Both split brain and blindsight are two extremely bizarre conditions, which strongly suggest a certain relation of phenomenal conscious experience to the wiring of the physical brain.
It’s hard for any of us without the syndrome to imagine what it would be like to have that experience. As Joe explains it doesn’t feel any different from before, the brain just adapts to it. It clearly shows that processes need not be conscious to work.
It’s tempting to think from the Doctors words in the conclusion that there is a central processor at the end that produces consciousness. However because it provides strong evidence for the modularity of the human brain (and for that matter probably other animal brain with similar anatomy), I would argue such a strong conclusion is misled. There are hundreds of neural networks in the human brain, each serving separate but interconnected functions. When a split occurs between two related networks the brain is unable to process information between them and this is reflected in distorted and separated phenomenal conscious experiences as shown in split brain syndrome. The final stage would not be possible with at least most of the earlier processes, and it functions in the same way as any neural network; parallel distributed processing PDP.
The brain does not have a soul, unified self or a central processor behind it. It functions using distributed and interconnected network processing, and the strange phenomenal experience related to lesions between such networks is clear evidence of this. However it does indicate that only once a certain level of processing has occurred, consciousness can emerge. This leads us nicely to “Blindsight”.
Blindsight occurs when damage in higher processing areas of the visual cortex, lead to a lack of visual phenomenal conscious experience in both or one eye (depending on whether the left or right hand side of the visual cortex is damaged.) The interesting part is that in experiments, researchers have shown that patients are able to point at a dot on a screen with something like 99.9% accuracy (clearly showing that this wasn’t luck.) without any visual conscious phenomenal experience whatsoever.
Thats pretty incredible. The experiment is clear evidence not only for the modularity of various brain functions, but also that phenomenal experience only emerges at a higher level of brain processing. Lower order visual functions (like point recognition) are possible by processing in lower order areas without the use of phenomenal experience that emerge from higher order processing. We can only draw firm conclusions from blind sight on the emergence of visual consciousness since it only demonstrates that aspect of consciousness. However it would be strange and very counter-intuitive to reason that it wouldn’t apply to at least the other 4 senses if not higher order cognition as well.
It seems to me to strongly indicate that only animals with the correct brain modules or at least the necessary complexity of neural network processing, would have any visual consciousness. Thus it is possible that many insects don’t have visual consciousness and all their functions are facilitated by lower order unconscious processing. I’m not an expert in neuroscience or the anatomy of animal brains so I’m not sure how high up the animal chain we can go here. All insects? All reptiles? All mammals but us? Perhaps if any neuroscientists reading this have the expertise they can shed some light.
This condition also has implications for AI. We might well argue, if we believe artificial consciousness is possible at all, that only AI programmed with the correct modules and complexity would have any consciousness, visual or other! This may seem obvious to many, but blindsight experiments (and split brain ones to for that matter) gives clear empirical evidence for it.
I’m not going to go any further here as I don’t have sophisticated knowledge of the neuroscience and biological anatomy of the brain, but hopefully the philosophical insights have been interesting and thought provoking.
