Figure 5.

Representational similarity analysis (RSA). A. The representational dissimilarity matrix (RDM) was computed in a priori ROIs from the pairwise Mahalanobis distance in the multi-voxel activity patterns evoked when face stimuli were presented at the time of F1 and F2. People were modeled separately when they were shown in the competence (left panel) and popularity contexts (right panel). B. The neural RDM was tested against model predictions of four separate dissimilarity matrices, including pairwise differences in the rank in the task-relevant dimension (D), pairwise Euclidean distances on the 2-D social space (E), the behavioral context indicating for which social hierarchy dimension the face was presented (C), and in which group (group 1 or 2) the face belonged during training (G). C. Kendall’s τ indicates to what extent a predictor RDM explains the pattern dissimilarity between voxels in each of the ROIs. The model RDMs of D and E, but not C or G, show robust effects on the pattern dissimilarity estimated in the HC, EC, and vmPFC/mOFC but not in amygdala and primary motor cortex (M1) (***, p_FWE<0.001 corrected for the number of ROIs as well as the number of comparisons with the Bonferroni-Holm method). D. The patterns dissimilarity in bilateral HC, EC, and vmPFC/mOFC increases in proportion to the true pairwise Euclidean distance between individuals in the 2-D abstract space. E and F. The pattern dissimilarity increases not only with the task-relevant distance (D) but also the task-irrelevant distance (I), suggesting that the HC-EC system utilizes 2-D space (E). G. The effects of pairwise Euclidean distance (E) between faces and the pattern dissimilarity in the HC, EC, and vmPFC/mOFC were separately analyzed for within-group (E Wth) and between-group relationships (G). Moreover, the interaction effect between E and G were separately analyzed also based on whether the faces had been directly compared during training (E Btw Hub) or not (E Btw Non). Effects are strongest for those individuals who had been previously compared during training. That is, activity patterns are better explained by E Wth and E Btw Hub than E Btw Non (two-sided Wilcoxon signed-rank test). The between-group E for novel pairs is only significant in HC. Multiple comparisons are corrected with the Holm-Bonferroni method (***, p_FWE<0.001). H. Whole-brain searchlight RSA indicates effects of E in the HC, EC, mOFC (a part of vmPFC), central OFC, and lateral OFC, among other regions (p_TFCE<0.05). I. The activity patterns in the HC, EC, and central and medial OFC are still explained by the model RDM for pairwise Euclidean distance (E) after partialling out its correlation with the model RDM for D (p_TFCE<0.05; Fig. S5B). For visualization purposes, the whole-brain searchlight maps are thresholded at p<0.005 uncorrected.