Hi all,
I’m working with flexible (FLOBS) HRF modeling and . I wanted to get community feedback on how we estimated latency using the FLOBS .
FLOBS gives three PEs per voxel (PE1, PE2, PE3), which are the weights on the three optimal basis functions. These don’t correspond to amplitude/timing/dispersion like in the Gamma + derivative approach, so PE2/PE1 is not a meaningful latency measure.
Instead, we reconstructed the full HRF curve at each voxel within the ROI using:
HRF(t) = PE1 × basis1(t) + PE2 × basis2(t) + PE3 × basis3(t)
where basis1, basis2, basis3 are the 559-timepoint FLOBS waveforms spanning 0-28 seconds. We did this at every voxel within the ROI, then averaged the reconstructed curves across voxels to get one curve per subject. We then found the time-to-peak of each subject’s curve, and ran a one-sample t-test against 5.5 seconds (canonical peak) across all subjects.
Questions:
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Is comparing the FLOBS time-to-peak against 5.5 seconds (canonical) a valid approach for testing latency shifts, or is there a more appropriate reference or statistical method?
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Any other suggestions on how to properly extract and compare latency between a fixed-shape model (Gamma) and a flexible model (FLOBS)?
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If any comment about the approach used for constructing the HRF curve that be highly appreciated as well.
Thank you and any comments or direction would be great!