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• Two-year-olds played tablet games requiring them to remember locations visited by characters and the temporal order with which they visited them. • Two-year-olds remembered spatial locations better than temporal order immediately after learning, and after a 20-minute and one-week delay. • Song-related hippocampal activation during sleep is associated with memory for temporal order. Nonhuman research has implicated developmental processes within the hippocampus in the emergence and early development of episodic memory, but research in humans has been constrained by the difficulty of examining hippocampal function during early development. In the present study, we assessed 48 2-year-olds with a novel paradigm in which participants completed two games on a tablet that required remembering associations between unique characters, the places they visited, and the temporal order with which they did so. At the completion of each game, a unique, novel song played. Toddlers remembered spatial locations better than temporal order during an immediate test, after a 20-minute delay, and after a week delay. After the last behavioral session, toddlers underwent an fMRI task during natural nocturnal sleep evaluating hippocampal activation in response to learned and novel songs. We found that the extent of hippocampal activation for learned songs compared to novel songs during sleep was correlated with memory for temproal order across all time delays, but not with memory for spatial locations. The results confirm that that the functional contribution of the hippocampus to early memory can be assessed during sleep and suggest that assessment of temporal aspects of memory in the current task best capture this contribution. [ABSTRACT FROM AUTHOR]

Relational memory improves during middle childhood and adolescence, yet the neural correlates underlying those improvements are debated. Although memory for spatial, temporal, and other associative relations requires the hippocampus, it is not established whether within-individual changes in hippocampal structure contribute to memory improvements from middle childhood into adolescence. Here, we investigated how structural changes in hippocampal head, body, and tail subregions predict improvements in the capacity to remember item-space, item-time, and item-item relations. Memory for each relation and volumes of hippocampal subregions were assessed longitudinally in 171 participants across 3 time points (M age at T1 = 9.45 years; M age at T2 = 10.86 years, M age at T3 = 12.12 years; comprising 393 behavioral assessments and 362 structural scans). Among older children, volumetric growth in: (a) head and body predicted improvements in item-time memory, (b) head predicted improvements in item-item memory; and (c) right tail predicted improvements in item-space memory. The present research establishes that changes in hippocampal structure are related to improvements in relational memory, and that sub-regional changes in hippocampal volume differentially predict changes in different aspects of relational memory. These findings underscore a division of labor along the anterior-posterior axis of the hippocampus during child development. [ABSTRACT FROM AUTHOR]

The present study investigated whether the presence or absence of peripubertal ovarian hormones affects sexual preference and conditioned place preference for paced mating in adult female rats primed with 10 μg estradiol benzoate and 1 mg progesterone. Ovariectomy (OVX) occurred either before or after pubertal development, and 4 weeks later rats began a series of behavioral tests. Rats with ovaries removed before the pubertal timeframe (Prepubertal OVX) were more active, more likely to withdrawal from the male compartment, and did not discriminate between mounts and intromissions during paced mating relative to rats with ovaries during puberty (Adult OVX). Both Adult OVX and Prepubertal OVX rats showed a higher preference for the male when hormone primed vs. oil treated and a conditioned place preference for paced mating behavior. The results of the present study demonstrate that some, but not all, aspects of female sexual behavior require ovarian hormones during puberty. [ABSTRACT FROM AUTHOR]