Figure 4.

Critical characteristics in temporal dynamics of bursts in dominant rhythms are a fundamental feature of cortical activity across the sleep–wake cycle, independent of thresholds used to define bursts. The functional form of θ- and δ-burst duration distributions is preserved for different threshold values Th imposed on the ratio R_θδ (Fig. 1). a, Probability distributions of θ-burst durations for control rats over a 24 h period (pooled data) evaluated using different Th values consistently follow the same power law behavior (red line), with a cutoff that is controlled by Th. With increasing Th the distribution cutoff shifts toward shorter burst durations. Inset, Data for different Th collapse onto a single universal function f_θ when we plot P(d)d^α versus Th^ϵd, with α = 2.4 and ϵ = 0.8. b, Rescaled distribution of δ-burst durations for control rats over a 24 h period (pooled data) obtained for different Th values collapse onto a single function following a Weibull behavior f(d; λ, β) (black line), with β = 0.71 and λ = 0.11. Distributions are rescaled by 〈d_δ〉^η, where 〈d_δ〉 is the mean δ-burst duration and η = 1.3. Inset, Distributions P_δ for different thresholds (not rescaled). c, Probability distributions of θ burst durations for VLPO-lesioned rats over a 24 h period (pooled data) evaluated using different Th values follow the same power law behavior, with a cutoff controlled by Th. Inset, Data collapse onto a single function f_θ by plotting P(d)d_α versus Th^ϵd with α = 2.8 and ϵ = 0.8 (same as for control rats in a). d, Rescaled distribution of δ-burst durations for VLPO-lesioned rats over a 24 h period (pooled data) obtained for different Th values collapse onto a single Weibull distribution f(d; λ, β) (black line) with λ = 0.12 and β = 0.72. Distributions are rescaled by .〈d_δ〉^η., with η = 1.3. Inset, Distributions P_δ for different thresholds Th (not rescaled). Results in all panels are obtained for a fixed scale of analysis, keeping the window size w = 4 s (Fig. 1). Results are consistent when considering separately light and dark periods (Figs. 5, 6).