Inserting data into matrix of zeros from another matrix

I have a matrix [signal] of 315954x64 of signal data. In another matrix [state.Flashing] (315954x1) there is logical 1 or 0 depending on an activation

I have categorized the signal matrix to obtain a matrix [FFsignal] (155520x64) of data when there is an activation:

for i = 1:length(signal)
FFlash = find (state.Flashing(1:i,1)==1);  
end

FFsignal= signal(FFlash);

I want to graph these activations(64 diff channels) with the x axis the scale of the signal(315954) so I need matrices of similar dimensions so I wanted to insert the categorized data into a matrix of zeros of size (315954x64)

For example the first group of activation is in rows 631-654 and when categorized I have data for those time points. I want to add this data to a matrix of zeros in the same time points if possible. Therego, zeros until 631-654 and so on through the 315954 rows. Please help and of course thanks in advance!!

[Shane Hagen]

I have edited this to be more clear