[FieldTrip] Time Frequency Analysis of <1 Hz

[Mick Lehmann]

Dear FT community,

I'm currently analyzing sleep EEG data and therefore I'm also interested in frequency ranges around 0.5/1 Hz. However, when I plot the data, it starts only from 1.25Hz and the cluster-based permutation can't be conducted when I include frequency ranges below 1.5 Hz.  

Any ideas on this issue based on the information provided blow? 

Best regards,
Mick

The raw data was read using the following script:

VP = dir('*.dat');                                           
cfg = [];
cfg.dataset                 = (VP.name);       % dataset  

cfg.trialdef.eventtype      = 'Comment';
cfg.trialdef.prestim        = 3;
cfg.trialdef.poststim       = 5;
      
cfg.trialdef.eventvalue     = {'HitHitReakt_LL' 'GainReakt_LL'}; 

cfg = ft_definetrial(cfg);

cfg.demean = 'yes';
cfg.baselinewindow = [-1 -.1];
HH_SlowOsc = ft_preprocessing(cfg);

HH_SlowOsc = renamechannels(HH_SlowOsc);

save HH_SlowOsc HH_SlowOsc



Afterwards, TF analysis was conducted using this script:

    load HH_SlowOsc
    

    cfg              = [];
    cfg.channel      = 'all';
    cfg.method       = 'wavelet';
    cfg.with         = 2; HERE, I'VE TRIED 2 AND 7 CYCLES. BOTH DIDN'T WORK
    cfg.output       = 'pow';
    cfg.foi          = 0.5:0.5:25;                     % Analysis from 2 to 30 Hz in 0.5 Hz steps
    cfg.toi          = -3:0.05:5;                  % time window "slides" from -1 to 2 sec in steps of 0.05 sec (50 ms)
%     cfg.keeptrials = 'yes';                         % für Single Trial Analysen

    TF_HH_SlowOsc = ft_freqanalysis(cfg, HH_SlowOsc);
    save TF_HH_SlowOsc TF_HH_SlowOsc; 
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