[Mne_analysis] spatio_temporal_clustering

Eric Larson larson.eric.d at gmail.com
Mon Apr 27 11:41:03 EDT 2020
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>
> 1. as the p_threshold is decreased there should be the less number of
> clusters. In our case its reverse. why?
>

Not necessarily. The initial p-value threshold (really the F_threshold you
pass to the clustering function) just determines which points are included
in clustering (at all). As this becomes more stringent, fewer points will
be included. Finding more clusters with p < 0.05 as this threshold gets
more stringent suggests that the data are somehow being denoised by being
more stringent.

FWIW TFCE is designed to make it so that you don't have to do this sort of
determination, as it will automatically step through a number of
thresholds, and the meaningful data (which for you seem to show up with
quite stringent thresholds) should be enhanced automatically.

2. each time the clusters are localised at different regions.
>

Same as above, which clusters you find will be affected by which points you
allow to be clustered in the first place. What you should find is that the
clusters you get at more stringent thresholds are a subset of clusters you
get at more relaxed thresholds. So for example if you have a cluster that
contains five spatio-temporal points at a given threshold, if you make the
threshold more stringent, this cluster should only shrink (or split) as the
threshold becomes more significant.

Eric
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