From Gordon Robertson
Clare Wilson reports research suggesting that sleep helps to consolidate new memories and make room for fresh ones (16 July, p 8). Sadly, my wife has dementia and now has no short-term memory. She remembers old basic skills, nursery rhymes and music, but cannot sign her name, only print it rather badly. She seems to have a good night's sleep: but what is her brain doing in that time if she has no new memories to process?
West Malling, Kent, UK
