Dear FreeSurfer experts,

I am currently using TRACULA( from freeSurfer 6.0), and on the freeview visualization of merged files of the probability distributions of the tracts, I don't understand the thing about the "20% threshold".

Indeed, on the tracula tutorial, it is written that the tracts are displayed in a way that they are at 20% of their maximum threshold. However, what does this mean? Is it the 20% of the most probable paths for each tracts? The adjustment bar on the side of the screen permits to vary this threshold, but when we reduce the level of the threshold, the size of the tracts increase, which seems in contradiction with the previous statements... I then suppose that my guess must be wrong?

Thank you for your time and consideration!

Sincerely,

Loïc