Try,
a = [0 0 0 0]; %where "a" would be your data channel number
a2 = [1 1 1 1];
b = [1 2 3 4]; %where "b" would be your Frequency
c = [4 3 9 1]; %where "c" would be your actual data for each PSD
c2 = 2*c
%a2 and c2 are just more example data, so you can see multiple plots on one axis
figure
hold on
grid minor
plot3(a,b,c)
plot3(a2,b,c2)
