It’s as fascinating as it is sad to watch a relative fall, piece by piece, to Alzheimer’s. I had always thought it was just anterograde- and progressive retrograde amnesia of episodic memory, but its worse. It’s affecting:
- Her skills (e.g. how to get dressed, or how much you need to chew in order to swallow).
- Her semantic knowledge (e.g. [it is dark outside] ⇒ [it is night], or what a bath is for).
- Her working memory (seems to be reduced to about 4 items: she can draw triangles and squares, but not higher polygons unless you walk her through it; and if you draw ◯◯▢◯▢▢ then ask her to count the circles, she says “one (pointing at the second circle), two (pointing at the third circle), that’s a square (pointing at the third square), three (pointing at the second circle again), four (pointing at the third circle again), that’s a pentagon (pointing at the pentagon I walked her through drawing); and if she is looking at a group of five cars, she’ll call it “lots of cars” rather than instantly seeing it’s five).
- The general concept of things existing on the left side as looked at. (I always thought this was an urban legend or a misunderstanding of hemianopsia, but she will look at a plate half-covered in food and declare it finished, and rotating that plate 180° will enable her to eat more; if I ask her to draw a picture of me, she’ll stop at the nose and miss my right side (her left); if we get her to draw a clock she’ll usually miss all the numbers, but if prompted to add them will only put them on the side that should be clockwise from 12 to 6).
- Connected-ness of objects, such as drawing the handle of a mug connected directly to the rim.
- Object permanence — if she can’t see a thing, sometimes she forgets the thing exists. Fortunately not all the time, but she has asserted non-existence separately to “I’ve lost $thing”.
- Vocabulary. I’m sure everyone has a fine example of word soup they can think of (I have examples, both of things I’ve said and also of frustratingly bad communications from a client), but this is high and increasing frequency — last night’s example was “this apple juice is much better than the apple juice”.
I know vision doesn’t work the way we subjectively feel it works. I hypothesise that it is roughly:
- Eyes →
- Object and feature detection, similar to current machine vision →
- Something that maps detected objects and features into a model of reality →
- “Awareness” is of that model
It fits with the way she’s losing her mind. Bit by bit, it seems like her vision is diminishing from a world full of objects, to a TV static with a few objects floating freely in that noise.