Changes in population rate dynamics can explain increasing similarity of spontaneous and evoked word distributions with development. A, The key experimental findings of . Top, KLdiv between spontaneous spiking activity [S], and activity during presentation of natural movies [M] in juvenile and adult ferrets. Bottom, KLdiv between the word distributions in actual data [M or S] and the word distributions predicted by MFR alone [M̃ or S̃, respectively]. B, Parameters of the raster marginals model used to reproduce the data in A. Top, MFRs on 16 electrodes. The MFRs of the 16 “S” (“spontaneous”) spike trains were drawn from a normal distribution with μ = 20 spikes/s, σ = 15 spikes/s, and μ = 60 spikes/s, σ = 45 spikes/s, for “juveniles” and “adults,” respectively. The “M” (“natural movie”) rates were obtained by multiplying the spontaneous rate of each spike train by a coefficient drawn from a normal distribution with μ = 2, σ = 0.5, and μ = 1.25, σ = 0.125, for juveniles and adults, respectively. Bottom, PRds, taken to be shifted lognormal as in cat V1 (see Materials and Methods). Blue and green points indicate parameters used to create synthetic juvenile and adult rasters, respectively. C, Comparison of the spontaneous and evoked word distributions produced by the model for the juvenile (top) and adult (bottom) conditions. D, Summary statistics for the raster marginals model, shown in the same format as A. Error bars indicate SDs over 100 repeats, one of which is shown in B and C.