White matter damage on diffusion tensor imaging correlates with age-related cognitive decline.
BACKGROUND
Damage to white matter tracts, resulting in "cerebral disconnection," may underlie age-related cognitive decline.


METHODS
Using diffusion tensor MRI (DTI) to investigate white matter damage, and magnetic resonance spectroscopy (MRS) to look at its underlying pathologic basis, the authors investigated the relationship between white matter structure and cognition in 106 healthy middle-aged and elderly adults. Fractional anisotropy (FA) and mean diffusivity (MD) values, whole brain white matter histograms, and regions of interest placed in the white matter of the centrum semiovale were analyzed. Correlations with executive function, working memory, and information-processing speed were performed.


RESULTS
There was a progressive reduction in FA and increase in diffusivity with age in both region of interest (r = 0.551, p < 0.001), and whole brain histograms (r = 0.625, p < 0.001). DTI values correlated with performance in all three cognitive domains. After controlling for age, DTI parameters correlated with working memory but not with the other two cognitive domains. MRS studies found a correlation of N-acetyl aspartate, a neuronal marker, with DTI parameters (r = 0.253, p < 0.05).


CONCLUSIONS
The results are consistent with white matter damage due to axonal loss, causing age- related cognitive decline. Working memory may be particularly dependent on complex networks dependent on white matter connections.
Charlton
R A
RA
Clinical Neuroscience, St. George's University of London, UK.
Barrick
T R
TR
McIntyre
D J
DJ
Shen
Y
Y
O'Sullivan
M
M
Howe
F A
FA
Clark
C A
CA
Morris
R G
RG
Markus
H S
HS
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000523:psychology*; D001921:Brain / Q000473:pathology*; D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology* / Q000523:psychology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests