[FieldTrip] Units powerspectrum time-frequency analysis

Alexander Mentink amentink at chdr.nl
Thu Aug 31 14:03:48 CEST 2017


Dear FieldTrip community,


I have a question regarding time-frequency analyses, it would be awesome if someone could help me out!


Does anyone perhaps know what the absolute units are of the TFRwave.powerspctrm that you get when performing a continuous wavelet transform:


cfg = [];
cfg.channel    = 'Cz';
cfg.method     = 'tfr';
cfg.width      = 7;
cfg.output     = 'pow';
cfg.foi        = 1:0.25:30;
cfg.toi        = -3:0.01:2.5;
TFRwave = ft_freqanalysis(cfg, trialdata);

cfg = [];
cfg.channel = 'Cz';
cfg.baseline     = [-0.5 -0.1];
cfg.baselinetype = 'absolute';
cfg.zlim         = 'maxabs';
cfg.xlim         = [-0.2 1.5];
cfg.showlabels   = 'yes';
figure
ft_singleplotTFR(cfg, TFRwave)


The single plot shows reliable results compared to the Hanning window method, however the values of the powerspectrum are in the hundred thousands (?) - see image attached.

This can't be uV^2/Hz, perhaps nV^2/Hz?


Thanks in advance!


Alex




Alexander Mentink
Centre for Human Drug Research
Zernikedreef 8
2333 CL Leiden
The Netherlands
T +31 (0) 71 7517166
amentink at chdr.nl
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