Keith Augustine in his article the case against immortality. He says the evidence for survival and psi is very weak compared to the evidence produced in neuroscience. Well true of course neuroscientific evidence is stronger however does it really support the view that consciousness is an emergent property of the brain. I would say no one of the data points Keith Augustine mentions a lot is the brain split experiments which don't really show two conscious streams of consciousness.
The brain split experiments don't show two conscious minds. http://kaffee.netfirms.com/Papers/PhilofMind3.htm
According to more than one author, the theory of two conscious minds seems incompatible with the over-all unity of mental functioning shown in split-brain patients outside the experimental (split-brain) setting. This unity would not be explainable through the dominance of one hemisphere and it would include complex motor skills such as playing the piano that involve the active participation of both the cerebral hemispheres. As Wolfgang Gasser formulates it nicely: "Cutting the lines of communication between the two sides of a brain (split brain patients) has incredibly few consequences. Primarily it is the soul which continues maintaining the coordination of the two sides." The unity of behavior after splitting the brain is even observed in non-human mammals, which in flagrant moral contradiction with the fact they are 'sacrificed' for research clearly suggests they are substantial selves just like humans.
Also in general, we already know that there are complex non-conscious or subconscious cognitive processes and that they may have a strong impact on behavior. Therefore, it is more parsimonious to explain split-brain phenomena by such known processses than to prefer an exotic new theory of the creation of two conscious minds by the severing of the corpus callosum, just for the sake of debunking radical substance dualism.
You can find more about this here
In Titus Rivas paper called a few remarks on the death of dualism.
Now another bulk of evidence Keith uses is from this site here.
I will leave it up to you does this evidence in this site show consciousness is an emergent property of the brain? or does it show that consciousness is filtered by the brain?.
About the Phineas Gage case. It appears the case is not a well supported case at all. Which can we found on wikipedia under the heading Distortion and misuse of case.