Dear all,
I like to write a matlab script to calculate fractional-ALFF and ALFF (Amplitude of low-frequency fluctuations).
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What is the right order for calculation:
Temporally band-pass filtered (0.01–0.0.8Hz) and then FFT
or
FFT and then to obtain the power spectrum across 0.01–0.08 Hz -
Should I apply linearly detrend on the input functional file? (for ALFF)
Can i apply melodic (ICA decomposition) and removal of noise components (with fsl_regfilt) and next to apply FFT? -
For fALFF should I calculate the entire frequency range of the whole brain or only the gray matter?
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For fALFF, should I divide by the entire frequency range (0-0.5 Hz, Nyquist frequency) my TR=1sec?
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For group comparison ALFF, f/ALFF should be both
- Divided by the global mean
and - transformed into Z-scores
Tali