Extended Data Fig. 5: Bootstrapping test for spike similarity index.

The change of similarity index (SI) during associative learning was compared using the bootstrapping method. PCA was performed from a resampled neuronal population, and this procedure was repeated 1,000 times to make 1,000 bootstraps. SI was calculated for each bootstrap, then SIs in T2 – T5 were subtracted by that in T1, to test if there was a significant distribution above or below zero. (a). (Top) In correct sessions in Fig. 2, SI for Odours A-B showed significant decrease in T5 compared to T1 (p = 0.039) whereas SI for Odours A-1 increased (p = 1.2e-10), confirming A-B separation and A-1 overlap. (Middle) In the error sessions, no A-B separation was observed (p > 0.05). Although A-1 distance decreased during the session (p < 0.05), SIAB stayed in negative values. (Bottom) The subtraction of bootstraps in error session from correct sessions confirms the difference in A-1 overlap (p < 0.05 in T3 and T5, right). *p < 0.05, **p < 0.01, ***p < 0.001; n = 1,000, bootstrapping test. (b). (Top) In dopamine control sessions, SI for Odours A-B showed significant decrease in T5 compared to T1 (p = 0.044) whereas SI for Odours A-1 increased (p =0.0082), confirming A-B separation and A-1 overlap. (Middle) In the unilateral inhibition sessions, although A-B separation was observed (p < 0.05), no A-1 overlap was observed (p > 0.05). (Bottom) The subtraction of bootstraps in inhibition session from control sessions confirms the effect of inhibition on A-1 overlap (p < 0.05 in T3 – T5, right). These data suggest that dopamine plays a critical role in establishing A-1 overlapped representations. *p < 0.05, **p < 0.01, ***p < 0.001; n = 1,000, bootstrapping test.