Tutorial 14: Noise covariance

Authors: Francois Tadel, Elizabeth Bock, John C Mosher, Sylvain Baillet

From continuous tutorials:

Noise covariance matrix

To estimate the sources properly, we need an estimation of the noise level for each sensor. A good way to do this is to compute the covariance matrix of the concatenation of the baselines from all the trials in both conditions.

• Select at the same time the two groups of trials (right and left). To do this: hold the Control (or Cmd on Macs) key and click successively on the Right and the Left trial lists.

• Right-click on one of them and select: Noise covariance > Compute from recordings. Set the baseline to [-104,-5] ms, to consider as noise everything that happens before the beginning of the stimulation artifact. Leave the other options to the default values. Click on Ok.

• This operation computes the noise covariance matrix based on the baseline of all the good trials (199 files). The result is stored in a new file "Noise covariance" in the (Common files) folder.