Age-Related Increases in Posterior Hippocampal Granularity Are Associated with Remote Detailed Episodic Memory in Development

Abstract

Episodic memory is critical to human functioning. In adults, episodic memory involves a distributed neural circuit in which the hippocampus plays a central role. As episodic memory abilities continue to develop across childhood and into adolescence, studying episodic memory maturation can provide insight into the development and construction of these hippocampal networks, and ultimately clues to their function in adulthood. While past developmental studies have shown that the hippocampus helps to support memory in middle childhood and adolescence, the extent to which ongoing maturation within the hippocampus contributes to developmental change in episodic memory abilities remains unclear. In contrast, slower maturing regions, such as the PFC, have been suggested to be the neurobiological locus of memory improvements into adolescence. However, it is also possible that the methods used to detect hippocampal development during middle childhood and adolescence are not sensitive enough. Here, we examine how temporal covariance (or differentiation) in voxel representations within anterior and posterior hippocampus change with age to support the development of detailed recollection in male and female developing humans. We find age-related increases in the distinctiveness of temporal activation profiles in the posterior, but not anterior, hippocampus. Second, we show that this measure of granularity, when present during postencoding rest periods, correlates with the recall of detailed memories of preceding stimuli several weeks postencoding, suggesting that granularity may promote memory stabilization.

Contextual features in the developing hippocampus: A representational similarity analysis

“…In contrast, finer granularity in the posterior region is capable of supporting representations with higher resolution (see also Yonelinas et al, 2019). Importantly, age‐related differences in the overall level of pattern similarity were observed in the posterior hippocampus, which is consistent with recent findings suggesting an age‐related increase in the granularity of this region (Callaghan et al, 2021). Critically, older children showed the same effect as adults in the posterior hippocampus but not the anterior region, suggesting earlier development of posterior regions compared to the anterior hippocampus.…”

“…From this perspective, the anterior hippocampus may specifically represent more readily task‐relevant features (Zeidman & Maguire, 2016). This division of labor across the longitudinal axis of the hippocampus is also supported by evidence that granularity increases from anterior to posterior regions of the hippocampus across a variety of tasks including spatial and nonspatial (Brunec et al, 2018; Callaghan et al, 2021) underscoring the hippocampus as key to processing cognitive maps in spatial tasks and relational memories in nonspatial tasks by representation of both types of information in the same network (Whittington et al, 2020). Accordingly, lower resolution of representations can be supported in the anterior hippocampus which might be critically used for retaining the task features that are more relevant to the current goals.…”

“…Consistent with this idea, Brunec et al (2018) found lower cross‐voxel correlation in the posterior compared to the anterior hippocampus regardless of whether participants were engaged in a navigation task or were resting. In the only developmental study examining this distinction, Callaghan et al (2021) found age‐related decreases in cross‐voxel correlations in the activity of the posterior hippocampus during a memory task consistent with the developmental improvements in the granularity of memory representations in this sub‐region. This resolution gradient account is consistent with contextual binding theory (Yonelinas et al, 2019) proposing that hippocampal activation may capture all aspects of context including slow‐changing features that are not directly relevant or manipulated in the experimental setting, but belong instead to the background.…”

Reward enhances memory via age-varying online and offline neural mechanisms across development

“…Eighty-nine participants ages 8- to 25-years-old (M age = 16.16, SD age = 4.67, 45 female) were included in analyses. A target sample size of n = 90, including 30 children, 30 adolescents, and 30 adults, was determined based on prior work using similar or smaller sample sizes to identify age-related differences in behavior and brain activation (Van Den Bos and Rodriguez, 2015; Insel et al, 2019; Callaghan et al, 2021). Data exclusions consisted of: eight participants with excessive motion (participants without at least one complete encoding, baseline arrows, and post-encoding arrows runs due to exclusions of runs with 15% or more timepoints censored with greater than 0.9 mm relative translational motion), seven participants who elected to not complete or terminate the fMRI scan, and five participants with incomplete datasets as a result of fMRI scanner malfunction.…”

Memories of structured input become increasingly distorted across development - Working Paper

“…For example, relatively greater developmental change has been observed in hippocampally-dependent processes like recollective as compared with familiarity-based memory (Billingsley et al, 2002;; and memory for associations as compared to memory for individual items (DeMaster & Ghetti, 2013;Ghetti, 2017;Ngo, Lin, et al, 2019;Riggins, 2014;Sluzenski et al, 2006). These demonstrations, in combination with neural investigations showing protracted structural maturation of the hippocampus (Daugherty et al, 2016;DeMaster et al, 2014;Gogtay et al, 2004;Riggins et al, 2018), point to the important refinements to hippocampal function that continue throughout childhood (Callaghan et al, 2021;Keresztes et al, 2017). Given the role of the hippocampus in creating a relational map of memory space both within and across experiences (Eichenbaum & Cohen, 2001), then, it is no wonder that recent years have seen a growing interest in how development may bring important differences in not only the fidelity (Ribordy et al, 2013) and persistence (Saragosa-Harris et al, 2021) of memories, but also in their representational structure (Gómez & Edgin, 2016;Keresztes et al, 2018;Ramsaran et al, 2019).…”