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HRF's are different for same snirf files

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Hi All,


My lab works on brain imaging of adult subjects using fNIRS. The data we use are of varying lengths (usually longer than 60 seconds).

I was looking at options to generate clean HRFs corresponding to the onset of resting state. I used GLM (new) option from Homer3 v 1.33 on two copies of a snirf file corresponding to the same session. All preprocessing steps before GLM computation are same for both cases.

On one, I removed all the stim markers after the first trial, but kept the entire session in the snirf file. On another, I segmented the snirf file to chop off the data after the first trial, but kept 60 second of data after the resting state onset.

HRF settings: gaussian function, OLS, time window of -2 to 60 seconds.


I was expecting the HRFs to be same for both cases, since I am providing the same amount of resting state data in both cases. But they seem different. Please refer to the attached pptx. Blue stimulus corresponds to start of rest.