title: Principal component analysis in mild and moderate Alzheimer's disease--a novel approach to clinical diagnosis.
abstract: Principal component analysis (PCA) provides a method to explore functional brain connectivity. The aim of this study was to identify regional cerebral blood flow (rCBF) distribution differences between Alzheimer's disease (AD) patients and controls (CTR) by means of volume of interest (VOI) analysis and PCA. Thirty-seven CTR, 30 mild AD (mildAD) and 27 moderate AD (modAD) subjects were investigated using single photon emission computed tomography with (99m)Tc-hexamethylpropylene amine oxime. Analysis of covariance (ANCOVA), PCA, and discriminant analysis (DA) were performed on 54 VOIs. VOI analysis identified in both mildAD and modAD subjects a decreased rCBF in six regions. PCA in mildAD subjects identified four principal components (PCs) in which the correlated VOIs showed a decreased level of rCBF, including regions that are typically affected early in the disease. In five PCs, including parietal-temporal-limbic cortex, and hippocampus, a significantly lower rCBF in correlated VOIs was found in modAD subjects. DA significantly discriminated the groups. The percentage of subjects correctly classified was 95, 70, and 81 for CTR, mildAD and modAD groups, respectively. PCA highlighted, in mildAD and modAD, relationships not evident when brain regions are considered as independent of each other, and it was effective in discriminating groups. These findings may allow neurophysiological inferences to be drawn regarding brain functional connectivity in AD that might not be possible with univariate analysis.
authors.affiliation: Institute of Cognitive Sciences and Technologies, CNR, Rome & Padua, Italy. marco.pagani@istc.cnr.it
authors.forename: Marco
authors.initials: M
authors.lastname: Pagani
authors.forename: Dario
authors.initials: D
authors.lastname: Salmaso
authors.forename: Guido
authors.initials: G
authors.lastname: Rodriguez
authors.forename: Davide
authors.initials: D
authors.lastname: Nardo
authors.forename: Flavio
authors.initials: F
authors.lastname: Nobili
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000523:psychology; D000704:Analysis of Variance; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging*; D001931:Brain Mapping / Q000379:methods; D002560:Cerebrovascular Circulation; D016002:Discriminant Analysis; D005260:Female; D006624:Hippocampus / Q000098:blood supply / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D010296:Parietal Lobe / Q000098:blood supply / Q000000981:diagnostic imaging; D025341:Principal Component Analysis / Q000379:methods; D019275:Radiopharmaceuticals; D012720:Severity of Illness Index; D019690:Technetium Tc 99m Exametazime; D013702:Temporal Lobe / Q000098:blood supply / Q000000981:diagnostic imaging; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime