Early emotional caregiving environment and associations with memory performance and hippocampal volume in adolescents with prenatal drug exposure

Early adversities, including prenatal drug exposure (PDE) and a negative postnatal emotional caregiving environment, impact children's long-term development. The protracted developmental course of memory and its underlying neural systems offer a valuable framework for understanding the longitudinal associations of pre- and postnatal factors on children with PDE. This study longitudinally examines memory and hippocampal development in 69 parent-child dyads to investigate how the early caregiving emotional environment affects children with PDE's neural and cognitive systems. Measures of physical health, drug exposure, caregiver stress, depression, and distress were collected between 0 and 24 months At age 14 years, adolescents completed multiple measures of episodic memory, and at ages 14 and 18 years, adolescents underwent magnetic resonance imaging (MRI) scans. Latent constructs of episodic memory and the caregiving environment were created using Confirmatory Factor Analysis. Multiple regressions revealed a negative emotional caregiving environment during infancy was associated with poor memory performance and smaller left hippocampal volumes at 14 years. Better memory performance at 14 years predicted larger right hippocampal volume at 18 years. At 18 years, the association between the emotional caregiving environment and hippocampal volume was moderated by sex, such that a negative emotional caregiving environment was associated with larger left hippocampal volumes in males but not females. Findings suggest that the postnatal caregiving environment may modulate the effects of PDE across development, influencing neurocognitive development.

Emotion regulation and reactivity are associated with cortical thickness in early to mid-childhood

This study explored the neural correlates of emotion regulation and emotional reactivity in early to mid-childhood. A sample of 96 children (70% White, mid-to-high socioeconomic status) aged 3-8 years provided structural neuroimaging data and caregivers reported on emotion regulation and emotional reactivity. The amygdala, insula, inferior frontal gyrus, anterior cingulate cortex, and medial orbitofrontal cortex were explored as a priori regions of interest (ROIs). ROI analyses revealed that emotion regulation was positively associated with cortical thickness in the insula, whereas emotional reactivity was negatively associated with cortical thickness in the inferior frontal gyrus. Exploratory whole-brain analyses suggested positive associations between emotion regulation and both left superior temporal thickness and right inferior temporal thickness, as well as negative associations between emotional reactivity and left superior temporal thickness. There were no significant associations between emotional regulation or reactivity and amygdala volume or cortical surface area. These findings support the notion that surface area and cortical thickness are distinct measures of brain maturation. In sum, these findings suggest that children may rely on a wider set of neural regions for emotion regulation and reactivity than adults, which is consistent with theories of interactive specialization across the life span.

Longitudinal Exploration of Binding Ability across Early Childhood: The Differential Contribution of Hits and False Alarms

Childhood is a period of pronounced improvements in children's ability to remember connections between details of an event (i.e. binding ability). However, the mechanisms supporting these changes remain unclear. Prior evidence is mixed, with some proposing that improvements in the ability to identify previous connections (i.e. increases in hits) account for memory changes, whereas other evidence suggests changes are additionally supported by the ability to identify inaccurate connections (i.e. decreases in false alarms). To disentangle the role of each process, we investigated changes in hits and false alarms within the same paradigm. The present study of 200 4-to-8-year-old children (100 female) used a cohort sequential design to assess longitudinal change in binding ability. Developmental trajectories of d', hit, and false alarm rates were examined using latent growth analysis. Findings demonstrated non-linear improvements in children's binding ability from age 4-to-8-years. Improvements were differentially supported by hits and false alarms. Hit rates improved non-linearly from 4-to-8-years, with greater growth from 4-to-6-years. False alarm rates did not significantly change from 4-to-6-years, but significantly decreased from 6-to-8-years. Overall, findings show improvements in binding ability are predominantly supported by increased hit rates between 4-to-6-years and by both increasing hit rates and decreasing false alarms rates between 6-to-8-years. Together, these results suggest that binding development is non-linear and that mechanisms underlying improvements differ across childhood.

Irritability in early to middle childhood: Cross-sectional and longitudinal associations with resting state amygdala and ventral striatum connectivity

BACKGROUND

Irritability is a common symptom that may affect children's brain development. This study aims to (1) characterize age-dependent and age-independent neural correlates of irritability in a sample of 4-8 year old children, and (2) examine early irritability as a predictor of change in brain connectivity over time.

METHODS

Typically developing children, ages 4-8 years, with varying levels of irritability were included. Resting state fMRI and parent-rated irritability (via Child Behavior Checklist; CBCL) were collected at up to three time points, resulting in a cross-sectional sample at baseline (N = 176, M = 6.27, SD = 1.49), and two subsamples consisting of children who were either 4 or 6 years old at baseline that were followed longitudinally for two additional timepoints, one- and two-years post-baseline. That is, a "younger" cohort (age 4 at baseline, n = 34, M age = 4.44, SD = 0.25) and an "older" cohort (age 6 at baseline, n = 29, M age = 6.50, SD = 0.30). Across our exploratory analyses, we examined how irritability related to seed-based intrinsic connectivity via whole-brain connectivity ANCOVAs using the left and right amygdala, and left and right ventral striatum as seed regions.

RESULTS

Cross-sectionally, higher levels of irritability were associated with greater amygdala connectivity with the posterior cingulate, controlling for child age. No age-dependent effects were observed in the cross-sectional analyses. Longitudinal analyses in the younger cohort revealed that early higher vs. lower levels of irritability, controlling for later irritability, were associated with decreases in amygdala and ventral striatum connectivity with multiple frontal and parietal regions over time. There were no significant findings in the older cohort.

CONCLUSIONS

Findings suggest that irritability is related to altered neural connectivity during rest regardless of age in early to middle childhood and that early childhood irritability may be linked to altered changes in neural connectivity over time. Understanding how childhood irritability interacts with neural processes can inform pathophysiological models of pediatric irritability and the development of targeted mechanistic interventions.

The fornix supports episodic memory during childhood

Episodic memory relies on the coordination of widespread brain regions that reconstruct spatiotemporal details of an episode. These topologically dispersed brain regions can rapidly communicate through structural pathways. Research in animal and human lesion studies implicate the fornix-the major output pathway of the hippocampus-in supporting various aspects of episodic memory. Because episodic memory undergoes marked changes in early childhood, we tested the link between the fornix and episodic memory in an age window of robust memory development (ages 4-8 years). Children were tested on the stories subtest from the Children's Memory Scale, a temporal order memory task, and a source memory task. Fornix streamlines were reconstructed using probabilistic tractography to estimate fornix microstructure. In addition, we measured fornix macrostructure and computed free water. To assess selectivity of our findings, we also reconstructed the uncinate fasciculus. Findings show that children's memory increases from ages 4 to 8 and that fornix micro- and macrostructure increases between ages 4 and 8. Children's memory performance across nearly every memory task correlated with individual differences in fornix, but not uncinate fasciculus, white matter. These findings suggest that the fornix plays an important role in supporting the development of episodic memory, and potentially semantic memory, in early childhood.

Socioeconomic disadvantage and episodic memory ability in the ABCD sample: Contributions of hippocampal subregion and subfield volumes

Socioeconomic disadvantage is associated with volumetric differences in stress-sensitive neural structures, including the hippocampus, and deficits in episodic memory. Rodent studies provide evidence that memory deficits arise via stress-related structural differences in hippocampal subdivisions; however, human studies have only provided limited evidence to support this notion. We used a sample of 10,695 9-13-year-old participants from two timepoints of the Adolescent Brain and Cognitive Development (ABCD) Study to assess whether socioeconomic disadvantage relates to episodic memory performance through hippocampal volumes. We explored associations among socioeconomic disadvantage, measured via the Area Deprivation Index (ADI), concurrent subregion (anterior, posterior) and subfield volumes (CA1, CA3, CA4/DG, subiculum), and episodic memory, assessed via the NIH Toolbox Picture Sequence Memory Test at baseline and 2-year follow-up (Time 2). Results showed that higher baseline ADI related to smaller concurrent anterior, CA1, CA4/DG, and subiculum volumes and poorer Time 2 memory performance controlling for baseline memory. Moreover, anterior, CA1, and subiculum volumes mediated the longitudinal association between the ADI and memory. Results suggest that greater socioeconomic disadvantage relates to smaller hippocampal subregion and subfield volumes and less age-related improvement in memory. These findings shed light on the neural mechanisms linking socioeconomic disadvantage and cognitive ability in childhood.

0110 Nap-Related Change in Memory Precision may be Related to Slow-Wave Sleep in Early Childhood

Introduction

In early childhood (3-5 years), naps comprise part of children’s 24-hr sleep. Naps support some types of learning (declarative, emotional), enhancing children’s ability to correctly identify previously seen items. During this time, children’s ability to form precise memories also improves, likely due to ongoing hippocampal development and maturation of processes allowing for pattern separation. Whether naps support the ability to form precise memory representations, allowing children to discriminate between previously seen vs. similar but novel items, is unclear. Here, we used a mnemonic similarity task to examine whether daytime naps support children’s recall of specific images more so than a period of wake. Further, we tested whether this nap-related improvement persists across overnight sleep. We hypothesized that task improvement would be associated with slow-wave sleep (SWS), as this stage has been shown to support episodic memory in preschool-aged children.

Methods

Participants (N=7, 4 females, Mage=56.1 mos) encoded items in the morning, verbally categorizing each image as something they would find “inside” or “outside”. They recalled items at three time points: immediately following encoding, after their nap/wake period, and the following morning after overnight sleep. Recall involved being shown a single image and responding whether it had been previously seen or not. Recall items included targets, foils, and lures. PSG was recorded during the nap and overnight sleep bouts.

Results

When controlling for age, children forgot fewer target items following a nap than a comparable period of wake (p=.05). Following a nap and overnight sleep, children also exhibited marginally less forgetting of target items than following a period of wake and overnight sleep (p=.102). Lure discrimination index (LDI; false alarm lures minus false alarm foils) did not differ between nap and wake conditions. Change in target recall following the nap was associated with SWS% during the nap (r=.96, p=.01), but not nap duration (p=.27).

Conclusion

Napping supported children’s ability to recall target items, but not to correctly reject lures, suggesting naps’ benefit towards more generalized memory. Nap SWS% was associated with less forgetting of target items, supporting its role in hippocampal-dependent memory consolidation. Analyses of overnight sleep data and inclusion of more participants may help better elucidate the relationship between preschool children’s sleep and memory development.

Support (If Any)

NSF BCS 1749280 NIH R21 HD094758 NIH R01 HL111695

A meta-analysis of the relation between hippocampal volume and memory ability in typically developing children and adolescents

Memory is supported by a network of brain regions, with the hippocampus serving a critical role in this cognitive process. Previous meta‐analyses on the association between hippocampal structure and memory have largely focused on adults. Multiple studies have since suggested that hippocampal volume is related to memory performance in children and adolescents; however, the strength and direction of this relation varies across reports, and thus, remains unclear. To further understand this brain–behavior relation, we conducted a meta‐analysis to investigate the association between hippocampal volume (assessed as total volume) and memory during typical development. Across 25 studies and 61 memory outcomes with 1357 participants, results showed a small, but significant, positive association between total hippocampal volume and memory performance. Estimates of the variability across studies in the relation between total volume and memory were not explained by differences in memory task type (delayed vs. immediate; relational vs. nonrelational), participant age range, or the method of normalization of hippocampal volumes. Overall, findings suggest that larger total hippocampal volume relates to better memory performance in children and adolescents and that this relation is similar across the memory types and age ranges assessed. To facilitate enhanced generalization across studies in the future, we discuss considerations for the field moving forward.

Mothers’ Attachment Representations and Children’s Brain Structure

Ample research demonstrates that parents’ experience-based mental representations of attachment—cognitive models of close relationships—relate to their children’s social-emotional development. However, no research to date has examined how parents’ attachment representations relate to another crucial domain of children’s development: brain development. The present study is the first to integrate the separate literatures on attachment and developmental social cognitive neuroscience to examine the link between mothers’ attachment representations and 3- to 8-year-old children’s brain structure. We hypothesized that mothers’ attachment representations would relate to individual differences in children’s brain structures involved in stress regulation—specifically, amygdala and hippocampal volumes—in part via mothers’ responses to children’s distress. We assessed 52 mothers’ attachment representations (secure base script knowledge on the Attachment Script Assessment and self-reported attachment avoidance and anxiety on the Experiences in Close Relationships scale) and children’s brain structure. Mothers’ secure base script knowledge was significantly related to children’s smaller left amygdala volume but was unrelated to hippocampal volume; we found no indirect links via maternal responses to children’s distress. Exploratory analyses showed associations between mothers’ attachment representations and white matter and thalamus volumes. Together, these preliminary results suggest that mothers’ attachment representations may be linked to the development of children’s neural circuitry related to stress regulation.

Developmental changes in episodic memory across early- to mid-childhood: insights from a latent longitudinal approach

Episodic memory is a cornerstone ability that allows one to recall past events and the spatiotemporal context in which they occur. In an effort to characterise the development of this critical ability, many different tasks have been used independently to assess age-related variations in episodic memory. However, performance on memory tasks is multiply determined, and the extent to which different tasks with varying features relate to each other and represent episodic memory as a latent cognitive construct across childhood is unclear. The present study sought to address this question by exploring the feasibility of using four different laboratory-based tasks to characterise changes in episodic memory ability during early- to mid-childhood in 200 typically developing children (4-8 years). Using longitudinal data and a structural equation modeling framework, results suggest that multiple tests of episodic memory can be utilised to indicate a comparable latent construct of episodic memory ability over this period of development, and that this ability improves consistently between 4 to 8 years. Overall, results highlight that episodic memory measured as a construct increases at a similar rate over early- to mid-childhood and demonstrate the benefits of using multiple laboratory tasks to characterise developmental changes in episodic memory.

Adapting event-related potential research paradigms for children: Considerations from research on the development of recognition memory

Most developmental event-related potential (ERP) research uses experimental paradigms modified from research with adults. One major challenge is identifying how to adapt these paradigms effectively for use with younger individuals. This paper provides guidance for developmental adaptations by considering research on the development of recognition memory. We provide a brief overview of recognition memory tasks and ERP components associated with recognition memory in children and adults. Then, we provide some general recommendations, discuss common differences between ERP studies of recognition memory in adults and children (e.g., the type of stimuli presented, response modalities), and provide suggestions for assessing the effect of task modifications on ERP components of interest. Specifically, we recommend (a) testing both children and adults on the modified paradigm to allow for a continuity of findings across development, (b) comparing children of different ages on the modified paradigm based on expectations regarding when developmental change occurs for the cognitive process of interest, and (c) empirically assessing the effect of methodological differences between paradigms. To illustrate the latter, we analyzed data from our lab comparing memory-related ERP components when children experienced a 1-day, 2-day, or 1-week delay between encoding and retrieval.

Interactions between the hippocampus and fronto-parietal regions during memory encoding in early childhood

The neural mechanisms underlying memory encoding have received much attention in the literature. Research in adults and school-age children suggest that the hippocampus and cortical regions in both frontal and parietal areas are involved in successful formation of memories. Overall, the hippocampus has been shown to interact with fronto-parietal regions to collaboratively support successful memory encoding for both individual items as well as item details (such as the source or color in which the item was originally encountered). To date, only one study has investigated neural regions engaged during memory encoding in children younger than 8 years of age, which is unfortunate since early childhood is a period of dramatic improvement in memory. This previous study indicated that both the hippocampus and cortical regions are involved during the encoding of subsequently remembered item details (i.e., sources). However, this study reported few interactions between these regions, and it did not explore item memory at a more general level. To fill these gaps, this article reanalyzed data from the previous report, aiming to examine the neural correlates of item memory during encoding in early childhood (4-8 years) and interactions between the hippocampus and fronto-parietal regions during encoding. Consistent with research in older individuals, both the hippocampus and fronto-parietal regions were found to participate in item memory encoding. Additionally, functional connectivity between hippocampus and fronto-parietal regions was significantly related to both subsequent item memory and subsequent source memory. Taken together, these findings suggest that not only the activation of individual brain regions (hippocampus and fronto-parietal regions) but also the functional connections between these regions are important for memory encoding. These data add to the growing literature providing insight into how the hippocampus and cortical regions interact to support memory during development.

Modeling longitudinal changes in hippocampal subfields and relations with memory from early- to mid-childhood

The hippocampus has been suggested to show protracted postnatal developmental growth across childhood. Most previous studies during this developmental period have been cross-sectional in nature and have focused on age-related differences in either hippocampal subregions or subfields, but not both, potentially missing localized changes. This study capitalized on a latent structural equation modeling approach to examine the longitudinal development of hippocampal subfields (cornu ammonis (CA) 2-4/dentate gyrus (DG), CA1, subiculum) in both the head and the body of the hippocampus, separately, in 165 typically developing 4- to 8-year-old children. Our findings document differential development of subfields within hippocampal head and body. Specifically, within hippocampal head, CA1 volume increased between 4-5 years and within hippocampal body, CA2-4/DG and subiculum volume increased between 5-6 years. Additionally, changes in CA1 volume in the head and changes in subiculum in the body between 4-5 years related to improvements in memory between 4-5 years. These findings demonstrate the protracted development of subfields in vivo during early- to mid-childhood, illustrate the importance of considering subfields separately in the head and body of the hippocampus, document co-occurring development of brain and behavior, and highlight the strength of longitudinal data and latent modeling when examining brain development.

Sleep and human cognitive development

Emerging studies across learning domains have shed light on mechanisms underlying sleep's benefits during numerous developmental periods. In this conceptual review, we survey recent studies of sleep and cognition across infancy, childhood, and adolescence. By summarizing recent findings and integrating across studies with disparate approaches, we provide a novel understanding of sleep's role in human cognitive function. Collectively, these studies point to an interrelation between brain development, sleep, and cognition. Moreover, we point to gaps in our understanding, which inform the agenda for future research in developmental and sleep science.

Hippocampal subregion volume in high-risk offspring is associated with increases in depressive symptoms across the transition to adolescence

BACKGROUND

The hippocampus has been implicated in the pathophysiology of depression. This study examined whether youth hippocampal subregion volumes were differentially associated with maternal depression history and youth's depressive symptoms across the transition to adolescence.

METHODS

74 preadolescent offspring (M_age=10.74+/-0.84 years) of mothers with (n = 33) and without a lifetime depression history (n = 41) completed a structural brain scan. Youth depressive symptoms were assessed with clinical interviews and mother- and youth-reports prior to the neuroimaging assessment at age 9 (M_age=9.08+/-0.29 years), at the neuroimaging assessment, and in early adolescence (M_age=12.56+/-0.40 years).

RESULTS

Maternal depression was associated with preadolescent offspring's reduced bilateral hippocampal head volumes and increased left hippocampal body volume. Reduced bilateral head volumes were associated with offspring's increased concurrent depressive symptoms. Furthermore, reduced right hippocampal head volume mediated associations between maternal depression and increases in offspring depressive symptoms from age 9 to age 12.

LIMITATIONS

This study included a modest-sized sample that was oversampled for early temperamental characteristics, one neuroimaging assessment, and no correction for multiple comparisons.

CONCLUSIONS

Findings implicate reductions in hippocampal head volume in the intergenerational transmission of risk from parents to offspring.

How Behavior Shapes the Brain and the Brain Shapes Behavior: Insights from Memory Development

Source memory improves substantially during childhood. This improvement is thought to be closely related to hippocampal maturation. As previous studies have mainly used cross-sectional designs to assess relations between source memory and hippocampal function, it remains unknown whether changes in the brain precede improvements in memory or vice versa. To address this gap, the current study used an accelerated longitudinal design (n = 200, 100 males) to follow 4- and 6-year-old human children for 3 years. We traced developmental changes in source memory and intrinsic hippocampal functional connectivity and assessed differences between the 4- and 6-year-old cohorts in the predictive relations between source memory changes and intrinsic hippocampal functional connectivity in the absence of a demanding task. Consistent with previous studies, there were age-related increases in source memory and intrinsic functional connectivity between the hippocampus and cortical regions known to be involved during memory encoding. Novel findings showed that changes in memory ability early in life predicted later connectivity between the hippocampus and cortical regions and that intrinsic hippocampal functional connectivity predicted later changes in source memory. These findings suggest that behavioral experience and brain development are interactive, bidirectional processes, such that experience shapes future changes in the brain and the brain shapes future changes in behavior. Results also suggest that both timing and location matter, as the observed effects depended on both children's age and the specific brain ROIs. Together, these findings add critical insight into the interactive relations between cognitive processes and their underlying neurologic bases during development.SIGNIFICANCE STATEMENT Cross-sectional studies have shown that the ability to remember the contextual details of previous experiences (i.e., source memory) is related to hippocampal development in childhood. It is unknown whether hippocampal functional changes precede improvements in memory or vice versa. By using an accelerated longitudinal design, we found that early source memory changes predicted later intrinsic hippocampal functional connectivity and that this connectivity predicted later source memory changes. These findings suggest that behavioral experience and brain development are interactive, bidirectional processes, such that experience shapes future changes in the brain and the brain shapes future behavioral changes. Moreover, these interactions varied as a function of children's age and brain region, highlighting the importance of a developmental perspective when investigating brain-behavior interactions.

Parental hostility predicts reduced cortical thickness in males

Although impacts of negative parenting on children's brain development are well-documented, little is known about how these associations may differ for males and females in childhood. We examined interactions between child sex and early and concurrent parental hostility on children's cortical thickness and surface area. Participants included 63 children (50.8% female) assessed during early childhood (Wave 1: M age = 4.23 years, SD = 0.84) and again three years later (Wave 2: M age = 7.19 years, SD = 0.89) using an observational parent-child interaction task. At Wave 2, children completed a structural MRI scan. Analyses focused on regions of interest. After correcting for multiple comparisons, Wave 1 parental hostility predicted males' reduced thickness in middle frontal and fusiform cortices, and Wave 2 parental hostility was concurrently associated with males' reduced thickness in the middle frontal cortex. Interactions between sex and parenting on children's surface area did not survive corrections for multiple comparisons. Our findings provide support for a male-specific neural vulnerability of hostile parenting across development. Results have important implications for uncovering neural pathways to sex-differences in psychopathology, learning, and cognitive disabilities.

Prefrontal cortical thickness mediates the association between cortisol reactivity and executive function in childhood

The impact of stress hormones, such as cortisol, on the brain is proposed to contribute to differences in executive function of school-age children from impoverished backgrounds. However, the association between cortisol reactivity, prefrontal cortex, and executive function is relatively unexplored in young children. The current longitudinal study examined whether 63 children's early preschool-age (3-5 years, Time 1) and concurrent school-age (5-9 years, Time 2) salivary cortisol reactivity were associated with executive function and prefrontal cortical thickness at school-age. Two measures of cortisol reactivity were calculated: area under the curve with respect to ground (AUCg; total cortisol release) and with respect to increase (AUCi; total change in cortisol). Results demonstrated that Time 2 total cortisol release was negatively associated with executive function, Time 1 total cortisol release positively related to right middle frontal cortical thickness, and Time 2 total cortisol change was negatively associated with right inferior frontal cortical thickness. Moreover, greater right middle frontal cortical thickness mediated the association between greater Time 1 total cortisol release and lower executive function. This study provides support for an early adversity framework in which individual differences in executive function in childhood are directly related to the variations of cortisol-release and the effects on the prefrontal cortex thickness.

Microstructural Integrity of the Hippocampus During Childhood: Relations With Age and Source Memory

The hippocampus is a brain structure known to be important for memory. However, studies examining relations between hippocampal volume and memory across development yield mixed results. This may be due in part to the fact that volume is a coarser measure of hippocampal composition. Studies have begun to examine measures of diffusion, which capture characteristics of the microstructure of the hippocampus, and thus may provide additional information about the integrity of the underlying neural circuits. The present study applied this approach to a developmental period characterized by dramatic changes in both hippocampal microstructure and memory behavior - early childhood. Specifically, measures of hippocampal microstructural integrity were related to age and source memory performance in 93 children aged 4-8 years. Results revealed significant negative associations between hippocampal mean diffusivity and both age and memory, even after controlling for differences in hippocampal volume. These results suggest that hippocampal diffusion may provide additional, independent information about hippocampal integrity compared to volume, particularly during early childhood when important developmental changes have been proposed.

It's All in the Details: Relations Between Young Children's Developing Pattern Separation Abilities and Hippocampal Subfield Volumes

The ability to keep similar experiences separate in memory is critical for forming unique and lasting memories, as many events share overlapping features (e.g., birthday parties, holidays). Research on memory in young children suggests their memories often lack high-resolution details, i.e., show impoverished pattern separation (PS). Recently developed assessments of PS suitable for children allow us to relate the formation of distinct, detailed memories for the development of the hippocampus, a neural structure critical for this ability in adults. The hippocampus displays a protracted developmental profile and underlies the ability to form detailed memories. This study examined age-related differences in hippocampal subfield volumes in 4- to 8-year-old children and relations with performance on a mnemonic similarity task (MST) designed to index memory specificity. Results revealed age-moderated associations between MST performance and cornu ammonis 2-4/dentate gyrus subfields. Specifically, age-related differences in the ability to form detailed memories tracked with normative patterns of volume increases followed by reductions over this age range. That is, greater volume correlated with better performance in younger children, whereas smaller volume correlated with better performance in older children. These findings support the hypothesis that developmental differences in hippocampal circuitry contribute to age-related improvements in detailed memory formation during this period.

Longitudinal Development of Memory for Temporal Order in Early to Middle Childhood

Existing studies examining the development of temporal order memory show that although young children perform above chance on some tasks assessing temporal order memory, there are significant age-related differences across childhood. Yet, the trajectory of children's ability to retrieve temporal order remains unclear as existing conclusions are drawn from cross-sectional studies. The present study utilized an accelerated longitudinal design in order to characterize the developmental trajectory of temporal order memory in a sample of 200 healthy 4- to 8-year-old children. Specifically, two tasks commonly used in the literature were tested longitudinally: a primacy judgment task and an ordering task. Results revealed that, even after controlling for differences in IQ, linearly increasing trajectories characterized age-related change in performance for both tasks; however, change appeared greater for the temporal ordering task. Further, performance on the two tasks was positively related, suggesting shared underlying mechanisms. These findings provide a more thorough understanding of temporal order memory in early to middle childhood by characterizing the developmental trajectories of two commonly used tasks and have important implications for our understanding of children's developing memory more broadly.

Learning From Others: The Effects of Agency on Event Memory in Young Children

Little is known about the influence of social context on children's event memory. Across four studies, we examined whether learning that could occur in the absence of a person was more robust when a person was present. Three-year-old children (N = 125) viewed sequential events that either included or excluded an acting agent. In Experiment 1, children who viewed an agent recalled more than children who did not. Experiments 2a and 2b utilized an eye tracker to demonstrate this effect was not due to differences in attention. Experiment 3 used a combined behavioral and event-related potential paradigm to show that condition effects were present in memory-related components. These converging results indicate a particular role for social knowledge in supporting memory for events.

Longitudinal development of hippocampal subregions from early- to mid-childhood

Early childhood is characterized by vast changes in behaviors supported by the hippocampus and an increased susceptibility of the hippocampus to environmental influences. Thus, it is an important time to investigate the development of the hippocampus. Existing research suggests subregions of the hippocampus (i.e., head, body, tail) have dissociable functions and that the relations between subregions and cognitive abilities vary across development. However, longitudinal research examining age-related changes in subregions in humans, particularly during early childhood (i.e., 4-6 years), is limited. Using a large sample of 184 healthy 4- to 8-year-old children, the present study is the first to characterize developmental changes in hippocampal subregion volume from early- to mid-childhood. Results reveal differential developmental trajectories in hippocampal head, body, and tail during this period. Specifically, head volume showed a quadratic pattern of change, and both body and tail showed linear increases, resulting in a pattern of cubic change for total hippocampal volume. Further, main effects of sex on hippocampal volume (males > females) and hemispheric differences in developmental trajectories were observed. These findings provide an improved understanding of the development of the hippocampus and have important implications for research investigating a range of cognitive abilities and behaviors.

0089 Sleep and Hippocampal Development in Early Childhood

Introduction

With sleep, memories are consolidated, leaving them less susceptible to interference. This process is believed to reflect transfer of memories from the hippocampus to the cortex. Research has established that naps benefit memory in typically napping children. This nap-benefit has been associated with sleep spindles during nREM2 sleep. Although research has separately related memory development to the hippocampus and to sleep, the association between hippocampal development and sleep physiology is not understood. The purpose of this investigation is to assess relations between sleep physiology and the hippocampus in early childhood.

Methods

Subjects are part of an ongoing longitudinal investigation. Preliminary analyses included 24 participants (Mage= 3.96 years, 14 females). Children participated in three consecutive visits, one week apart. During the first two visits, they completed a visuospatial memory task before and after a wake or nap period (order counterbalanced). Sleep physiology was assessed via polysomnography and hippocampal volumes were obtained via Freesurfer v5.1 using T1-weighted scans (.9 mm3).

Results

Preliminary results showed that total hippocampal volume was positively related to minutes spent in nREM2 sleep when controlling for age and gender (B=14.7, p=0.03). Further analysis showed that this relation held for left but not right hippocampus (B=10.1, p=0.01). Results also indicate a positive relation between sleep spindle count and left but not right hippocampal volume when controlling for age and gender (B=16.1, p=0.02).

Conclusion

Results show that greater time spent in nREM2 and greater sleep spindles across nREM2 are both related to a larger hippocampus in early childhood. These findings demonstrate an association between sleep physiology and the hippocampus during an important period of memory development, early childhood. Future analyses will assess differences in hippocampal volume between typical nappers and non-nappers at the second wave of data collection.

Support

Support was provided by NIH (HD094758) and NSF (BCS 1749280).

0334 Hippocampal Development, Slow Wave Activity, and Nap-Dependent Memory Consolidation in Early Childhood

Introduction

Naps support memory consolidation in early childhood. In adults, nap-dependent declarative consolidation is associated with SWA. SWA increases from early childhood into adulthood, and the shift of SWA from occipital to frontal distribution (F/O-ratio) is a marker of brain maturation. Thus, we explored how electrophysiological and structural characteristics of brain development relate to nap-dependent declarative learning in early childhood.

Methods

Twelve preschool-age children (8 female, M=48 months, SD=0.44) have completed three sessions (~1wk apart) within a larger study. In the first two sessions, children completed a visuo-spatial task before and after a 2-hr nap or wake interval. During the third visit, children underwent MRI assessment. Using PSG, SWA was measured in the delta band over frontal and occipital regions for nREM2 and nREM3 sleep.

Results

While F/O-ratio of SWA does not currently predict the F/O-ratio of cortical thickness (r(12)=.383, p=.219), right parahippocampal thickness positively correlates with F/O-ratio of SWA in nREM2 (r(12)=.591, p=.043). Nonetheless, children’s performance change following the nap was not associated with either parahippocampal thickness or F/O-ratio of SWA in any sleep stage (all ps>.538). However, performance in children who showed a post-nap benefit (n=5) positively correlated with right parahippocampal thickness (r(5)=.915, p=.029). This was not the case for children who did not show a post-nap benefit (r(7)=-.199, p=.668).

Conclusion

Although the F/O-ratio of SWA did not predict a similar ratio of cortical thickness, the association between right parahippocampal thickness and F/O-ratio of SWA is evidence that development of SWA parallels cortical development. While there is no overall association between post-nap performance and brain development characteristics, the relation between performance and right parahippocampal thickness in children showing a nap benefit suggests that memory during this age may depend on structural (rather than electrophysiological) brain development changes.

Support

NIH R21 HD094758 & NSF BCS 1749280

Early childhood cumulative risk is associated with decreased global brain measures, cortical thickness, and cognitive functioning in school-age children

Children exposed to multiple risk factors early in life are increasingly more likely to suffer from a host of cognitive impairments across development. However, little work has identified the neurobiological mechanisms linking early cumulative risk and cognitive functioning. The current study examined the impact of cumulative risk assessed during early childhood on neural and cognitive outcomes measured 3 years later when children were school-aged. Participants included 63 children assessed during preschool (age: M = 4.23 years, SD = 0.84) and 3 years later (age: M = 7.19 years, SD = 0.89). Early cumulative risk was defined by the presence of low family income, a single parent household, low parental education, child exposure to parental depression, child exposure to high parental hostility, and high levels of stressful life events. Children's exposure to stressors in the past year, cognitive abilities, and brain structure were assessed at follow-up. Early cumulative risk was prospectively associated with reduced total gray matter volume, cortex volume, right superior parietal and inferior parietal thickness, and poorer attention shifting and memory. Right superior parietal thickness mediated associations between early risk and recall memory. Results highlight neural variations associated with early cumulative risk and suggest potential neural pathways from early risk to later childhood cognitive impairments.

Empathic responding and hippocampal volume in young children

Empathic responding-the capacity to understand, resonate with, and respond sensitively to others' emotional experiences-is a complex human faculty that calls upon multiple social, emotional, and cognitive capacities and their underlying neural systems. Emerging evidence in adults has suggested that the hippocampus and its associated network may play an important role in empathic responding, possibly via processes such as memory of emotional events, but the contribution of this structure in early childhood is unknown. We examined concurrent associations between empathic responding and hippocampal volume in a sample of 78 children (ages 4-8 years). Larger bilateral hippocampal volume (adjusted for intracranial volume) predicted greater observed empathic responses toward an experimenter in distress, but only for boys. The association was not driven by a specific subregion of the hippocampus (head, body, tail), nor did it vary with age. Empathic responding was not significantly related to amygdala volume, suggesting specificity of relations with the hippocampus. Results support the proposal that hippocampal structure contributes to individual differences in children's empathic responding, consistent with research in adults. Findings shed light on an understudied structure in the complex neural systems supporting empathic responding and raise new questions regarding sex differences in the neurodevelopment of empathy in early childhood. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Empirical Evidence Supporting Neural Contributions to Episodic Memory Development in Early Childhood: Implications for Childhood Amnesia

Memories for events that happen early in life are fragile-they are forgotten more quickly than expected based on typical adult rates of forgetting. Although numerous factors contribute to this phenomenon, data show one major source of change is the protracted development of neural structures related to memory. Recent empirical studies in early childhood reveal that the development of specific subdivisions of the hippocampus (i.e., the dentate gyrus) are related directly to variations in memory. Yet the hippocampus is only one region within a larger network supporting memory. Data from young children have also shown that activation of cortical regions during memory tasks and the functional connectivity between the hippocampus and cortex relate to memory during this period. Taken together, these results suggest that protracted neural development of the hippocampus, cortex, and connections between these regions contribute to the fragility of memories early in life and may ultimately contribute to childhood amnesia.

Age- and performance-related differences in source memory retrieval during early childhood: Insights from event-related potentials

Across early childhood, children's ability to remember individual items and the details that accompany these items (i.e., episodic memory) improves greatly. Given that these behavioral improvements coincide with increases in age, effects of age and performance are often confounded. This study used event-related potentials (ERPs) to investigate age- and performance-related differences in the neural processes underlying the development of memory for details during early childhood. Using a source memory paradigm, ERP components related to episodic memory, the negative component (Nc), and late slow wave (LSW) were examined in 4- to 8-year-old children. Analyses focused on trials for which children correctly remembered the source related to an item versus trials where the item was remembered but the source was forgotten. Results revealed LSW, but not Nc, differed as a function of age and performance. Specifically, LSW effects were similar across source correct and source incorrect trials in all high-performing children and in low-performing older children; however, LSW effects differed across conditions in low-performing younger children. Results show developmental differences in retrieval processes across early childhood and highlight the importance of considering age and performance when examining electrophysiological correlates of episodic memory during development.

Lasting effects of stress physiology on the brain: Cortisol reactivity during preschool predicts hippocampal functional connectivity at school age

Prolonged exposure to glucocorticoid stress hormones, such as cortisol in humans, has been associated with structural and functional changes in the hippocampus. The majority of research demonstrating these associations in humans has been conducted in adult, clinical, or severely maltreated populations, with little research investigating these effects in young or more typically developing populations. The present study sought to address this gap by investigating longitudinal associations between preschool (3−5 years) and concurrent (5–9 years) cortisol reactivity to a laboratory stressor and hippocampal functional connectivity during a passive viewing fMRI scan. Results showed that, after controlling for concurrent cortisol reactivity, greater total cortisol release in response to a stressor during preschool predicted increased anterior and posterior hippocampal connectivity with the precuneus and cingulate gyrus at school-age. These findings are consistent with literature from adult and non-human investigations and suggest lasting impacts of early stress physiology on the brain.

Measuring Neural Mechanisms Underlying Sleep-Dependent Memory Consolidation During Naps in Early Childhood

Sleep is critical for daily functioning. One important function of sleep is the consolidation of memories, a process that makes them stronger and less vulnerable to interference. The neural mechanisms underlying the benefit of sleep for memory can be investigated using polysomnography (PSG). PSG is a combination of physiological recordings including signals from the brain (EEG), eyes (EOG), and muscles (EMG) that are used to classify sleep stages. In this protocol, we describe how PSG can be used in conjunction with behavioral memory assessments, actigraphy, and parent-report to examine sleep-dependent memory consolidation. The focus of this protocol is on early childhood, a period of significance as children transition from biphasic sleep (consisting of a nap and overnight sleep) to monophasic sleep (overnight sleep only). The effects of sleep on memory performance are measured using a visuospatial memory assessment across periods of sleep and wakeful-rest. A combination of actigraphy and parent report is used to assess sleep rhythms (i.e., characterizing children as habitual or non-habitual nappers). Finally, PSG is used to characterize sleep stages and qualities of those stages (such as frequencies and the presence of spindles) during naps. The advantage of using PSG is that it is the only tool currently available to assess sleep quality and sleep architecture, pointing to the relevant brain state that supports memory consolidation. The main limitations of PSG are the length of time it takes to prepare the recording montage and that recordings are typically taken over one sleep bought. These limitations can be overcome by engaging young participants in distracting tasks during application and combining PSG with actigraphy and self/parent-report measures to characterize sleep cycles. Together, this unique combination of methods allows for investigations into how naps support learning in preschool children.

Handling Multiplicity in Neuroimaging Through Bayesian Lenses with Multilevel Modeling

Here we address the current issues of inefficiency and over-penalization in the massively univariate approach followed by the correction for multiple testing, and propose a more efficient model that pools and shares information among brain regions. Using Bayesian multilevel (BML) modeling, we control two types of error that are more relevant than the conventional false positive rate (FPR): incorrect sign (type S) and incorrect magnitude (type M). BML also aims to achieve two goals: 1) improving modeling efficiency by having one integrative model and thereby dissolving the multiple testing issue, and 2) turning the focus of conventional null hypothesis significant testing (NHST) on FPR into quality control by calibrating type S errors while maintaining a reasonable level of inference efficiency. The performance and validity of this approach are demonstrated through an application at the region of interest (ROI) level, with all the regions on an equal footing: unlike the current approaches under NHST, small regions are not disadvantaged simply because of their physical size. In addition, compared to the massively univariate approach, BML may simultaneously achieve increased spatial specificity and inference efficiency, and promote results reporting in totality and transparency. The benefits of BML are illustrated in performance and quality checking using an experimental dataset. The methodology also avoids the current practice of sharp and arbitrary thresholding in the p-value funnel to which the multidimensional data are reduced. The BML approach with its auxiliary tools is available as part of the AFNI suite for general use.

Early positive parenting and maternal depression history predict children's relational binding ability at school-age

Research has indicated age-related improvements in relational binding, an important process of episodic memory, across development. However, little research has focused on individual differences in relational binding and factors contributing to this variation. Although differences may arise from various sources, early caregiving has been shown to impact aspects of memory related to relational binding and also the hippocampus, a structure critical to binding. The present study investigated the influences of early and concurrent parenting and maternal lifetime depression history on children's ability to successfully bind details and retain this information across a delay. A total of 97 children are included in this report. Children were part of a longitudinal study with testing at preschool age (Time 1: 3-5 years) and school age (Time 2: approximately 3 years later). At both time points, positive and negative parenting behaviors were assessed during observational parenting tasks and maternal depression history was assessed with a clinical interview. At Time 2, a composite binding score was derived from two episodic memory tasks: a source memory task and a feature binding task. Findings indicated that early positive parenting predicted higher binding scores later in childhood whereas maternal depression was associated with lower scores. These results were robust even after taking into account child age, general cognitive ability, race, and parental education. These findings highlight 2 factors related to the caregiving environment, parenting and maternal depression, that contribute to individual differences in children's relational binding ability and underscore the importance of early experience on episodic memory development. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Relations between neural structures and children's self-derivation of new knowledge through memory integration

Accumulation of semantic or factual knowledge is a major task during development. Knowledge builds through direct experience and explicit instruction as well as through productive processes that permit derivation of new understandings. In the present research, we tested the neural bases of the specific productive process of self-derivation of new factual knowledge through integration of separate yet related episodes of new learning. The process serves as an ecologically valid model of semantic knowledge accumulation. We tested structure/behavior relations in 5- to 8-year-old children, a period characterized by both age-related differences and individual variability in self-derivation, as well as in the neural regions implicated in memory integration, namely the hippocampus and prefrontal cortex. After controlling for the variance in task performance explained by age, sex, verbal IQ, and gray-matter volume (medial prefrontal cortex, mPFC, only), we observed relations between right mPFC thickness and memory for information explicitly taught to the children as well as the new information they self-derived; relations with the volume of the right hippocampus approached significance. This research provides the first evidence of the neural substrate that subserves children's accumulation of knowledge via self-derivation through memory integration, an empirically demonstrated, functionally significant learning mechanism.

The influence of age and performance on hippocampal function and the encoding of contextual information in early childhood

Studies in school-aged children and adults consistently implicate hippocampus, cortical regions, and their interaction as being critical for memory. However, few studies have examined this neural network in younger children (<8 years), despite the fact that behavioral studies consistently report substantial improvements in memory earlier in life. This study aimed to fill this gap by integrating task-based (i.e., memory encoding task) and task-free fMRI scans in 4- to 8-year-old children. Results showed that during memory encoding the hippocampus and several cortical regions (e.g., inferior frontal gyrus, IFG) were activated, consistent with findings in older individuals. Novel findings during memory encoding showed: 1) additional regions (i.e., orbital frontal gyrus, OFG) were recruited, 2) hippocampal activation varied due to age and performance, and 3) differentiation of connectivity between hippocampal subregions and IFG was greater in older versus younger participants, implying increased speicalization with age. Novel findings from task-free fMRI data suggested the extent of functional differentiation along the longitudinal axis of the hippocampus, particularly between hippocampus and OFG, was moderated by both age and performance. Our findings support and extend previous research, suggesting that maturation of hippocampal activity, connectivity, and differentiation may all contribute to development of memory during early childhood.

P300 development from infancy to adolescence

This article provides an overview of P300 research from infancy through adolescence. First, a brief historical overview is provided highlighting seminal studies that began exploration of the P300 component in developmental groups. Overall, these studies suggest that the P300 can be detected in children and appears to reflect similar cognitive processes to those in adults; however, it is significantly delayed in its latency to peak. Second, two striking findings from developmental research are the lack of a clear P300 component in infancy and differential electrophysiological responses to novel, unexpected stimuli in children, adolescents, and adults. Third, contemporary questions are described, which include P300-like components in infancy, alteration of P300 in atypically developing groups, relations between P300 and behavior, individual differences of P300, and neural substrates of P300 across development. Finally, we conclude with comments regarding the power of a developmental perspective and suggestions for important issues that should be addressed in the next 50 years of P300 research.

Neural correlates of developing theory of mind competence in early childhood

Theory of mind (ToM) encompasses a range of abilities that show different developmental time courses. However, relatively little work has examined the neural correlates of ToM during early childhood. In this study, we investigated the neural correlates of ToM in typically developing children aged 4-8 years using resting-state functional magnetic resonance imaging. We calculated whole-brain functional connectivity with the right temporo-parietal junction (RTPJ), a core region involved in ToM, and examined its relation to children's early, basic, and advanced components of ToM competence assessed by a parent-report measure. Total ToM and both basic and advanced ToM components, but not early, consistently showed a positive correlation with connectivity between RTPJ and posterior cingulate cortex/precuneus; advanced ToM was also correlated with RTPJ to left TPJ connectivity. However, early and advanced ToM components showed negative correlation with the right inferior/superior parietal lobe, suggesting that RTPJ network differentiation is also related to ToM abilities. We confirmed and extended these results using a Bayesian modeling approach demonstrating significant relations between multiple nodes of the mentalizing network and ToM abilities, with no evidence for differences in relations between ToM components. Our data provide new insights into the neural correlates of multiple aspects of ToM in early childhood and may have implications for both typical and atypical development of ToM.

When less is more: Thinner fronto-parietal cortices are associated with better forward digit span performance during early childhood

Although research shows that working memory improves during early childhood, it remains unclear how the fronto-parietal network of cortical regions, known to support this ability in adults, relates to changes in young children. Measures of cortical thickness may be useful in investigating this association as they reflect age-related differences in gray matter and have been proposed to support age-related improvements in other cognitive abilities, but have only sparingly been tested empirically in early childhood. The present study sought to investigate relations between cortical thickness and performance on a digit span task in 200 4- to 8-year-old children using both a priori defined regions of interest related to working memory (superior frontal cortex, middle frontal cortex, anterior cingulate cortex, superior parietal cortex) and whole brain analyses. Results indicated a significant association between cortical thickness in each a priori defined fronto-parietal region and performance on digit span, such that those with a thinner cortex recalled more items than those with a thicker cortex. Similar regions emerged from the whole brain analyses, as did several other regions not typically included in the fronto-parietal network. Results of a mediation analysis indicated that age-related differences in behavior were partially explained by variations in thickness of anterior cingulate cortex, suggesting a potentially important role for this structure during early childhood. Overall, these results suggest that in children as young as 4 years of age there are associations between working memory abilities and thickness in cortical areas known to support working memory in adults.

Protracted hippocampal development is associated with age-related improvements in memory during early childhood

The hippocampus is a structure that is critical for memory. Previous studies have shown that age-related differences in specialization along the longitudinal axis of this structure (i.e., subregions) and within its internal circuitry (i.e., subfields) relate to age-related improvements in memory in school-age children and adults. However, the influence of age on hippocampal development and its relations with memory ability earlier in life remains under-investigated. This study examined effects of age and sex on hippocampal subregion (i.e., head, body, tail) and subfield (i.e., subiculum, CA1, CA2-4/DG) volumes, and their relations with memory, using a large sample of 4- to 8-year-old children. Results examining hippocampal subregions suggest influences of both age and sex on the hippocampal head during early childhood. Results examining subfields within hippocampal head suggest these age effects may arise from CA1, whereas sex differences may arise from subiculum and CA2-4/DG. Memory ability was not associated with hippocampal subregion volume but was associated with subfield volume. Specifically, within the hippocampal head, relations between memory and CA1 were moderated by age; in younger children bigger was better, whereas in older children smaller was superior. Within the hippocampal body, smaller CA1 and larger CA2-4/DG contributed to better memory performance across all ages. Together, these results shed light on hippocampal development during early childhood and support claims that the prolonged developmental trajectory of the hippocampus contributes to memory development early in life.

Cohort-Sequential Study of Conflict Inhibition during Middle Childhood

This longitudinal study examined developmental changes in conflict inhibition and error correction in three cohorts of children (5, 7, and 9 years of age). At each point of assessment children completed three levels of Luria's tapping task (1980), which requires the inhibition of a dominant response and maintenance of task rules in working memory. Findings suggest that both conflict inhibition and error detection and correction improve significantly during middle childhood. When cognitive demands were high, conflict inhibition, as shown by initial response accuracy, improved steadily across middle childhood. In contrast, the ability to detect and correct for errors improved between 5 and 6 years of age. Further, variability in conflict inhibition decreased with age and individual differences in conflict inhibition were stable across the one-year period in 7- and 9-year-old, but not 5-year-old children. These findings are discussed in relation to previous research on the development of inhibition.

White matter structural connectivity and episodic memory in early childhood

Episodic memory undergoes dramatic improvement in early childhood; the reason for this is poorly understood. In adults, episodic memory relies on a distributed neural network. Key brain regions that supporting these processes include the hippocampus, portions of the parietal cortex, and portions of prefrontal cortex, each of which shows different developmental profiles. Here we asked whether developmental differences in the axonal pathways connecting these regions may account for the robust gains in episodic memory in young children. Using diffusion weighted imaging, we examined whether white matter connectivity between brain regions implicated in episodic memory differed with age, and were associated with memory performance differences in 4- and 6-year-old children. Results revealed that white matter connecting the hippocampus to the inferior parietal lobule significantly predicted children's performance on episodic memory tasks. In contrast, variation in the white matter connecting the hippocampus to the medial prefrontal cortex did not relate to memory performance. These findings suggest that structural connectivity between the hippocampus and lateral parietal regions is relevant to the development of episodic memory.

Long-term effects of prenatal drug exposure on the neural correlates of memory at encoding and retrieval

The objective of the current study was to examine what stage of memory (encoding or retrieval) may be compromised in adolescents with a history of prenatal drug exposure (PDE) and how the effects of PDE on memory ability are substantiated at the neural level. To achieve this goal, we examined memory performance and associated brain activations in adolescents with and without a history of PDE via event-related fMRI during encoding and retrieval. Consistent with previous studies, we found that PDE subjects remembered fewer items than community comparison subjects. However, there were no differences in behavior after adjusting for correct rejections (i.e., d'). Novel extensions of previous work are findings that PDE is associated with changes in brain activation during memory encoding but not during retrieval. These results suggest that less optimal memory performance often observed in adolescents with a history of PDE may result from variations in encoding rather than retrieval processes.

Age- and performance-related differences in encoding during early childhood: insights from event-related potentials

Previous studies have found that children show rapid and significant improvements in their ability to remember individual items and the contextual details that surround these items (i.e., episodic memory) during early childhood. Encoding processes have been suggested to contribute to the development of episodic memory; however, few studies have investigated encoding processes. The goal of the current study was to examine age- and performance-related effects on encoding in children between 4 and 8 years of age using event-related potentials (ERPs). Results revealed effects of both age and performance on encoding, as indexed by the ERPs response. However, the nature of these effects differed between subsequent recognition and subsequent recollection, as well as for the two ERP components (i.e., Nc and LSW) examined. These findings are important as they contribute empirical evidence that encoding processes show developmental change across early childhood. In addition, these findings highlight the importance of controlling for performance differences in future studies examining developmental changes in episodic memory.

Age-related differences in subjective recollection: ERP studies of encoding and retrieval

The ability to mentally re-experience past events improves significantly from childhood to young adulthood; however, the mechanisms underlying this ability remain poorly understood, partially because different tasks are used across the lifespan. This study was designed to address this gap by assessing the development of event-related potential (ERP) correlates associated with subjective indices of recollection. Children, adolescents, and adults performed Tulving's () remember/know paradigm while ERPs were recorded during memory encoding (Experiment 1) and retrieval (Experiment 2). Behaviorally, children recognized fewer items than adolescents and adults. All age groups reliably made subjective judgments of recollection, although the ability to make these judgments improved with age. At encoding, the ERP effect associated with recollection was present and comparable across age groups. In contrast, the ERP effect associated with recollection at retrieval differed as a function of age group; specifically, this effect was absent in children, topographically widespread in adolescents, and, consistent with previous literature, maximal over left centro-parietal leads in adults. These findings suggest that encoding processes associated with the subsequent subjective experience of recollection may be similar among children, adolescents, and adults and that age-related improvement in recollection may be primarily attributable to the development of processes that follow the initial encoding of stimuli (i.e., consolidation, storage, retrieval).

Development of hippocampal functional connectivity during childhood

The hippocampus is a medial temporal lobe structure involved in memory, spatial navigation, and regulation of stress responses, making it a structure critical to daily functioning. However, little is known about the functional development of the hippocampus during childhood due to methodological challenges of acquiring neuroimaging data in young participants. This is a critical gap given evidence that hippocampally-mediated behaviors (e.g., episodic memory) undergo rapid and important changes during childhood. To address this gap, the present investigation collected resting-state fMRI scans in 97, 4- to 10-year-old children. Whole brain seed-based analyses of anterior, posterior, and whole hippocampal connectivity were performed to identify regions demonstrating stable (i.e., age-controlled) connectivity profiles as well as age-related differences in connectivity. Results reveal that the hippocampus is a highly connected structure of the brain and that most of the major components of the adult network are evident during childhood, including both unique and overlapping connectivity between anterior and posterior regions. Despite widespread age-controlled connectivity, the strength of hippocampal connectivity with regions of lateral temporal lobes and the anterior cingulate increased throughout the studied age range. These findings have implications for future investigations of the development of hippocampally-mediated behaviors and methodological applications for the appropriateness of whole versus segmented hippocampal seeds in connectivity analyses. Hum Brain Mapp 38:182-201, 2017. © 2016 Wiley Periodicals, Inc.

Event-related potential study of intentional and incidental retrieval of item and source memory during early childhood

The event related potential (ERP) technique is a useful methodology for studying neural changes underlying memory development during childhood. However, systematic comparisons of differences in memory tasks and retrieval demands are lacking. To address this gap, the present study explored the effects of memory task (i.e., item versus source) and retrieval paradigm (i.e., intentional versus incidental) on 4- to 5-year-old children's memory performance and associated electrophysiological responses. Children were familiarized with items in a play-like setting and then asked to retrieve item or source memory details while their brain activity was recorded (intentional retrieval) or while they passively viewed images of the items with no explicit task (incidental retrieval). Memory assessments for the incidental groups followed ERP recording. Analyses of the ERP data suggested that the brain's response during intentional retrieval of source information differed from the other three conditions. These results are discussed within a two-component framework of memory development (e.g., Shing et al., 2010), and implications for future methodological decisions are presented. © 2016 Wiley Periodicals, Inc. Dev Psychobiol 58: 556-567, 2016.

Hippocampal functional connectivity and episodic memory in early childhood

Episodic memory relies on a distributed network of brain regions, with the hippocampus playing a critical and irreplaceable role. Few studies have examined how changes in this network contribute to episodic memory development early in life. The present addressed this gap by examining relations between hippocampal functional connectivity and episodic memory in 4- and 6-year-old children (n = 40). Results revealed similar hippocampal functional connectivity between age groups, which included lateral temporal regions, precuneus, and multiple parietal and prefrontal regions, and functional specialization along the longitudinal axis. Despite these similarities, developmental differences were also observed. Specifically, 3 (of 4) regions within the hippocampal memory network were positively associated with episodic memory in 6-year-old children, but negatively associated with episodic memory in 4-year-old children. In contrast, all 3 regions outside the hippocampal memory network were negatively associated with episodic memory in older children, but positively associated with episodic memory in younger children. These interactions are interpreted within an interactive specialization framework and suggest the hippocampus becomes functionally integrated with cortical regions that are part of the hippocampal memory network in adults and functionally segregated from regions unrelated to memory in adults, both of which are associated with age-related improvements in episodic memory ability.

Developmental Differences in Relations Between Episodic Memory and Hippocampal Subregion Volume During Early Childhood

Episodic memory shows striking improvement during early childhood. However, neural contributions to these behavioral changes are not well understood. This study examined associations between episodic memory and volume of subregions (head, body, and tail) of the hippocampus-a structure known to support episodic memory in school-aged children and adults-during early childhood (n = 45). Results revealed significant positive relations between episodic memory and volume of the hippocampal head in both the left and right hemispheres for 6- but not 4-year-old children, suggesting brain-behavior relations vary across development. These findings add new information regarding neural mechanisms of change in memory development during early childhood and suggest that developmental differences in hippocampal subregions may contribute to age-related differences in episodic memory ability.