Based on Tononi's earlier work on Integrated Information Theory, apparently, Maguire et al. have come up with a formulation of consciousness as a lossless integration of information that requires noncomputable functions, which implies that consciousness cannot be modeled computationally.
http://www.newscientist.com/article/dn25560-sentient-robots-not-possible-if-you-do-the-maths.html
I'm personally skeptical of this, but their paper (seen here: http://arxiv.org/abs/1405.0126v1) has some impressive looking formal mathematical proofs that I will admit I lack the mathematical competence to judge the veracity of. Anyone with greater mathematical acumen want to take a look?
To be fair to yourself, would you reject it if it were a proof of something you agreed with?
If they had gone out and 'proven' mathematically that sentient robots ARE possible, I'd be equally skeptical - not of the conclusion, but of the validity of the proof, because the core of the question is not mathematical in nature.