Can human consciousness exist without a brain?
There's no solid evidence in support of this hypothesis, which lies at the core of most religious dogma and mystical practices. Sure, the notion of an immaterial conscious soul is appealing, as this would survive bodily death.
Almost everyone would agree that immortality is more desirable than the alternative: dying and not existing, forever. So I understand why people cling to the possibility that brains aren't the real us.
After I wrote a blog post, "Unmediated experience doesn't exist," where I said that experience isn't possible without a brain, I got an email from someone who challenged this assumption:
"The boy with no brain" gives a completely different dimension to the conclusion stated in your "unmediated experience" posting.
He shared a link to a Buddhism and Science talk by Ajahn Brahmavamso that included a description of the boy with no brain. Brahmavamso felt this unusual scientific finding demonstrated the separability of mind and brain.
Well, not really.
The original story of this clinical curiosity was published in the well-respected journal, Science, back in 1980. Though provocatively titled "Is Your Brain Really Necessary?" the article doesn't suggest that the boy in question, who functioned normally, actually had no brain.
Download Is Your Brain Really Necessary?
Rather, neuroanatomist John Lorber reported that the university student had hydrocephalus, resulting in "a cranium filled mainly with cerebrospinal fluid." This finding was based on the rather crude CT brain scans available in the 1970's. Nobody opened up the boy's head and peered inside.
The article contains cautionary interpretations from other experts. The boy could have more brain tissue than was evident in the scan. Other areas of his brain could have taken over functions usually performed by a normal cerebral cortex.
What's indisputable is that the boy definitely did have a brain, albeit a damaged one. Yet on Yahoo Answers, someone asked how a young man could live without a brain. This was a response from a Ph.D. in Biochemistry/Neuroscience.
One should certainly be careful about accounts such as these, as I think it is pretty well documented, and proven, that a human cannot survive without a brain. The individual referred to in this question, and examined by Lorber, more than likely has sufficient gray matter and a brain stem, to support normal function. Probably even has cortical matter to support cognition and intellect.
The criticism of the study is that Lorber mis-interpreted the CAT scan, as CAT scans can be tricky to read. Lorber himself admits that reading a CAT scan can be tricky. He also has said that he would not make such a claim without evidence. In answer to attacks that he has not precisely quantified the amount of brain tissue missing, he added, "I can't say whether the mathematics student has a brain weighing 50 grams or 150 grams, but it is clear that it is nowhere near the normal 1.5 kilograms."
I also found a good critique of Lorber's "almost no brain" claim from an anthropologist, John Hawks. He notes the logical flaw in focusing on the small proportion of people who have serious brain damage, yet can function almost completely normally.
Consider an analogy: take a large sample of high-speed rollover auto accidents and study all the victims who received no injuries requiring hospitalization. This sample of victims is a large set, although it is a small minority of the total number of victims. Now, what conclusions will we draw from our set of low injury accident victims?
Perhaps we will conclude that seat belts actually increase risk of injury, because uninjured victims were preferentially thrown clear of the crash. Or perhaps we will conclude that swerving to avoid hitting a squirrel is better than running it down, because rollover accidents present no significant risk of injury. Whatever we conclude, the biased sample is likely to mislead us, particularly if we do not recognize the direction of the bias.
The human brain is marvelously adaptive. It can rewire itself after an injury. Yet the fact remains that usually brain damage results in reduced capabilities. Just because some people have injured brains and function normally doesn't demonstrate the separability of mind and matter.
Neurological case studies like the "boy with no brain" are interesting. They illustrate how marvelously complex the brain is, and how little we know about many aspects of brain function.
But there's still no convincing evidence that consciousness is possible without a brain.