Changed dynamic of Izhikevich neuron, now it is:
dV[t+1]/dt = k*(Vm[t] - Vr)*(Vm[t] - Vt) - Um[t] + Ie[t] + Isyn[t]
if ( Um[t] < Vr ):
	dU[t+1]/dt = a*(b_1*(Vm[t] - Vb)**p_1 - Um[t]);
else:
	dU[t+1]/dt = a*(b_2*(Vm[t] - Vb)**p_2 - Um[t]);

if V[t+1] > Vpeak:
	V[t+1] = c
	U[t+1] = U[t+1] + d