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

Publication Type	Academic Article
Authors	Volkow N, Zhu W, Felder C, Mueller K, Welsh T, Wang G, de Leon M
Journal	Psychiatry Res
Volume	114
Issue	1
Pagination	39-50
Date Published	02/15/2002
ISSN	0165-1781
Keywords	Alzheimer Disease, Cerebral Cortex, Tomography, Emission-Computed
Abstract	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.
DOI	10.1016/s0925-4927(01)00130-5
PubMed ID	11864808