Ever since researchers discovered that the mammalian brain produces neurons during adulthood, neuroscientists have been wondering what roles these new nerve cells play. One area where the cells crop up is the dentate gyrus, which helps to record memories in a way that distinguishes them as unique and thus prevents them from blurring one into the next. The newly born neurons turn out to be key to this discriminatory activity, called pattern separation, as is evident from what happens when the cells are blocked from being produced; in response to such treatment, animals have trouble differentiating between experiences they have had in similar settings.

People who suffer from anxiety-related conditions, such as post-traumatic stress disorder (PTSD), have deficits in the ability to tell the difference between innocuous situations and terrifying experiences from the past. This feature of their condition suggested that the dentate gyrus and its cadre of young nerve cells could be involved. In “Add Neurons, Subtract Anxiety,” published in the July 2014 Scientific American, Mazen Kheirbek and René Hen review evidence supporting the role of new neurons in pattern separation and the possibility that a shortage of such cells could contribute to anxiety disorders.

In the interview, recorded for the Groks Science Radio Show on PRX, Kheirbek expands on the prevalence and nature of anxiety disorders and discusses how stress can impede the formation of new neurons. In addition, he describes exciting new studies in his lab that take advantage of a technique called optogenetics to directly turn on—or shut off—specific target neurons. These studies revealed that neurons located in different regions of the dentate gyrus in mice can either eradicate or exacerbate anxiety—findings that suggest researchers may need to delve deep into neural circuitry to discover the most effective way to treat anxiety disorders. The discussion of the optogenetic research starts shortly after the 17-minute mark.