What’s the science?
‘Cognitive reserve’ refers to an individual’s capacity to maintain good brain function despite aging or a disease affecting the brain, such as Alzheimer’s. IQ is often used as a proxy for measuring cognitive reserve, however, cognitive reserve specifically refers to the resilience of the brain. Several studies have attempted to use functional magnetic resonance imaging (fMRI) to understand how the brain’s cognitive networks might be resilient. These studies have focused on performance on (typically one) cognitive task, but cognitive reserve is likely utilized for a range of tasks. This week in NeuroImage, Stern and colleagues performed fMRI experiments to elucidate a brain network related to cognitive reserve across many tasks.
How did they do it?
The authors included healthy individuals (ages 20-80: 255 individuals in main sample, 149 in a replication sample), who completed 12 cognitive tasks as part of the Reference Ability Neural Network study, while undergoing fMRI. The 12 tasks probed cognitive abilities: vocabulary, perceptual speed, fluid reasoning, and episodic memory. An additional memory task and executive control task were used for validation of the cognitive reserve network identified during analysis. Brain structure (cortical thickness) and brain function (fMRI) data were collected. IQ was measured using the NART IQ test. The authors analyzed brain regions where activity (fMRI blood oxygen-dependent signal) covaried with IQ in a task-invariant way. Age was included as a covariate in analyses because it was correlated with IQ.
What did they find?
The authors identified a cognitive network/activity pattern of brain regions in which activity co-varied with IQ in a task-invariant way (during cognition, across all tasks). Generally, the network was located in the cerebellum, temporal and parietal lobes, the medial frontal gyrus, inferior frontal gyrus, and anterior cingulate. Brain activity in the identified cognitive reserve brain network was significantly positively or negatively related to IQ in different brain regions. After accounting for brain structure (cortical thickness), brain function in the identified cognitive reserve network explained additional variance in fluid reasoning (beyond variance in fluid reasoning explained by brain structure). Further, the authors found an interaction whereby there was a greater relationship between fluid reasoning and brain structure in individuals with a lower cognitive reserve network score (less strong expression of the pattern/network).
What’s the impact?
This is the first study to assess the concept of cognitive reserve in a wide array of tasks, using neuroimaging. A pattern of brain activity during a variety of cognitive tasks was found to be related to IQ, and is referred to as a cognitive reserve network. The study has future implications for diseases in which cognitive reserve may be critical for protection against cognitive decline, such as Alzheimer’s.
Y. Stern et al., A task-invariant cognitive reserve network. NeuroImage (2018). Access the original scientific publication here.