(read Part I below first)
Another possibility raised by the findings of this research team is to link the event of ego-loss to the collapse of the integrated baseline brain state. If the so-called hubs that connect and thereby integrate different brain regions show a significant reduction of access on psychedelic drugs, one can speculate that the notion of ego or 'I' is dependent on the operation of the interconnecting nodes in the cerebral structure. As the brain parts lose their baseline integration yet stay operational, one of the main things that are lost is the very epitome of integration, the idea of 'me'.
Unlike Carhart-Harris I don't believe that the brain remains in some disorganized, chaotic state after losing the hub connectivity, but rather re-organizes itself into something else, probably with larger portions of the mammalian and reptile brains in play. However, with sufficiently large doses the re-organization may not result in a different type of consciousness, but rather the loss of ego is followed by a truly transcendental state marked by profound, cosmic ideation, non-dualism, unearthly bliss and so on. Where this transcendental state (level 4 on the General Trip Model) originates in consciousness, if it indeed comes from consciousness at all, is a matter where so little is known that we don't even know what questions to ask. As for the ego-less state however, it is significant that the ego always returns as the effect of the psychedelic compound wears off; in the perspective of Nutt's and Carhart-Harris' research group, this would mark a reactivation of the connecting hubs in the cerebral network, and a re-emergence of the familiar, baseline configuration of the mind.
Finally, a few words on memory in and out of the psychedelic state. The British research team made another unexpected find here, which is that on psilocybin, the brain activity during memory access and memory processing did not primarily show in the memory parts of the brain, but rather in parts that deal with perception and emotion. Carhart-Harris explains this as the experiece of the memory being much more vivid and living whe under psychedelics than in the normal, baseline states. This seems accurate enough, both logically and experientially, but it does not explain why the revisited memory is more vivid and living in this state. One might say that it's a function of the general magnification of all perceptual and emotional processes, but the memory retrieval is an entirely internal affair to the brain which does not necessarily pass through the same perceptual-cognitive machinery as external data does. So it's not a given, even if it appears likely that internal visualizations are magnified and deepened in much the same manner as external impressions are.
Carhart-Harris mentions one subject's dramatic recollection of a (presumably suppressed) memory of importance, and how the subject stated that "...there was nothing that prompted it, it happened spontaneously." This is brought up in a manner more anecdotal than significant, but once more it appears to me a failure to understand the holistic, self-healing tendency of the higher psychedelic state. Important memories whose recognition can help untangle psycho-dynamic traumas do not appear randomly during psychedelics, just as they do not appear randomly (much less frequently) in night dreams. The drive towards psychological healing in the early stages, and spiritual healing and a teacher/guide vocation in the more advanced stages, is a governed process which I refer to as the Overseer. Anyone who has taken a few steps under the aegis of the Overseer will testify that there is nothing random or disorganized about it.
Despite my objections, I found both David Nutt's presentation and Robin Carhart-Harris' video quite valuable, which should be obvious from the amount of text they triggered. Thanks for your patience.