Alzheimer's disease

入試問題では下線部の和訳が課されています。挑戦してみてください。
   Imagine your brain as a house filled with lights. Now imagine someone turning off the lights one by one. That's what Alzheimer's disease does. It turns off the lights so that the flow of ideas, emotions and memories from one room to the next slows and eventually ceases. And sadly --- as anyone who has ever watched a parent, a sibling, or a spouse succumb to the spreading darkness knows there is no way to stop the lights from turning off, no way to switch them back on once they've grown dim.
[from 2001 Tokushima-dai]

最近は「認知症」といわれている「アルツハイマー病」。この呼称は関係の専門家の間では評判が悪いようだ。「老人性痴呆」は、senile dementiaで、「痴呆」はdementia。dementiaの訳語として「認知症」は誤解を招く、というのが反対の理由。それでdementiaに｢認知失調症｣という呼び名を提案しています。ちなみに「アルツハイマー老人性痴呆」は、英語でsenile dementia Alzheimer's type（SDAT）。

運動によって予防が可能、という趣旨の最新のnews。
Exercise helps to flush a toxic molecule from the brain and causes a beneficial one to move in and protect nerve cells, research on mice shows. The discovery might help to explain why staying fit and keeping mentally active seem to fend off Alzheimer's  disease in humans.
[...]
Mattson(a researcher at the National Institute on Aging, in Baltimore)notes that the link between exercise and brain health is still not certain in humans, although the evidence is mounting up. Other research has found that staying mentally agile or even maintaining a slim physique may help to protect against Alzheimer's and other brain disorders.
[2 December 2005, [email protected]]

discoveryとはどういうことかまとめてみましょう。