Figure 3.

Sparsification process in developing cortex. (a) Postnatal changes of the network’s stationary firing dynamics. The same format is used as in Fig. 1b; unstable dynamics (yellow region), ISN (light-yellow region), and Non-ISN (pink region). (b) The existence of a hidden unstable state (black dot) in the firing activity of developing networks. The same format is used as in Fig. 2e, panel I. The networks were frozen at the rest state ($t=-150$ ms). (c) Postnatal changes of the network’s transient firing dynamics where cluster activity was triggered by an impulse perturbation. The same format is used as in Fig. 1c. P3: early period of physiological blindness, P10: a few days before eye-opening, P14: the day after eye-opening, and P20: a few days after eye-opening. Green dots represent the stable FPs. (d) Developmental changes in the size of cluster activities, estimated qualitatively by $P{S}_{\mathrm{net}}^{\mathrm{amp}}$. (e) Developmental changes in the area of the FP-domain (AOD) of Non-ISN and ISN operating regimes, and the ratio AOD _ISN/Unstable of areas of ISN and unstable FP-domains. The developmental increase in AOD _ISN/Unstable indicates that the unstable FP-domain was effectively decreased, and replaced by the ISN FP-domain. For each panel, the values were normalized to the maximum value during all four stages. At each of these stages, the AOD s were computed based on the square E _r-I _r-plane with the lower-left corner located at the rest state (origin) and the upper-right corner (i.e. $[E_{\mathrm{r}}^{\max },I_{\mathrm{r}}^{\max }]$) at [10,10] Hz. Moreover, the developmental decrease in $AO{D}_{\mathrm{Non}-\mathrm{ISN}}$ just means that the E-activity rate after which the Non-ISN FP-domain starts in the E _r-I _r-plane, was shifted to higher levels. See Table 2 for details about technical terms.