You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: spm_fx_fmri_dcm.m
    path of file: ./repos/bspm/thirdparty/spm12
    
    the code of the file until where you have to start completion: function [y] = spm_fx_fmri_dcm(x,u,P,M)
% state equation for a two state DCM of fMRI
% responses
% FORMAT [y] = spm_fx_dcm(x,u,P,M)

    
function [y] = spm_fx_fmri_dcm(x,u,P,M)
% state equation for a two state DCM of fMRI
% responses
% FORMAT [y] = spm_fx_dcm(x,u,P,M)
% x      - state vector
%   x(:,1) - excitatory neuronal activity             ue
%   x(:,2) - vascular signal                          s
%   x(:,3) - rCBF                                  ln(f)
%   x(:,4) - venous volume                         ln(v)
%   x(:,5) - deoyxHb                               ln(q)
%   x(:,6) - inhibitory neuronal activity             ui
%
% y      - dx/dt
%__________________________________________________________________________
%
% References for state equations:
% 1. Marreiros AC, Kiebel SJ, Friston KJ. Dynamic causal modelling for 
%    fMRI: a two-state model.
%    Neuroimage. 2008 Jan 1;39(1):269-78. 
%
% 2. Stephan KE, Kasper L, Harrison LM, Daunizeau J, den Ouden HE,
%    Breakspear M, Friston KJ. Nonlinear dynamic causal models for fMRI.
%    Neuroimage 42:649-662, 2008.
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging
 
% Karl Friston
% $Id: spm_fx_fmri_dcm.m 3705 2010-02-01 20:51:28Z karl $
 
 
% hemodynamic parameters
%--------------------------------------------------------------------------
%   H(1) - signal decay                                   d(ds/dt)/ds)
%   H(2) – auto-regulation                                d(ds/dt)/df)
%   H(3) - transit time                                   (t0)
%   H(4) - exponent for Fout(v)                           (alpha)
%   H(5) - resting oxygen extraction                      (E0)
%   H(6) - ratio of intra- to extra-vascular components   (epsilon)
%          of the gradient echo signal

 
% neuronal states
%==========================================================================
 
% excitatory connections
%--------------------------------------------------------------------------
for i = 1:size(P.B,3)
    P.A = P.A + u(i)*P.B(:,:,i);
end