Frontal connections and cognitive changes in normal aging rhesus monkeys: a DTI study.
Recent anatomical studies have found that cortical neurons are mainly preserved during the aging process while myelin damage and even axonal loss is prominent throughout the forebrain. We used diffusion tensor imaging (DT-MRI) to evaluate the hypothesis that during the process of normal aging, white matter changes preferentially affect the integrity of long corticocortical association fiber tracts, specifically the superior longitudinal fasciculus II and the cingulum bundle. This would disrupt communication between the frontal lobes and other forebrain regions leading to cognitive impairments. We analyzed DT-MRI datasets from seven young and seven elderly behaviorally characterized rhesus monkeys, creating fractional anisotropy (FA) maps of the brain. Significant age-related reductions in mean FA values were found for the superior longitudinal fasciculus II and the cingulum bundle, as well as the anterior corpus callosum. Comparison of these FA reductions with behavioral measures demonstrated a statistically significant linear relationship between regional FA and performance on a test of executive function. These findings support the hypothesis that alterations to the integrity of these long association pathways connecting the frontal lobe with other forebrain regions contribute to cognitive impairments in normal aging. To our knowledge this is the first investigation reporting such alterations in the aging monkey.
Makris
Nikos
N
Harvard Medical School Department of Neurology, Center for Morphometric Analysis, Massachusetts General Hospital, Boston, MA 02129, United States. nikos@cma.mgh.harvard.edu
Papadimitriou
George M
GM
van der Kouwe
Andre
A
Kennedy
David N
DN
Hodge
Steven M
SM
Dale
Anders M
AM
Benner
Thomas
T
Wald
Lawrence L
LL
Wu
Ona
O
Tuch
David S
DS
Caviness
Verne S
VS
Moore
Tara L
TL
Killiany
Ronald J
RJ
Moss
Mark B
MB
Rosene
Douglas L
DL
D000375:Aging / Q000473:pathology*; D000818:Animals; D016880:Anisotropy; D001931:Brain Mapping; D003072:Cognition Disorders / Q000473:pathology* / Q000503:physiopathology / Q000523:psychology; D003337:Corpus Callosum / Q000473:pathology / Q000503:physiopathology; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005625:Frontal Lobe / Q000473:pathology* / Q000503:physiopathology; D008253:Macaca mulatta; D008297:Male; D009434:Neural Pathways / Q000473:pathology* / Q000503:physiopathology; D009483:Neuropsychological Tests