Fiber Optics in the Brain Shed Light on Mental Disorders

Fiber optics implanted in the brains of mice are shedding new light on mental disorders, both figuratively and literally. Susanne Ahmari, a University of Pittsburgh researcher, is studying how pulses of light directed at certain parts of the brain affect behavior.

The technique is known as optogenetics, and the light is an important tool because it is used to either stimulate or inhibit certain neurons. Although we know that many mental disorders have physical roots in the brain, specifics for most are poorly understood. Seeing how the mice react to light aimed at specific areas gives clues on what might be going on physically to trigger certain disorders.

New Clues About OCD

Ahmari, who studies obsessive-compulsive disorder (OCD), found a possible causal link between certain brain activity and OCD behaviors. Many people with OCD are compelled to repetitively perform certain behaviors, even though they're aware of what they're doing and don't want to do it. Ahmari said the compulsion comes from "the intense anxiety and dread they feel from having these obsessive thoughts. They are really convinced that if they don’t do the compulsive ritual, a bad thing that their obsession suggests will happen."

Brain imaging in humans already offers a clue to the physical process going on behind the scenes. When people with OCD have obsessive thoughts, a circuit between parts of their frontal cortex and a deeper structure known as the striatum is hyperactive. However, it's unknown whether that activity causes the thoughts or visa versa.

Ahmari's work suggests that the brain activity is behind the compulsion. She pulsed blue laser light into that part of the mice brains for several days, and they started grooming excessively. The behavior continued once the light was stopped, although it gradually tapered off to normal.

A Link to Many Disorders

Ahmari isn't alone in her work. More than 1,000 research groups worldwide are using similar techniques to study everything from drug addiction to bipolar disorder. Not only does her work show promise in pinpointing how mental illness is triggered within the brain, but it may also lead to treatments. Researchers using optogenetics have used the technique to reduce cravings for drugs in mice and stopped epileptic seizures.

A human brain would likely require a different type of stimulation, as early work with monkeys shows that mammal brains need much stronger light pulses to stimulate changes. In the meantime, counseling and medication continue to be the front line treatments for mental disorders.