Dear Thijs and Max,
Thanks for this perfect explanation on why averaging the response function. My turn to second Felix (friend and French colleague) on problems that we encountered by using the same response in a group of subjects.
In our experience (mainly focused on Diffusion gradient scheme and TWI adaptation for computing cranial and peripheral nerves atlas), using an average response text file instead of those yielded from an individual dataset led to a “denoising” aspect of the tractogramm (ie. on the visual analysis of the TWI map, whatever the contrast type -FOD amplitude, length…- or use of super resolution properties).
In other words, small distal tracts or nerves could “disappear” by averaging the response function, which could be problematic at the group level, depending of the disease model.
I assume this could be less important for brain white matter fascicles…but any help would be appreciated