[FieldTrip] Smoothing before permutation test

David Groppe david.m.groppe at gmail.com
Wed Nov 2 14:43:18 CET 2016

Since permutation tests exploit correlations between variables to increase
sensitivity, smoothing each trial will increase your sensitivity.

On Wed, Nov 2, 2016 at 6:41 AM, Ramirez Pasos, <Ramirez_U at ukw.de> wrote:

> Dear Fieldtrippers,
> I have a set of subcortical LFP signals from 8 patients, which I have
> analyzed with fieldtrip in order to obtain event-related time-frequency
> plots. Unfortunately, I have only three repetitions for each of my 4
> conditions, so there's a lot of noise in the subject-averages of
> time-frequency data. I'm interested in testing baseline vs activation for
> each condition as well as comparisons between my 4 conditions (A1A2, A1B1,
> B1B2, A2B2).
> Could anyone tell me their take on smoothing before permuting? Is that a
> valid procedure with such a small sample size? I've searched for literature
> discussing smoothing before permuting (mostly the Holmes papers), where
> much talk of smoothing refers to concepts such as "locally pooled variance"
> and "pseudo t-statistics," but I don't know how this fits with fieldtrip's
> cluster statistics functions.
> Any thoughts would be greatly appreciated!
> U. Ramirez
> University of Wuerzburg
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