When antipsychotic and antidepressant drugs became more commonly prescribed, the prevalence of these invasive, irreversible techniques reduced, but the lessons learnt for the brain areas involved would become important for deep brain stimulation as we know it today.

In 2002, deep brain stimulation was approved to treat Parkinson’s disease. It has been extremely effective and more than 40,000 patients have now been treated. Though it’s largely used for tremor disorders, this heralded its use in the treatment of other conditions, such a severe depression in the case of patients like Anna. To perform deep brain stimulation, first scientists use a drill to put a burr hole in a patient’s skull. After that, they place electrodes onto the brain itself. The patient is often awake, enabling researchers to test the specific area while the brain is stimulated.

In Anna’s case the target area for stimulation was the nucleus accumbens, which is part of the brain’s reward centre and an important area for processing pleasure. The area has been linked to depression – as depressed individuals show a reduced interest in pleasure. “You can observe an emotional response by a patient when you are stimulating [this area],” explains Munte, who spoke to BBC Future about his patient, as she wishes to remain anonymous. His analysis was written up in the journal Neurocase.

Treating obesity

Obesity in some individuals, can be due to an altered reward system in the brain, says Munte. Some obese people even show differing brain patterns when exposed to pictures of delectable-looking food than do thinner people. The theory is that the nucleus accumbens is the area that draws addicted people to the object of their desire, be it food, alcohol or drugs. Usually the area of our brain that helps us act rationally prevents the impulsive immediate-reward-hungry part our brain from taking over. But our reward system can, at times “overtake our good manners,” says neurosurgeon Piotr Zielinski, of the University of Physical Education and Sport in Gdansk, Poland. The diet industry flourishes thanks to our nucleus accumbens, he says.