Exercising the Brain to Avoid Cognitive Decline

Examining the Evidence

William E Reichman; Alexandra J Fiocco; Nathan S Rose

Disclosures

Aging Health. 2010;6(5):565-584. 

In This Article

Cognitive & Brain Reserve in Humans

The concept of reserve refers to a threshold model of vulnerability to injury or the cumulative effects of aging. For example, there appears to be significant variability among individuals in the clinical consequences and severity of disability associated with a similar level of pathological burden within the brain.[29] This has been demonstrated in AD, stroke and traumatic brain injury. Stern and collaborators have argued that although the terms 'brain reserve' and 'cognitive reserve' are often used interchangeably, they each represent a different concept.[30] Specifically, in their framework brain reserve refers to the physical endowment of the brain in terms of cranial capacity (a proxy for brain size), the density of neurons and the degree of connectivity between them (synaptic density). Cognitive reserve, on the other hand, refers to the potential to increase the efficiency and capacity of existing neural pathways and/or to recruit new pathways that are not typically used to accomplish a task. Several perspectives have been delineated to link theories of brain and cognitive reserve. One perspective is that of computational redundancy and flexibility;[31] an individual with high reserve will display more flexible cognitive processes (i.e., high cognitive reserve) and a greater number of redundant neural pathways (i.e., high brain reserve) and thus, will experience a longer asymptomatic period despite neurological insult. Furthermore, two individuals with the same level of brain reserve may display differential symptoms following brain insult depending on complexity and flexibility of their cognitive processes.

Thus, the greater the degree of anatomical brain reserve that exists, the higher the threshold of pathological burden that needs to be crossed before brain changes are significant enough to lead to clinical features of illness (i.e., cognitive impairment). It has been demonstrated that brain reserve can be influenced and is not merely fixed: a variety of studies have demonstrated that aerobic physical exercise leads to morphological changes such as increased brain volume within the rodent as well as the adult human.[32] It is less clear whether cognitive exercises can induce the same type of structural alterations. However, Stern and colleagues have posited that intellectually enriching activities throughout life (education, mentally challenging work and certain leisure activities) and perhaps, as well, structured cognitive training could enhance cognitive reserve.[33] As a consequence, cognitive reserve could theoretically modulate the potential impact of age-related and pathological brain changes on cognitive performance. A number of human studies have addressed whether enhancement of reserve is possible through cognitive exercise. The following section of the article reviews studies that have assessed whether cognitive training techniques can enhance cognitive function and possibly alter reserve in later years.

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