I have noticed something interesting about my 25I experiences: My memory is much better than normal. I've experienced this only while on 25I and remembering experiences that occurred during that same trip. In other words, 25I makes it somewhat difficult to recall things that happened in the past before the trip. After the trip, I have trouble remembering things that happened during the trip. But, while I'm tripping, I remember more than normal about events that happened within the past few hours. I've never tried before, but it would be interesting to perform a memory test before and during a 25I experience.
Disclaimer: 25I is the particular drug that I was on when I notice this effect, but I find the experience to be subjectively very similar to the LSD experience, so I'm not trying to make a connection between memory and 25I in particular, but more so between memory and certain types of psychedelic experiences.
My understanding of why this might occur is that psychedelics increase neuroplasticity, thus allowing for new connections, and thus new memories, to be formed very easily at the expense of older memories that have to share the same neural space. After the trip is over, neuroplasticity decreases and the brain, in performing some neural housecleaning, throws out some of the new connections that were formed during the psychedelic experience in order to better organize and make sense of older, and thus more rooted, memories.
Another theory I have for why this happens is that the brain does not create new connections, but finds novel ways to use preexisting neural connection schemes to store information. For example, there is substructure of neurons in my brain that is trained to find a light switch in the dark. During a psychedelic experience, other parts of my brain can make use of this structure and use it to optimize other tasks, effectively mapping its functions to a different purpose. As a result, when I need to actually find a light switch in the dark, the task is performed very clumsily because that neural structure is being hijacked by another part of my brain.
Every day I am thankful that I was introduced to psychedelic drugs.