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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US">Dear Pia<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US">It is perfectly valid to do cluster-based permutation tests on the time series of a single channel without the need for spatial clustering.
If you have a hypothesis about a specific channel location, this is indeed the best thing to do.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US">However, be aware that the goal of identifying significant temporal clusters is ill-posed, as the test does not test for ”significant
clusters” but tests the interchangeability of the condition labels on your data.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US">This also means that the “validity” of a cluster is not comparable across tests with different complexities, i.e., single channel or full
sensor array, as the two tests are testing different hypotheses, namely the interchangeability of the condition labels on the full sensor array or the interchangeability of the condition labels on the a priori selected channel.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US">It is explained in more detail here:
<a href="https://www.fieldtriptoolbox.org/faq/how_not_to_interpret_results_from_a_cluster-based_permutation_test/">
https://www.fieldtriptoolbox.org/faq/how_not_to_interpret_results_from_a_cluster-based_permutation_test/</a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US">Best regards<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US">Mikkel
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Aptos",sans-serif;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span lang="DE" style="font-size:12.0pt;font-family:"Aptos",sans-serif;color:black">Fra:
</span></b><span lang="DE" style="font-size:12.0pt;font-family:"Aptos",sans-serif;color:black">fieldtrip <fieldtrip-bounces@science.ru.nl> på vegne af Pia Reinfeld via fieldtrip <fieldtrip@science.ru.nl><br>
<b>Dato: </b>onsdag, 17. april 2024 kl. 15.18<br>
<b>Til: </b>fieldtrip@science.ru.nl <fieldtrip@science.ru.nl><br>
<b>Cc: </b>Pia Reinfeld <pia.reinfeld@outlook.com>, Paul Steinfath <steinfath@cbs.mpg.de><br>
<b>Emne: </b>[FieldTrip] Cluster-based permutation test on single channel in time-domain<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">Dear FieldTrip Community,</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt"> </span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">I'm currently working on a project where I'm interested in exploring single channel differences between two conditions using cluster-based permutation tests. My aim is to only identify significant
temporal clusters, without considering spatial clusters across multiple channels. I've configured my analysis as follows:</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt"> </span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats = [];</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.neighbours = [];</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.channel = 'ECG';</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.latency = time_stat;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.avgovertime = 'no';</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.minnbchan = 0;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.parameter = 'avg';</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.correctm = 'cluster';</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.method = 'montecarlo';</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.statistic = 'depsamplesT';</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.clusterstatistic = 'maxsum';</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.alpha = 0.05;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.correcttail = 'prob';</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.clustertail = 0;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.clusteralpha = 0.025;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.numrandomization = 1000;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt"> </span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">Nsubj = length(reference);</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">design = zeros(2, Nsubj*2);</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">design(1,:) = [1:Nsubj 1:Nsubj];</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">design(2,:) = [ones(1,Nsubj) ones(1,Nsubj)*2];</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg.design = design;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg.uvar = 1;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg.ivar = 2;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.design = design;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.uvar = 1;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">cfg_stats.ivar = 2;</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt"> </span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">stat = ft_timelockstatistics(cfg_stats, reference{:}, target{:});</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt"> </span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">My question is whether this approach of focusing solely on temporal clusters within a single channel is justifiable and valid?</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">Additionally, I am curious about the comparability of the clusters found solely in the time domain with those identified through both time and space domain analyses. Does focusing only on the
time domain potentially simplify the detection of significant clusters? In other words, are clusters which are only identified in time more prone to being detected due to the reduced complexity of the analysis, or does this approach yield results that are
comparable in validity to those obtained through spatial-temporal cluster analyses?</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt"> </span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">Further, if there are any suggestions for improving this configuration or if there are alternative approaches that I should consider, I would greatly appreciate your input.</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt"> </span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">Thank you for your time and assistance.</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt"> </span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">All the best</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt">Pia</span><span lang="DE" style="font-size:11.0pt"><o:p></o:p></span></p>
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