function V = lifModel(~, V,opt)
% t - Time in msec.
% V - Membrane potential in Volts.
% opt - Structure with fields:
% * dt - Time simulated in one step in milli seconds.
% * V_PEAK - Peak value for membrane potential in Volts.
% * V_RESET - Reset value for membrane potential in Volts.
% * V_TH - Threshold voltage for spike in Volts.
% V - Updated membrane potential in Volts.
% Leaky Integrate and Fire (LIF) model.
% Florian Raudies, 09/07/2014, Boston University.
dt = opt.dt; % Step width in milli seconds
V_PEAK = opt.V_PEAK; % Peak value in Volts.
V_RESET = opt.V_RESET; % Reset value in Volts.
V_TH = opt.V_TH; % Threshold value in Volts.
C_MEM = 5.5; % Membrane capacitance in nano Farad.
G_LEAK = 10; % Membrance leaky conductance in nano Siemens.
% Does any of the potentials have the peak value or above?
AbovePeak = V>=V_PEAK;
% If they have they have the peak value or above then reset.
% Does any of the potentials reach a value above threshold?
AboveTh = V>V_TH;
% If a potental is above threshold set it to the peak value.
V(AboveTh) = V_PEAK;
% Update all membrane potentials not updated thus far by using the lif eq.
Update = ~AbovePeak & ~AboveTh;
V(Update) = V(Update) + dt*10^-3*(G_LEAK/C_MEM*(V_RESET-V(Update)) ...