BE CAREFUL BELIEVING YOUR OWN METAPHORS: I've cautioned students against using metaphors; though they make writing more vivid, and sometimes more persuasive, they often obscure more than they reveal. Part of the problem is that they are literally false -- if they were true, they wouldn't be metaphors. Sometimes the literal falsehood reveals a deeper truth, but sometimes it's just plain false.

Scientists performing experimental brain surgery on a man aged 50 have stumbled across a mechanism that could unlock how memory works.

The accidental breakthrough came during an experiment originally intended to suppress the obese man's appetite, using the increasingly successful technique of deep-brain stimulation. Electrodes were pushed into the man's brain and stimulated with an electric current. Instead of losing appetite, the patient instead had an intense experience of déjà vu. He recalled, in intricate detail, a scene from 30 years earlier. More tests showed his ability to learn was dramatically improved when the current was switched on and his brain stimulated.

Scientists are now applying the technique in the first trial of the treatment in patients with Alzheimer's disease. If successful, it could offer hope to sufferers from the degenerative condition, which affects 450,000 people in Britain alone, by providing a "pacemaker" for the brain.

Active people could be up to 10 years 'younger' than couch potatoes, at least according to one measure of biological age. Tim Spector, director of the Twin Research Unit at St Thomas’ Hospital in London, looked at the levels of physical activity of 2,401 twins and assessed the length of their telomeres - the 'caps' on the ends of their chromosomes that help to protect the DNA from wearing down during the replication process that replenishes cells. Telomeres shorten over an individual’s lifetime and are thought to function as a marker for ageing. Smokers and obese people were already known to have shorter telomeres than their healthier counterparts.