# EGI sensor layout **URL:** \ **Category:** Mailing List Archive (read-only)\ **Tags:** list-archive\ **Created:** [February 14, 2017, 1:28pm UTC](https://mne.discourse.group/t/egi-sensor-layout/1171 "2017-02-14T13:28:05Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [February 14, 2017, 1:28pm UTC](https://mne.discourse.group/t/egi-sensor-layout/1171/1 "2017-02-14T13:28:05Z")
Hello all, I have a question about the sensor layout map for EGI hydrocel sensor nets. I have been studying the two figures attached - one is the 128 channel map provided by EGI, the other is the sensor positions determined by using the commands mne.channels.read\_montage('GSN-HydroCel-128') and mne.viz.plot\_sensors. While there are similarities, some definite differences exist - notably, 81 has shifted from the occipital midline to close to the vertex. Has this been addressed before? And if so, what is the advice you recommend? Many thanks! Emily -------------- next part -------------- An HTML attachment was scrubbed... URL: [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20170214/74963921/attachment-0001.html](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20170214/74963921/attachment-0001.html) -------------- next part -------------- A non-text attachment was scrubbed... Name: hcgsn\_128.pdf Type: application/pdf Size: 164670 bytes Desc: hcgsn\_128.pdf Url : [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20170214/74963921/attachment-0001.pdf](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20170214/74963921/attachment-0001.pdf) -------------- next part -------------- A non-text attachment was scrubbed... Name: mne\_channel\_layout.png Type: image/png Size: 93450 bytes Desc: mne\_channel\_layout.png Url : [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20170214/74963921/attachment-0001.png](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20170214/74963921/attachment-0001.png) ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [February 14, 2017, 2:14pm UTC](https://mne.discourse.group/t/egi-sensor-layout/1171/2 "2017-02-14T14:14:42Z")
Hi Emily, I'm unable to replicate this. Looks like some channels are missing from your plot. Can you copy-paste the commands you run to plot this figure? -Jaakko ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [February 14, 2017, 4:35pm UTC](https://mne.discourse.group/t/egi-sensor-layout/1171/3 "2017-02-14T16:35:42Z")
Hi Jaakko, I think we may have resolved this? The updated code is file = '/Users/delfin/Documents/RPKPILOT/RAW/PILOT002\_GONOGO.set' ### read channel names and get raw data mon = mne.channels.read\_montage('GSN-HydroCel-128') raw = mne.io.read\_raw\_eeglab(file, preload=True) raw.set\_montage(mon) ## !! ### look at channels mne.viz.plot\_sensors(raw.info, show\_names=True) raw.plot\_sensors(show\_names=True) raw.plot\_sensors('3d') Sorry for any confusion! Hopefully we are correct and this is the right layout! ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [February 14, 2017, 9:01pm UTC](https://mne.discourse.group/t/egi-sensor-layout/1171/4 "2017-02-14T21:01:04Z")
Hi Emily The plot you showed from MNE in your original post is the layout map for the much-older GSN 200 2.1 nets. For the past many years (decade?) EGI has sold the HCGSN nets, which have a slightly different layout (as shown in the "official" EGI layout you attached). As you noticed, a telltale sign is whether the bottom-most centre electrode in the layout map is 81 (new) or 82 (old). I haven't tried importing EGI data into MNE yet, so I can't speak directly to your issue. However I do know that EEGLAB for years (and possibly still) by default uses the old layout when using their EGI importer. The EEGLAB folks did, however, post a layout map file for the new HCGSN configuration, which you can find at [https://sccn.ucsd.edu/bugzilla/show\_bug.cgi?id=1643](https://sccn.ucsd.edu/bugzilla/show_bug.cgi?id=1643) It should be in a standard format that hopefully MNE recognizes, or could be adapted pretty easily. Getting EGI data into MNE has been on my to-do list but I haven't tried it yet! Best, Aaron ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [February 15, 2017, 7:32am UTC](https://mne.discourse.group/t/egi-sensor-layout/1171/5 "2017-02-15T07:32:14Z")
I believe that the problem here was actually the montage reader. The channel names were read incorrectly in mne versions 0.12 and older, causing duplicate channel names. So updating mne to the latest version should fix the problem. The workflow looks correct. HTH -Jaakko ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [February 15, 2017, 9:20am UTC](https://mne.discourse.group/t/egi-sensor-layout/1171/6 "2017-02-15T09:20:11Z")
Many thanks to you both! It seems possible that in my first attempt there was some issue with 3d to 2d conversion - the back row of electrodes seemed folded 'under' and ended up towards the center of the projection? Anyway, I'm moving forward with the current layout - thank you again!