“…Notably, there is significant variability in the severity of ageârelated memory decline experienced between individuals, which may be due in part to differential effects of aging on the physiological and neurobiological processes in the hippocampus (Ash et al, ; Gallagher et al, ; Rapp & Amaral, ; Stark, Yassa, & Stark, ; TomĂĄs Pereira, Gallagher, & Rapp, ). Critically, individual differences in the trajectory of ageârelated changes in cognition and neural systems may be influenced by modifiable protective factors such as physical activity (PA; Hayes et al, ; Suwabe et al, , ) and cardiorespiratory fitness (CRF), which is influenced largely by genetics and PA (Hayes, Forman, & Verfaellie, ; Hayes, Hayes, Williams, Liu, & Verfaellie, ).…”