% % FH_run.m % % Interface to solve the FitzHugh-Nagumo equations and plot: % subplot1 Voltage response and recovery response (over time) % subplot2) V versus R % % Tamara Hayes, BME-OHSU 03/07 (modified from: Pat Roberts, 01/07) % clear all; %--- Set parameters for Fitzhugh-Nagumo equations --------------- % Wilson's values Tau = 0.1; % time constant of voltage response TauR = 0.5; % Time constant of the recovery response a = 1.25; % constant modifying voltage contribution to dR/dt b = 1; % constant modifying recovery contribution to dR/dt c = 1.5; % constant added to dR/dt FH_param = [Tau TauR a b c]; % Load parameter vector % stimulus parameters tstop = 20; % Duration of simulation del = 2; % delay in start of stimulus dur = 5; % duration of stimulus I = -3.0; % Input stimulus amplitude (modifying dV/dt) stim_param = [del dur I]; % Load parameter vector %--- Compute variables ------------------------------------------- X0 = [-1.5 -3/8]'; % initial values of [V, R] : steady state with no input [t,x] = ode23(@fhp,[0 tstop],X0,[],FH_param,stim_param); % Runge-Kutta algorithm %--- Plotting functions ------------------------------------------- f1=figure('Color', 'w', 'Name', sprintf('Fitzhugh-Nugamo: stimulus %5.2f (%3.1fs starting %3.1f)', I, dur,del)); % Isocline without stimulus Xiso = -3.2:0.01:3.2; % X for Isoclines Isocline1 = Xiso - Xiso.^3/3; Isocline2 = Xiso*a + c; % Isocline with stimulus IsoclineS1 = Xiso - Xiso.^3/3 + I; IsoclineS2 = Xiso*a + c; % Plot voltage, recovery, and stimulus variables subplot('Position', [.1 .4 .375 .55]) plot(t,x(:,1), 'b',t,x(:,2), 'r') ylabel('V (blue), R(red)','fontsize',14) subplot('Position', [.1 .125 .375 .175]) Ptime = 0:0.1:tstop; stim=zeros([length(Ptime), 1]); stim(find(Ptime>del & Ptime