Table 2.

Strategies of preservation of cognitive function.

Domain	Feature	Characteristics related to the preservation of cognitive function
Brain maintenance (slowing/prevention of decline and pathology)
	Resting-state functional connectivity	Maintained CA3 > CA1 connectivity (Liang et al., 2020).
	Gene expression changes	Maintenance of immune, synaptic, cholesterol/lipid metabolism pathways (Burger, 2010; Smith et al., 2020).
Cognitive reserve (adaptation/plasticity to maintain cognitive function in the presence of aging and pathology)
	Cellular resilience	Regulation of Ca2+ homeostasis, inflammation, oxidative stress, cellular waste disposal pathways (Blalock et al., 2003; Neuner et al., 2016, 2019a,c; Mattson and Arumugam, 2018; Foster, 2019; Smith et al., 2020).
	Network efficiency	Increased efficiency (i.e., less activation) in CA1, mPFC (Kelly and Deadwyler, 2002; Paban et al., 2013; Sampedro-Piquero et al., 2015; Tomas Pereira et al., 2015; Ianov et al., 2016; Yagi et al., 2016; Hernandez et al., 2018; Smith et al., 2020).
	Network capacity	Increased capacity (greater activation) in the dentate gyrus during spatial memory tasks (Yau et al., 1996; Vann et al., 2000; He et al., 2002; Blalock et al., 2003; Colombo et al., 2003; Palop et al., 2003; Small et al., 2004; Rowe et al., 2007; Deipolyi et al., 2008; VanElzakker et al., 2008; Penner et al., 2011; Marrone et al., 2012; Gheidi et al., 2013; Fletcher et al., 2014; Benito et al., 2015; Weber et al., 2015; Bernstein et al., 2019).
	Network compensation/flexibility	Shift to non-hippocampal memory systems to compl, ete task (allocentric > egocentric, CA1 > basal ganglia, amygdala activation; Cabeza et al., 2002; Burger et al., 2007; Deipolyi et al., 2008; Grady, 2008; Epp and Galea, 2009; Steffener et al., 2009; Morris et al., 2012; Olvera-Cortés et al., 2012; Steffener and Stern, 2012; Zelikowsky et al., 2013; Snigdha et al., 2017; Cabeza et al., 2018; Pignataro et al., 2019; Smith et al., 2020).