Although no one can say with certainty how conscious experience is realized in relation to the brain's activity, all the evidence seems to indicate that it must occur somewhere downstream from the LGN (lateral geniculate nucleus). The reason I say "downstream" is because the optic nerve connecting the retina to the LGN is an afferent nerve through which information is passed in one direction only.
The retina is, of course, an integral part of the overall nervous system, but it's activity seems to be primarily in preparation for sending information to the brain. Within the retina, there is a complex system of intercellular inhibition which seems to be a means of regulating any given cell's response in relation to that of neighboring cells. Another aspect of this preparatory activity is the transformation of graded potentials to action potentials which is analogous to transforming analog signals to digital. This may be a way to minimize errors during the transmission of the signal. In addition to this, the mind distinguishes between neural signals from different sense organs not according to any characteristic of the signals themselves but according to which pathway conveys the signal to the brain. That rules out the possibility that neural signals are somehow transporting phenomenal qualities from the outside world.
In my opinion, all of these physiological facts seem to be more consistent with the sense-data theories which were predominant prior to the 20th century. John Searle is an example of modern philosophy's opposition to sense-data theories. He claims that our conscious experience gives us direct access to the objects of perception (see Intentionality, p.45), but he also makes some assertions which seem to oppose the possibility of such a theory. For example, he recognizes that perceived attributes are distinct from how the "world really is" (Intentionality, p.75). He also acknowledges the causal nature of physiology and even asserts that visual experience occurs within the brain:
"Notice that this story is a causal account, it tells us how the visual experience is caused by the firing of a vast number of neurons in literally millions of synapses. But where, then, is the visual experience in this account? It is right there in the brain where these processes have been going on. That is, the visual experience is caused by the functioning of the brain in response to external optical stimulation of the visual system, but it is also realized in the structure of the brain." (Intentionality, p.267)
If visual experience occurs within the dark recesses of the cranium and has no means to access the world as it is upstream from the LGN, it's difficult to imagine in what sense we can be said to have a direct access to the objects of perception. Michael Tye is another philosopher opposed to sense-data theory, and according to his account, consciousness is "transparent". Of course, he gives no physiological explanation how that might be possible.
My question is: Among the philosophers who make similar claims, such as to having direct access to the objects of perception or that consciousness is transparent, are there any that have attempted to explain that in physiological terms?