Area-specific Biased Global Efficiency in Functional Connectivity Provides Features Negatively Correlated with Age

It has been acknowledged that graph-theoretical coefficients computed from the adjacency matrix of cerebral resting-state functional connectivity (RSFC) represent aging of the brain and its plasticity facilitating cognitive reserve. In particular, global efficiency (GE) has been recognized as a crucial graph index for age-dependent RSFC. Using the dataset of the Nathan Kline Institute-Rockland Sample [NKI-RS], we found that the regions of the brain in which GE values decay with age were located in the subcortical zone and the cerebellum, whereas an opposite relationship was found in many frontal and parietal regions. Based on this systematic tendency, a new coefficient was proposed that corrects GE, referred to as biased GE (BGE); BGE is calculated by changing the sign of the weight between the superior and the inferior parts of the brain before separately averaging the respective sign groups of area-specific corrected GE values, to influence the raw global network GE. The BGE showed a significant negative correlation with age, irrespective of the scan condition, and strong consistency as an information source of a subjects identity. We propose that this new index could play an important role in the clinical context of preventive medicine and the maintenance of healthy brains.