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Temporal association tracts and the breakdown of episodic memory in mild cognitive impairment
Metzler-Baddeley, Claudia Hunt, Sarah Jones, Derek Kenton Leemans, Alexander Aggleton, John P. O'Sullivan, Michael J.
Metzler-Baddeley, Claudia
Hunt, Sarah
Jones, Derek Kenton
Leemans, Alexander
Aggleton, John P.
O'Sullivan, Michael J.
Abstract
Objective: To examine the pattern of association between microstructure of temporal lobe connections and the breakdown of episodic memory that is a core feature of mild cognitive impairment ( MCI ). Methods: Twenty-five individuals with MCI and 20 matched controls underwent diffusion MRI and cognitive assessment. Three temporal pathways were reconstructed by tractography: fornix, parahippocampal cingulum ( PHC ), and uncinate fasciculus. Tissue volume fraction—a tract-specific measure of atrophy—and microstructural measures were derived for each tract. To test specificity of associations, a comparison tract ( corticospinal tract ) and control cognitive domains were also examined. Results: In MCI, tissue volume fraction was reduced in the fornix. Axial and radial diffusivity were increased in uncinate and PHC implying more subtle microstructural change. In controls, tissue volume fraction in the fornix was the predominant correlate of free recall. In contrast, in MCI, the strongest relationship was with left PHC. Microstructure of uncinate and PHC also correlated with recognition memory, and recognition confidence, in MCI. Conclusions: Episodic memory in MCI is related to the structure of multiple temporal association pathways. These associations are not confined to the fornix, as they are in healthy young and older adults. In MCI, because of a compromised fornix, alternative pathways may contribute disproportionally to episodic memory performance.
Keywords
Date
2012
Type
Journal article
Journal
Neurology
Book
Volume
79
Issue
23
Page Range
2233-2240
Article Number
ACU Department
Relation URI
Source URL
Event URL
Open Access Status
License
File Access
Controlled