Dr Hutter speculates that a sense of humour contributes to aging well because smiling and laughing provide the same benefits as exercise - she refers to laughing as internal jogging. Laughter raises blood pressure just long enough to increase oxygen and blood supply to tissues. It alters the breathing cycle so that more oxygen is inhaled and toxic carbon dioxide exhaled. Muscles throughout the body tense and relax during laughter in exactly the same way as with stress reduction techniques such as yoga.Herbert Lefcourt and colleagues at Waterloo University in Ontario recently established that exposure to humour improves immune system functioning, producing significant rises in the body's natural defences, such as antibodies in the bloodstream.Low antibody levels predict greater likelihood of future disease, yet what was particularily intriguing about Dr. Lefcourt's study was that, given something to laugh at, those with a good sense of humour experienced the highest rises in antibody levels.The ability of a good sense of humour to help cope with stress is now regarded as one of the most powerful defense mechanisms for dealing with problems over which you can do little.Recent research has also established that electrical brainwave patterns of the right and left hemisphere tend to co-ordinate more when we experience humour. This is important because evidence shows that depression is accompanied by less co-ordination in brainwave patterns between the two sides. What is particularily fascinating about the latest discoveries is that they confirm some of the oldest ideas about humour.Freud, who wrote one of the most unfunny books in the English Language, Jokes and Their Relation to the Unconscious, believed humour was a mechanism for anxiety release because a joke always has two halves. The first builds up psychic tension which is then broken by the ridiculous punchline. We are therefore allowed to release bottled up unease safely in a burst of laughter.But the punchline has to resolve the tension it sets up successfully and surprisingly - in other words, all jokes are really problems that have a clever but unexpected answer.Modern neurologists have found damage to the right brain - the emotional hemisphere - leads to acceptance of any incongruity as funny - sufferers laugh too much and often inappropriately.Meanwhile, damage to the left brain - the logical analytical hemisphere - leads to an inability to understand the incongruity in a joke - producing too much seriousness.This would suggest that humour is produced in the brain when the left hemisphere recognizes the incongruity in a joke while the right hemisphere - better at understanding the big picture rather than logical detail - resolves the anomaly. In other words the left cortex sets up the joke and the right gets it.Dr. Peter Derks, a psychologist at William and Mary College in Virginia, has found that electrical brainwave patterns confirming the brain has picked up an incongruity are vital for us to find a joke funny. The latest brain scanning technology, functional Magnetic Resonance Imaging (fMRI), is able accurately to localize brain activity. Research using fMRI is revealing where the humour centre in the brain is.