Fornix Microstructure and Memory Performance Is Associated with Altered Neural Connectivity during Episodic Recognition

Abstract

Objective The purpose of this study was to assess whether age-related differences in white matter microstructure are associated with altered task-related connectivity during episodic recognition. Method Using functional magnetic resonance imaging and diffusion tensor imaging from 282 cognitively healthy middle-to-late aged adults enrolled in the Wisconsin Registry for Alzheimer's Prevention, we investigated whether fractional anisotropy (FA) within white matter regions known to decline with age was associated with task-related connectivity within the recognition network. Results There was a positive relationship between fornix FA and memory performance, both of which negatively correlated with age. Psychophysiological interaction analyses revealed that higher fornix FA was associated with increased task-related connectivity amongst the hippocampus, caudate, precuneus, middle occipital gyrus, and middle frontal gyrus. In addition, better task performance was associated with increased task-related connectivity between the posterior cingulate gyrus, middle frontal gyrus, cuneus, and hippocampus. Conclusions The findings indicate that age has a negative effect on white matter microstructure, which in turn has a negative impact on memory performance. However, fornix microstructure did not significantly mediate the effect of age on performance. Interestingly, dynamic functional connectivity was associated with better memory performance. The results of the psychophysiological interaction analysis further revealed that alterations in fornix microstructure explain–at least in part–connectivity among cortical regions in the recognition memory network. Our results may further elucidate the relationship between structural connectivity, neural function, and cognition.

Dentate Gyrus Volume Mediates the Effect of Fornix Microstructure on Memory Formation in Older Adults

“…Our finding of a positive association between fornix FA and memory performance is in line with previous studies in both young and older adults (Rudebeck et al, 2009;Douet and Chang, 2014;Ly et al, 2016). Ly et al (2016) found that variability in fornix microstructure in middle-to-late aged adults was related to face recognition memory and partly explained preserved functional connectivity within hippocampal networks.…”

“…Our finding of a positive association between fornix FA and memory performance is in line with previous studies in both young and older adults (Rudebeck et al, 2009;Douet and Chang, 2014;Ly et al, 2016). Ly et al (2016) found that variability in fornix microstructure in middle-to-late aged adults was related to face recognition memory and partly explained preserved functional connectivity within hippocampal networks. A study by Metzler-Baddeley et al (2011) further suggested that specifically age-related degradation of fornix microstructure as derived from individual fiber tracking was linked to memory recall performance in strategic and visual memory tasks in older adults (Metzler-Baddeley et al, 2011).…”

Melatonin modulates daytime‐dependent synaptic plasticity and learning efficiency

“…Clarifying the role of melatonin within hippocampus‐dependent learning and memory will foster our understanding of circadian rhythm organization in cognition. Lastly, it was shown that disturbance of the hippocampal circuity severely affects sleep and cognition in fish and in humans . In light of an increased awareness of the link between sleep‐wake disturbances in a 24‐hour society and cognitive and neurodegenerative disorders in humans, a better understanding of how the circadian clock modulates hippocampal circuity and the role of melatonin within this mechanism have great merit.…”

Longitudinal white matter microstructural change in Parkinson's disease

“…Diffusion weighted imaging data were preprocessed using a robust pipeline also used in a number of previous studies (Adluru et al, 2014; Ly et al, 2016; Merluzzi et al, 2016; Racine et al, 2017). DWI data from baseline and follow-up visits were first converted from Digital Imaging and Communication in Medicine (DICOM) format to Neuroimaging Informatics Technology Initiative (NIFTI) format and visually inspected for artifacts.…”