Recent research suggests the anterior and posterior hippocampus form part of two distinct functional neural networks. Here we investigate the structural underpinnings of this functional connectivity difference using diffusion-weighted imaging-based parcellation. Using this technique, we substantiated that the hippocampus can be parcellated into distinct anterior and posterior segments. These structurally defined segments did indeed show different patterns of resting state functional connectivity, in that the anterior segment showed greater connectivity with temporal and orbitofrontal cortex, whereas the posterior segment was more highly connected to medial and lateral parietal cortex. Furthermore, we showed that the posterior hippocampal connectivity to memory processing regions, including the dorsolateral prefrontal cortex, parahippocampal, inferior temporal and fusiform gyri and the precuneus, predicted interindividual relational memory performance. These findings provide important support for the integration of structural and functional connectivity in understanding the brain networks underlying episodic memory.

Aging is accompanied by declines in executive control abilities and changes in underlying brain network architecture. Here, we examined brain networks in young and older adults during a task-free resting-state and an N-back task and investigated age-related changes in the modular network organization of the brain. Compared to young adults, older adults showed larger changes in network organization between resting-state and task. While young adults exhibited increased connectivity between lateral frontal regions and other network modules during the most difficult task condition, older adults also exhibited this pattern of increased connectivity during less demanding task conditions. Moreover, the increase in between-module connectivity in older adults was related to faster task performance and greater fractional anisotropy (FA) of the superior longitudinal fasciculus. These results demonstrate that older adults who exhibit more pronounced network changes between a resting-state and task have better executive control performance and greater structural connectivity of a core frontal-posterior white matter pathway.

In recent years, several laboratory studies have indicated that healthy older adults exhibit a reduction in mind-wandering frequency compared with young adults. However, it is unclear if these findings extend to daily life settings. In the current study, using experience sampling over the course of a week in the daily life of 31 young and 20 older adults, we assessed age-related differences in: (a) mind-wandering frequency, (b) the relationship between affect and mind-wandering frequency, and (c) content of mind wandering. Older adults mind wandered less than young adults in daily life. Across age groups, negative affect was positively associated with mind-wandering occurrence. Finally, older adults reported that their thoughts were more pleasant, interesting, and clear compared with young adults, who had thoughts that were more dreamlike, novel, strange, and racing. Our results provide the first demonstration using thought sampling that older adults exhibit a reduction in mind-wandering frequency in daily life. Implications for current theories of age-related reductions in mind-wandering frequency are discussed. (PsycINFO Database Record

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These data contribute to the growing body of evidence that loss of white matter continues in moderate and severe TBI even after the acute neurological effects of TBI have resolved. As the fornix plays a critical role in memory, this may be a contributing factor to the poor clinical outcomes observed in these patients.