# Setting number of dipoles to be equal to the number of channels

**URL:** <https://mne.discourse.group/t/setting-number-of-dipoles-to-be-equal-to-the-number-of-channels/9272>\
**Category:** Support & Discussions\
**Created:** [September 2, 2024, 4:56pm UTC](https://mne.discourse.group/t/setting-number-of-dipoles-to-be-equal-to-the-number-of-channels/9272 "2024-09-02T16:56:24Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![codZeus](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@codZeus](https://mne.discourse.group/u/codZeus)\
**Post date:** [September 2, 2024, 4:56pm UTC](https://mne.discourse.group/t/setting-number-of-dipoles-to-be-equal-to-the-number-of-channels/9272/1 "2024-09-02T16:56:24Z")

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Hi everyone,

Please is there a way to set the number of dipoles to be equal to the number of channnels (let’s say number of channels that are in the mne.channels.make\_standard\_montage(‘standard\_1020’))?  
Few months ago I asked about how to set the number of dipoles and this link was provided  
[setting up number of dipoles](https://mne.discourse.group/t/setting-up-the-number-of-dipoles/8211). After playing with things, I used the

```python
mne.setup_source_space(subject, spacing='oct5', add_dist="patch",subjects_dir=subjects_dir)

```

This gave me 1026 dipoles for each hemisphere, from the image below

 ![seeting_up](https://global.discourse-cdn.com/free1/uploads/mne/original/2X/3/347b0f7871863aa60a4ff9fd09c2e8ed132baca8.png)

So, I want to know if it is possible to reduce the number of dipoles to match the 24 or 32 channels.

Suggestions and possible solutions are welcome.

Thanks

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**Author:** ![wmvanvliet](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/wmvanvliet/32/100_2.png) [@wmvanvliet](https://mne.discourse.group/u/wmvanvliet)\
**Post date:** [September 4, 2024, 10:20am UTC](https://mne.discourse.group/t/setting-number-of-dipoles-to-be-equal-to-the-number-of-channels/9272/2 "2024-09-04T10:20:51Z")

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With so little dipoles, you are no longer performing a “distributed source estimate” as techniques like MNE assume. Can you give us a little more information of what you study is and what you are trying to achieve?

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**Author:** ![codZeus](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@codZeus](https://mne.discourse.group/u/codZeus)\
**Post date:** [September 5, 2024, 1:47am UTC](https://mne.discourse.group/t/setting-number-of-dipoles-to-be-equal-to-the-number-of-channels/9272/3 "2024-09-05T01:47:46Z")

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Hi,

Okay.

I am trying to understand and study dipole locations that match the locations of electrodes of a standard montage. I want to know if by chance I could get specific dipole locations that match lets say the 10-20 electrode position system.

That’s why I asked if the dipoles could be reduced to suit the number of electrodes.

I hope my explanation helps you understand.

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**Author:** ![SBeumer](https://avatars.discourse-cdn.com/v4/letter/s/f0a364/32.png) [@SBeumer](https://mne.discourse.group/u/SBeumer)\
**Post date:** [September 6, 2024, 8:20am UTC](https://mne.discourse.group/t/setting-number-of-dipoles-to-be-equal-to-the-number-of-channels/9272/4 "2024-09-06T08:20:22Z")

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It sounds like you would like to see how each dipole influences each specific electrode. This is something that you will not get with subsampling the source space to 20 dipoles.

What you can do, however, is calculate the sensitivity maps from the forward operator. These sensitivity maps can show, for each electrode, their sensitivity to activity from the different sources.

Have a look at:  
[https://mne.tools/stable/generated/mne.sensitivity\_map.html#mne.sensitivity\_map](https://mne.tools/stable/generated/mne.sensitivity_map.html#mne.sensitivity_map)

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<div class="post-metadata">

**Author:** ![codZeus](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@codZeus](https://mne.discourse.group/u/codZeus)\
**Post date:** [September 6, 2024, 6:48pm UTC](https://mne.discourse.group/t/setting-number-of-dipoles-to-be-equal-to-the-number-of-channels/9272/5 "2024-09-06T18:48:45Z")

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Yes, that’s what I am trying to understand.

Thanks for the resource! .