Hi,
For the code snippet you have provided, here are some modifications that will work.
% Create contrived image
img = 1500*rand(100,100);
% Create contrived image
img = 1500*rand(100,100);
% Create contrived statistic
stat = 10*rand(100,100);
% Create and filter contrived significance value to p <= 0.05
sig = rand(100,100);
sig_thresh = zeros(size(sig));
sig_thresh(find(sig<=0.05)) = 1;
f = figure;
ax1 = axes('Parent',f); set(ax1,'Visible','off');
ax2 = axes('Parent',f); set(ax2,'Visible','off');
h_beta=imshow(img,'InitialMagnification',800,'DisplayRange',[1 1500],'Parent',ax1); % Psuedo MR image
ax1.Colormap = gray;
hold on;
h_stat=imshow(stat,'InitialMagnification',800,'DisplayRange',[0 10],'Parent',ax2); % Pseudo stat map
ax2.Colormap = jet;
% Make non-significant stat pixels transparent
set(h_stat,'AlphaData',sig_thresh)