Author(s): Jeanyung Chey, M Justin Kim, Yaakov Stern, Minyoung Shin, Hong-Sik Byun and Christian Habeck
Cognitive decline in dementia does not correspond precisely to the amount of neurodegeneration in the brain. This discrepancy in brain damage and its clinical manifestation has been explicated by the concept of reserve. Brain reserve inferred from the brain size had moderate success in explaining the discrepancy, and numerous studies have reported the effects of education supporting cognitive reserve. Yet the neural substrates of reserve have been elusive. Utilizing optimized voxel-based morphometry, we have identified brain regions that were significantly smaller in individuals with low cognitive performance (LCP) compared to those with normal cognitive performance (NCP) in community-residing non-demented elderly people both with low educational attainment. It was assumed that the cognitive performance in this population reflected long-standing cognitive functioning of the individual, possibly the reserve, based on their stable follow-up performance and clinical interviews. Bilateral precuneus, right superior frontal gyrus and left middle frontal gyrus were smaller in individuals with LCP. Further, the LCP individuals had weaker correlation between the gray matter volume of those regions and the rest of the cortex. On the other hand, volume of these regions was more tightly correlated with the K-DRS Total score in these individuals. Finally, an outcome study of the community sample from which this study's participants were recruited from reported five times higher risk of dementia in the LCP group. Precuneus and prefrontal cortex are proposed as key sites comprising the neural substrates that underlie the reserve.
