Cognitive reserve is a term often used in neuropsychology. It is invoked to explain the differences in functioning between people with a similar level of dementia. One person at the fourth level of a senile dementia may be able to live independently, yet another person at this level may require supervision. Current research suggests that cognitive reserve is not related to human brain size or circumference of the head. It is related, however, to years of education and the level of one’s physical activity.
Education has been extensively studied for its influence on the incidence of Alzheimer’s Disease. Large studies on Alzheimer’s risk factors have been performed around the world, and years of education is consistently an important variable. The greater the years of education, the lower the incidence of Alzheimer’s Disease. Though it may actually reflect the intelligence of the person, these huge studies rarely obtain IQ scores on thousands of subjects. Educational attainment is a number that is much easier to acquire than an intelligence quotient, which takes approximately two hours to measure. Currently, a person’s educational attainment is the single most valuable estimate of dementia risk.
Exercise is another factor that appears to lower the risk of dementia and increase cognitive reserve. It lacks the practical appeal of education’s influence on cognitive reserve. Why would straining one’s heart and muscles lead to better cognition? As mentioned in the Lifestyle section of this website, exercise has a significant impact on the cognitive performance of children. It is associated with improved academic performance. For the elderly, exercise is an important aide to stroke recovery. Exercise reduces geriatric memory loss, reduces the risk of Alzheimer’s Disease by 45% (Walsh, 2011), and reduces the risk of other dementing conditions as well. Exercise programs of one to three months offer significant cognitive benefits, but those lasting more than six months are more beneficial. The benefits are even more significant if the exercise lasts more than thirty minutes, and combines both aerobic and strength training components.
Cognitive reserve is definitely not related to the conjecture that most humans use only ten percent of their brain. This statement is absurd, both academically and evolutionarily. Watch a child sticking out their tongue while drawing a novel figure. They are using one hundred percent of their brain capacity. The brain’s subconscious processing of streaming data is far more than ten percent. This is neglecting the intentional conscious processing of sensory data that occurs throughout our waking lives. Evoluntionarily, neurons are the most expensive kind of cells. They use ten times the energy of a muscle cell by volume. Mother nature distributes brain cells in a very jealous fashion, and it requires a very high return on investment to make them worthwhile.
It appears that education and exercise are two variables that increases cognitive reserve. The whole notion of cognitive reserve is a bit sloppy, as it is vague explanation for a complex phenomenon. As researchers learn more about dementia risk factors, the term may die a natural death. For example, innate intelligence or a specific type of cognitive activity may underlay the differences in functioning between a similar level of dementia. Subsequent research may define specific factors explaining the variance that is now broadly labelled as cognitive reserve. Perhaps the dementia tests themselves are biased towards those with less education, falsely classifying the level of dementia in those with more education. It is too early to tell. Much like the use of “dark matter” in astronomy to explain the inexplicable, “cognitive reserve” serves as a patch to bridge this gap in knowledge. Perhaps it should be called “dark cognition,” as a nod to our friends in astronomy.