effects when genetic risk is low, though they did not replicate. Conclusions Reproducible additive effects of PRS and family environment on ADHD symptoms were found, but GxE interaction effects were not replicated and appeared confounded by ancestry. Results highlight the potential value of combining exposures and PRS in clinical prediction algorithms. The observed differences in risks across ancestry groups warrant further study to avoid health care disparities.
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