Cognitive reserve
Elizabeth Buchen, neuroscientist, science writer and advisor to Lumos Labs, explains the concept of ‘cognitive reserve’, and why people with more education are generally better at coping with brain damage.
The first Alzheimer’s diseased brain I ever touched looked horrific. The cortex was shriveled, the ventricles were large, cavernous voids, and when I stained the sample I saw a galaxy of proteinaceous tangles and masses. The brain had clearly been degenerating stea
dily for over a decade, and it was difficult to imagine how the patient could have functioned. I was shocked to discover that, according to his charts, the patient’s dementia had only been detectable for a few years. In contrast, certain brains I analyzed appeared dramatically more intact, yet came from patients who had suffered from severe dementia for over a decade.
These patients exemplify the dramatically different ways people can respond to neurodegenerative changes. Even when confronted with the same disease and comparable severity, people vary considerably in the extent of cognitive decline. Specifically, people with higher levels of education and occupational attainment are more successful at coping with the same amount of brain damage.
One hypothesis that accounts for this discrepancy is the concept of cognitive reserve. The cognitive reserve hypothesis posits that people who have challenged their minds for significant portions of their lives (i.e. they didn’t just start playing Sudoku at the age of 60) can compensate for brain damage or degeneration by recruiting alternate brain networks as backup or “reserve.” In support of this hypothesis, functional brain imaging shows that “high-functioning” older adults activate significantly more areas of their brains than both “low-functioning” older adults and young adults when performing certain cognitive tasks. This indicates neural compensation; the “high-functioning” old engage in alternative neural strategies in response to neural deficits or declines in cognitive abilities. Importantly, this type of compensation may be facilitated by a more flexible organization of the brain, which results from early cognitive experience.
Of course, people who did not start challenging themselves until later in life should not despair. Other requisites of compensation, such as plasticity (including the birth of new neurons and enhanced signaling between neurons), may be improved by cognitive experience throughout life (although the earlier the better). Further, in a complementary aspect of cognitive reserve, people who challenge their brains throughout life may be able to protect their existing brain networks. Intellectually stimulating activities may increase the efficiency and capacity of these networks, enabling them to withstand a greater degree of age-related change while maintaining intact functioning (again, the earlier the better).
