Fig. 2

Graphical description of brain maintenance theory [8]. The theory proposes that a construct of brain change, theoretically defined as any task-related change in the brain in aging (i.e., lack of preservation), causes aging-related decrements in a cognitive ability construct. Brain change is operationally defined as within-person change in neuroimaging measures of brain structure (e.g., volume, white matter microstructure, and vascular pathology) and brain function over time. Change in cognitive ability is manifested as change in cognitive performance. The theory proposes no constructs other than brain change to explain changes in cognitive ability. In addition to the core of the theory illustrated, the theory also proposes that factors that may play a role in a resilience process, such as education or physical activity, or shape changes in cognitive ability by minimizing brain change. Circles represent unobserved variables (scientific constructs) and squares represent observed variables (data). Thick arrows represent observed associations and dashed lines represent unobserved associations