Understanding relational binding in early childhood: Interacting effects of overlap and delay

Differential attentional demands on implicit and explicit associative memory in children 8-12 years old

Associative memory improves during childhood, suggesting an age-related improvement in the binding mechanism responsible for linking information together. However, tasks designed to measure associative memory not only measure binding, but also place demands on attention. This makes it difficult to dissociate age-related improvements in memory from the development of attention. One way to reduce attentional demands is to test memory implicitly versus explicitly. In this study, children (8-, 10-, and 12-years-old) completed separate implicit and explicit associative memory tests. For the implicit task, children incidentally encoded pairs of objects by making an object categorization decision. At test, they completed the same task, but unbeknownst to the participants, the pairs were either intact, rearranged, or new. Next, children completed another incidental encoding phase, then an explicit test in which they indicated whether the pairs were intact, rearranged, or new. For the implicit test, all age groups had faster reaction times for intact than rearranged pairs (indicative of implicit associative memory). In the explicit test, memory performance (d') improved with age. A separate measure of attention related to performance in both the explicit and implicit tasks. Together, these results support that attentional mechanisms contribute to age-related improvements in associative memory.

Setting boundaries: Development of neural and behavioral event cognition in early childhood

The ongoing stream of sensory experience is so complex and ever-changing that we tend to parse this experience at "event boundaries," which structures and strengthens memory. Memory processes undergo profound change across early childhood. Whether young children also divide their ongoing processing along event boundaries, and if those boundaries relate to memory, could provide important insight into the development of memory systems. In Study 1, 4-7-year-old children and adults segmented a cartoon, and we tested their memory. Children's event boundaries were more variable than adults' and differed in location and consistency of agreement. Older children's event segmentation was more adult-like than younger children's, and children who segmented events more like adults had better memory for those events. In Study 2, we asked whether these developmental differences in event segmentation had their roots in distinct neural representations. A separate group of 4-8-year-old children watched the same cartoon while undergoing an fMRI scan. In the right hippocampus, greater pattern dissimilarity across event boundaries compared to within events was evident for both child and adult behavioral boundaries, suggesting children and adults share similar event cognition. However, the boundaries identified by a data-driven Hidden Markov Model found that a different brain region-the left and right angular gyrus-aligned only with event boundaries defined by children. Overall, these data suggest that children's event cognition is reasonably well-developed by age 4 but continues to become more adult-like across early childhood. RESEARCH HIGHLIGHTS: Adults naturally break their experience into events, which structures and strengthens memory, but less is known about children's event perception and memory. Study 1 had adults and children segment and remember events from an animated show, and Study 2 compared those segmentations to other children's fMRI data. Children show better recognition and temporal order memory and more adult-like event segmentation with age, and children who segment more like adults have better memory. Children's and adults' behavioral boundaries mapped onto pattern similarity differences in hippocampus, and children's behavioral boundaries matched a data-driven model's boundaries in angular gyrus.

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.

Has the concept of systems consolidation outlived its usefulness? Identification and evaluation of premises underlying systems consolidation

Systems consolidation has mostly been treated as a neural construct defined by the time-dependent change in memory representation from the hippocampus (HPC) to other structures, primarily the neocortex. Here, we identify and evaluate the explicit and implicit premises that underlie traditional or standard models and theories of systems consolidation based on evidence from research on humans and other animals. We use the principle that changes in neural representation over time and experience are accompanied by corresponding changes in psychological representations, and vice versa, to argue that each of the premises underlying traditional or standard models and theories of systems consolidation is found wanting. One solution is to modify or abandon the premises or theories and models. This is reflected in moderated models of systems consolidation that emphasize the early role of the HPC in training neocortical memories until they stabilize. The fault, however, may lie in the very concept of systems consolidation and its defining feature. We propose that the concept be replaced by one of memory systems reorganization, which does not carry the theoretical baggage of systems consolidation and is flexible enough to capture the dynamic nature of memory from inception to very long-term retention and retrieval at a psychological and neural level. The term "memory system reorganization" implies that memory traces are not fixed, even after they are presumably consolidated. Memories can continue to change as a result of experience and interactions among memory systems across the lifetime. As will become clear, hippocampal training of neocortical memories is only one type of such interaction, and not always the most important one, even at inception. We end by suggesting some principles of memory reorganization that can help guide research on dynamic memory processes that capture corresponding changes in memory at the psychological and neural levels.

Intraobject and extraobject memory binding across early development

The ability to bind, or link, different aspects of an experience in memory undergoes protracted development across childhood. Most studies of memory binding development have assessed extraobject binding between an object and some external element such as another object, whereas little work has examined the development of intraobject binding, such as between shape and color features within the same object. In this work, we investigate the development of intra- and extraobject memory binding in five-year-olds, eight-year-olds, and young adults with a memory interference paradigm. Between two experiments, we manipulate whether stimuli are presented as coherent objects (Experiment 1: n5-year-olds = 32, 19 males, 13 females; n8-year-olds = 30, 15 males, 15 females; nadults = 30, 15 males, 15 females), requiring intraobject binding between shape and color features, or as spatially separated features (Experiment 2: n5-year-olds = 24, 16 males, 8 females; n8-year-olds = 41, 19 males, 22 females; nadults = 31, 13 males, 18 females), requiring extraobject binding. To estimate the contributions of different binding structures to performance, we present a novel computational model that mathematically instantiates the memory binding, forgetting, and retrieval processes we hypothesize to underlie performance on the task. The results provide evidence of substantial developmental improvements in both intraobject and extraobject binding of shape and color features between 5 and 8 years of age, as well as stronger intraobject compared with extraobject binding of features in all age groups. These findings provide key insights into memory binding across early development. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Children show adult-like hippocampal pattern similarity for familiar but not novel events

The ability to detect differences among similar events in our lives is a crucial aspect of successful episodic memory performance, which develops across early childhood. The neural substrate of this ability is supported by operations in the medial temporal lobe (MTL). Here, we used representational similarity analysis (RSA) to measure neural pattern similarity in hippocampus, perirhinal cortex, and parahippocampal cortex for 4- to 10-year-old children and adults during naturalistic viewing of clips from the same compared to different movies. Further, we assessed the role of prior exposure to individual movie clips on pattern similarity in the MTL. In both age groups, neural pattern similarity in hippocampus was lower for clips drawn from the same movies compared to those drawn from different movies, suggesting that related content activates processes focused on keeping representations with shared content distinct. However, children showed this only for movies with which they had prior exposures, whereas adults showed the effect regardless of any prior exposures to the movies. These findings suggest that children require repeated exposure to stimuli to show adult-like MTL functioning in distinguishing among similar events.