Genetic evidence for cognitive reserve: variations in memory and related cognitive functions.

Variations in cognitive functions across individuals are observed universally, and such observations serve as the basis of cognitive reserve (CR). Broadly, cognitive reserve refers to the inconsistency between neuropathology and clinical severity. The causes of such individual variations are likely to be multi-factorial. In this review, I present studies which suggest that genes are likely to be the contributing causes, and these genes interact with environmental factors to produce even greater variations in cognitive functions. A number of animal and human studies are beginning to reveal the role of genetic contributions to cognitive functions like memory, memory decline, general intelligence, and language. Twin studies suggest that there is a substantial heritable component for memory and related cognitive functions, such as general intelligence and language, but not for others. Thus, heritability estimates vary by cognitive domain. Animal studies and some human studies have identified genes or candidate loci that contribute to memory as well as other related cognitive phenotypes. Yet, our current understanding is limited. It will require interdisciplinary efforts from a number of different fields to better define the neuropsychological phenotype. At the same time, it is necessary to take into account both genetic and environmental factors to understand the complex network underlying CR.