Faculty Bibliography

PURPOSE OF REVIEW/OBJECTIVE:We review the state of the literature examining associations between early life stress (ELS), gut microbiota, and neurocognitive development and mental health in animals and humans. We identify gaps in current models and areas for future research. RECENT FINDINGS/RESULTS:ELS is associated with changes in gut microbiota, which correspond to changes in affective and cognitive functioning in both animals and humans. Some of these ELS-induced psychological changes can be remedied by supplementation with probiotics in early life, suggesting a potential area for intervention for ELS-exposed children. Prenatal stress exposure is rarely studied in humans in relation to gut microbiota, but animal work has suggested important associations between prenatal stress and fetal programming that should be tested in humans. The gut microbiota plays an important role in the association between ELS, neurocognitive development, and mental health. More work is needed to fully understand these associations in humans.

Characteristics of the home language environment, independent of socioeconomic background, may account for disparities in early language abilities. Past studies have reported links between the quantity of language input within the home and differences in brain function during early childhood. The current study examined associations between home language input and EEG brain activity in a socioeconomically diverse sample of 6- to 12-month-old infants (N = 94). Replicating past studies, a positive correlation was found between measures of socioeconomic status and language input. Examining links between language input and brain activity, analyses yielded a negative association, with children who heard more adult words in the home demonstrating reduced EEG beta power (13-19 Hz) in the parietal region. Exploratory analyses revealed a significant interaction between language input and the amount of chaos and disorganization in the home. Specifically, among children living in high-chaos households, children who heard more adult words tended to have reduced EEG activity. Among children living in low-chaos homes, there was no link between adult word count and children's EEG activity. These findings demonstrate the importance of the early home environment context in shaping neurocognitive trajectories.

Chronic stress has been increasingly linked with aberrations in children's behavioral, cognitive, and social development, yet the effect of chronic physiological stress on neural development during the first year of life is largely unknown. The present study aims to link a physiological index of chronic stress (maternal hair cortisol concentration) to maturational differences in infant functional brain development during the first year of life. Participants were 94 mother-infant dyads. To index chronic physiological stress, maternal hair samples were assayed for the previous three months' cortisol output. To examine the development of brain function during the first year of life, six-to-twelve-month-old infants (N = 94) completed a resting electroencephalography (EEG) recording. Infants of mothers with evidence of higher physiological stress showed increased relative low-frequency (theta) power and reduced relative high-frequency (alpha, high-gamma) power, compared to infants of mothers with evidence of low physiological stress. This pattern of findings is consistent with other studies suggesting that early life stress may lead to alterations in patterns of infant brain development. These findings are important given that maturational lags in brain development can be long-lasting and are associated with deficits in cognitive and emotional development. The present research also suggests that reducing maternal physiological stress may be a useful target for future interventions aiming to foster neurodevelopment during the first year of life.

Although electrophysiological (electroencephalography) measures of executive functions (e.g. error monitoring) have been used to predict academic achievement in typically developing children, work investigating a link between error monitoring and academic skills in children with autism spectrum disorder is limited. In this study, we employed traditional electrophysiological and advanced time-frequency methods, combined with principal component analyses, to extract neural activity related to error monitoring and tested their relations to academic achievement in cognitively able kindergarteners with autism spectrum disorder. In total, 35 cognitively able kindergarteners with autism spectrum disorder completed academic assessments and the child-friendly "Zoo Game" Go/No-go task at school entry. The Go/No-go task successfully elicited an error-related negativity and error positivity in children with autism spectrum disorder as young as 5 years at fronto-central and posterior electrode sites, respectively. We also observed increased response-related theta power during errors relative to correct trials at fronto-central sites. Both larger error positivity and theta power significantly predicted concurrent academic achievement after controlling for behavioral performance on the Zoo Game and intelligence quotient. These results suggest that the use of time-frequency electroencephalography analyses, combined with traditional event-related potential measures, may provide new opportunities to investigate neurobiological mechanisms of executive function and academic achievement in young children with autism spectrum disorder.

Research using electroencephalography (EEG) as a measure of brain function and maturation has demonstrated links between cortical activity and cognitive processes during infancy and early childhood. The current study examines whether neonatal EEG is correlated with later atypical socioemotional behaviors or neurocognitive delays. Parental report developmental assessments were administered to families with children ages 24 to 36 months who had previously participated in a neonatal EEG study (N = 129). Significant associations were found between neonatal EEG (higher frequencies in the frontal polar, temporal, and parietal brain regions) and BITSEA ASD risk scores. Infants with lower EEG power in these brain areas were more likely to have higher risk of socioemotional problems. When examining sex differences, significant links were found for males but not for females. These results demonstrate some promising associations between early neural biomarkers and later risk for atypical behaviors, which may shape early neurobehavioral development and could lead to earlier identification and intervention.

The use of global, standardized instruments is conventional among clinicians and researchers interested in assessing neurocognitive development. Exclusively relying on these tests for evaluating effects may underestimate or miss specific effects on early cognition. The goal of this review is to identify alternative measures for possible inclusion in future clinical trials and interventions evaluating early neurocognitive development. The domains included for consideration are attention, memory, executive function, language, and socioemotional development. Although domain-based tests are limited, as psychometric properties have not yet been well-established, this review includes tasks and paradigms that have been reliably used across various developmental psychology laboratories.

Studies have reported associations between cortical thickness (CT) and socioeconomic status (SES), as well as between CT and cognitive outcomes. However, findings have been mixed as to whether CT explains links between SES and cognitive performance. In the current study, we hypothesized that this inconsistency may have arisen from the fact that socioeconomic factors (family income and parental education) may moderate the relation between CT and neurocognitive skills. Results indicated that associations between CT and cognitive performance did vary by SES for both language and executive function (EF) abilities. Across all ages, there was a negative correlation between CT and cognitive skills, with thinner cortices associated with higher language and EF scores. Similarly, across all cognitive skills, children from higher-SES homes outperformed their age-matched peers from lower-SES homes. Moderation analyses indicated that the impact of SES was not constant across CT, with SES more strongly predictive of EF skills among children with thicker cortices and more strongly predictive of language skills among children with thinner cortices. This suggests that socioeconomic advantage may in some cases buffer against a neurobiological risk factor for poor performance. These findings suggest that links between brain structure and cognitive processes vary by family socioeconomic circumstance.

Infants perceptually tune to the phonemes of their native languages in the first year of life, thereby losing the ability to discriminate non-native phonemes. Infants who perceptually tune earlier have been shown to develop stronger language skills later in childhood. We hypothesized that socioeconomic disparities, which have been associated with differences in the quality and quantity of language in the home, would contribute to individual differences in phonetic discrimination. Seventy-five infants were assessed on measures of phonetic discrimination at 9 months, on the quality of the home environment at 15 months, and on language abilities at both ages. Phonetic discrimination did not vary according to socioeconomic status (SES), but was significantly associated with the quality of the home environment. This association persisted when controlling for 9-month expressive language abilities, rendering it less likely that infants with better expressive language skills were simply engendering higher quality home interactions. This suggests that infants from linguistically richer home environments may be more tuned to their native language and therefore less able to discriminate non-native contrasts at 9 months relative to infants whose home environments are less responsive. These findings indicate that home language environments may be more critical than SES in contributing to early language perception, with possible implications for language development more broadly.