Efficiency, capacity, compensation, maintenance, plasticity: emerging concepts in cognitive reserve

Highlights • We examine cognitive reserve and related concepts (brain reserve/maintenance, cognitive flexibility, scaffolding). • These concepts are complementary rather than competing. • Cognitive and brain reserve influence one another and are interconnected. • Cognitive reserve is compatible with neuroprotective theories, such as brain maintenance. • To be truly useful, all models must identify underlying neural and cognitive mechanisms.