Hi everyone !

I am new to Brian2 and I am trying to connect two conductance based point LIF neuron model through alpha synapses. Neuron n1 receives sinusoidal input and Neuron n2 receives input from neuron n1 through alpha synapse. Here is my code :

```
import pandas as pd
import numpy as np
from scipy import signal
start_scope()
seed(11922)
# Parameters
n_n1=5
n_n2=5
# Neuron Parameters
# n_n1
E_l_n1=-70*mV # Leak Reversal Potential
E_e_n1=0*mV # Excitatory synaptic reversal potential
E_i_n1=-80*mV # Inhibitory synaptic reversal potential
C_m_n1=198*pF # Membrane Capacitance
tau_n1=20*ms # Membrane time constant
g_L_n1=C_m_n1/tau_n1 # Leak conductance
tau_e_n1=5*ms # Excitatory synaptic time constant
tau_i_n1=10*ms # Inhibitory synaptic time constant
tau_r_n1=5*ms # Refractory period
V_th_n1=-55*mV # Firing threshold
V_r_n1=E_l_n1 # Reset potential
# Synapse parameters
w_e_n1=0.05*nS # Excitatory synaptic conductance
w_i_n1=1.0*nS # Inhibitory synaptic conductance
# n_n2
E_l_n2=-70*mV # Leak Reversal Potential
E_e_n2=0*mV # Excitatory synaptic reversal potential
E_i_n2=-80*mV # Inhibitory synaptic reversal potential
C_m_n2=198*pF # Membrane Capacitance
tau_n2=20*ms # Membrane time constant
g_L_n2=C_m_n2/tau_n2 # Leak conductance
tau_e_n2=5*ms # Excitatory synaptic time constant
tau_i_n2=10*ms # Inhibitory synaptic time constant
tau_r_n2=5*ms # Refractory period
V_th_n2=-53*mV # Firing threshold
V_r_n2=E_l_n2 # Reset potential
# Synapse parameters
w_e_n2=0.05*nS # Excitatory synaptic conductance
w_i_n2=1.0*nS # Inhibitory synaptic conductance
t_recorded=np.arange(int(20000*ms/defaultclock.dt))*defaultclock.dt
I_rec_1_sin=TimedArray(I1_1_sin*amp,dt=defaultclock.dt)
eqs_n1='''
dv/dt=(I_syn_e/C_m_n1)+(I/(g_L_n1*tau_n1))+(g_L_n1*(v-E_l_n1)+g_e*(v-E_e_n1)+g_i*(v-E_i_n1))/C_m_n1:volt
I_syn_e=g_e*(E_e_n1-v):amp
I=I_rec_1_sin(t):amp
dg_e/dt=(s_e-g_e)/tau_e_n1:siemens
dg_i/dt=(s_i-g_i)/tau_i_n1:siemens
ds_e/dt=-s_e/tau_e_n1:siemens
ds_i/dt=-s_i/tau_i_n1:siemens
'''
eqs_n2='''
dv/dt=(I_syn_e/C_m_n2)+(g_L_n2*(v-E_l_n2)+g_e*(v-E_e_n2)+g_i*(v-E_i_n2))/C_m_n2:volt
I_syn_e=g_e*(E_e_n2-v):amp
dg_e/dt=(s_e-g_e)/tau_e_n2:siemens
dg_i/dt=(s_i-g_i)/tau_i_n2:siemens
ds_e/dt=-s_e/tau_e_n2:siemens
ds_i/dt=-s_i/tau_i_n2:siemens
'''
G_n1=NeuronGroup(n_n1,eqs_n1,threshold='v>V_th_n1',reset='v=V_r_n1',refractory='tau_r_n1',method='rk2')
G_n2=NeuronGroup(n_n2,eqs_n2,threshold='v>V_th_n2',reset='v=V_r_n2',refractory='tau_r_n2',method='rk2')
# Random initial membrane potential values and conductances
G_n1.v='E_l_n1+rand()*(V_th_n1-E_l_n1)'
G_n1.g_e='rand()*w_e_n1'
G_n1.g_i='rand()*w_i_n1'
G_n2.v='E_l_n2+rand()*(V_th_n2-E_l_n2)'
G_n2.g_e='rand()*w_e_n2'
G_n2.g_i='rand()*w_i_n2'
S_n1_n2=Synapses(G_n1,G_n2,on_pre='s_e+=w_e_n1',method='rk2')
S_n1_n2.connect(p=0.5)
# Record the spikes
M_n1=SpikeMonitor(G_n1)
M_n2=SpikeMonitor(G_n2)
# Record the membrane voltage
V_n1=StateMonitor(G_n1,'v',record=True)
V_n2=StateMonitor(G_n2,'v',record=True)
run(20*second)
```

I found that neuron n2 is not spiking at all inspite of increasing Excitatory synaptic conductance of neuron n1 (which I am using to increment variable s_e while making synaptic connection from n1 to n2. Is my implementation of conductance based neuron with alpha synapses correct ?

Hoping for an early response.

Thanks and Regards

Shavika Rastogi

PhD Scholar