[FieldTrip] ft_timelockstatistics cluster correction using ECoG data

[Kristen Berry]

Dear all,

I am using an intracranial EEG dataset to compare average high gamma power
waveforms between conditions. I want to correct for multiple comparisons
across time, but not across number of electrodes. Here is my input code:

cfg=[];

cfg.latency = [0.05 .5];

cfg.parameter = 'trial';

cfg.method = 'montecarlo';

cfg.correctm = 'cluster';

cfg.neighbours = [];

cfg.numrandomization = 1000;

cfg.statistic = 'indepsamplesT';

cfg.channel = ‘all’;

cfg.alpha = 0.05;

cfg.clusteralpha = 0.05;

cfg.tail = 0;

stats = ft_timelockstatistics(cfg, data,control);

Fieldtrip’s montecarlo reference page (
http://fieldtrip.fcdonders.nl/reference/ft_statistics_montecarlo) says, “If
you specify an empty neighbourhood structure, clustering will only be done
in frequency and time (if available) and not over neighbouring channels.”

However, my input code corrects for the number of channels as well. As an
example, when cfg.channel = ‘all’ for ft_timelockstatistics, then Elec11 is
not significant. However, if the analysis is limited to Elec11 (cfg.channel
= 11), then Elec11 has a significant cluster.

Is there a mistake in my code that is causing this? Or is there an older
version of fieldtrip that doesn’t correct for # of channels, when
cfg.neighbours is empty? Thank you for your input!

Best regards,

Kristen

Kristen Berry

Research Assistant

NYU School of Medicine
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