Figure 2

Signatures of criticality as a function of the cortical spiking variability. (a) Scaling relation across the variability spectrum per animal (five urethane-anesthetized rats), where open (filled) symbols correspond to the left (right) side of Eq. (4). Each animal is represented by a different symbol type. (b) Group data for the rat experiments shown in (a). (b),(e) Solid thin (solid thick) line corresponds to the left (right) side of Eq. (4). The shadow around each curve represents its standard deviation. The dashed curve represents the relative residence time across CV values. Gray stripe in (b) represents the critical value of ⟨ CV ⟩ * = 1.4 ± 0.2 , where Eq. (4) holds, considering the standard deviations. (c) Power-law relation between size and lifetime of spike avalanches across different levels of spiking variability [same symbols as Fig. 1]. (d) Group data of the DFA exponent α as a function of the difference between the scaling properties in (b). (Inset) Root-mean-squared fluctuation F of the detrended time series of the firing rates vs window width w , across different levels of spiking variability [symbols as in (c)]. (e) Group data of scaling relation [Eq. (4)] across the variability spectrum for freely moving mice ( n = 14 , N B = 10 and Δ T = 25 ms ). Lines as in (b), with ⟨ CV ⟩ * = 1.1 ± 0.2 . (f) Scaling relation across the variability spectrum for one anesthetized monkey. Lines as in (b). (g) Linear relation between the size and lifetime critical exponents across animals. We also plot other experimental results from the ex vivo visual cortex of the turtle [28], cortical slices of the rat brain [25], freely moving mice [23], and one anesthetized monkey [22], as well as those obtained by a model [15, 29]. Lower (upper) hatched regions represent the values (within standard deviations) of ( τ , τ t ) at ⟨ CV ⟩ * for the urethane-anesthetized rats (freely moving mice).