How to add data points to a segment when using a logical vector to index into a matrix?

Hi all,

I have a MxN double matrix A containing neural data, where M is the amount of channels and N the data points.

I have a logical vector B with a length equal to matrix A(N) containing 0's for samples when a stimulus was presented and 1's when there was no stimulus present.

My goal is to create a peri-stimulus-time plot per channel in matrix A for every presentation of the stimulus (0's in vector B).

My real question is: How do I select each stimulus window (0's) plus 1 second before and after the stimulus?

*my sampling frequency is 20000Hz, the stimulus window is 200 msec and there is a 3.023 seconds stimulus interval (In case this information is needed).