[FieldTrip] ICA and covariance matrix for CSP

[Bethel Osuagwu]

Hi Everyone,

I want to ask a general mathematical question relating to ICA and common spatial pattern. Hopefully someone will help me out.

I have noticed that after using ICA to remove artifact in my signal, I can no longer compute the covariance matrices needed for common spatial pattern without matlab giving me warning regarding the accuracy of the estimated matrix. Indeed the estimated matrix is not accurate. This does not happen if I use only a small subset of my channels after removing noise with ICA.  If I do not use ICA at all the warning disappears.

I want to ask if anybody knows why ICA causes this issue and how I can fix it.

Thanks a lot.
Bethel Osuagwu