Figure 4.
Analysis of similarity scores of rats from the different behavioral groups. A similarity score of 1 indicates a complete overlap of the neuronal ensembles activated by epoch 1 and epoch 2 (no remapping), whereas a similarity score of 0 indicates no overlap beyond that predicted by chance (complete remapping; see Materials and Methods). a, In both CA3 and CA1, the similarity scores from rats of the A/Aobj, A/Aconf, and A/Ab groups were significantly different from the A/A and A/B groups (p < 0.02) but were not different from each other (p > 0.82). Thus, in both CA3 and CA1, all alterations to environment A (here termed A′ and comprising groups A/Aobj, A/Aconf, and A/Ab) produced a similar effect on the neural ensemble response in that cell population. Notably, the similarity score of the A/A′ rats was greater in CA3 compared with CA1 (**p = 0.001). b, Correlation between the CA3 and CA1 similarity scores for each rat. Note that the CA3 similarity scores for the A/A′ rats tended to be higher than those for CA1, as indicated by the majority of points being above the 45 ° line. Furthermore, the CA3 similarity scores of the A/B group were lower than those of CA1 in the same rats (all points of the A/B group are below the 45 ° line). These findings, as visualized in a and b, indicate that CA3 separates well dissimilar representations (A vs B), but when the threshold for remapping is not met (as in the A/A and A/A′ groups), then the initiated pattern completion will de-emphasize mild perturbations of the environment. In CA1, in contrast, differences in the environment are represented more continuously (see Results and Discussion for details).