Sorry to post this issue again, but I was hoping for some clarification so I can progress with my analysis.
I just have a question about the detrending and filtering. I have been looking at ROI time courses at various stages of detrending and filtering.
I have noticed that after detrending, the linear trend does indeed seem to be removed, as is expected.
After filtering (.008 to .08 Hz) only (without detrending), I can clearly see the slower oscillations, although the linear trend is still present, as would be expected.
However, after detrending + filtering, the oscillations become very regular, and the time course has a strong linear trend.
This seems strange to me. Does the trend get added back into the time course during filtering? Does this sound normal?
Thanks for your help,