Complex sentence: Braak stages I and II are used when NFT involvent is confined mainly to the transentorhinal region of the brain, stages III and IV when there's also involvement of limbic regions such as the hippocampus, and V and VI when there's extensive neocortical involvement.
Split into simpler sentences: Braak stages I and II are used when NFT involvent is confined mainly to the transentorhinal region of the brain. Stages III and IV indicated involvement of limbic regions such as the hippocampus, and V and VI when there's extensive neocortical involvement.