5). The results for the perceptual matching study (i.e. A-A; see Fig. 5A) support the neural compensation hypothesis of cognitive reserve, as the activated regions underlying task performance

differed in the younger and older groups. The older group recruited the bilateral frontal superior gyri more than the younger one, as in the PASA phenomenon, even at the lowest attentional load level (i.e. three letters). In addition, the elderly participants were found to use neural compensation and neural reserve concurrently to cope with increasing attentional load (i.e. five letters) for perceptual find more processing. These results support a previous study (Townsend et al., 2006) which investigated auditory and visual selective attention and cross-modal attention shifts using fMRI. They showed age-related differences in BOLD responses. The most striking of these differences were bilateral frontal and parietal regions of significantly increased activation in older adults during both focused and shifting attention. These data suggest that this increased activation reflected not new recruitment but reliance on brain regions typically used by younger adults when task demands are greater. These patterns may reflect compensatory neural recruitment. The results for the

naming matching study (i.e. a-A; see Fig. 5B) indicate a load-dependent Talazoparib datasheet PASA, supporting the hypothesis that an enhanced compensatory mechanism is required for the most demanding Mirabegron condition (i.e. five letters). Thus, cerebral

reorganization of visual selective attention implies an intrahemispheric PASA phenomenon suggesting neural compensation. To cope with increased cognitive demand, neural reserve can also be recruited in basic perceptual processing (i.e. A-A; five letters), while the recruitment of compensation mechanisms increases in more complex processing (i.e. a-A; five letters). Taken together, these results suggest that the two neural mechanisms, compensation and reserve, are engaged in a flexible and adaptive manner, and are deployed depending on cognitive demand and on the nature of the required processing. Some of the evidence discussed here suggests that the functional reorganization of the brain that allows for the preservation of cognitive abilities takes many different forms, which cannot be universally predicted. Successful cognitive aging relies on neurofunctional flexibility, which enables the aging brain to cope with the challenges posed by declining neural structures. This flexibility is provided by dynamic neurofunctional adaptive mechanisms (a form of cerebral plasticity) that allow for the optimal engagement of the age-affected resources and recourse to the most advantageous distribution of cognitive processing and resources within the aging brain. This evidence suggests that neurofunctional reorganization in aging is based on a more flexible and adaptive neurofunctional process than had previously been proposed.