Aging is associated with reduced white matter connectivity and fractional anisotropy in cortical autonomic regions

Alterations in the functional activity of regions in the cortical autonomic network (CAN) occur with aging. This study tested the hypothesis that the structural connectivity and fractional anisotropy (FA) of gray matter regions in the CAN would be compromised with aging. Diffusion tensor imaging (BrainVoyager) was used to perform tractography and measure FA in the anterior and posterior insular cortex (IC), the subgenual anterior cingulate cortex (sACC), and the posterior cingulate cortex (PCC) in 11 young (25±3 yr), 10 older hypertensive (HT; 58±6 yr), and 12 older normotensive participants (NT; 64±3 yr). In young, connections were observed between the anterior IC-sACC (left, 7/11; right, 9/11), as well as between the posterior IC-PCC (left, 10/11; right, 8/11). In HT, connections were observed between the anterior IC-sACC (left, 6/12; right 7/12), as well as between the posterior IC-PCC (left, 11/12; right, 6/12). In NT, few connections were observed between anterior IC-sACC (left, 1/10; right, 1/10), and more posterior IC-PCC connectivity (left, 9/10; right, 6/10). The FA values were not different between HT and NT and these values were grouped. Compared to young, the FA values were lower in the older groups for each of the left anterior IC (0.29 vs. 0.26), the left posterior IC (0.29 vs. 0.26), the right anterior IC (0.27 vs. 0.23), and the right posterior IC (0.33 vs. 0.30) (all P<0.05). The FA of the sACC was not different between young, HT or NT whereas FA of the PCC was higher in the older groups (0.30) compared to young (0.20; P<0.05). It was concluded that in this group, aging was associated with reduced white matter connectivity between CAN regions that degrade anteriorly. The microstructural alterations in the insula may contribute to autonomic dysregulation in aging.