Fig. 2: Pairmate similarity scores change at the behavioral inflection point.

a Regions of interest included CA3/dentate gyrus (CA3/DG, pink) and CA1 (blue) in the hippocampus, the parahippocampal place area (PPA, yellow), and early visual cortex (EVC, green). b Correlation matrix illustrating how pairmate similarity scores were computed at the behavioral inflection point. See Methods for details. c Pairmate similarity scores at the behavioral inflection point (IP) and just prior to the inflection point (pre-IP) across different regions of interest (ROIs). Pairmate similarity scores significantly varied by ROI (p = 0.009, repeated measures ANOVA) and there was a significant interaction between ROIs and behavioral state (p = 0.037, repeated measures ANOVA). In CA3/DG, pairmate similarity scores at the IP were significantly lower than 0 (p = 0.025, two-tailed one-sample t-test) and significantly lower than the pre-IP state (p = 0.033, two-tailed paired samples t-test). In PPA, pairmate similarity scores decreased from pre-IP to IP (p = 0.030, two-tailed paired samples t-test). d A permutation test (1000 iterations) was performed by shuffling, within participants, the mapping between the behavioral inflection point and scene pairmates. In CA3/dentate gyrus the actual mean group-level pairmate similarity score at the IP was lower than 98.70% of the permuted mean similarity scores (p = 0.013, one-tailed permutation test). e Pairmate similarity scores calculated by correlating the learned round (LR) with each of the three preceding rounds (– distance to LR) and each of the three succeeding rounds (+ distance to LR). [Note: the inflection point was defined as the correlation between the LR and the immediately preceding round (LR − 1); the inflection points are depicted by filled circles and are the same values as in c]. In CA3/dentate gyrus, pairmate similarity scores were significantly lower when the LR was correlated with preceding rounds compared to succeeding rounds (p = 0.006, two-tailed paired samples t-test). The difference was not significant for any other ROIs (CA1: p = 0.435; PPA: p = 0.955; EVC: p = 0.760; two-tailed paired sample t-tests). f Conceptual illustration of a decrease in pairmate similarity scores from pre-IP to IP. In the pre-IP state (top panel), A₁ and A₂ are nearby in representational space. In the IP state (bottom panel), the representational distance between A₁ and A₂ has been exaggerated. When pairmates (e.g., A₁ and A₂) are farther apart in representational space than non-pairmates (e.g., A₁ and B₂) the pairmate similarity score will be negative (i.e., pairmate similarity < non-pairmate similarity), consistent with a repulsion of competing representations. Notes: *p < 0.05, **p < 0.01. No correction for multiple comparisons was applied given the a priori predictions for CA3/dentate gyrus. Data were presented as mean ± SEM and all data reflect n = 31 independent participants. Source data are provided as a Source Data file.