Never thought of it that way, that his heart transfers chakra to the rest of his body So maybe so.What I'm wondering is how someone can even form any thought-processes without a brain. :/
Chakra is transmitted to different parts of his body through that core, including his head...so he more than likely isn't 100% immune to genjutsu.
That can be because they have chakra flowing throughout their body.Pretty sure white zetsu clones don't have brains, and they've been caught in genjutsu before.