Fig. 2

Fitted curves and random effects at culture level. (a) Estimates of the global population curve (dashed line) and the culture-specific curves (solid lines). Horizontal red dotted lines represent estimates of \(\rho ^{(0)}\) and \(\alpha ^{(0)}\). (b) Random-effects estimates at the culture level. The parameters of the culture-specific curves are obtained by adding the random-effect estimates from the (b) panel to the fixed- effect estimates. Notably, in the absence of significant interaction terms between any of the three fixed parameters and the experimental condition in the final selected model, the fitted global population curve was the same for both experimental conditions. Similarly, the six fitted culture-specific curves were the same for both experimental conditions. Indeed, the fixed effects at culture level were the same for any of the three parameters. In addition, the experimental condition was applied at the neuron-and not at the culture level-in this experimental design, thus preventing from properly defining the interaction term between random effects at culture level and experimental condition.