Parameters & Units

All physical quantities in the codebase use the same unit system: ms for time, mV for voltage, nF for capacitance, μS for conductance, nA for current, Hz for rates. Time fields carry an explicit _ms suffix (sim_ms, ref_ms_E, tau_gaba); CLI flags follow the same convention (—t-ms 600). A Δt of 1 means 1 ms, not 1 s.

Quantities

Quantity	Unit	Typical value	Variable
Integration step	ms	0.25	dt, DT_MS
Simulation length	ms	600	sim_ms
Membrane time constant	ms	20 (E), 5 (I)	tau_m_E, tau_m_I
Refractory period	ms	3 (E), 1.5 (I)	ref_ms_E, ref_ms_I
AMPA decay	ms	2	tau_ampa
GABA decay	ms	9	tau_gaba
Resting / leak potential	mV	−65	E_L
Spike threshold	mV	−50	V_th
Reset potential	mV	−65	V_reset
AMPA reversal	mV	0	E_e
GABA reversal	mV	−80	E_i
Membrane capacitance	nF	1.0 (E), 0.5 (I)	C_m_E, C_m_I
Leak conductance	μS	0.05 (E), 0.1 (I)	g_L_E, g_L_I
External drive	μS	0.0006 (async), 0.003 (PING)	t_e_async, t_e_ping
Input current (CUBA)	nA	20 per spike	input_scale
CUBA weight std	nA	32	W_STD_CUBA
Max input rate	Hz	25	max_rate_hz
Population firing rate	Hz	20–80	r_E, r_I
Gamma frequency	Hz	30–80	f_0

COBA / PING biophysical constants

Used by COBA and PING on the model ladder. Values follow neuroscience conventions (cf. Dayan & Abbott, Gerstner Neuronal Dynamics); the E:I asymmetry in $\tau_m, C_m, g_L, \tau_{\text{ref}}$ produces the timescale separation that makes PING dynamics possible.

Parameter	E population	I population
$\tau_m$ (ms)	20	5
$C_m$ (nF)	1.0	0.5
$g_L$ (µS)	0.05	0.1
$\tau_{\text{ref}}$ (ms)	3	1.5
$E_L$ (mV)	−65	−65
$V_{\text{th}}$ (mV)	−50	−50
$V_{\text{reset}}$ (mV)	−65	−65
$E_e$ (mV, reversal)	0	0
$E_i$ (mV, reversal)	−80	−80

Synapse time constants: $\tau_{\text{AMPA}} = 2$ ms (excitation), $\tau_{\text{GABA}} = 9$ ms (inhibition). These set the ceiling on PING’s Δt-stability: once $\Delta t \gtrsim \tau_{\text{GABA}}$ the E→I→E loop cannot complete within one step.

Internal consistency

The chosen units are self-consistent — no conversion factors appear in the integration code. Two equations carry the whole system.

The membrane time constant is $\tau = C / g$ . With $C$ in nF and $g$ in μS,

\tau_{[\text{ms}]} = \frac{C_{[\text{nF}]}}{g_{[\text{μS}]}}

so $C_m = 1$ nF and $g_L = 0.05$ μS give $\tau_m = 20$ ms directly.

The LIF voltage update is $dv = (\Delta t / C)(-g_L(v - E_L) + I)$ . With $\Delta t$ in ms, $C$ in nF, $v, E$ in mV, $g$ in μS, and $I$ in nA,

dv_{[\text{mV}]} = \frac{\Delta t_{[\text{ms}]}}{C_{[\text{nF}]}} \cdot I_{[\text{nA}]}

because ms·nA / nF = mV exactly.

Conductance-current products share the same ledger: $g(v - E)$ is μS × mV = nA, so synaptic currents fold into $I$ alongside any direct input current without a scale factor.

Why not SI?

Pure SI (F, S, V, A, s) forces every value to a large negative exponent — $C_m = 10^{-9}$ F, $g_L = 5 \times 10^{-8}$ S, $\Delta t = 2.5 \times 10^{-4}$ s. The neuroscience convention (ms, mV, nF, μS, nA) keeps every typical value between $10^{-3}$ and $10^2$ , which makes numerical debugging and human intuition faster. The tradeoff is that readers have to trust the unit consistency rather than verify it by plugging into SI formulas — this page is here so that trust is auditable.