terub_gpe

terub_gpe - Terman Rubin neuron model

Description

terub_gpe is an implementation of a spiking neuron using the Terman Rubin model based on the Hodgkin-Huxley formalism.

  1. Post-syaptic currents: Incoming spike events induce a post-synaptic change of current modelled by an alpha function. The alpha function is normalised such that an event of weight 1.0 results in a peak current of 1 pA.

  2. Spike Detection: Spike detection is done by a combined threshold-and-local-maximum search: if there is a local maximum above a certain threshold of the membrane potential, it is considered a spike.

References

1

Terman, D. and Rubin, J.E. and Yew, A. C. and Wilson, C.J. Activity Patterns in a Model for the Subthalamopallidal Network of the Basal Ganglia The Journal of Neuroscience, 22(7), 2963-2976 (2002)

2

Rubin, J.E. and Terman, D. High Frequency Stimulation of the Subthalamic Nucleus Eliminates Pathological Thalamic Rhythmicity in a Computational Model Journal of Computational Neuroscience, 16, 211-235 (2004)

Author

Martin Ebert

Parameters

Name

Physical unit

Default value

Description

E_L

mV

-55mV

Resting membrane potential.

g_L

nS

0.1nS

Leak conductance.

C_m

pF

1.0pF

Capacity of the membrane.

E_Na

mV

55mV

Sodium reversal potential.

g_Na

nS

120nS

Sodium peak conductance.

E_K

mV

-80.0mV

Potassium reversal potential.

g_K

nS

30.0nS

Potassium peak conductance.

E_Ca

mV

120mV

Calcium reversal potential.

g_Ca

nS

0.15nS

Calcium peak conductance.

g_T

nS

0.5nS

T-type Calcium channel peak conductance.

g_ahp

nS

30nS

afterpolarization current peak conductance.

tau_syn_ex

ms

1.0ms

Rise time of the excitatory synaptic alpha function.

tau_syn_in

ms

12.5ms

Rise time of the inhibitory synaptic alpha function.

E_gg

mV

-100mV

reversal potential for inhibitory input (from GPe)

t_ref

ms

2ms

refractory time

I_e

pA

0pA

constant external input current

State variables

Name

Physical unit

Default value

Description

V_m

mV

E_L

Membrane potential

gate_h

real

0.0

gating variable h

gate_n

real

0.0

gating variable n

gate_r

real

0.0

gating variable r

Ca_con

real

0.0

gating variable r

Equations

\[\frac{ dV_{m} } { dt }= \frac 1 { C_{m} } \left( { (-(I_{Na} + I_{K} + I_{L} + I_{T} + I_{Ca} + I_{ahp}) \cdot \mathrm{pA} + I_{e} + I_{stim} + I_{ex,mod} \cdot \mathrm{pA} + I_{in,mod} \cdot \mathrm{pA}) } \right)\]
\[\frac{ dgate_{h} } { dt }= \frac 1 { \mathrm{ms} } \left( { g_{\phi,h} \cdot (\frac{ (h_{\infty} - gate_{h}) } { \tau_{h} }) } \right)\]
\[\frac{ dgate_{n} } { dt }= \frac 1 { \mathrm{ms} } \left( { g_{\phi,n} \cdot (\frac{ (n_{\infty} - gate_{n}) } { \tau_{n} }) } \right)\]
\[\frac{ dgate_{r} } { dt }= \frac 1 { \mathrm{ms} } \left( { g_{\phi,r} \cdot (\frac{ (r_{\infty} - gate_{r}) } { \tau_{r} }) } \right)\]
\[\frac{ dCa_{con} } { dt }= g_{\epsilon} \cdot (-I_{Ca} - I_{T} - g_{k,Ca} \cdot Ca_{con})\]

Source code

neuron terub_gpe:
  state:
    r integer = 0 # counts number of tick during the refractory period

    V_m mV = E_L #  Membrane potential

    gate_h     real = 0.0 # gating variable h
    gate_n     real = 0.0 # gating variable n
    gate_r     real = 0.0 # gating variable r
    Ca_con     real = 0.0 # gating variable r
  end

  equations:
    # Parameters for Terman Rubin GPe Neuron
    inline g_tau_n_0 ms = 0.05 ms
    inline g_tau_n_1 ms = 0.27 ms
    inline g_theta_n_tau mV = -40.0 mV
    inline g_sigma_n_tau mV = -12.0 mV

    inline g_tau_h_0 ms = 0.05 ms
    inline g_tau_h_1 ms = 0.27 ms
    inline g_theta_h_tau mV = -40.0 mV
    inline g_sigma_h_tau mV = -12.0 mV
    inline g_tau_r ms = 30.0 ms

    # steady state values for gating variables
    inline g_theta_a mV = -57.0 mV
    inline g_sigma_a mV =  2.0 mV
    inline g_theta_h mV = -58.0 mV
    inline g_sigma_h mV = -12.0 mV
    inline g_theta_m mV = -37.0 mV
    inline g_sigma_m mV = 10.0 mV
    inline g_theta_n mV = -50.0 mV
    inline g_sigma_n mV = 14.0 mV
    inline g_theta_r mV = -70.0 mV
    inline g_sigma_r mV = -2.0 mV
    inline g_theta_s mV = -35.0 mV
    inline g_sigma_s mV = 2.0 mV

    # time evolvement of gating variables
    inline g_phi_h real =  0.05
    inline g_phi_n real =  0.1 #Report: 0.1, Terman Rubin 2002: 0.05
    inline g_phi_r real = 1.0

    # Calcium concentration and afterhyperpolarization current
    inline g_epsilon 1/ms =  0.0001 /ms
    inline g_k_Ca real = 15.0 #Report:15,  Terman Rubin 2002: 20.0
    inline g_k1 real = 30.0

    inline I_ex_mod real = -convolve(g_ex, spikeExc) * V_m
    inline I_in_mod real = convolve(g_in, spikeInh) * (V_m-E_gg)

    inline tau_n real = g_tau_n_0 + g_tau_n_1 / (1. + exp(-(V_m-g_theta_n_tau)/g_sigma_n_tau))
    inline tau_h real = g_tau_h_0 + g_tau_h_1 / (1. + exp(-(V_m-g_theta_h_tau)/g_sigma_h_tau))
    inline tau_r real = g_tau_r

    inline a_inf real = 1. / (1. + exp(-(V_m-g_theta_a)/g_sigma_a))
    inline h_inf real = 1. / (1. + exp(-(V_m-g_theta_h)/g_sigma_h))
    inline m_inf real = 1. / (1. + exp(-(V_m-g_theta_m)/g_sigma_m))
    inline n_inf real = 1. / (1. + exp(-(V_m-g_theta_n)/g_sigma_n))
    inline r_inf real = 1. / (1. + exp(-(V_m-g_theta_r)/g_sigma_r))
    inline s_inf real = 1. / (1. + exp(-(V_m-g_theta_s)/g_sigma_s))

    inline I_Na  real =  g_Na  * m_inf * m_inf * m_inf * gate_h    * (V_m - E_Na)
    inline I_K   real =  g_K   * gate_n * gate_n * gate_n * gate_n * (V_m - E_K )
    inline I_L   real =  g_L                                       * (V_m - E_L )
    inline I_T   real =  g_T   * a_inf* a_inf * a_inf * gate_r     * (V_m - E_Ca)
    inline I_Ca  real =  g_Ca  * s_inf * s_inf                     * (V_m - E_Ca)
    inline I_ahp real =  g_ahp * (Ca_con / (Ca_con + g_k1))        * (V_m - E_K )

    # synapses: alpha functions
    ## alpha function for the g_in
    kernel g_in = (e/tau_syn_in) * t * exp(-t/tau_syn_in)
    ## alpha function for the g_ex
    kernel g_ex = (e/tau_syn_ex) * t * exp(-t/tau_syn_ex)

    # V dot -- synaptic input are currents, inhib current is negative
    V_m' = ( -(I_Na + I_K + I_L + I_T + I_Ca + I_ahp) * pA + I_e + I_stim + I_ex_mod * pA + I_in_mod * pA) / C_m

    # channel dynamics
    gate_h' = g_phi_h *((h_inf-gate_h) / tau_h) / ms # h-variable
    gate_n' = g_phi_n *((n_inf-gate_n) / tau_n) / ms # n-variable
    gate_r' = g_phi_r *((r_inf-gate_r) / tau_r) / ms # r-variable

    # Calcium concentration
    Ca_con' = g_epsilon*(-I_Ca - I_T - g_k_Ca * Ca_con)
  end

  parameters:
    E_L        mV = -55 mV  # Resting membrane potential.
    g_L        nS = 0.1 nS  # Leak conductance.
    C_m        pF = 1.0 pF # Capacity of the membrane.
    E_Na       mV = 55 mV   # Sodium reversal potential.
    g_Na       nS = 120 nS # Sodium peak conductance.
    E_K        mV = -80.0 mV# Potassium reversal potential.
    g_K        nS = 30.0 nS # Potassium peak conductance.
    E_Ca       mV = 120 mV  # Calcium reversal potential.
    g_Ca       nS = 0.15 nS # Calcium peak conductance.
    g_T        nS = 0.5 nS  # T-type Calcium channel peak conductance.
    g_ahp      nS = 30 nS   # afterpolarization current peak conductance.
    tau_syn_ex ms = 1.0 ms  # Rise time of the excitatory synaptic alpha function.
    tau_syn_in ms = 12.5 ms # Rise time of the inhibitory synaptic alpha function.
    E_gg       mV = -100 mV # reversal potential for inhibitory input (from GPe)
    t_ref      ms = 2 ms    # refractory time

    # constant external input current
    I_e pA = 0 pA
  end

  internals:
    refractory_counts integer = steps(t_ref)
  end

  input:
    spikeInh nS <- inhibitory spike
    spikeExc nS <- excitatory spike
    I_stim pA <- continuous
  end

  output: spike

  update:
    U_old mV = V_m
    integrate_odes()

    # sending spikes: crossing 0 mV, pseudo-refractoriness and local maximum...
    if r > 0:
      r -= 1
    elif V_m > 0 mV and U_old > V_m:
      r = refractory_counts
      emit_spike()
    end

  end

end

Characterisation