I don't think it is really about different brains as much as it is the same vulnerability that allows 1. The a'dam / The Domination Band; 2. Linking; 3. 13/13 Circle turning to the Dark. That is, I think the ability to channel allows one's spirit/mind to be opened to (and therefore vulnerable to) possession by outside spiritual forces (whether it is merging or domination produced by a direct link) or the possibility of being turned to the dark. This is not the same as rewiring the brain like in compulsion, which works equally well on channelers and non-channelers despite their "different brains." Rather, the Binders, a'dam, and 13/13 Circles all work around linking abilities. You also don't need to embrace the Source to be bound by an a'dam or controlled by a domination band and presumably the 13/13 circles wouldn't work if one only had to resist touching the Source to escape its powers. I also believe that the Warder bonds work more like a link and like the OR. This is another bond/binding that can be used to control others. Just look at Logain's control over the AS he bonded. It is absolute like the OR, not a matter of controlling consciousness like compulsion.