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

[Michael Wibral]

Dear David, dear Eric,

there is one additional side effect of specifying a LARGE minnbchan that actually leads to SMALLEr clusters in a certain sense. If I understand correctly, at any point in time&frequency the cluster has to have a spatial extension of minnbchan+1. So when you specify a large value the cluster may more easily be cut up into several smaller ones along the space&time dimension - which may or may not  be desirable.

Michael

-----Ursprüngliche Nachricht-----
Von: "David Groppe" <dgroppe at cogsci.ucsd.edu>
Gesendet: Feb 8, 2011 7:18:59 PM
An: "Email discussion list for the FieldTrip project" <fieldtrip at donders.ru.nl>
Betreff: Re: [FieldTrip] What exactly does 'minnbchan' refer just to spatial neighbors?

>On Tue, Feb 8, 2011 at 11:01 AM, Eric Maris <e.maris at donders.ru.nl> wrote:
>> Dear David,
>>
>>
>>> 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?
>>
>> Your reasoning is correct and mine was incorrect. I should read better
>> before I write. My apologies for this.
>
>Got it. Thanks very much for clarifying Eric.
>
>>
>> I do have to qualify that with minnbchan=0 it may also happen that your
>> significant cluster contains more than one electrode (the electrode with the
>> true effect plus some surrounding ones that by accident exceed the threshold
>> that is used to identify clusters).
>
>That makes perfect sense.  Since our lab uses only a limited number of
>electrodes (32), I wanted to make sure I understood the minimum number
>of electrodes an effect needs to span to be detected.
>      once again, I very much appreciate your answers to my questions,
>              -David
>
>> Best,
>>
>> Eric
>>
>>
>>
>>
>>>      again, thanks very much for the help,
>>>             -David
>>>
>>>
>>> > 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/
>>> >> _______________________________________________
>>> >> fieldtrip mailing list
>>> >> fieldtrip at donders.ru.nl
>>> >> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>>> >
>>> > _______________________________________________
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>>> >
>>>
>>>
>>>
>>> --
>>> David Groppe, Ph.D.
>>> Postdoctoral Researcher
>>> Kutaslab
>>> Dept. of Cognitive Science
>>> University of California, San Diego
>>> http://www.cogsci.ucsd.edu/~dgroppe/
>>>
>>> _______________________________________________
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>>> fieldtrip at donders.ru.nl
>>> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>>
>>
>>
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>
>
>
>-- 
>David Groppe, Ph.D.
>Postdoctoral Researcher
>Kutaslab
>Dept. of Cognitive Science
>University of California, San Diego
>http://www.cogsci.ucsd.edu/~dgroppe/
>
>_______________________________________________
>fieldtrip mailing list
>fieldtrip at donders.ru.nl
>http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
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