Fig. 2. Representational changes in the hippocampus are modulated by prior knowledge and mediate memory.

a Pairs were grouped based on memory in the later associative memory test (remembered pairs include high-confidence hits), and prior knowledge (PK/no prior knowledge, n-PK). The multivoxel activity patterns of items in each pair were correlated before and after learning, and the pre- to post-learning difference in correlation values (Fisher-transformed) was calculated. b The results from the left anterior hippocampus. Similarity after learning was lower between members of PK pairs, in contrast to an increase in similarity in n-PK pairs. Similarity differences were specific to remembered pairs. Δ Similarity: difference in similarity values from before to after learning. N = 18. Data in the bar graphs are presented as mean values, error bars reflect +/− SEM. ⊗ Interaction of pair type (PK/n-PK) by memory (remembered/forgotten) in a repeated- measure ANOVA: P = 0.0055. **P = 0.008, *P = 0.02, ~P = 0.07, the results of a paired-sample two-tailed t test between pairs of conditions, as depicted by the black lines. c Dots reflect individual participants’ Δ Similarity reduction due to prior knowledge (PK-remembered pairs minus n-PK-remembered pairs). To protect copyrights, all faces in the figures are of novel faces, and we obtained permission to use these photos. Participants in the study saw famous and novel faces, as detailed in the Methods.