By Paula McGrath Health check, BBC World Service For centuries, the brain was a mystery. Only in the last few decades have scientists begun to unravel its secrets. In recent years, using the latest technology and powerful computers further key discoveries have been made. However, much remains to be understood about how the brain works. Here are five important areas of study attempting to unlock the last secrets of the brain. How to fix it When we think, move, speak, dream and even love - it all happens in the grey matter. But our brains are not simply one colour. White matter matters too. Much of the research into dementia has focused on the tell-tale plaques of beta amyloid and tau protein tangles which occur in the grey matter. But one British scientist, Dr Atticus Hainsworth says the white matter - and its blood supply - may be equally important. The white colour results from fatty sheaths around the axons - which are extensions of the nerve cell bodies and help the cells to commu