[FieldTrip] Cluster Analysis - electrodes not clustering

[mikkelcv at drcmr.dk]

Hi Alice

This often happen if you have a sparse EEG layout so the neighbouring electrodes a too far away when you define which electrodes are “neighbours”. The solution is to make sure the frontal electrodes are connected to neighbouring electrodes in the output from ft_prepare_neighbours. You can easily inspect this with ft_neighbourplot (sse example here: https://github.com/mcvinding/cluster-stat-workshop/blob/main/tutorial.md#non-parametric-cluster-based-permutation-tests-on-all-channel-data).

To change the neighbour definition, see the options in documentation for ft_prepare_neighbours.

Best regards
Mikkel

Fra: fieldtrip <fieldtrip-bounces at science.ru.nl> på vegne af Milne, Alice via fieldtrip <fieldtrip at science.ru.nl>
Dato: torsdag, 6. oktober 2022 kl. 17.00
Til: fieldtrip at science.ru.nl <fieldtrip at science.ru.nl>
Cc: Milne, Alice <a.milne at ucl.ac.uk>
Emne: [FieldTrip] Cluster Analysis - electrodes not clustering
Hello!

I am running cluster analysis on a really clear effect in fronto-central electrodes when you plot data.
The cluster analysis identifies these electrodes but is identifying each one as a separate cluster. No two electrodes, even when neighbours are part of the same cluster.

This is a within subjects effect – 22 subjects and two conditions. I am not sure how this issue could to the cluster analysis settings as they seem quite standard ( and have been used previously in the lab).

I can also plot the topographies etc and the neighbours are all where they should be.

Has anyone come across this issue before?

Many thanks for your time 😊
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