Illuminating circuitry relevant to psychiatric disorders with optogenetics

•Optogenetic dissection of disease-relevant neural circuits is accelerating the pace of preclinical research into the etiology and treatment of mental illness.•Optogenetics enables the complex neural circuitry impacted by psychiatric disease to be parsed into tractable, experimenter-defined elements that can be studied individually.•Efforts to date have primarily focused on neural circuits relevant to anxiety, conditioned fear, addiction, depression, and obsessive compulsive disorder.•These studies have revealed distinct synaptic and behavioral roles for anatomically- and genetically-defined cell types within numerous brain regions.•Proof-of-concept studies have demonstrated the potential of optogenetics to reverse or ameliorate maladaptive neural or behavioral changes in rodent models of psychiatric disease.

The brain's remarkable capacity to generate cognition and behavior is mediated by an extraordinarily complex set of neural interactions that remain largely mysterious. This complexity poses a significant challenge in developing therapeutic interventions to ameliorate psychiatric disease. Accordingly, few new classes of drugs have been made available for patients with mental illness since the 1950s. Optogenetics offers the ability to selectively manipulate individual neural circuit elements that underlie disease-relevant behaviors and is currently accelerating the pace of preclinical research into neurobiological mechanisms of disease. In this review, we highlight recent findings from studies that employ optogenetic approaches to gain insight into normal and aberrant brain function relevant to mental illness. Emerging data from these efforts offers an exquisitely detailed picture of disease-relevant neural circuits in action, and hints at the potential of optogenetics to open up entirely new avenues in the treatment of psychiatric disorders.