(A) Trial Structures in the Experimental Task.

(i) In the Initial Encoding phase, participants were instructed to remember object-location pairs by creating a story or making a “mental photo” of the scene, memorizin the exact location of each object within the scene. (ii) In the Learning Phase, participants chose on location out of three choices and received feedback for their response. The feedback was given in the form of a smiley face, with a happy face denoting a correct answer, a sad face denoting an incorrect answer, an a sleeping face denoting a missed response. After receiving feedback, the correct object-locatio association was shown again. (iii) In the Retrieval Phase participants chose the location of the object in the scene out of three options without feedback. The retrieval phase took place in the MR scanner. (B) Experimental Procedure. The testing took place across three days. On Day 0, participants learned 60 object-location associations (remote items). On Day 1, participants learned 30 new object-location associations (recent items). For retrieval (short delay), 30 remote pairs learned on Day 0 and 30 recent pairs learned on Day 1 were retrieved. A similar procedure was followed on Day 14 (long delay), with another 30 new object-location associations. Across all testing days, participants also completed socio-demographic questionnaires and other psychometric tests, which were distributed across sessions. Note: RT – reaction time; s – second, fMRI – functional magnetic resonance imaging. (C) Overview of Learning Performance. Children needed on average between two to four learning-retrieval cycles to reach the criterion of 83% correct responses, while young adults needed on average two cycles. (D) Final Learning Performance. Final learning accuracy is calculated as the percentage of correct responses during the last learning cycle for both children and young adults. Final learning accuracy was significantly higher in young adults compared to children across all sessions. Grey dashed line indicates the criteria of 83% correctly learned items.

Retention rates for initially correctly learned items.

Memory accuracy is operationalized as the percentage of correct responses in the retrieval task conducted during the MRI scanning sessions for items that were initially correctly learned, indicating initially strong memories. Memory accuracy for recently consolidated items did not differ between sessions in young adults and children and was collapsed across recent memory accuracy on Day was higher than on Day 14. Memory accuracy for remotely consolidated items differed between sessions in both young adults and children, showing higher remote memory accuracy on Day 1 than on Day 14. All tests used Sidak correction for multiple comparisons. Red dashed line indicates the threshold for random performance. *p < .05; **p < .01; ***p < .001(significant difference); non-significant differences were not specifically highlighted. Error bars indicate standard error based on the underlying LME-model.

Mean Signal Differences Between Correct Remote and Recent Memories.

The figure presents mean signal difference for remote > recent memories on Day 1 and Day 14 in children and adults during the object presentation time window in (A) anterior and posterior hippocampus; (B) anterior an posterior parahippocampal gyrus; (C) cerebellum; (D) medial prefrontal cortex; (E)ventrolateral prefrontal cortex; cerebellum; (F) precuneus; (G) retrosplenial cortex; (H) lateral occipital cortex. Note: Bars represent the average signal difference. The colour indicated the age groups: purple for children and khaki yellow for young adults. Solid-lined bars represent data from Day 1, while dashed-lined bars depict data from Day 14. Across all panels, mean of individual subject data are shown with transparent points. The connecting faint lines reflect within-subject differences across sessions. Error bars indicate standard error of the mean. *p < .05; **p < .01; ***p < .001(significant difference); non-significant differences were not specifically highlighted. Significance main and interaction effects are highlighted by the corresponding asterisks. All main and interactions p-values were FDR-adjusted for multiple comparisons.

Multivariate short- and long-delay brain profiles of neural upregulation (remote versus recent neural activation differences) are associated with variations in memory accuracy.

A) Short Delay Brain Profile. Latent variables weights or saliences for each ROI build up one latent variable that expresses a composite short-delay brain profile. Stability of salience elements is defined by Z-scores (depicted as red line: a value larger/smaller than ± _1.96 is treated as reliably robust at (a <0.05). B) Association between Short Delay Retention Rate and Short Delay Brain Score. Within-participant short delay brain scores that represents a within-participant robust expression of the defined latent variable’s profile is plotted against short delay memory retention rates defined as percentage of correctly recalled items on Day 1 relative to Day 0. C) Long Delay Brain Profile. Latent variables weights or saliences for each ROI build up one latent variable that expresses a composite long-delay brain profile. D) Association between Long Delay Retention Rate and Long Delay Brain Score. Within-participant long delay brain scores that represents a within-participant robust expression of the defined latent variable’s profile is plotted against long delay memory retention rates defined as percentage of correctly recalled items on Day 14 relative to Day 0. Note: PHGa – anterior parahippocampal gyrus; PHGp – posterior parahippocampal gyrus; HCa – anterior hippocampus; HCp – posterior hippocampus; PC– precuneous; vlPFC – ventrolateral prefrontal cortex; mPFC – medial prefrontal cortex; RSC – retrosplenial cortex; LOC – lateral occipital cortex; CE – cerebellum; r – Spearman’s rank order correlation index.

Representational Similarity Analysis.

(A) Index Computation (Scene). A representational similarity index was computed by assessing the averag similarity between fixation and scene time window separately for recent, remote (Day 1), and remote (Day 14) scenes. (B) Scene-Specific Reinstatement. A corrected scene-specific reinstatement index was computed b assessing the average similarity in fixation and scene time window within each trial and subtracting from it the average set similarity between the fixation and scene time window across trials. S – scene time window; F – fixation time window; r – Pearson’s correlation index; Δ z – difference between two Fisher transformed r values. * - Activation patterns.

Corrected scene-specific neural reinstatement.

Scene-specific neural reinstatement defined as the difference between Fisher-transformed scene-specific and set-specific representational similarity. (A) Hippocampus Anterior; (B) Hippocampus Posterior; (C) Parahippocampal Gyrus Anterior; (D) Parahippocampal Gyrus Posterior; (E) Cerebellum; (F) Medial Prefrontal Cortex; (G) Ventrolateral Prefrontal Cortex; (H) Precuneus; (I) Retrosplenial Cortex; (J) Lateral Occipital Cortex. *p < .05; **p < .01; ***p < .001(significant difference). Error bars indicate standard error. Δ z – difference between two Fisher transformed r values.

Sample characteristics by age group
Statistical overview of LME-model based Sidak corrected post hoc comparisons for scene-specifi reinstatement analysis (based on LME-model described in Table S8).

Representational Similarity Analysis.

(A) Index Computation (Gist). A representational similarity index was computed by assessing the averag similarity for fixation time window for within-category and between-category scenes separately for recent, remote (Day 1), and remote (Day 14) scenes. The diagonal (similarity of fixation time window with itself) was exclude from the analysis. (B) Gist-like Reinstatement. A gist-like reinstatement index was computed by assessing the average similarity in fixation time window for the same-category pairs and subtracting from it the any-other-category pairs. S – scene time window; F – fixation time window; r – Pearson’s correlation index. Δ z – difference between two Fisher transformed r values.

Gist-like Reinstatement.

Gist-like reinstatement is reflected by the difference in Fisher’s z (Δ z) between within-category and between-category representational similarity during fixation time window, where participants were instructed to reinstate the scene associated with the learned object before the actual scenes were shown. Higher values mean higher gist-lik reinstatement. The index was tested for significance against zero and all results were FDR corrected for multiple comparisons. Significant reinstatement of gist-like information is highlighted by a green rectangle (A) Hippocampus Anterior; (B) Medial Prefrontal Cortex; (C) Precuneus; *p < .05; **p < .01; ***p < .001(significant difference); non-significant difference was not specifically highlighted. Error bars indicate standard error.

Multivariate short- and long-delay brain profiles of scene-specific reinstatement are associated with variations in memory accuracy.

A) Short Delay Brain Profile. Latent variables weights or saliences for each ROI build up one latent variable that expresses a composite short-delay scene-specific reinstatement brain profile. Stability of salience elements is defined by Z-scores (depicted as red line: a value larger/smaller than ± _1.96 is treated as reliably robust at (a <0.05). B) Association between Short Delay Retention Rate and Short Delay Scene-Specific Reinstatement Brain Score. Within-participant short delay scene-specific reinstatement brain scores that represents a within-participant robust expression of the defined latent variable’s profile is plotted against short dela memory retention rates defined as percentage of correctly recalled items on Day 1 relative to Day 0. C) Long Delay Brain Profile. Latent variables weights or saliences for each ROI build up one latent variable that expresses a composite long-delay scene-specific reinstatement brain profile. Stability of salience elements is defined by Z-scores (depicted as red line: a value larger/smaller than ± _1.96 is treated as reliably robust at (a <0.05). B) Associatio between Long Delay Retention Rate and Long Delay Scene-Specific Reinstatement Brain Score. Within-participant long delay scene-specific reinstatement brain scores that represents a within-participant robust expression of the defined latent variable’s profile is plotted against long delay memory retention rates defined as percentage of correctly recalled items on Day 14 relative to Day 0. Note: PHGa – anterior parahippocampal gyrus; PHGp – posterior parahippocampal gyrus; HCa – anterior hippocampus; HCp – posterior hippocampus; PC– precuneous; vlPFC – ventrolateral prefrontal cortex; mPFC – medial prefrontal cortex; RSC – retrosplenial cortex; LOC – lateral occipital cortex; CE – cerebellum; r – Spearman’s rank order correlation index.

Multivariate short- and long-delay brain profiles of gist-like reinstatement are associated with variations in memory accuracy.

A) Short Delay Brain Profile. Latent variables weights or saliences for each ROI build up one latent variable that expresses a composite short-delay gist-like reinstatement brain profile. Stability of salience elements is defined by Z-scores (depicted as red line: a value larger/smaller than ± _1.96 is treated as reliably robust at (a <0.05). B) Association between Short Delay Retention Rate and Short Delay Gist-Like Reinstatement Brai Score. Within-participant short delay gist-like reinstatement brain scores that represents a within-participant robust expression of the defined latent variable’s profile is plotted against short delay memory retention rates defined as percentage of correctly recalled items on Day 1 relative to Day 0. C) Long Delay Brain Profile. Latent variables weights or saliences for each ROI build up one latent variable that expresses a composite long-delay gist-lik reinstatement brain profile. Stability of salience elements is defined by Z-scores (depicted as red line: a value larger/smaller than ± _1.96 is treated as reliably robust at (a <0.05). B) Association between Long Delay Retention Rate and Long Delay Gist-Like Reinstatement Brain Score. Within-participant long delay gist-like reinstatement brain scores that represents a within-participant robust expression of the defined latent variable’s profile is plotted against long delay memory retention rates defined as percentage of correctly recalled items on Day 14 relative to Day 0. Note: HCa – anterior hippocampus; PC– precuneous; mPFC – medial prefrontal cortex; r – Spearman’s rank order correlation index.