[FieldTrip] Connectivity comparison across conditions

[Jose Rebola]

Hi Jan,

Regarding the time-resolved PLV, isn't it different to do it with
mtmconvol, which in my view provides a TFR, than with a time signal based
on the Hilbert transform which estimates instantaneous phase.

My doubt is that the time-resolved PLV will need three or four cycles for
good spectral estimation, and two things can happen:
1 - I analyse non-overlapping chunks and get a low number of time-points.
2 - I analyse highly overlapping segments and thus a lot of PLV estimations
but not really independent from each other and therefore biasing the
comparison to other conditions

With the Hilbert derived transform I would theoretically have as many
independent estimates of the PLV, right?

Is there a caveat in my line of thought? I might be missing something
here...

Thanks,

Jose Rebola

On Thu, Jul 9, 2015 at 11:23 AM, Schoffelen, J.M. (Jan Mathijs) <
jan.schoffelen at donders.ru.nl> wrote:

>  Hi Jose,
>
>  1.
> I want to perform this analysis intra-subject.
> I have a plv value for the elctrode combination 1&2 at 30Hz for condition
> 1, and another value for condition 2 (they both have 80 trials)
> Not sure I understand what you mean by permuting the trial labels and what
> I would do with the obtained values.
>
>
>  See:
>
>  Maris E., Schoffelen J.M., Fries P.*Nonparametric statistical testing of
> coherence differences.
> <http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17395267>* J
> Neurosci Methods. 2007 Jun 15;163(1):161-75.
>
>    2.
> Also, is it not possible to do this along time?
>
>
>  Yes, in principle one could compute a time-resolved PLV. This should be
> done with cfg.method = ‘mtmconvol’, in ft_freqanalysis.
>
>  Jan-Mathijs
>
>
>
>
>   On Thu, Jul 9, 2015 at 10:33 AM, Schoffelen, J.M. (Jan Mathijs) <
> jan.schoffelen at donders.ru.nl> wrote:
>
>> Hi Jose,
>>
>>  I can think of one out of 2 things:
>> -you formulate a null hypothesis pertaining to a group of subjects, and
>> do statistical inference across subjects (e.g. by permuting the condition
>> labels), or
>> -you formulate a null hypothesis pertaining to the observations belonging
>> to the individual conditions, and do statistical inference across
>> observations, e.g. by permuting the trial labels.
>>
>>  Best wishes,
>> Jan-Mathijs
>>
>>
>>
>>   Jan-Mathijs Schoffelen, MD PhD, Senior researcher
>>
>> Max Planck Institute for Psycholinguistics
>> Donders Centre for Cognitive Neuroimaging
>>
>> E-mail: j.schoffelen at donders.ru.nl
>> Telephone: +31-24-3614793
>>
>> http://www.hettaligebrein.nl
>> http://www.fieldtriptoolbox.org
>>
>>
>>
>>
>>   On Jul 9, 2015, at 11:24 AM, Jose Rebola <jrebola at gmail.com> wrote:
>>
>>    Hi,
>>
>>  Is there a straightforward way to compare any connectivity measure at a
>> given frequency (say, plv at 30Hz between electrodes 1 and 2) across
>> conditions? I end up with one value per channel combination per frequency
>> per condition, so what is the right way to compare?
>>
>>  Thanks in advance,
>>
>>  Jose Rebola
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