The salience network contributes to an individual's fluid reasoning capacity.

Fluid reasoning is the ability to think flexibly and logically, analyze novel problems and identify the relationships that underpin these problems independent of acquired knowledge. Although many functional imaging studies have investigated brain activation during fluid reasoning tasks, the neural correlates of fluid reasoning remain elusive. In the present study, we aimed to uncover the neural correlates of fluid reasoning by analyzing correlations between Raven's Standard Progressive Matrices (RSPM), an effective measure of fluid reasoning, and measures of regional gray matter volume (GMV) and regional homogeneity (ReHo) in a voxel-wise manner throughout the whole brain in 297 healthy young adults. The most important finding was that RSPM scores were positively correlated with both GMV and ReHo values in brain areas that belong to the salience network, including the dorsal anterior cingulate cortex and the fronto-insular cortex. Additionally, we found positive or negative correlations between RSPM scores and GMV or ReHo values in brain areas of the central-executive, default-mode, sensorimotor and visual networks. Our findings suggest that fluid reasoning ability is related to a variety of brain areas and emphasize the important contribution of the salience network to this ability.