Re-visiting cognitive reserve: The importance of multiple brain measures

The term 'cognitive reserve' broadly refers to better-than-expected cognitive abilities in old age, presumed to reflect environmental/lifestyle factors earlier in life. This commentary addresses the question of what determines 'better than expected' cognition; specifically, whether cognitive reserve can be 'explained away' by considering multiple brain measurements. Using simulations, I show that, once one allows for multiple brain properties related to cognition, differential maintenance of those properties can reproduce the clinical picture associated with cognitive reserve. Using real data, I then show that white-matter microstructure and functional connectivity explain significant additional variance in fluid intelligence beyond grey-matter volume (at least cross-sectionally), supporting the importance of measuring multiple brain properties. Using multimodal, longitudinal data to identify changes in those brain properties that are especially important for changes in cognition will help decide which interventions are most likely to be effective at maintaining cognition in old age.