Normal age-related brain morphometric changes: nonuniformity across cortical thickness, surface area and gray matter volume?

Abstract

Normal aging is accompanied by global as well as regional structural changes. While these age-related changes in gray matter volume have been extensively studied, less has been done using newer morphological indexes, such as cortical thickness and surface area. To this end, we analyzed structural images of 216 healthy volunteers, ranging from 18 to 87 years of age, using a surface-based automated parcellation approach. Linear regressions of age revealed a concomitant global age-related reduction in cortical thickness, surface area and volume. Cortical thickness and volume collectively confirmed the vulnerability of the prefrontal cortex, whereas in other cortical regions, such as in the parietal cortex, thickness was the only measure sensitive to the pronounced age-related atrophy. No cortical regions showed more surface area reduction than the global average. The distinction between these morphological measures may provide valuable information to dissect age-related structural changes of the brain, with each of these indexes probably reflecting specific histological changes occurring during aging.

Figure 1

Scatter plots and simple linear regressions of total volume (a.), mean thickness (b.) and total surface area (c.) on age for both cerebral hemispheres.

Figure 2

Effects of age on cortical volume (a.), thickness (b.) and surface area (c.) for each region of the brain. On the left, regression maps are superimposed onto an average pial surface (n = 216) and displayed without statistical threshold in % of region per year for cortical volume and surface, and in mm per year for cortical thickness (blue color scale for reductions and red color scale for increases). On the right, horizontal barplots of the corresponding age-related effect on the 33 bilateral cortical regions as parcellated by the automatic labeling procedure in FreeSurfer (*** p < 0.001, ** p < 0.01 corrected for False Discovery Rate).

Figure 3

Cortical regions where the age-related reductions in volume (blue), thickness (red) or both (green) exceeded the global variations at the statistical level of p < 0.05 corrected for False Discovery Rate. Maps are superimposed onto an average pial surface (n = 216).