Figure 4.

Summary of potential factors affecting frontal and cerebellar morphology and processing speed. On the left side of the figure, aging affects brain morphology through the damaging effects of oxidative stress and inflammation (small vessel disease is in red because of consistent evidence linking cerebral small vessel disease to structural declines and slowed processing speed). These detrimental effects are likely buffered by neuroprotective factors such as (1) leptin and growth factor levels that limit the impact of oxidative stress, (2) norepinephrine or blueberry limits on inflammatory responses in animal models (Heneka et al., 2010; Willis et al., 2010), (3) neurotrophic factors (Kim et al., in press; Raz et al., 2009), and (4) positive lifestyle behaviors such as aerobic exercise (Rosano et al., 2010; Voss et al., 2010). The gray arrow indicates that oxidative stress and inflammation likely affects cerebellar morphology, in comparison to the black arrows for which there is empirical evidence of significant associations. The right side of the figure is designed to emphasize that early development has a significant influence on the degree to which older adults will demonstrate atypical morphology and impaired processing speed (Deary et al., 2006, 2010), but could also influence the expression of neuroprotective factors and the development of lifestyle patterns of behavior and modulate risk for age-related neural declines. While this summary figure is general in nature, it is designed to emphasize the multifactorial and interactive effects of aging neural systems on processing speed.