Scientists and doctors long baffled by the multiple causes and brain processes for depression may now have a single "holy grail" brain pathway to focus on for treatment, according to a new research study released on Thursday.

Studying the brains of rats, researchers at the Stanford University School of Medicine have discovered a single brain circuit that appears to funnel all the mechanisms and treatments of depression.

Depression-related behaviour is manifested in changes in electrical signals moving through the circuit, according to the study released on the journal Science's website.

Karl Deisseroth, a professor of bioengineering and of psychiatry and behavioral sciences, said the circuit can help explain why there can be many causes and treatments of depression. "It also helps us understand conceptually how something that seems as hard to get traction on as depression can have a really quantitative, concrete basis," he said in a summary of the study.

Deisseroth led a research team to see if they could demonstrate how malfunctions in brain circuitry could be at the root of depression.

They studied the electrical activity of still-active slices of the hippocampus section of rat brains treated with flourescent dye, using high-speed high-resolution cameras to record activity in brain neurons in real time.