ALFF/fALFF calculate together before filtering?

Submitted by Freshman2013 on

Dear Experts in rfmri,

1. I calculated ALFF/fALFF using dparsfA2.3:

Firstly, I got the file named "FunImgARCWS" just like the attachment file.

Secondly, I calculated ALFF/fALFF based on the "FunImgARCWS" files. I checked the  "ALFF/fALFF" and then checked the filtering "Band(Hz):0.01-0.08" which is behind the "ALFF/fALFF" .

Are the steps which I mentioned on ALFF/fALFF calculation using dparsfA2.3 right?

2. I found that: In the matlab, these steps which I mentioned abouve:  did both ALFF/fALFF calculation together and generated the related "results" files; finally did filtering. But In the literatures, they said, after filtering, they did the ALFF calculation.

Since I am not expert in matlab programming, I could understand the .m file. Could you please explain the details on ALFF/fALFF calculation on dparsfA？ Why put the ALFF/fALFF together but not divided them?

Many thanks in advance.

Freshman2013

Freshman2013

Fri, 08/22/2014 - 15:38

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Thanks very much for your quick reply.

Since ALFF/fALFF calculate before filtering, that means the file named "FunImgARCWSF"  could not be used in the ALFF/fALFF calculation. If that is right, then how the  filtering paramenters (Band 0.01-0.08Hz) could be employed in the ALFF/fALFF calculation?

I read the paper: Yan, C.G., Cheung, B., Kelly, C., Colcombe, S., Craddock, R.C., Di Martino, A., Li, Q., Zuo, X.N., Castellanos, F.X., Milham, M.P., 2013. A comprehensive assessment of regional variation in the impact of head micromovements on functional connectomics. Neuroimage 76, 183-201. for this order.

It said,"Temporal filtering (0.01–0.1 Hz) was applied to the data with each correction method prior to calculating derivatives, except for frequency-based R-fMRI indices (ALFF and fALFF)." and during the ALFF/fALFF calculation, "Amplitude measures: amplitude of low frequency fluctuations (ALFF) (Zang et al., 2007) and fractional ALFF (fALFF) (Zou et al., 2008). ALFF is the sum of amplitudes within a specific low frequency range (0.01–0.1 Hz in the current study), while fALFF is the ratio of the ALFF of a given low frequency band (here, 0.01–0.1 Hz) to the sum of amplitudes across the entire frequency range detectable in a given signal."-----That means the filtering paramenters employed in the ALFF/fALFF calculation.

Hence,  I thought that the   filtering paramenters (Band 0.01-0.08Hz) when I mentioned above employed inthe ALFF/fALFF calculation, but the filtering step didn't conduct during ALFF/fALFF calculation. Am I right?

So if I would write the paper using the steps I mentioned above, I could refer your paper Yan, C.G., et al, 2013. A comprehensive assessment of regional variation in the impact of head micromovements on functional connectomics. Neuroimage 76, 183-201.

 

Finally, I would like to click the Google ads at the bottom of the rfmri page. But my confused how to do:  I just click it and don't make its webpage open? Or I should click it and allow the ads webpage open? The two methods, which one could really help the RFMRI.ORG?

Thanks very much for your wonderful tool and kind direction.

Hi,

Please look at rfmri.org/Course Part III 35:00~37:00 carefully. (f)ALFF band and filtering band are defined differently.

For Google AdSense, it's pretty clever in pushing something you might be interested in according to your search history. Please do NOT "click it and don't make its webpage open". If there is some information interested you, just go ahead what you will do normally.

Thanks,

Chao-Gan

Freshman2013

Sat, 08/23/2014 - 03:25

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Chao-Gan, thanks very much for your patient reply.

It's my mental set. When mentioned Band, I thought ALFF/fALFF should be filtered within the Band. 

After reading your paper, it said,“ALFF is the sum of amplitudes within a specific low frequency range (0.01–0.1 Hz in the current study), while fALFF is the ratio of the ALFF of a given low frequency band (here, 0.01–0.1 Hz) to the sum of amplitudes across the entire frequency range detectable in a given signal.” and reviewed the Chinese course PartIII 1:18:39-01:20:18 and  the Chinese course PartI55:31-58:57. You have explained in detailed.

I  exactly understand  the calculation of ALFF/fALFF now. 

Many many thanks.

And click the ads at the bottom of the web page and  make its webpage open.OK, so interesting.

 

 

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