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A burgeoning literature has recently begun investigating the links between socioeconomic inequality and the developing brain. This work suggests widespread disparities in both brain structure and function that begin as early as the first year of life. Here we review disparities in neural structure that have been reported in both cortical and subcortical gray matter, as well as in white matter. Disparities in brain function have also been reported, particularly in circuits that support language, memory, executive functioning, and emotion processing. We additionally review recent work investigating the mechanisms that underlie socioeconomic disparities in brain development. Taken together, this work has the potential to identify important targets for intervention in policy and practice.

Background Socioeconomic factors have been consistently linked with the structure of children’s hippocampus and anterior cingulate cortex (ACC). Chronic stress—as indexed by hair cortisol concentration—may represent an important mechanism underlying these associations. Here, we examined associations between hair cortisol and children’s hippocampal and ACC structure, including across hippocampal subfields, and whether hair cortisol mediated associations between socioeconomic background (family income-to-needs ratio, parental education) and the structure of these brain regions. Methods Participants were 5- to 9-year-old children (N = 94; 61% female) from socioeconomically diverse families. Parents and children provided hair samples that were assayed for cortisol. High-resolution, T1-weighted magnetic resonance imaging scans were acquired, and FreeSurfer 6.0 was used to compute hippocampal volume and rostral and caudal ACC thickness and surface area (n = 37 with both child hair cortisol and magnetic resonance imaging data; n = 41 with both parent hair cortisol and magnetic resonance imaging data). Results Higher hair cortisol concentration was significantly associated with smaller CA3 and dentate gyrus hippocampal subfield volumes but not with CA1 or subiculum volume. Higher hair cortisol was also associated with greater caudal ACC thickness. Hair cortisol significantly mediated associations between parental education level and CA3 and dentate gyrus volumes; lower parental education level was associated with higher hair cortisol, which in turn was associated with smaller volume in these subfields. Conclusions These findings point to chronic physiologic stress as a potential mechanism through which lower parental education level leads to reduced hippocampal volume. Hair cortisol concentration may be an informative biomarker leading to more effective prevention and intervention strategies aimed at childhood socioeconomic disadvantage.

Getting Ready for School (GRS) is a new school readiness intervention for teachers and parents, designed to help children develop early literacy, math, and self-regulation skills. GRS was implemented in 19 Head Start classrooms. In the present study we examined variability in different aspects of intervention fidelity including dosage, adherence, and child engagement. In addition, we studied the association among classroom, teacher and student characteristics and fidelity, and whether measures of fidelity were associated with children’s growth in math, early literacy, and self-regulation skills across the preschool year. Findings indicate that on average teachers reported completing almost 80% of the activities assigned, and that they were observed to adhere fairly well to the lessons. Child engagement was observed to be moderate to high across classrooms. Classroom quality, as measured by the CLASS, and age of children were positively associated with adherence. Teachers that had participated in GRS for two years were more likely to complete more activities. Different components of fidelity were associated with child outcomes. Percentage completion of math and literacy activities were positively associated with growth in math and literacy skills. Children in classrooms in which teachers adhered more faithfully to the curriculum made significantly greater gains in literacy, math, and self-regulation skills. Child engagement was positively associated with a measure of executive function. Results highlight the importance of examining implementation fidelity. Implications for preschool teachers are discussed.

Evidence suggests that increased use of screens early in life may have negative developmental consequences for children. However, little is known concerning parental factors that predict initial screen exposure in infancy. The primary goal of this study was to examine whether parental educational attainment and maternal stress were associated with infant screen exposure by 6 months of age. A diverse sample of mothers (N = 93) was recruited prenatally. In a follow-up visit when the infants were six months of age (N = 82), we examined factors that may be associated with initial infant exposure to screens. First, mothers reported whether they had already exposed their infants to screens. Thereafter, those mothers who reported already having exposed their infants to screens were further queried to determine the extent of infant screen use. Results demonstrated that among infants exposed to screens, mothers reported an average of nearly 3 h of daily screen use. Average parental educational attainment, but not maternal stress, was significantly associated with initial infant exposure. Of those families who endorsed screen exposure by 6 months, 70 % reported a screen in the room where the child sleeps, nearly half reported using screens to help calm the infant, and about a third reported using a screen at least sometimes during meals, when going to sleep, and while waiting. Parental education around infant screen use behaviors may be important to help promote child development and outcomes.

Socioeconomic disadvantage is consistently linked with higher risk for internalizing problems, and stress is likely one important mechanism explaining this increased risk. Few studies have examined socioeconomic differences in hair cortisol, a novel biomarker of long-term adrenocortical activity and chronic stress. Moreover, no studies have examined whether differences in hair cortisol might explain socioeconomic disparities in internalizing problems. To address these gaps, we first examined relations of socioeconomic status (SES; family income and parental education) to variation in both parents’ and children’s hair cortisol concentrations (HCC) and then tested whether HCC and perceptions of stress mediated relations of SES to parents’ and children’s internalizing symptoms. Participants were a socioeconomically diverse sample of 35 parents and 26 children (ages 5–7). Parents completed questionnaires, and hair samples were collected from parents and children. Parents reported on children’s internalizing symptoms on average 2 years after the initial visit. Results demonstrated that lower parental education was associated with higher HCC for both parents and children. Effects for child HCC held even after controlling for parent HCC. Lower family income was associated with higher parent HCC, but not child HCC. This relation was nonlinear, such that the relation between HCC and income was strongest among the most disadvantaged parents. Furthermore, associations of SES with parental anxiety were significantly mediated by parental perceptions of stress and marginally mediated by parent HCC. These findings suggest that socioeconomic disadvantage is associated with greater accumulation of cortisol in hair in parents and children, and that both perceived and biological markers of stress capture important facets of the experiences that underlie socioeconomic disparities in adult anxiety.

Past research has demonstrated links between cortical activity, measured via EEG power, and cognitive processes during infancy. In a separate line of research, family socioeconomic status (SES) has been strongly associated with children’s early cognitive development, with socioeconomic disparities emerging during the second year of life for both language and declarative memory skills. The present study examined associations among resting EEG power at birth, SES, and language and memory skills at 15-months in a sample of full-term infants. Results indicate no associations between SES and EEG power at birth. However, EEG power at birth was related to both language and memory outcomes at 15-months. Specifically, frontal power (24–48Hz) was positively correlated with later Visual Paired Comparison (VPC) memory scores. Power (24–35Hz) in the parietal region was positively correlated with later PLS-Auditory Comprehension language scores. These findings suggest that SES disparities in brain activity may not be apparent at birth, but measures of resting neonatal EEG power are correlated with later memory and language skills independently of SES.

Multiple factors contribute to individual differences in reading ability. The two most thoroughly examined are socioeconomic status (SES) and phonological awareness (PA). Although these factors are often investigated individually, they are rarely considered together. Here we propose that SES systematically influences the relationship between PA and reading ability, and test this prediction in 150 first-graders of varying SES and PA. Results confirm a multiplicative relationship between SES and PA in decoding skills, such that decreased access to resources may amplify cognitive risk factors for poor decoding, whereas greater access to resources may buffer reading skills among children with weaker PA. Attempts to identify the cognitive and experiential factors driving development must acknowledge the complex, synergizing relations between these factors.

Brain imaging studies examining the component processes of reading using words, non-words, and letter strings frequently report task-related activity in the left extrastriate cortex. Processing of these linguistic materials involves varying degrees of semantic, phonological, and orthographic analysis that are sensitive to individual differences in reading skill and history. In contrast, single letter processing becomes automatized early in life and is not modulated by later linguistic experience to the same degree as are words. In this study, skilled readers attended to different aspects (single letters, symbols, and colors) of an identical stimulus set during separate sessions of functional magnetic resonance imaging (fMRI). Whereas activation in some portions of ventral extrastriate cortex was shared by attention to both alphabetic and non-alphabetic features, a letter-specific area was identified in a portion of left extrastriate cortex (Brodmann's Area 37), lateral to the visual word form area. Our results demonstrate that while minimizing activity related to word-level lexical properties, cortical responses to letter recognition can be isolated from figural and color characteristics of simple stimuli. The practical utility of this finding is discussed in terms of early identification of reading disability.