[Mne_analysis] Noise covariance matrix

[Laura Munkki]

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Hi,
I am registered now, so posting again.
I am analyzing auditory evoked responses (N100).
I calculated NCM for pre-stimulus activity (500 ms long epochs).
For the ERPs I used filter 0.5-20, and I applied the same for the NCM
epochs. The dSPM was totally messy. Then I tried to calculate the NCM
without filters, and, surprisingly, the N100 was localized perfectly to the
auditory cortex.
Is it necessary to use the same filter before the NCM calculations?
I used filter 0.5-20 Hz for the averaged ERPs, I didn't filter data before
averaging. But the NCM is calculated from epochs, so may be it is incorrect
to filter epochs?
Thank you,
Laura
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