aeif_cond_exp

aeif_cond_exp - Conductance based exponential integrate-and-fire neuron model

Description

aeif_cond_exp is the adaptive exponential integrate and fire neuron according to Brette and Gerstner (2005), with post-synaptic conductances in the form of truncated exponentials.

The membrane potential is given by the following differential equation:

\[\begin{split}C_m \frac{dV_m}{dt} = -g_L(V_m-E_L)+g_L\Delta_T\exp\left(\frac{V_m-V_{th}}{\Delta_T}\right) - g_e(t)(V_m-E_e) \\ -g_i(t)(V_m-E_i)-w +I_e\end{split}\]

and

\[\tau_w \frac{dw}{dt} = a(V_m-E_L) - w\]

Note that the membrane potential can diverge to positive infinity due to the exponential term. To avoid numerical instabilities, instead of \(V_m\), the value \(\min(V_m,V_{peak})\) is used in the dynamical equations.

References

1

Brette R and Gerstner W (2005). Adaptive exponential integrate-and-fire model as an effective description of neuronal activity. Journal of Neurophysiology. 943637-3642 DOI: https://doi.org/10.1152/jn.00686.2005

See also

iaf_cond_exp, aeif_cond_alpha

Parameters

Name

Physical unit

Default value

Description

C_m

pF

281.0pF

membrane parametersMembrane Capacitance

t_ref

ms

0.0ms

Refractory period

V_reset

mV

-60.0mV

Reset Potential

g_L

nS

30.0nS

Leak Conductance

E_L

mV

-70.6mV

Leak reversal Potential (aka resting potential)

a

nS

4nS

spike adaptation parametersSubthreshold adaptation.

b

pA

80.5pA

Spike-trigg_exred adaptation.

Delta_T

mV

2.0mV

Slope factor

tau_w

ms

144.0ms

Adaptation time constant

V_th

mV

-50.4mV

Threshold Potential

V_peak

mV

0mV

Spike detection threshold.

E_ex

mV

0mV

synaptic parametersExcitatory reversal Potential

tau_syn_ex

ms

0.2ms

Synaptic Time Constant Excitatory Synapse

E_in

mV

-85.0mV

Inhibitory reversal Potential

tau_syn_in

ms

2.0ms

Synaptic Time Constant for Inhibitory Synapse

I_e

pA

0pA

constant external input current

State variables

Name

Physical unit

Default value

Description

V_m

mV

E_L

Membrane potential

w

pA

0pA

Spike-adaptation current

Equations

\[\frac{ dV_{m} } { dt }= \frac 1 { C_{m} } \left( { (-g_{L} \cdot (V_{bounded} - E_{L}) + I_{spike} - I_{syn,exc} - I_{syn,inh} - w + I_{e} + I_{stim}) } \right)\]
\[\frac{ dw } { dt }= \frac 1 { \tau_{w} } \left( { (a \cdot (V_{bounded} - E_{L}) - w) } \right)\]

Source code

neuron aeif_cond_exp:

  state:
    V_m mV = E_L   # Membrane potential
    w pA = 0 pA    # Spike-adaptation current
  end

  equations:
    inline V_bounded mV = min(V_m, V_peak) # prevent exponential divergence
    kernel g_in = exp(-t / tau_syn_in)
    kernel g_ex = exp(-t / tau_syn_ex)

    # Add inlines to simplify the equation definition of V_m
    inline exp_arg real = (V_bounded - V_th) / Delta_T
    inline I_spike pA = g_L * Delta_T * exp(exp_arg)
    inline I_syn_exc pA = convolve(g_ex, spikesExc) * (V_bounded - E_ex)
    inline I_syn_inh pA = convolve(g_in, spikesInh) * (V_bounded - E_in)

    V_m' = (-g_L * (V_bounded - E_L) + I_spike - I_syn_exc - I_syn_inh - w + I_e + I_stim) / C_m
    w' = (a * (V_bounded - E_L) - w) / tau_w
  end

  parameters:
    # membrane parameters
    C_m pF = 281.0 pF       # Membrane Capacitance
    t_ref ms = 0.0 ms       # Refractory period
    V_reset mV = -60.0 mV   # Reset Potential
    g_L nS = 30.0 nS        # Leak Conductance
    E_L mV = -70.6 mV       # Leak reversal Potential (aka resting potential)

    # spike adaptation parameters
    a nS = 4 nS             # Subthreshold adaptation
    b pA = 80.5 pA          # Spike-triggered adaptation
    Delta_T mV = 2.0 mV     # Slope factor
    tau_w ms = 144.0 ms     # Adaptation time constant
    V_th mV = -50.4 mV      # Threshold Potential
    V_peak mV = 0 mV        # Spike detection threshold

    # synaptic parameters
    E_ex mV = 0 mV            # Excitatory reversal Potential
    tau_syn_ex ms = 0.2 ms    # Synaptic Time Constant Excitatory Synapse
    E_in mV = -85.0 mV        # Inhibitory reversal Potential
    tau_syn_in ms = 2.0 ms    # Synaptic Time Constant for Inhibitory Synapse

    # constant external input current
    I_e pA = 0 pA
  end

  internals:
    # refractory time in steps
    RefractoryCounts integer = steps(t_ref)
    # counts number of tick during the refractory period
    r integer
  end

  input:
    spikesInh nS <- inhibitory spike
    spikesExc nS <- excitatory spike
    I_stim pA <- continuous
  end

  output: spike

  update:
    integrate_odes()

    if r > 0: # refractory
      r -= 1 # decrement refractory ticks count
      V_m = V_reset # clamp potential
    elif V_m >= V_peak: # threshold crossing detection
      r = RefractoryCounts + 1
      V_m = V_reset # clamp potential
      w += b
      emit_spike()
    end

  end

end

Characterisation

Synaptic response

aeif_cond_exp_nestml

f-I curve

aeif_cond_exp_nestml