Abstract:

The concept of reserve appears in the neurological literature in the 1940s arising from the observation that there is no linear relationship between neurological damage and severity of the clinical symptoms. Basically, this concept sustains that the experiences pursued during life-span enrich the brain by making it more resilient to neuronal damage. However, in the last three decades the reserve concept has become very popular in the scientific field, mainly associated with the pathophysiological mechanisms underlying the Alzheimer’s Disease (AD). In this time period the concept has been substantially modified, passing from a structural conceptthe brain reserve (BR)–to a more functional concept–the neural reserve (NR)–by way of a cognitive concept-the cognitive reserve (CR). The BR is related to the brain structure in terms of number of neurons, synapses, and dendrites, and postulates that individuals with larger brain cope better with the neurological damage than subjects with smaller brains. The concept of CR is related to the efficiency of cognitive functioning, and postulates that subjects with higher level of CR use more efficiently the pre-existent cognitive processes or are able to enlist alternative cognitive functions to cope better with brain damages. The NR is a sort of summa of the previous concepts. Indeed, NR is related to the efficiency of brain networks, namely subjects with higher NR are able to engage more efficiently different brain routes to use more effectively the cognitive functions withstanding the cerebral damage. Moreover, Stern (2017) introduced the concept of brain maintenance that postulates that life experiences (including cognitive, social and physical activities) reshape the brain, such increasing the ability to maintain the cognitive integrity. It is well known that several factors that may be associated with genetic background and also with environmental factors impact positively or negatively on brain resilience making subjects able or not to counteract the damages. An important part of the research on the reserves is dedicated to identify the better proxy measure to capture brain changes due to reserves’ mechanisms (BR, CR, NR).