This assumes that the laws of nature distinguish between living beings and the neurons which encode memories. If someone changes the past so their memories are changed, the neurons would be sent to the DBT.
Memory is just as "physical" as data stored on a computer. Memories are simply data stored in the brain, its part of your physical being (as the brain is part of your body).
I understand what you're getting at and why the Grandfather Paradox exists the way it does. I still think that this can be explained.
The point I was trying to make is that there is fourth dimensional time as we know it and is the normal flow of time and what the time periods exist in. Then, there is a time flow outside of time, and the only way I've found to explain it so far is by proposing that there is a fifth-dimensional level in the Chrono Universe where along this second "time" axis one can move back and forth across fourth dimensional time.
So, once one begins travel throughout 4-D time and changes 4-D time, in order to retain these "old" memories of 4-D time (Time Traveler's Immunity), there must be a 5-D "time" axis along which the time traveler must be residing so that he or she is immune to such changes. This doesn't just include a living being that can remember, but also any object. Take the Wings of Time for example - its ability to travel in 4-D time makes it that it can reside on the 5-D axis.
Now, the problem with Marle comes into play. The problem with her is that she jeopordized her ability to reside on any axis of existence, not just 1-D, 2-D, 3-D, and 4-D. She made a change that must have affected her ability to come under the constraints of 5-D as well. As such, she was (probably) sent to the DBT, which I propose to be a patch of 5-D space where anything that doesn't belong in existence goes to reside (this may even be a 6-D plane... I'm still trying to figure it out). There she is still able to remember what happened there because she is technically still on some "time" axis.
Now, as far as the problem of "If she can disappear from existence, why don't her memories change?" goes, I'm approaching it thinking that there has to be certain conditions that need to be met for time traveler's immunity to happen. One of these conditions must be that the object or person must be able to physically exist along the 5-D "time" axis. So, in other words, changing time has its limits - memories along a 5-D axis are retained by the time traveler, but eventually if 4-D time is changed in a way that affects 5-D time, the consequences can be disastrous (as in Marle's case).
For now, this is the best solution I can propose for the Grandfather Paradox.
