One of the most problematic issues in panexperientialist theories is how purported centers of experience at the microexperiential level relate to each other and to human consciousness at the macroexperiential level. A related issue is whether there is one, all embracing experience which encompasses the whole Universe.
In the past I have rejected the notion of an overarching experience (which, for want of a better term, I’ll call “the One") as unnecessary, and regarded the postulation of such as wishful thinking on the part of the religiously or “New Age” inclined. I have also found Whitehead’s postulation of God as the necessary ground of creative potentiality difficult to understand and unconvincing.
On reflection, however, it seems to me that if one accepts that experience is not restricted to brains, then there are no a priori reasons why one should reject the concept of the One. Therefore, I think that each claim should be assessed on it’s merits.
Philosophers who support the notion of the One have a long lineage of course, most notably Hegel, Spinoza and Eastern traditions. However, I prefer to focus on reading those who have developed their ideas in the light of contemporary scientific knowledge (as an aside, from a sociological point of view I think that linking the One to panexperientialism will make the latter less likely to be taken seriously by the broader scientific and philosophical community, but that issue is separate from the issue of the merit of the claims).
Two contemporary philosophers who advocate both panexperientialism and the One are Freya Mathews and Timothy Sprigge.
Mathews in her book "For Love Of matter" (which, despite the title, I found to be generally well argued, though very speculative in later chapters) argues that the concept of the One solves the dilemma of the relationship between the generally indiscrete and discontinuous nature of space and matter and the unified, discrete character of experience. Microexperientiality is not even entailed under Mathews' views, which, following a Spinozistic model, only attribute centers of experience to entities showing purposeful or conative characteristics. Mathews' view that physical reality as a whole can be regarded as an indivisible unity is argued for at greater length in her earlier book, “The Ecological Self” ,which I don’t have at the moment so can’t comment on.
Timothy Sprigge in his book “The Vindication of Absolute Idealism” argues that if one accepts panexperientialism then the likelihood of the One existing follows. This is based on the view that things can only relate to each other through making up a whole together, and the only whole which experiences can form together is that of an overarching experience.
I found Sprigge’s argument rigorous, complex and difficult. Unforuntately, I no longer have access to the book, but hope to return to it some time in the future.