I am not sure if this is accurate but intuitively, in strong psychedelic experiences it feels that both the DMN and DAT are active at the same time, which leads to, among many other things, a clearheaded view of mental processes that are hard to observe otherwise. One example would be observing emotions and how they affect your state of mind, while at the same time being totally detached from them. Some studies [1] propose that this happens because of an increase in connectivity between various parts of the brain, which could also be the thing that leads to ego dissolution.

[1] https://www.cell.com/current-biology/fulltext/S0960-9822(16)...