The human mind can be literally divided with a knife. Have you heard of the peculiar effects of callosotomies -- the severing of commissures connecting both brain hemispheres (once used as a treatment for conditions like severe epilepsy)? Once a living brain is dissected via the corpus callosum, both hemispheres become independent centres of awareness. You get two minds in one body! Moreover, they often disagree with each other in opinion, beliefs, and control of the body.
It has even been reported that some split-brain patients possess one God-fearing religious hemisphere in contrast to a neighbouring atheistic one! According to some religions, one half of the brain should be going to heaven while the other one goes to hell...
But jokes about afterlives aside, consciousness is a real mystery. Why should any complex system of matter become aware of itself and often, but not a requisite, the surrounding world?
I am currently reading Sam Harris's "Waking Up -- A Guide to Spirituality Without Religion," and after mentioning what the phenomenon of binocular rivalry entails in healthy brains, he points out something quite profound about consciousness.
Imagine that each of your eyes are visually stimulated in different ways. One is shown a house, and the other, a face. Intuitively, you would expect to see a blending of images -- or a superposition of both -- in consciousness. But this is not the case. Rather, you see the house for a few seconds, then the face, then back to the house, and so on...
Surprised at this switching at random intervals? The input remains constant, and yet, conscious and unconscious components of vision continuously change as they occur in the brain. While you are conscious of one image, you become unconscious of the other. But wait! I haven't mentioned the greater mystery yet...
The subjects experiencing binocular rivalry are CONSCIOUS throughout the experiment! This implies that consciousness runs deeper than just being aware of sensory stimuli. Now, if you were to take away all the senses, surely, a "naked" awareness would remain, wouldn't it?
Even I'm racking my brains at that one. It seems that two different sets of visual data arrive in the brain but they are delivered one at a time interval (never simultaneously) to consciousness. And while we can say that when the individual is conscious of the house he is unconscious of the face and vice versa, we must acknowlege that consciousness is present throughout. At no point does the individual become unconscious.
Now, it could be argued -- against the implication that consciousness runs deeper -- that while we are aware of seeing the house (in its prominent appearance in consciousness), we also see the face. But because the house perhaps had more of an impact on the neurons, we forget that we saw the face, too. Subsequently, as the brain is aware that there is another stimulus to take into consideration, it removes the house (as it had enough conscious exposure) and introduces the face into visual awareness. Indeed memory and consciousness interrelate. Now, this is just a hypothetical explanation. I don't know why the binocular rivalry should be. Perhaps the brain hemispheres wrestle even when they are attached to each other as one prefers the face while the other prefers the house.
This is redolent of something else. Split-brain patients can draw two different things at the same time with ease: the left hand can draw a dog while the right draws a person. People with their brains intact, like you and me, will find this exercise next to impossible as one hand will tend to copy the other.
And then we arrive at lucid dreaming. Someone here once posed the question of whether or not dream characters are conscious. After all the talk about callosotomies and binocular rivalries, such proposition doesn't seem so far-fetched. Perhaps they represent the intelligent and conscious right hemisphere while the dreamer is mostly representative of the left hemisphere. Who knows! Split-brain individuals, funnily enough, report having only mundane dreams where Split-brain individuals, funnily enough, report having only mundane dreams where oneiric environments differ very little from the real world. It seems these poor people are deprived of the more surreal settings which tend to provide escapist adventures.
In our ordinary dreams, the dreamer lacks control and lucidity while dream characters seem as alive as ever and appear to know the dream setting well. But the dreamer quickly seems to rob them of their apparent elan vitale when lucidity is attained. Perhaps Waggoner wasn't far-off from the truth when he said that there is a kind of intelligence behind the dream. Some may want to argue that the right hemisphere does not deal in language and therefore isn't conscious. But I would dispute that by saying that experimenters are able to communicate with the right just as well as the left. The right hemisphere can recognise the shapes of written words and may use this to answer questions. It also exhibits more consciousness than an infant.
More to the point of this discussion, I don't believe in the afterlife (especially not the religious hereafter scenarios). Neuroscientific evidence strongly suggests that at death you've had it. But we must remember that consciousness is still a mystery. Just because I don't believe -- and just because evidence is strongly indicative of zero experience once the brain dies -- doesn't mean there is nothing. The debate hasn't really been settled as the scientific side that struggles to even define consciousness hasn't really provided us with something absolutely conclusive. Perhaps part of the conundrum is the fact that consciousness is trying to study consciousness. Could this be an impasse? I don't know.
When you open the brain and have a look, there is nothing to suggest that it's a locus of experience. Tomorrow, I could be surprised to find that consciousness is something independent of the brain. This, of course, would not necessarily confirm the existence of ghosts, miracles, gods, and eternal life.