Table 2.

Overview of technical terms and analysis metrics.

Abbreviation	Description
RNN	Recurrent neural network (RNN) of one E-I pair of synaptically coupled populations*.
STP-RNN & Static-RNN	A RNN composed of synaptic connections with short-term plasticity (STP-RNN) which renders the synaptic efficacies dynamic over time. The RNN with constant efficacies is a Static-RNN†.
Frozen STP-RNN	A STP-RNN with the synaptic efficacies frozen e.g. at the FP; thus, a Static-RNN-type model$.
E r-I r-plane	A 2D phase plane of E- and I-population activity rates ($I_{\mathrm{r}}$ vs. $E_{\mathrm{r}}$)‡.
FP	A fixed point (FP) is the steady state of a network, and is determined as the intersection of (quasi) E r- and I r- nullclines in the E r-I r-plane‡.
Spontaneous activity	Network activity in the absence of stimulus (or sensory input)*.
Attractor	A non-quiescent stable FP (in this paper); also known as memory or persistent activity state.
Attraction domain	For a stable FP (in this paper), a region in phase plane comprising all initial conditions that lead to that FP.
Amplification-threshold	The outer border of the attraction domain of the rest state in the Frozen STP-RNN, beyond which network perturbations undergo an overall continuous growing (in the Frozen STP-RNN) or will effectively trigger cluster activity (in the STP-RNN).
Nullcline	For example, an excitatory nullcline is a set of points (a curve) in E r-I r-plane for which $d{E}_{\mathrm{r}}/dt=0$ ‡.
FP-domain	For example, an unstable FP-domain is a domain of all potential FPs in the E r-I r-plane, at which the network will be unstable¶.
$AOD$	Area of domain (AOD); for example, AOD Unstable is the area of the unstable FP-domain¶.
ISN	Inhibition-stabilized network (vs. Non-ISN) which requires sufficiently strong, dynamic inhibitory feedback to preserve its overall stability.§
AOD ISN/Unstable	=AOD ISN/AOD Unstable; this ratio is used to measure the relative area of the ISN FP-domain vs. unstable FP-domain¶.
PS	The near coincident firing of many neurons is often referred to as population spike (PS)#.
Cluster activity	Network spike (PSnet), which involves both E- and I-populations; i.e. both PSE and PSI #.
$P{S}_{\mathrm{net}}^{\mathrm{amp}}$	The scaled amplitude of PSnet, which provides a qualitative approximation to the cluster activity size#.

This table lists the descriptions for abbreviations and definitions which we used in our study. The sections in Supplementary Methods providing detailed descriptions: *Model description, ^†STP-RNN, ^$Frozen STP-RNN, ^‡Computation of 2D phase planes, ^¶Operational FP-domains, ^§Characterization of operating regimes, and ^#Population spike.