I suppose the central question to Buddhism and other non-materialist systems is: "If consciousness does not arise from neural processes, then what exactly is the role of such processes, what is the role of the brain?" Is there anything in Buddhism that addresses the obviously profound connection between mental phenomena and neural events ... ?
What you are saying here is dependent on materialist assumptions which need not be accepted by Buddhists.
Clearly if the brain is damaged the individual in question will change as a result in various ways. Certain senses may malfunction or be altogether lost. This cannot be denied.
However, that does not necessitate that the brain produces
consciousness, but could just as well be the physical receiver for it as some have suggested in the past. This isn't really an issue for Buddhism though.
The process of seeing has the eye as the faculty, though traditionally the mental consciousness is said to have no immediate basis in the body (the tactile faculty is associated with the body). The mental faculty (manêndriya
) could very well have the brain as its basis, though that is just an aspect of the mind and in particular thought or reasoning associated with symbols/marks/dharmas, and not the totality of the mind.
The mind is composed of four aggregates, with rupa
being often defined as matter and being physical, though this is problematic because it dissolves into the four elements which are associated with mere perceptions and nothing more substantial than that. The mind-matter dualism I don't think was historically relevant to many Buddhist thinkers.
In the absence of any strict mind-matter duality it isn't really a problem to suggest the brain acts as a faculty basis for the faculty of thought. Again, rupa
includes the four great elements of wind, fire, earth and water, which likewise dissolve into movement, warmth, firmness and moistness. Rupa
in itself is not a basis or foundation upon which the rest of the aggregates are built upon. In reality rupa
is a result of karma. Our universe is the collective result of all beings' actions.
From that perspective we slide into a more "idealistic" paradigm, though "idealistic" is a western label that might not be so applicable. If matter and subsequently the brain arise from past volitional action (karma), then the brain is just a perception
in our collective reality which like any other matter or energy dissolves under analysis. If the brain is damaged this is indeed perceived by both the victim and observers, though it is the ripening of karma perceived in a neat narrative of damaged organ resulting in damaged faculties and all the subsequent changes that occur without regard for all the innumerable causes and conditions behind it. One could look at the analysis a bit further and see karmic ripening at work when someone suffers a brain injury, though that model of causality is not so tangible for most people. It is easier to just witness a damaged faculty resulting in damaged senses or malfunctioning mental processes, though there is much more behind the occurrence.
This is of course a radically different perspective from what modernity generally believes, where matter takes primacy and such a materialist explanatory apparatus is employed to interpret phenomena, both "objective" and "subjective", meaning the brain is assumed to exist as is and definitely.
Again, if any strict mind-matter duality is set aside, the brain and all the other faculties are just a result of old karma
and merely perceptions in our mind-streams. If you give primacy to matter this makes no sense, but if you give equal primacy to all other realms of experience then it isn't fallacious at all. There is perception of matter constituting organs like the brain or heart, but what is the ultimate quality of that matter?
In any case, if Stevenson and Tucker's research on children with past life memories is accurate, the theory of the brain producing consciousness and agency can be discarded. If consciousness can transit from one person to another then such a theory can be dismissed. The problem is reproducing past life memories scientifically, which is probably not possible, though nevertheless there is overwhelming well-documented evidence suggestive of the phenomena, to say nothing of metaphysical approaches to the subject.
The other issue with asserting that matter produces consciousness is a question of emergentism versus panpsychism. http://plato.stanford.edu/entries/panpsychism/http://en.wikipedia.org/wiki/Emergentism
In short, it begs the question at what point does consciousness arise from matter? Why does consciousness only arise in certain combinations of matter? Or does all matter inherently contain the quality of primitive consciousness (if that's true you get panpsychism)?