<p>Apparently, this can happen when your ROI is near the edge of the brain as reported <a href="https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=spm;bcd35412.0804">here</a>. The thread is pretty old though so this might have been fixed by today and there is another reason in your case.</p>

CC BY-SA 3.0
2016-08-12T16:12:08.297Z
2016-08-12T16:12:08.297Z
awakenting
<p>I've estimated a model for an fMRI dataset, so I now have a <code>beta_*.nii</code> file for each regressor in my model.  In a seperate step, I've defined ROIs using marsbar and proceeded to extract the corresponding voxels in one of these β-maps.</p>

<p>However, the ROI extracted from said β-map contains only <code>NaN</code> values.  Why should there be NaNs at all?  What does such a null value represent in the context of model βs?</p>

<fmri><spm>
What do NaNs represent in an SPM β-map?
Louis Thibault
# What do NaNs represent in an SPM β-map?

(Asked by: username_0 on 2016-06-06)

I've estimated a model for an fMRI dataset, so I now have a `beta_*.nii` file for each regressor in my model. In a seperate step, I've defined ROIs using marsbar and proceeded to extract the corresponding voxels in one of these β-maps.

However, the ROI extracted from said β-map contains only `NaN` values. Why should there be NaNs at all? What does such a null value represent in the context of model βs?

**Tags:** fmri, spm


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## 1 answers

### Answer by username_1 on 2016-08-12. Score: 5 | Accepted answer

Apparently, this can happen when your ROI is near the edge of the brain as reported [here](https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=spm;bcd35412.0804). The thread is pretty old though so this might have been fixed by today and there is another reason in your case.


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