Animal research provides clues to obsessive compulsive disorder

On, off; on, off; on, off; on, off. Charles Walker, a British member of Parliament, has to turn the light switch on and off exactly four times before he leaves the room, otherwise his mind fills with dread that something bad will happen to him. He also feels the need to wash his hands frequently, often hundreds of times a day.

As you may have guessed, Walker suffers from obsessive compulsive disorder (OCD), a condition that takes him to "dark places", as he described in a profile last year in Britain's The Daily Telegraph.

Two out of every 100 people suffer from OCD, a condition that can be debilitating and destructive. To be "a little OCD" is a phrase that's widely heard nowadays, uttered by unaffected individuals who simply have quirky habits. Sadly, this trivialises a disorder that the World Health Organisation has classified as an important cause of illness-related disability.

OCD consists of obsessions and compulsions which can develop to such an extent that they are a handicap to daily life. The first part of this disorder are obsessive thoughts, which recur frequently and can lead to severe anxiety. The second part is compulsive behaviour: repetitive actions performed to reduce the anxiety associated with the obsessive thoughts.

By imaging the brain, scientists have identified dysfunctional activity between regions thought to be linked to OCD. The first of these involves neural circuits located between a region in the front of the brain, called the orbitofrontal cortex, and cerebral structures located deeper at the base of the brain.

Another key area of research is communication in the brain between the neocortex and the striatum, a part of the brain related to decision-making, planning and response to reward, as well as problematic behaviour such as addiction and repetitive actions.