Fig. 4.

Brain–memory associations in younger and older adults. (a) Brain regions involved in slow wave and spindle generation and memory processing contribute to the latent variable capturing the common variance between participants’ age and brain structure (quantified using voxel-based morphometry). Latent variable weights (in Z-scores) demonstrate that all regions have a stable negative relation with age (all BSR ≤ −6.12). Bar colors correspond to the colors of the masked regions. (b) Each participant’s expression of the latent variable is plotted against age. Overlap between the age groups is indicated by dashed boxes. Younger and older participant groups with clearly differing brain structure are outlined by a solid line. (c) Median behavioral performance for all subgroups is shown. The first and third quartile is depicted as an error bar. Memory gain (shaded in light gray) is similar in all subgroups. Memory maintenance (shaded in darker gray) differs between younger and older adults, even when they express the same structural brain integrity. Brain structure itself does not modulate behavior within age groups. (d–f) Each participant’s latent brain structure score plotted against the behavioral measures. Spearman’s rank-order correlation coefficients for the whole sample are displayed. Maintenance of both medium- and high-quality memories relates to the latent brain structure score across age groups. BSR: bootstrap ratio, YA: younger adults, OA: older adults, yY: young–Young (= younger adults showing a clearly distinct brain structure profile from older adults), oY: old–Young (= younger adults exhibiting a brain structure profile comparable to older adults), yO: young–Old (= older adults with a ‘youth-like’ brain structure profile), oO: old–Old (=older adults with a brain structure profile clearly distinct from younger adults).