Hello,
For many repetitions in my experiments I have observed a discontinuity
in the raw MEG data. This happens in some of my individual trials, and
it is not always across several channels simultaneously. The attached
picture shows an example of this type of noise, for a particular trial
and channel. When I notice such pattern during recordings, reheating
the sensor usually works. However, I don't catch them all the time, so
it's often the case that I see this pattern in recorded data. These
are my questions:
1) What causes this noise? Can the channel be "trusted" even if it
shows the pattern a few times?
2) If I run my data through SSS, this pattern seems to appear in many
more channels. That means that I need to discard many more repetitions
after running SSS. Is this something intrinsic to the SSS algorithm
(i.e. to multiply this noise)? What is the reason for it to appear
across more channels after SSS?
3) If I clean up my raw data prior to SSS (e.g. discard the
repetitions with such pattern), and create a new FIF raw file from
this new data, my data won't be continuous in time anymore. I don't
think SSS will have a problem with it (unless I use the temporal
extension). Is that correct?
4) Would you suggest a more accurate way to deal with these
discontinuities (eg. wavelets?), instead of discarding (sometimes
precious) trials?
5) Assuming SSS has no problems with this new "clean" raw file, can
the SSS algorithm create such discontinuities by itself? If so, why?
Thanks,
Gus
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