Returning to this topic, in an attempt to elaborate an understanding of the Abhidhamma that does not contradict current knowledge in Neuroscience. I propose the following hypothesis: the brain integrates the sensory structures of the physical body and, together with them, constitutes one of the conditions for the arising of the rūpa-pasāda.
For example, in the case of vision, one of the conditions for the arising of the cakkhu-pasāda is that, in addition to a functional eyeball, the brain area associated with vision must also be intact. Thus, it is possible for a person to have an intact eyeball and yet be unable to see — a condition known as cortical blindness.
When the visual apparatus of the body (eye + visual cortex) is intact, and there’s favorable kamma, the cakkhu-pasāda manifests. When contact occurs between the cakkhu-pasāda and a visual object, the cakkhu-viññāṇa arises. With the cakkhu-viññāṇa as condition, the hadaya-vatthu (heart-base) supports the arising of the other cittas derived from vision. The same reasoning applies to the other senses, except for the mind-door (which will be addressed separately).
In summary:
- The bodily sensory base (sense organ + brain) conditions, together with kamma, the arising of the rūpa-pasāda.
- Contact between rūpa-pasāda and object conditions the arising of viññāṇa.
- With viññāṇa as condition, from the hadaya-vatthu arise the other cittas related to the sensory process.
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In the case of purely mental objects (abstract, so to speak), the beginning of this process does not depend on any physical base (rūpa). At the threshold of the mind’s contact with a mental object, the consciousness that cuts off the stream of the life-continuum (bhavaṅgupaccheda-citta) arises. From this citta, the hadaya-vatthu (in beings endowed with rūpa) generates the other consciousnesses associated with the mental object.
This explanation of the Abhidhamma does not recognize the brain as a condition for the cognition of purely mental objects. Such initial processing would occur exclusively through the hadaya-vatthu, by mental processes that, at least initially, would be independent of the physical body. It should be noted that, in this case, the hadaya-vatthu does not necessarily have to be associated with the physical heart in order to perform its functions.