The version of mind brain interaction most popular in neuroscience these days is a version of physical monism called epiphenomenalism. Some form of epiphenomenalism is essentially required from a physical monist perspective to account for anything resembling mind or qualia. This perspective describes an emergence of consciousness or mind from the biological complexity of the brain. Hoffstadter and others assume this perspective, and argue that new phenomenon arise from complexity in many physical systems. Examples often given include the complexity of fluid motion not being clearly predictable from the observation of a single water molecule. Other philosophers find the concept so revolting that they don’t even dignify it as a legitimate perspective at all.
Arguments from complexity do create interesting an interesting delima, however. If the number of molecules in the Empire State Building meet a critical number, could they interact in a manner analogous to consciousness? If the number of Chinese in China reach a critical mass, does the country itself gain the quality of consciousness? David Chalmers and others argue that, in fact, China would become a conscious being at the level of a nation due only to complexity itself. Each person would have at least the interactivity of a neuron, and if enough interacted that would mirror neural nets, and if the total reached a critical mass then “consciousness” would arise. Although the experts who defend the complexity argument are forced to this position in order to maintain a coherent perspective, it is an increasingly difficult position to reasonably defend, in my opinion. What might be defined as the consciousness of a country or other large aggregate of interacting materials seems woefully different than what each of us experience as consciousness on a day to day basis, largely based upon the difficulty of defining who or what might actually experience that form of consciousness.
A key foundation of the principle of epiphenomenalism is the assumption that consciousness is an unintended byproduct of neuronal complexity. The corollary of this assumption is that consciousness, or perhaps mind, flows from the biology of the system, and could not even in theory control or alter the biological system itself, given that it is an unintended byproduct. Recent studies employing brain scanning technology bring this a priori assumption into serious question.