Figure 4 .

Within-category neural reinstatement during retrieval mediates the relationship between neural differentiation during encoding and memory performance. (A) Older adults with greater neural differentiation during encoding also show greater within-category neural reinstatement during retrieval. Within-category neural reinstatement was defined as the mean of Pearson’s r values calculated for all unique pairs of encoding and retrieval trials within the same categories (i.e., face–face or scene–scene) (for details, see Materials and Methods). (B) Within-category neural reinstatement depicted in (A) is illustrated using RS matrices from the same two individuals shown in (A) and in Figure 3: a 70-year-old superager (indicated by a red circle/arrow in (A); top matrix here) whose within-category neural reinstatement was 0.61/0.38 for face–word/scene–word pairs; and a 64 year-old typical older adult (indicated by a blue circle/arrow in (A); bottom matrix here) whose within-category neural reinstatement was 0.07/0.05 for face–word/scene–word pairs. These matrices show that the brains of superagers exhibit greater RS than that of typical older adults when the regional brain activity during the initial learning of categories of visual information is compared with regional brain activity when that information is subsequently retrieved from memory. (C) The degree of within-category neural reinstatement during retrieval fully mediated the relationship between neural differentiation during encoding and associative recognition memory performance. That is, older adults who show greater neural differentiation during encoding of visual information in distinct categories also show greater reinstatement (i.e., a higher degree of similarity in brain activity between encoding and retrieval); greater reinstatement, in turn, leads them to remember more individual image–word pairs when tested.