Information Integration Theory of Consciousness
According to this theory, consciousness corresponds to the capacity of a system to integrate information . There are two main concepts which are central to this theory: differentiation and integration.
Indeed, in this context consciousness is characterized as a balance between differentiation and integration. Differentiation refers to the availability of a huge repertoire of possible conscious experiences. Each particular experience is differentiated (or discriminated) from the others. Integration refers to the unity of each of these experiences, i.e. conscious contents are experienced as a unity, even though they might be composed by many dimensions.
Tononi introduced the Φ value as a measure of the quantity of consciousness available to a system. Actually, as consciousness is characterized as the ability to integrate information, Φ provides a measure of the amount of information that a system can integrate. From : “Φ is the amount of causally effective information that can be integrated across the informational weakest link of a subset of elements”.
The main implication of the hypothesis proposed by Tononi is that any physical system able to integrate information is conscious to the extent indicated by the Φ measure. This implies that also artificial implementations able to integrate information and having a high Φ would have conscious experiences. See The Possibility of Building Conscious Machines.
Read more about Information Integration Theory:
 Tononi, G. An information integration theory of consciousness. BMC Neuroscience 2004, 5:42. 2004. http://www.biomedcentral.com/1471-2202/5/42