Fornix white matter microstructure differentially predicts false recollection rates in older and younger adults.

Healthy aging is accompanied by increased false remembering in addition to reduced successful remembering in older adults. Neuroimaging studies implicate age-related differences in the involvement of medial temporal lobe and fronto-parietal regions in mediating highly confident false recollection. However, no studies have directly examined the relationship between white matter microstructure and false recollection in younger and older adults. Using diffusion-weighted imaging and probabilistic tractography, we examined how white matter microstructure within tracts connecting the hippocampus and the fronto-parietal retrieval network contribute to false recollection rates in healthy younger and older adults. We found only white matter microstructure within the fornix contributed to false recollection rates, and this relationship was specific to older adults. Fornix white matter microstructure did not contribute to true recollection rate, nor did common white matter contribute to false recollection, suggesting fornix microstructure is explicitly associated with highly confident false memories in our sample of older adults. These findings underlie the importance of examining microstructural correlates associated with false recollection in younger and older adults.

Shared neural recruitment across working memory and motor control tasks as a function of task difficulty and age.

Past research suggests that working memory (WM) and motor control may engage similar cognitive and neural mechanisms in older adults, particularly when task difficulty increases. However, much of this evidence arises from comparisons across behavioral and imaging studies that test only one of the foregoing functional domains. The current study used fMRI within the same group of older adults to investigate whether WM and motor control recruit common mechanisms, and whether recruitment increased with task demand and age. A conjunction analysis across WM and motor tasks revealed engagement of several frontoparietal regions as a function of increasing task demand. A separate conjunction analysis which included age as a predictor showed comparable regions exhibit increased recruitment with both increasing task demand and age. Results suggest that the recruitment of common frontoparietal regions across WM and motor tasks in response to task difficulty is maintained across the older adult lifespan.