This mismatch suggests that neurofunctional reorganization occurs with age, allowing the brain to compensate for the various structural losses. A possible answer to this mismatch has been captured by Stern (2009) in his concept of ‘cognitive reserve’. The

notion of cognitive reserve refers to the existence of an ability to optimize performance that supports cognition in healthy, high-performing older individuals. The neural bases of these cognitive abilities would either be forced to make optimal use of an existing neural network (neural reserve) or, alternatively or concurrently, would engage neural networks normally not engaged in this given cognitive ability (neural compensation). As revealed by neuroimaging, neural reserve appears to be associated with enhanced Lapatinib in vivo activations of areas or networks known to be associated with a given cognitive ability, whereas neural compensation appears as relying on the activation of areas or networks not normally known to be associated with this cognitive ability. Thus, for Stern (2009) the notion of cognitive reserve would account for the paradox NVP-BEZ235 purchase posed by the degradation of the physical brain on one hand vs. the preservation of cognitive abilities in some older individuals on the other hand. In support of the general concept of cognitive reserve, neurofunctional

reorganization phenomena have been reported in neuroimaging studies of young and older individuals whose performance levels remain high. These phenomena have been interpreted according to several forms of neurofunctional reorganization posited to occur in healthy cognitive aging. Cabeza (2002) observed that elderly individuals who had maintained a given cognitive ability were characterized by the presence of

patterns Dynein of activation that were bilateral as opposed to more lateralized activations in younger high-performing individuals as well as older, less performing, individuals. This pattern was interpreted as suggesting that age-related hemispheric asymmetry reductions may have a compensatory function by engaging additional brain areas, such as homologous contralateral regions (Reuter-Lorenz & Lustig, 2005; Reuter-Lorenz & Cappell, 2008; Reuter-Lorenz & Park, 2010). Other studies that examined the hemispheric distribution of attentional resources (Banich, 1998) supported this explanation (Reuter-Lorenz et al., 1999; Reuter-Lorenz & Lustig, 2005; Ansado et al., 2009). Together, these studies show a shift in efficiency from within- to across-hemisphere processing with aging in order to maintain performance. These results suggest that elderly adults use both hemispheres to process information in relatively easy tasks whereas young adults do so only for tasks that are more difficult.