The critical impairment in Alzheimer’s disease is the breaking down of the bridge from Working Memory to Semantic Memory. Working Memory (WM) can on average hold several items for tens of seconds. This is long enough to do mental arithmetic, e.g. change from a £10 note. After this short time it is lost, or WM can try to send it across the bridge to Long Term (or Semantic) Memory (LTM), which is virtually unlimited. The bridge is a metaphor for the hippocampus, a sea-horse shaped piece of the brain.
The “pack animals on bridge” graphic illustrates WM ↔ LTM by analogy with trade to a remote Himalayan village. Villagers export their cheese and hides to the city, and in exchange get flour, medicine and cooking oil. Seven animals go back wards and forwards, unloading at village and city. Eight will break the bridge.
Recognising impairment. Normal ageing is mainly recognised by slower speed of information processing. General knowledge and vocabulary change little in the 70s and 80s. Speed, and hence parallel tasking drops steeply. Think of counting stops while on the London Underground. Then think of the same task but in a foreign script, e.g. Japanese hiragana. At age 50 you might read 8 characters in the 15 seconds on the platform. At age 75 you might only read four. Please grow old gracefully!
Time, place, person are three areas are changing all the time, so they make demands on the bridge from working memory. A person may tell a good story, play scrabble and recall films on the TV, but seem “forgetful”. A doctor would start the mini Mental State Examination tests by asking “What day is it?” (T), “Where are we now” (P) and “Who am I?” (P). Difficulty with TPP indicates the WM ↔ LTM bridge is deteriorating.
Working around this bridge is difficult, but we have to try. In the metaphor, we can think that some planks have given way. Then the villagers may have to manage with what they can produce themselves, and only very important things can be dragged across the laborious two rope system.
Cognitive workarounds during an impairment
Rehearsal, saying the same phrase several times is the most basic strategy. The language App
Duolingo typically repeats a new foreign word by 10 or 15 repetitions. For a person with early Alzheimer’s, learning the name of a new carer might take 20 or 50 repetitions. Names are not very important information, whereas appointments or a new address are very important. So you might have to say “Tuesday! Doctor!” dozens of times.
Work around gaps in vocabulary. The bilingual has long experience of getting round a missing word. They can give the shop, colour, and price of the item “Asda groceries, green, roundish, £1 each”) if the rare noun (“avocado”) is forgotten. They can give a brand name (“Transit”) if the generic noun (“commercial box van”) is forgotten. Or they can mime, draw, or point, ratheter than getting stuck at the missing word.
Reminiscence therapy, especially music appropriate to our teens/ 20s, can give good feelings, even if disoriented!
Reality orientation. An album of recent photos can re-establish year, place and person. This is almost the opposite of Reminiscence Therapy. It is reserved for high priority information. Most of the time it does not matter what day it is, or the price of bread, if someone else is doing the shopping. Two one litre water bottles can remind the person to drink the day’s water, and they can be colour-coded for husband and wife. This is more effective than “have you had a drink?” A calendar clock like the Véfaîî in the picture can give priority information.
