[FieldTrip] Extracting a timecourse from cluster of channels

[Clara A. Scholl]

Thanks Eric!

Do you think it's reasonable to take the intersection, or union, of
channels over time in a given space-time cluster?
Do you know of any publications that have dealt with this issue
(choosing channels from a space-time cluster for timecourse
extraction) that I could look at & reference?
Thanks, Clara

On Sat, Jul 30, 2011 at 9:31 AM, Eric Maris <e.maris at donders.ru.nl> wrote:
> Dear Clara,
>
>> I am using fieldtrip's cluster-based permutation test to identify a
>> significant channel-time cluster showing an effect.  Now I would like
>> to extract a timecourse averaged over these channels (for the purpose
>> of comparing different conditions, not used to generate the cluster),
>> but I'm not sure if it makes sense to do so because the channels
>> belonging to the cluster change over time -- would the timecourse have
>> contributions from different channels at different time points?  Do I
>> need to limit my cluster to fixed channels across time? (And if so,
>> how do I do that?)
>
> Yes, you should fix channels across time. The most important point in
> selecting the channels is finding evidence for the fact that the channels
> reflects a single source only. This is not a statistical issue, and
> therefore there is not a p-value that can guide you in this choice. If you
> have collected MEG data, the best evidence is a dipolar topography of your
> effect.
>
> Best,
>
> Eric Maris
>
>
>>
>> Thanks!
>> Clara
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