Before revision:  Integrated Information Theory (IIT) provides a mathematical approach to quantify the level of integration in a system . Nevertheless , it is not yet well understood how integration scales up with the size of a system or with different temporal scales of activity, nor how a system maintains its integration as its interacts with its environment.
After revision:  Integrated Information Theory (IIT) provides a mathematical approach to quantify the level of integration in a system , yet its computational cost generally precludes its applications beyond relatively small models. In consequence , it is not yet well understood how integration scales up with the size of a system or with different temporal scales of activity, nor how a system maintains its integration as its interacts with its environment.