The relevance of short-range fibers to cognitive efficiency and brain activation in aging and dementia.
The integrity of structural connectivity in a functional brain network supports the efficiency of neural processing within relevant brain regions. This study aimed to quantitatively investigate the short- and long-range fibers, and their differential roles in the lower cognitive efficiency in aging and dementia. Three groups of healthy young, healthy older adults and patients with Alzheimer's disease (AD) participated in this combined functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) study on prospective memory (PM). Short- and long-range fiber tracts within the PM task engaged brain networks were generated. The correlation between the fMRI signal change, PM performance and the DTI characters were calculated. FMRI results showed that the PM-specific frontal activations in three groups were distributed hierarchically along the rostrocaudal axis in the frontal lobe. In an overall PM condition generally activated brain network among the three groups, tractography was used to generate the short-range fibers, and they were found impaired in both healthy older adults and AD patients. However, the long-range fiber tracts were only impaired in AD. Additionally, the mean diffusivity (MD) of short-range but not long-range fibers was positively correlated with fMRI signal change and negatively correlated with the efficiency of PM performance. This study suggests that the disintegrity of short-range fibers may contribute more to the lower cognitive efficiency and higher compensatory brain activation in healthy older adults and more in AD patients.
Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, P. R. China; Alzheimer's Disease Research Network, Strategic Research Theme of Healthy Aging, The University of Hong Kong, Hong Kong, P. R. China.
Junling
J
Gao
Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, P. R. China; Research Center of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, P. R. China.
Raymond T F
RT
Cheung
Research Center of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, P. R. China; Department of Physiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, P. R. China.
Ying-Shing
YS
Chan
Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, P. R. China; Alzheimer's Disease Research Network, Strategic Research Theme of Healthy Aging, The University of Hong Kong, Hong Kong, P. R. China.
Leung-Wing
LW
Chu
Department of Radiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, P. R. China.
Henry K F
HK
Mak
Laboratory of Cognitive Affective Neuroscience, Faculty of Social science, The University of Hong Kong, Hong Kong, P. R. China; The State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong, P. R. China; Laboratory of Neuropsychology, Faculty of Social Science, The University of Hong Kong, Hong Kong, P. R. China.
Tatia M C
TM
Lee
D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging; D000544:Alzheimer Disease / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003071:Cognition; D056324:Diffusion Tensor Imaging / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009412:Nerve Fibers; D009415:Nerve Net; D011859:Radiography