Figure 2. Maintenance.
A. Consistent with the idea stable cognitive performance is associated with maintenance,33 individuals aged 65–80 yrs who showed minimal episodic memory decline on verbal immediate free recall and delayed cued recall tasks during a 4-year period (maintainers) also showed less hippocampal volume decline, as measured by FreeSurfer using the Desikan-Killiany atlas, over 4 years compared to decliners (from REF.71). B. Also consistent with maintenance, over a period of two decades, Old-maintainers (mean age = 68.8 yrs) who showed no significant episodic memory decline on verbal immediate free recall and delayed cued recall tasks compared to young adults (mean age = 35.3), also displayed comparable levels of hippocampal activity during an fMRI study of face-name associative encoding, compared to young adults. In contrast, Old-decliners showed longitudinal episodic memory decline in the aforementioned verbal tasks, and exhibited significantly lower hippocampal activity during associative encoding, compared to young adults and Old-maintainers (from REF.73). Consistent with the idea that there can be high-maintenance and low-maintenance, in these studies, maintainers and decliners were defined independently of their absolute levels of memory and hippocampal activity. It is impossible in these studies to know if maintenance involved repair or just absence of decline.