function [tt,xxs]=BGCT_subfun(delay,v_sr,open1,open2)
% This MATLAB code is a subfunction version of BGCT model described in the
% following paper:
% Title: Bidirectional Control of Absence Seizures by the Basal Ganglia: A
% Computational Evidence (2014)
% Authors: Mingming Chen, Daqing Guo*, Tiebin Wang, Wei Jing, Yang Xia, Peng Xu,
% Cheng Luo, Pedro A. Valdes-Sosa1, and Dezhong Yao*
% Journal: PLoS Computational Biology
% Emails: twqylsf@gmail.com and dqguo@uestc.edu.cn
%
% Parameters: "open1" and "open2" are gating parameters for the SNr-TRN
% pathway and SNr-SRN pathway, with 1 open and 0 close;
% "delay" represents GABA_B delay paramter;
% "v_sr" is the coupling strength of the TRN-SRN pathway
%
rand('state', sum(100*clock));
dt=0.00005; % Intergation step
time=13; % Simulation time
% open1=1; % SNr-TRN pathway, 1 open and 0 close
% open2=1; % SNr-SRN pathway, 1 open and 0 close
KK=1; % Scale factor
% Maximum firing rate (Table 1 A)
Qmax_i=250;
Qmax_d1=65;
Qmax_d2=65;
Qmax_p1=250;
Qmax_p2=300;
Qmax_xi=500;
Qmax_s=250;
Qmax_r=250;
% Mean firing threshold (Table 1 B)
theta_i=15e-3;
theta_d1=19e-3;
theta_d2=19e-3;
theta_p1=10e-3;
theta_p2=9e-3;
theta_xi=1e-2;
theta_s=15e-3;
theta_r=15e-3;
% Coupling strength (Table 1 C)
v_ee=1.0e-3;
v_ei=1.8e-3;
v_re=5.0e-5;
v_rs=5.0e-4;
v_d1e=1.0e-3;
v_d1d1=2.0e-4;
v_d1s=1.0e-4;
v_d2e=7.0e-4;
v_d2d2=3.0e-4;
v_d2s=5e-5;
v_p1d1=1.0e-4;
v_p1p2=3.0e-5;
v_p1xi=3e-4; % STN-SNr
v_p2d2=3.0e-4;
v_p2p2=0.75e-4;
v_p2xi=4.5e-4;
v_xip2=4.0e-5;
v_es=1.8e-3;
v_se=2.2e-3;
v_xie=0.1e-3;
v_sp1=open2*3.5e-5;
v_rp1=KK*open1*3.5e-5;
% Other parameters (Table 1 D)
gamma_e=100;
alpha=50;
beta=200;
sigma=0.006;
v_sn_phi_n=2.0e-3;
xdelay=zeros(1,ceil(delay/dt)+1);
xxs=zeros(1,time/dt);
%random initial condition
x=0.5*[0*rand;-1500+6000*rand;0.02*rand;-2*3.5*rand;0.04*rand;-0.7+1.5*rand;0.001+0.025*rand;
-0.4+rand;0.004+0.013*rand;-0.15+0.4*rand;0.0005+0.0035*rand;-0.12+0.22*rand;-0.001+0.0055*rand;
-0.1+0.2*rand;-0.09+0.1*rand;-4+7*rand;0.025*rand;-0.6+2*rand];
xm=zeros(18,1);
for t=1:time/dt
xdelay(1:end-1)=xdelay(2:end);
xdelay(end)=x(17);
S_i=Qmax_i/(1+exp(-pi/sqrt(3)*(x(3)-theta_i)/sigma));
S_d1=Qmax_d1/(1+exp(-pi/sqrt(3)*(x(5)-theta_d1)/sigma));
S_d2=Qmax_d2/(1+exp(-pi/sqrt(3)*(x(7)-theta_d2)/sigma));
S_p1=Qmax_p1/(1+exp(-pi/sqrt(3)*(x(9)-theta_p1)/sigma));
S_p2=Qmax_p2/(1+exp(-pi/sqrt(3)*(x(11)-theta_p2)/sigma));
S_xi=Qmax_xi/(1+exp(-pi/sqrt(3)*(x(13)-theta_xi)/sigma));
S_s=Qmax_s/(1+exp(-pi/sqrt(3)*(x(15)-theta_s)/sigma));
S_r=Qmax_r/(1+exp(-pi/sqrt(3)*(x(17)-theta_r)/sigma));
S_r_lag=Qmax_r/(1+exp(-pi/sqrt(3)*(xdelay(1)-theta_r)/sigma));
xm=x;
k1=dt*xm(2);
k2=dt*(xm(2)+k1/2);
k3=dt*(xm(2)+k2/2);
k4=dt*(xm(2)+k3);
x(1)=xm(1)+(k1+2*k2+2*k3+k4)/6;
k1=dt*(gamma_e^2*(-xm(1)+S_i)-2*gamma_e*xm(2));
k2=dt*(gamma_e^2*(-xm(1)+S_i)-2*gamma_e*(xm(2)+k1/2));
k3=dt*(gamma_e^2*(-xm(1)+S_i)-2*gamma_e*(xm(2)+k2/2));
k4=dt*(gamma_e^2*(-xm(1)+S_i)-2*gamma_e*(xm(2)+k3));
x(2)=xm(2)+(k1+2*k2+2*k3+k4)/6;
k1=dt*xm(4);
k2=dt*(xm(4)+k1/2);
k3=dt*(xm(4)+k2/2);
k4=dt*(xm(4)+k3);
x(3)=xm(3)+(k1+2*k2+2*k3+k4)/6;
k1=dt*(alpha*beta*(-xm(3)+v_ee*xm(1)+v_es*S_s-v_ei*S_i)-(alpha+beta)*xm(4));
k2=dt*(alpha*beta*(-xm(3)+v_ee*xm(1)+v_es*S_s-v_ei*S_i)-(alpha+beta)*(xm(4)+k1/2));
k3=dt*(alpha*beta*(-xm(3)+v_ee*xm(1)+v_es*S_s-v_ei*S_i)-(alpha+beta)*(xm(4)+k2/2));
k4=dt*(alpha*beta*(-xm(3)+v_ee*xm(1)+v_es*S_s-v_ei*S_i)-(alpha+beta)*(xm(4)+k3));
x(4)=xm(4)+(k1+2*k2+2*k3+k4)/6;
k1=dt*xm(6);
k2=dt*(xm(6)+k1/2);
k3=dt*(xm(6)+k2/2);
k4=dt*(xm(6)+k3);
x(5)=xm(5)+(k1+2*k2+2*k3+k4)/6;
k1=dt*(alpha*beta*(-xm(5)+v_d1e*xm(1)-v_d1d1*S_d1+v_d1s*S_s)-(alpha+beta)*xm(6));
k2=dt*(alpha*beta*(-xm(5)+v_d1e*xm(1)-v_d1d1*S_d1+v_d1s*S_s)-(alpha+beta)*(xm(6)+k1/2));
k3=dt*(alpha*beta*(-xm(5)+v_d1e*xm(1)-v_d1d1*S_d1+v_d1s*S_s)-(alpha+beta)*(xm(6)+k2/2));
k4=dt*(alpha*beta*(-xm(5)+v_d1e*xm(1)-v_d1d1*S_d1+v_d1s*S_s)-(alpha+beta)*(xm(6)+k3));
x(6)=xm(6)+(k1+2*k2+2*k3+k4)/6;
k1=dt*xm(8);
k2=dt*(xm(8)+k1/2);
k3=dt*(xm(8)+k2/2);
k4=dt*(xm(8)+k3);
x(7)=xm(7)+(k1+2*k2+2*k3+k4)/6;
k1=dt*(alpha*beta*(-x(7)+v_d2e*xm(1)-v_d2d2*S_d2+v_d2s*S_s)-(alpha+beta)*xm(8));
k2=dt*(alpha*beta*(-x(7)+v_d2e*xm(1)-v_d2d2*S_d2+v_d2s*S_s)-(alpha+beta)*(xm(8)+k1/2));
k3=dt*(alpha*beta*(-x(7)+v_d2e*xm(1)-v_d2d2*S_d2+v_d2s*S_s)-(alpha+beta)*(xm(8)+k2/2));
k4=dt*(alpha*beta*(-x(7)+v_d2e*xm(1)-v_d2d2*S_d2+v_d2s*S_s)-(alpha+beta)*(xm(8)+k3));
x(8)=xm(8)+(k1+2*k2+2*k3+k4)/6;
k1=dt*xm(10);
k2=dt*(xm(10)+k1/2);
k3=dt*(xm(10)+k2/2);
k4=dt*(xm(10)+k3);
x(9)=xm(9)+(k1+2*k2+2*k3+k4)/6;
k1=dt*(alpha*beta*(-xm(9)-v_p1d1*S_d1-v_p1p2*S_p2+v_p1xi*S_xi)-(alpha+beta)*xm(10));
k2=dt*(alpha*beta*(-xm(9)-v_p1d1*S_d1-v_p1p2*S_p2+v_p1xi*S_xi)-(alpha+beta)*(xm(10)+k1/2));
k3=dt*(alpha*beta*(-xm(9)-v_p1d1*S_d1-v_p1p2*S_p2+v_p1xi*S_xi)-(alpha+beta)*(xm(10)+k2/2));
k4=dt*(alpha*beta*(-xm(9)-v_p1d1*S_d1-v_p1p2*S_p2+v_p1xi*S_xi)-(alpha+beta)*(xm(10)+k3));
x(10)=xm(10)+(k1+2*k2+2*k3+k4)/6;
k1=dt*xm(12);
k2=dt*(xm(12)+k1/2);
k3=dt*(xm(12)+k2/2);
k4=dt*(xm(12)+k3);
x(11)=xm(11)+(k1+2*k2+2*k3+k4)/6;
k1=dt*(alpha*beta*(-xm(11)-v_p2d2*S_d2-v_p2p2*S_p2+v_p2xi*S_xi)-(alpha+beta)*xm(12));
k2=dt*(alpha*beta*(-xm(11)-v_p2d2*S_d2-v_p2p2*S_p2+v_p2xi*S_xi)-(alpha+beta)*(xm(12)+k1/2));
k3=dt*(alpha*beta*(-xm(11)-v_p2d2*S_d2-v_p2p2*S_p2+v_p2xi*S_xi)-(alpha+beta)*(xm(12)+k2/2));
k4=dt*(alpha*beta*(-xm(11)-v_p2d2*S_d2-v_p2p2*S_p2+v_p2xi*S_xi)-(alpha+beta)*(xm(12)+k3));
x(12)=xm(12)+(k1+2*k2+2*k3+k4)/6;
k1=dt*xm(14);
k2=dt*(xm(14)+k1/2);
k3=dt*(xm(14)+k2/2);
k4=dt*(xm(14)+k3);
x(13)=xm(13)+(k1+2*k2+2*k3+k4)/6;
k1=dt*(alpha*beta*(-xm(13)+v_xie*xm(1)-v_xip2*S_p2)-(alpha+beta)*xm(14));
k2=dt*(alpha*beta*(-xm(13)+v_xie*xm(1)-v_xip2*S_p2)-(alpha+beta)*(xm(14)+k1/2));
k3=dt*(alpha*beta*(-xm(13)+v_xie*xm(1)-v_xip2*S_p2)-(alpha+beta)*(xm(14)+k2/2));
k4=dt*(alpha*beta*(-xm(13)+v_xie*xm(1)-v_xip2*S_p2)-(alpha+beta)*(xm(14)+k3));
x(14)=xm(14)+(k1+2*k2+2*k3+k4)/6;
k1=dt*xm(16);
k2=dt*(xm(16)+k1/2);
k3=dt*(xm(16)+k2/2);
k4=dt*(xm(16)+k3);
x(15)=xm(15)+(k1+2*k2+2*k3+k4)/6;
k1=dt*(alpha*beta*(-xm(15)-v_sp1*S_p1+v_se*xm(1)-v_sr*S_r-v_sr*S_r_lag+v_sn_phi_n)-(alpha+beta)*xm(16));
k2=dt*(alpha*beta*(-xm(15)-v_sp1*S_p1+v_se*xm(1)-v_sr*S_r-v_sr*S_r_lag+v_sn_phi_n)-(alpha+beta)*(xm(16)+k1/2));
k3=dt*(alpha*beta*(-xm(15)-v_sp1*S_p1+v_se*xm(1)-v_sr*S_r-v_sr*S_r_lag+v_sn_phi_n)-(alpha+beta)*(xm(16)+k2/2));
k4=dt*(alpha*beta*(-xm(15)-v_sp1*S_p1+v_se*xm(1)-v_sr*S_r-v_sr*S_r_lag+v_sn_phi_n)-(alpha+beta)*(xm(16)+k3));
x(16)=xm(16)+(k1+2*k2+2*k3+k4)/6;
k1=dt*xm(18);
k2=dt*(xm(18)+k1/2);
k3=dt*(xm(18)+k2/2);
k4=dt*(xm(18)+k3);
x(17)=xm(17)+(k1+2*k2+2*k3+k4)/6;
k1=dt*(alpha*beta*(-xm(17)+v_rs*S_s+v_re*xm(1)-v_rp1*S_p1)-(alpha+beta)*xm(18));
k2=dt*(alpha*beta*(-xm(17)+v_rs*S_s+v_re*xm(1)-v_rp1*S_p1)-(alpha+beta)*(xm(18)+k1/2));
k3=dt*(alpha*beta*(-xm(17)+v_rs*S_s+v_re*xm(1)-v_rp1*S_p1)-(alpha+beta)*(xm(18)+k2/2));
k4=dt*(alpha*beta*(-xm(17)+v_rs*S_s+v_re*xm(1)-v_rp1*S_p1)-(alpha+beta)*(xm(18)+k3));
x(18)=xm(18)+(k1+2*k2+2*k3+k4)/6;
xxs(t)=xm(1);
end
tt=dt:dt:time;