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spm_DEM_MEG.m
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Mon, Mar 3, 05:16

spm_DEM_MEG.m
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function [R] = spm_DEM_MEG(DEM,dt,n,graphics)
% as for spm_DEM_EEG but plots the causal and hidden errors
% FORMAT [R] = spm_DEM_MEG(DEM,dt,n,graphics)
% DEM - DEM structure
% dt - time bin (seconds)
% n - level[s]
% g - graphics switch
%
% R{i} - response over peri-stimulus time (whitened error): level i
%
% These simulated response assume that LFPs are generated by superficial
% pyramidal cells that correspond to units encoding precision-weighted
% prediction error.
%
% see also spm_DEM_ERP
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging
% Karl Friston
% $Id: spm_DEM_MEG.m 4187 2011-02-01 20:13:57Z karl $
% defaults
%--------------------------------------------------------------------------
if ~nargout; graphics = 1; end
try
dt;
catch
try
dt = DEM.U.dt;
catch
dt = 1;
end
end
try, n; catch, n = 1; end
try, graphics; catch, graphics = 0; end
% loop over hierarchical (cortical) levels
%--------------------------------------------------------------------------
if graphics, hold off; end
z = DEM.qU.z;
w = DEM.qU.w;
pst = [1:size(z{1},2)]*dt*1000;
for k = 1:length(n)
% level
%----------------------------------------------------------------------
i = n(k);
% precisions
%----------------------------------------------------------------------
V = DEM.M(i).V;
h = DEM.M(i).hE;
for j = 1:length(h)
V = V + DEM.M(i).Q{j}*exp(h(j));
end
% precisions
%----------------------------------------------------------------------
W = DEM.M(i).W;
g = DEM.M(i).gE;
for j = 1:length(DEM.qH.g{i})
W = W + DEM.M(i).R{j}*exp(g(j));
end
% ERPs
%----------------------------------------------------------------------
R{k,1} = spm_sqrtm(V)*z{i};
try
R{k,2} = spm_sqrtm(W)*w{i};
end
if graphics
plot(pst,R{k,1},'r'), hold on
try
plot(pst,R{k,2},'r:')
end
end
end
% labels
%--------------------------------------------------------------------------
if graphics
xlabel('peristimulus time (ms)')
ylabel('LFP (micro-volts)')
box on
hold off
drawnow
end

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