Hello Saad,
your completely right in that there is no way to know when axonal connections stop, and yes the lgn example is unsound.
However, consider different examples:
Say you have a small MS lesion somewhere in the distal pyramidal tract. A certain proprotion of samples will reach the lesion from a seed set proximally and pass "through" it reaching the cortex. Others however will reach the lesion but will not "make" it just one further voxel rostrally.
Or look at rare cases of band heterotopia. Histologically, tracts end in the band of grey matter, others pass through it and reach the cortex proper.
So in probabilistic tractography terms some samples, taking the exact same "route", should, given chance alone, at times pass through a structure, in other cases go no further (i.e. terminate exactly there). That's what I'm looking for: to calculate the proportion of samples terminating at a given point vs. those passing through (it and i.e. reaching a more distal structure).
Regards.
Stefan Kreisel
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