It is somehow able to keep the organs they were designed for alive without any need for the rest of the organs needed to support life. This may be because of the strange green fluids inside each tank.
The tanks are able to be attached to a host body to allow for movements, and offer the brain limited control over the host's movements.
It is unknown if anything in the support system is responsible for the organs being able to talk despite a lack of mouth.
In The Smell of Vengeance, it is revealed that the Brain tank has an escape rocket.