The title is a familiar mantra I hear from philosophers, a mantra that was largely accepted upon publication of Consciousness Explained. It is advanced as both an anatomical fact and a functional fact. What evidence is cited from neuroanatomy in support of the anatomical claim? I couldn’t find anything in Dennett’s book.
Before writing up something more detailed, I’ll just sketch where I plan on going. Most importantly the mantra needs to be clarified. What evidence would convince someone that a certain region of the brain was indeed “where it all comes together”? What is the scope of the ‘all’ in ‘it all comes together’? I suppose it means ‘There is no nucleus or cortical area that receives inputs from all sensory modalities’ or something like that. But there are plenty of candidates for such sensory convergence: basal ganglia, certain thalamic nuclei especially the reticular nucleus, the reticular formation in the brain stem, and perhaps some areas in the frontal cortex (e.g., some of the premotor areas). Note, I’m not saying any of these regions are the locus of consciousness, though some are probably important.
Ultimately what is important for Dennett is the functional claim rather than the anatomical claim (in personal correspondence, he agreed with this). That is, the claim that there is no Cartesian Theatre is orthogonal to the anatomical claim that there is no place (in the brain) where it all comes together.
So, that’s the direction I’m going. I was just wondering if, perhaps, I had missed some evidence the philosophers were using for the anatomical interpretation of the mantra. Since the functional arguments never really convinced me, and there doesn’t seem to be evidence for the anatomical side of the claim, I am not convinced there is no Cartesian Theatre. As Dennett says “It sure seems as if there is a Cartesian Theater” (italics mine).