[FieldTrip] What exactly does 'minnbchan' refer just to spatial neighbors?

David Groppe dgroppe at cogsci.ucsd.edu
Tue Feb 8 15:18:07 CET 2011

On Tue, Feb 8, 2011 at 1:17 AM, Eric Maris <e.maris at donders.ru.nl> wrote:
> Dear David,
>> I can't tell if "minimum number of neighbors" means just spatial
>> neighbors (i.e., nearby sensors) or if includes temporal and frequency
>> neighbors as well.  Could someone clarify?
> It means ONLY spatial neighbors.
>> Also, just to be clear, if I want to be able to detect an effect that
>> I think is at only a single electrode, I should set minnbchan to 0,
>> yes?  If understand the parameter correctly, any greater value of
>> minnbchan will ignore clusters that are restricted to a single
>> electrode.
> No, with minnbchan=0, there are no constraints on the clusters. If you want
> clusters to be local (as opposed to stretched over a large part of the
> scalp), minnbchan should be given a high value.

Thanks very much for the email Eric, but I'm confused as to why you
answered "No" to my second comment.  From what I understand, if you
use a value of minnbchan that is greater than 0, then any significant
clusters will necessarily spread across multiple electrodes.  For
example, if you set minnbchan to 1, then all significant clusters will
have to include at least two electrodes so that each significant
"voxel" has at least one neighbor at another electrode.  Thus, if your
effect is truly at only a single electrode, having a value of
minnbchan greater than 0 will force you to miss the effect or to think
it occurs at more electrodes than it really does.  What part of my
reasoning is incorrect?
     again, thanks very much for the help,

> Best,
> Eric
> dr. Eric Maris
> Donders Institute for Brain, Cognition and Behavior
> Radboud University
> P.O. Box 9104
> 6500 HE Nijmegen
> The Netherlands
> T:+31 24 3612651
> Mobile: 06 39584581
> F:+31 24 3616066
> mailto:e.maris at donders.ru.nl
> http://www.nphyscog.com/
>>     thanks for your help,
>>         -David
>> --
>> David Groppe, Ph.D.
>> dgroppe at cogsci.ucsd.edu
>> http://www.cogsci.ucsd.edu/~dgroppe/
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David Groppe, Ph.D.
Postdoctoral Researcher
Dept. of Cognitive Science
University of California, San Diego

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