Researchers have shown exactly how the anaesthetic ketamine helps depression with images that show the orbitofrontal cortex — the part of the brain that is overactive in depression — being ‘switched off’. Ketamine, an anaesthetic that is popular with doctors on the battlefield and also with vets because it allows a degree of awareness without pain, is a new hope for the treatment of depression — but the minute-by-minute images show how the drug achieves this in an unexpected way.