# Noise covariance matrix

**URL:** <https://mne.discourse.group/t/noise-covariance-matrix/2121>\
**Category:** Mailing List Archive (read-only)\
**Tags:** list-archive\
**Created:** [March 26, 2020, 12:22pm UTC](https://mne.discourse.group/t/noise-covariance-matrix/2121 "2020-03-26T12:22:33Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [March 26, 2020, 12:22pm UTC](https://mne.discourse.group/t/noise-covariance-matrix/2121/1 "2020-03-26T12:22:33Z")

</div>

External Email - Use Caution

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  
-------------- next part --------------  
An HTML attachment was scrubbed...  
URL: [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20200326/ee45e3fb/attachment-0001.html](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20200326/ee45e3fb/attachment-0001.html)

---

<div class="post-metadata">

**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [March 26, 2020, 1:54pm UTC](https://mne.discourse.group/t/noise-covariance-matrix/2121/2 "2020-03-26T13:54:32Z")

</div>

External Email - Use Caution

see answer from Denis yesterday:  
[https://mail.nmr.mgh.harvard.edu/pipermail//mne\_analysis/2020-March/006640.html](https://mail.nmr.mgh.harvard.edu/pipermail//mne_analysis/2020-March/006640.html)

Alex  
-------------- next part --------------  
An HTML attachment was scrubbed...  
URL: [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20200326/8b3347bb/attachment.html](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20200326/8b3347bb/attachment.html)