White matter integrity and cortical metabolic associations in aging and dementia.
BACKGROUND
Studies show that white matter hyperintensities, regardless of location, primarily affect frontal lobe metabolism and function. This report investigated how regional white matter integrity (measured as fractional anisotropy [FA]) relates to brain metabolism, to unravel the complex relationship between white matter changes and brain metabolism.


OBJECTIVE
To elucidate the relationship between white matter integrity and gray matter metabolism using diffusion tensor imaging and fluorodeoxyglucose-positron emission tomography in a cohort of 16 subjects ranging from normal to demented (age, >55 years).


METHODS
Mean FA values from white matter regions underlying the medial prefrontal, inferior-lateral prefrontal, parietal association, and posterior temporal areas and the corpus callosum were regressed with glucose metabolism (by positron emission tomography), using statistical parametric mapping (P < 0.005; voxel cluster, >100). Regional cerebral glucose metabolism was the primary outcome measure. According to our hypothesis, those hypometabolic cortical regions affected by Alzheimer's disease would correlate with a lower FA of associated tracks.


RESULTS
Our data show inter-regional positive correlations between FA and gray matter metabolism for the prefrontal cortex, temporal, and parietal regions. Our results suggest that left prefrontal FA is associated with left temporal and parietal metabolism. Further, left posterior temporal FA correlated with left prefrontal metabolism. Finally, bilateral parietal FA correlated with bilateral temporal metabolism.


CONCLUSIONS
These regions are associated with cognitive processes affected in Alzheimer's disease and cerebrovascular disease, suggesting a link with white matter degeneration and gray matter hypometabolism. Therefore, cortical function and white matter degeneration are related in aging and dementia.
Helen Wills Neuroscience Institute, University of California at Berkeley, USA. beth.kuczynski@gmail.com
Beth
B
Kuczynski
Elizabeth
E
Targan
Cindee
C
Madison
Michael
M
Weiner
Yu
Y
Zhang
Bruce
B
Reed
Helena C
HC
Chui
William
W
Jagust
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D000544:Alzheimer Disease / Q000150:complications / Q000175:diagnosis / Q000378:metabolism; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000378:metabolism*; D002561:Cerebrovascular Disorders / Q000150:complications / Q000378:metabolism / Q000473:pathology; D015331:Cohort Studies; D003337:Corpus Callosum / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D003704:Dementia / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009483:Neuropsychological Tests; D049268:Positron-Emission Tomography / Q000379:methods; D012189:Retrospective Studies
D019788:Fluorodeoxyglucose F18