> It’s a challenge not only for panpsychist approaches to consciousness, but also materialist approaches: How do parts, like neurons, combine into a whole, a single consciousness?

What makes you think there really is a whole single consciousness? Maybe we're just a bubbling cauldron of all kinds of signals encoding thoughts, emotions and sensations, and the strength of these signals dictates which ones drive our observable actions in the moment. The signals that yield "pleasure" signals get boosted, those that yield "pain" signals are suppressed, and over time, structure emerges that we recognize as "personality". I'm not sure this structure that privileges and suppresses a network of signals would qualify as a "whole, single consciousness"; a "single consciousness" in this framework would be an illusion.

For a decent tech analogy, there is no "whole, single Internet", that's merely a euphemism we use for a dynamically changing network of computers. The routing tables encode the structure of preferred pathways based on current semi-optimal routes, basically boosting or suppressing some routes as their performance characteristics change. So it may be with consciousness.