Bunge, S. A. | bioRxiv Science

bioRxiv2019

Changes in anterior and posterior hippocampus differentially predict item-space, item-time, and item-item memory improvement

Relational memory requires the hippocampus, but whether distinct hippocampal mechanisms along the anterior-posterior axis are required for different types of relations is debated. We investigated the contribution of structural changes in hippocampal head, body, and tail subregions to 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 (Mage at T1= 9.45 years; Mage at T2= 10.86 years, Mage 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 volumetric changes in hippocampal subregions differentially predict changes in different aspects of relational memory, underscoring a division of labor along the hippocampal anterior-posterior axis.

neuroscience↗

bioRxiv2018

The more you know: Investigating why adults get a bigger memory boost from semantic congruency than children

Humans possess the capacity to employ prior knowledge in the service of our ability to remember; thus, memory is oftentimes superior for information that is semantically congruent with our prior knowledge. This congruency benefit grows during development, but little is understood about neurodevelopmental differences that underlie this growth. Here, we sought to explore the brain mechanisms underlying these phenomena. To this end, we examined the neural substrates of semantically congruent vs. incongruent item-context associations in 116 children and 25 young adults who performed encoding and retrieval tasks during functional MRI data collection. Participants encoded item-context pairs by judging whether an item belonged in a scene. Episodic memory was then tested with a source memory task. Consistent with prior work, source memory accuracy improved with age, and was greater for congruent than incongruent pairs; further, this congruency benefit was greater in adults than children. Age-related differences were observed across univariate, functional connectivity, and multivariate analyses, particularly in lateral prefrontal cortex (PFC). In sum, our results revealed two general age differences. First, left ventrolateral/rostrolateral PFC exhibited age-related increases in univariate activity, as well as greater functional connectivity with temporal regions during the processing of congruency. Second, right rostrolateral PFC activation was associated with successfully encoded congruent associations in adults, but not children. Finally, multivariate analyses provided evidence for stronger veridical memory in adults than children in right ventrolateral PFC. These effects in right lateral PFC were significantly correlated with memory performance, implicating them in the process of remembering congruent associations. These results connect brain regions associated with top-down control in the congruency benefit and age-related improvements therein.

neuroscience↗