Dear Alfonso or CONN experts,

Could you please help in these 2 questions?

1- If I got it right,  CONN bases its PCA for white matter on Behzadi et al 2007, but the latter proposes the "broken stick" method and does not specify a specific number of PCA components.

 Could you please explain the motivation to use 16 components in CONN?

2- From what I understood, the last components (from 6 to 16) might reflect physiological noise (e.g. aliased cardiac or respiratory signals) or scanner-related artifacts not shared across regions, and these subtle patterns can reflect microvascular or motion-induced effects often missed by dominant components.

Would you happen to know if there is any explanation on what the 6th, 7th and so on until the 16th might be explaining? 

Thank you very much.

All best

Renzo