ALFF Frequency Band Issue

Hello,

I'm trying to perform ALFF/fALFF analyses at specific frequency subbands and am running into some problems.  I'm able to create ALFF/fALFF maps at the .01-.1, .01-.08, and .073-.198 frequency bands but not at the .01-.027, .027-.073, .01-.073, and .198-.25 bands.  The .01-.027 band returns only nan values while the other bands return only one value for the entire map (e.g. ALFF of 31.9095 for the .027-.073 band, 37.3064 for the .198-.25 band).  The Temporal Dynamics 4d file shows changes across, but not within, timepoints.  Any idea what the issue is?  I'm using scans with a TR of .8 and 383 frames.

Thank you,

James

Forums:

Seems you filted before ALFF/fALFF analysis?

This is static ALFF or dynamic ALFF?

This is static ALFF.  I reran this on unprocessed resting state data and got the same issue so filtering doesn't seem to be the problem.  The nans in the .001-.027 band may be due to the relatively short scan time but I'm not sure what would cause the value uniformity in the other bands.

 

Thank you,

James

I can not replicate this problem.

Could you show your settings, and show a time course of your data? DPABI->Viewer->More->Time Courses.

https://imgur.com/a/6lN2wlx

You are using 30 TR as a window, and 0.8 as TR. Thus for each window it's 30*0.8=24s.

You can not get anything under 1/24=0.042 Hz, and probably higher.

Thank you,  changing the window size fixed the issue.