Figure 6. Heterogeneity increases synchrony and decreases competition between cell assemblies. Ai, Model schematic showing two excitatory assemblies, E1 and E2, receiving rhythmic AMPAergic inputs with equal spike counts and time-varying Poisson rates modulated at frequencies f1 and f2, respectively. The assemblies compete through a shared pool of inhibitory interneurons (I-cells), and τI = 5 ms and τI = 13 ms were used for these results. Bi, For homogeneous assemblies (left) driven by external rhythms, the assembly with a more resonant input (e.g., 20 Hz) suppresses spiking in the assembly driven by a less resonant input (e.g., 50 Hz). Heterogeneity of cell intrinsic properties decreases this competition (right) and increases synchrony between the two assemblies (i.e., the fraction of 10-ms bins with spiking in both E1 and E2). Ci, Heterogeneity decreases competition (Δ) across all pairs of input frequencies and increases synchrony for inputs separated by >30 Hz. Solid lines represent the f1 – f2 shown in the above raster plots. Di, Ei, Similar raster plots and plots of competition and synchrony for τI = 13 ms. Again, heterogeneity decreases competition across all pairs of input frequencies and increases synchrony for inputs separated by >30 Hz. Aii, Model schematic showing two assemblies, E1 and E2, receiving external rhythmic and background noise inputs, respectively, with the latter driving a local rhythm at the natural frequency of E2 (as in Fig. 5A). Bii, The less resonant input from Bi strongly suppresses an assembly driven by a nonrhythmic Poisson input with equal spike count and constant rate. Heterogeneity decreases competition and increases synchrony. Cii, Heterogeneity again decreases competition for all input frequencies and increases synchrony for frequencies >20 Hz. Dii, Eii, Similar raster plots and plots of competition and synchrony for τI = 13 ms; again, heterogeneity decreases competition and increases synchrony in a very similar manner to τI = 5 ms. Solid lines represent the f1 shown in the above raster plots. F, Plots show differences (heterogeneous – homogeneous) in mean competition and synchrony for τ = 5 ms plotted as f1 against f2 on separate axes. G, Same as F except τ = 13 ms.