Structural correlation in the default mode network in Alzheimer´s disease

Structural magnetic resonance imaging (MRI) studies have reported that gray matter density or volume covaried in most brain regions. The previous studies showed that resting-state functional connectivity reflected structural connectivity, but it is currently unclear whether brain regions in default mode network correlated in gray matter volume. This study applied Person´s correlation analytic approach to investigate connectivity within the default mode network in structural MRI in 12 patients with Alzheimer´s disease (AD) [5 males and 7 females, 58-81 years old] and 14 normal subjects [6 males and 8 females, 61-82 years old]. Eight regions of interest (ROI) were defined within the default mode network. The average volume of gray matter in eight ROIs was calculated respectively as input variables in correlation analysis. The within-group correlation coefficients in two groups were positive. With the threshold set at p<;0.05, all the correlation coefficients in AD group were significant. The correlation coefficients in all ROls except right lateral parietal cortex and medial prefrontal cortex (MPFC) were significant in normal subjects. The between-group correlation differences revealed that the correlation in posterior cingulate cortex (PCC) and right lateral parietal cortex, as well as MPFC and lateral parietal cortex, significantly increased in AD patients compared with normal subjects. Structural correlation in the default mode network helps us understand the pattern of regional covariance network in AD.