Changes in brain functional homogeneity in subjects with Alzheimer's disease

• Published in: Psychiatry research Vol. 114; no. 1; pp. 39 - 50
• Main Authors: Volkow, Nora D, Zhu, Wei, Felder, Christoph A, Mueller, Klaus, Welsh, Tomihisa F, Wang, Gene-Jack, de Leon, Mony J
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 15.02.2002; Elsevier
• Subjects: Aged; Aged, 80 and over; Alzheimer Disease - diagnostic imaging; Alzheimer Disease - physiopathology; Biological and medical sciences; Brain Mapping; Cerebral Cortex - diagnostic imaging; Cerebral Cortex - physiopathology; Coefficient of variation (CV); Discriminant analysis; Dominance, Cerebral - physiology; FDG; Female; Fluorodeoxyglucose F18; Geriatrics; Heterogeneity; Humans; Laterality; Male; Medical sciences; Middle Aged; Parietal Lobe - diagnostic imaging; Parietal Lobe - physiopathology; Positron emission tomography; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Reference Values; Temporal Lobe - diagnostic imaging; Temporal Lobe - physiopathology; Tomography, Emission-Computed; FDG; Coefficient of variation (CV); Heterogeneity; Discriminant analysis; Laterality; Positron emission tomography; Radionuclide study; Human; Nervous system diseases; Cerebral cortex; Senescence; Hemispheric specialization; Alzheimer disease; Central nervous system; Metabolism; Cerebral disorder; Central nervous system disease; Degenerative disease; Elderly; Age; Comparative study; Variation coefficient; Brain (vertebrata); Positron; Emission tomography
• ISSN: 0925-4927; 0165-1781; 1872-7506
• DOI: 10.1016/S0925-4927(01)00130-5

Imaging studies have reported marked reductions in brain glucose metabolism in Alzheimer's Disease (AD). However, less is known about disruptions in the patterns of brain metabolic activity. Here we questioned whether AD affects the patterns of homogeneity/heterogeneity in brain metabolism. PET images of 35 AD subjects were compared with those of 35 controls. A template was applied to extract a cortical rim, which was partitioned into 990 contiguous regions. Estimates of metabolic homogeneity were obtained using the coefficient of variation (CV). The CV of the entire cortex was found to be significantly larger in AD, suggesting increased heterogeneity at the whole brain level. In contrast, regional CV was significantly lower in AD in temporal and parietal cortices, which were the regions that along with the precuneus had the largest metabolic decrements, though the precuneus had increased CV. The enhanced heterogeneity for the global cortical pattern most likely reflects variability in the degree of pathology among brain regions as well as neuroanatomical disconnection. The enhanced homogeneity in parietal and temporal cortices is likely to reflect loss of regional differentiation (i.e. macrocolumnar disorganization). The enhanced CV in precuneus, despite its marked reductions in metabolism, suggests that increases in regional homogeneity in parietal and temporal cortices are not a mere reflection of the decrement in metabolism.