It's been very hard for me to quantify what is different in my head than before whatever happened to me. It occurred to me that perhaps it is measurable. I found some online tests that check things like memory speed and accuracy of recall. I'll post these as I find them.

http://cognitivelabs.com/global_cog_map1.htm

https://www.testmybrain.org/index.html

So far, what I'm finding is that my memory accuracy isn't too bad although it's not as good as it used to be. For example, I missed recognizing some fairly common faces that I do know but couldn't remember the name. What I primarily see, so far, is that the speed is really slowed down. In fact, in some tests I'm dramatically slower than the average. This is seems to match up with what I'm experiencing subjectively. I can remember things and I can do things but it's like slogging through molasses.