Health, Psychology

Alzheimer’s

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:

  1. Eyes →
  2. Object and feature detection, similar to current machine vision →
  3. Something that maps detected objects and features into a model of reality →
  4. “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.

An artistic impression of her vision. The image is mostly hidden by noise, but a red British-style telephone box is visible, along with a shadow, and a flag. The 'telephone' sign is floating freely, away from the box.

How might she see the world?

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