I believe it is impossible for neuroscience to ever show with certainty that consciousness is a production of the brain, because for every bit of evidence that neuroscience can show that points to consciousness being linked to the brain, there is always an alternative way to view that evidence that points to the opposite.
When you really get down to it, most of the evidence we have that the brain produces consciousness is correlatory.
If you hit your head, you may lose some memory and cognitive function. If you take a drug, you may experience an altered state of consciousness. We can relate certain brain states to states of consciousness.
However, if you were to take the opposite of the conventional view – that the brain regulates and limits consciousness, rather than produces consciousness, you effectively have an alternative working explanation for every supposed piece of evidence that the brain creates consciousness.
This view is summarized very well by Cyril Burt:
“The brain is not an organ that generates consciousness, but rather an instrument evolved to transmit and limit the processes of consciousness and of conscious attention so as to restrict them to those aspects of the material environment which at any moment are crucial for the terrestrial success of the individual”
Now, there are always at least two ways to view any correlate involving the mind and the brain. For example, is brain activity supposedly correlating to conscious states the cause of those conscious states, or is it merely the measure of the brain's response to those conscious states?
When you take a drug, is it your brain that alters the way it produces consciousness, or is it the brain's regulatory function over consciousness that is out of whack?
Did hitting your head cause your brain to mechanically be unable to produce consciousness in the same way, or did you damage your regulatory unit’s ability to open itself to consciousness?
Not only does this alternative view not conflict with modern neuroscience, but I believe it actually explains many neurological mysteries better than the conventional view.
For example, in ‘Acquired Savant Syndrome’, people can suffer brain damage, and rather than lose cognitive function, they gain Savant-like abilities. This is easily explained if you believe consciousness to be external to the brain. The limiting function of the regulatory system of the brain was damaged in such a way to allow more consciousness to be experienced. The materialist is in a much weaker position in explaining how brain damage leads to such a radical increase in mental ability.
There was a case of severe hydrocephalus that was circulating the news. I believe the article was called ‘Tiny brain normal life’, and it was about a French Civil servant who had lived a normal life with only a small fraction of a normal brain. His affliction is called hydrocephalus.
In severe cases of hydrocephalus patients can be left with less than 5% of the brain mass of a normal person. Even in these severe cases there are people who have above average IQs – some actually have very high IQs and seemingly no mental deficits. Again, this is easily explainable for those who believe consciousness to be separate from the brain, and much harder to explain for materialists, who often chock it up to redundancy.
The last example I’ll cite here is ‘Terminal Lucidity’ and dementia. In severe cases of dementia, as a result of progressive brain damage, some patients will be unable to remember the faces and names of family members. They won’t be able to find words, or hold a proper conversation.
Sometimes when these patients approach death, they’ll enter a lucid state where they are able to remember names, faces, and hold a proper conversation, as if they did not have dementia.
I would say this is no problem if you believe the brain to be a regulatory system for consciousness, because that implies consciousness and memory are external from the brain. The memory still exists, and while under duress the brain’s regulatory ability to limit itself is diminishing, allowing what once was blocked to be experienced.
If you view consciousness as material, and memory to be physically stored in the brain this is more difficult, because the brain degeneration supposedly responsible for their inhibited consciousness and memory is still very much there when they enter this lucid state.