[Mne_analysis] problem with setting up the source space

[Lin Wang]

Thanks so much, Eric!
It makes sense to me now. I'll take your suggestion to use the 'oct6'. :-)

Best,
Lin

On Mon, May 22, 2017 at 3:35 PM, Eric Larson <larson.eric.d at gmail.com>
wrote:

> I used ico5 to have a better spatial resolution. I saw several other
>> papers used this setting.
>>
>
> I wouldn't expect it to give much better spatial resolution in practice,
> at least for distributed solvers. (Not sure about sparse ones, but I doubt
> it.)
>
> But I still don't understand why the higher resolution causes this error.
>> I thought the smaller spacing should result in more neighbors...
>>
>
> The "neighbors" here aren't probably aren't quite what you're thinking of,
> which sound like neighbors in the *low-resolution* mesh that results from
> setting up the source space.
>
> IIRC the source space is constructed by downsampling the high-resolution
> FreeSurfer mesh, specifically by recursively subdividing a standard
> icosahedron (ico) or octahedron (oct), doing a nearest-neighbor mapping to
> the subject's high-resolution sphere surface, and then de-duplicating any
> vertices that are nearest neighbors to more than one of the ico/oct
> vertices. The de-duplication thus uses the neighbors according to the
> high-resolution mesh triangulation. This error suggests that there are no
> neighbors left to choose from, i.e. they are all already in the source
> space, and thus the deduplication process could not succeed.
>
> In theory we might be able to work around this in the code by e.g.
> removing any vertices (or really equating them in their mesh with their
> best duplicate) that happen to have this problem. This might lead lead to
> some unintended consequences, though, such as a less uniform sampling of
> the surfaces, so it would need some thought, work, and testing to get right.
>
> Eric
>
>
> _______________________________________________
> Mne_analysis mailing list
> Mne_analysis at nmr.mgh.harvard.edu
> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/mne_analysis
>
>
> The information in this e-mail is intended only for the person to whom it
> is
> addressed. If you believe this e-mail was sent to you in error and the
> e-mail
> contains patient information, please contact the Partners Compliance
> HelpLine at
> http://www.partners.org/complianceline . If the e-mail was sent to you in
> error
> but does not contain patient information, please contact the sender and
> properly
> dispose of the e-mail.
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20170522/e0f37bf3/attachment.html