Science News: A pair of studies have examined how dopamine-producing nerve cells can be activated and deactivated using laser light to trigger depressive behavior. Using mice genetically engineered to store light-responsive proteins, the researchers delivered pulses of light via fiber optics to a region of the brain called the ventral tegmental area. The first study examined mice that were subjected to chronic stress over several days. The researchers showed that by increasing the activity of the dopamine-producing cells with just a single brief flash of light, signs of depression went away immediately. Similarly, decreasing the activity immediately exacerbated the depressive behavior. The second study examined the effect of light stimulation on more acute stress responses. The researchers found that only a specific pattern of stimulation was effective in altering the response behavior. Stanford University’s Karl Deisseroth, a coauthor on both studies, says the research opens the door to potential treatments for depression and similar illnesses. However, he cautions that any such treatment is still a long way off.