[FieldTrip] PSD units

[Adam Grinberg]

Hello,
My question concerns the Fieldtrip PSD function. I am running the code on some EEG data and comparing it with the MATLAB periodogram function. While the FFT produces similar graphical shape of the spectrogram, the units are different.
The periodogram function's units are µV^2/Hz, which is the common output for power (before converting to Db). However, the values that I get with the Fieldtrip freqanalysis function seem to be ~120 times lower. I cannot understand what they are. I looked at the code and still do not get it. I suppose that this is due to some normalization method done but I am not certain as to the rationale for the particular one used.

Tanks.


/Adam
______________________________________________________________________________________
Adam Grinberg, PT, PhD
Department of Community Medicine and Rehabilitation, Physiotherapy
Umeå University
Umeå, Sweden
Tel: +46 (0) 90 786 96 30

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