# How to get an inverse filter?

**URL:** <https://mne.discourse.group/t/how-to-get-an-inverse-filter/3132>\
**Category:** Support & Discussions\
**Created:** [May 13, 2021, 1:09pm UTC](https://mne.discourse.group/t/how-to-get-an-inverse-filter/3132 "2021-05-13T13:09:09Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![kyuwanchoi](https://avatars.discourse-cdn.com/v4/letter/k/a698b9/32.png) [@kyuwanchoi](https://mne.discourse.group/u/kyuwanchoi)\
**Post date:** [May 13, 2021, 1:09pm UTC](https://mne.discourse.group/t/how-to-get-an-inverse-filter/3132/1 "2021-05-13T13:09:09Z")

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Dear MNE users,

For example, I have EEG data (64x256) (channel, time). Here, I think by multiplying an inverse filter (Maybe 256x 20484, time and num of vertexes), we can get the cortical activities in source space. Do you know how I can get this inverse filter?

Best,  
Kyu

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**Author:** ![sappelhoff](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/sappelhoff/32/3276_2.png) [@sappelhoff](https://mne.discourse.group/u/sappelhoff)\
**Post date:** [October 18, 2021, 7:15pm UTC](https://mne.discourse.group/t/how-to-get-an-inverse-filter/3132/2 "2021-10-18T19:15:14Z")

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Hi @kyuwanchoi, I don’t know an answer to your question, but adding some context to your question (e.g., in the form of scientific paper references) might help other people to know how to help you.

Just “inverse filter” by itself is a little too broad of a topic to write a concise answer to.

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**Author:** ![drammock](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/drammock/32/4_2.png) [@drammock](https://mne.discourse.group/u/drammock)\
**Post date:** [October 18, 2021, 7:21pm UTC](https://mne.discourse.group/t/how-to-get-an-inverse-filter/3132/3 "2021-10-18T19:21:43Z")

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[https://mne.tools/stable/generated/mne.minimum\_norm.make\_inverse\_operator.html](https://mne.tools/stable/generated/mne.minimum_norm.make_inverse_operator.html)

the function is called `make_inverse_operator` (linked above). It gets one dimension (number of channels) from an `Info` object, and the other dimension (number of vertices on the cortex) from a `SourceSpace` object. The number of time points is irrelevant / unchanged.