Affiliations: [a] Brain and Ageing Research Program, School of Psychiatry, University of New South Wales, Randwick, NSW, Australia | [b] Neuropsychiatric Institute, Prince of Wales Hospital, Randwick, NSW, Australia | [c] Primary Dementia Collaborative Research Centre, School of Psychiatry, Faculty of Medicine, University of New South Wales, Randwick, NSW, Australia | [d] Department of Developmental Disability Neuropsychiatry, School of Psychiatry, University of New South Wales, Randwick, NSW, Australia
Correspondence:
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Correspondence to: Dr. Wei Wen, Brain and Ageing Research Program, School of Psychiatry, University of New South Wales, Randwick, NSW 2031, Australia. Tel.: +61 2 9382 3730; Fax: +61 2 9382 3774; E-mail: w.wen@unsw.edu.au.
Abstract: The fornix is a major efferent tract of the hippocampus, a structure critical for normal memory function. However, the role of structural degradation of the fornix in memory dysfunction in mild cognitive impairment (MCI) has remained unclear. We used diffusion tensor tractography to measure microstructural properties of the fornix and the corticospinal tract (CST), as a control tract, in 206 cognitively normal subjects, 76 amnestic MCI (aMCI) and 51 non-amnestic MCI (naMCI) subjects. Hippocampal volumes were measured using deformation-based morphometry. We found significant fractional anisotropy reductions in the left fornix and radial diffusivity (RD) increases in bilateral fornices in aMCI, but not in naMCI, compared with controls. No significant changes in the CST were found in aMCI subjects, but naMCI subjects showed significantly increased RD and axial diffusivity of the right CST, compared with controls. Increased left fornical RD measure was correlated with poor verbal memory performance in aMCI subjects. In addition, reduced microstructural integrity of the fornix was associated with hippocampal atrophy in aMCI. This study suggests that microstructural alteration of the fornix is a contributor to early episodic memory dysfunction in non-demented individuals.
