Imaging a brighter future.

The first functional magnetic resonance imaging (fMRI) study of a psychiatric illness appeared in The American Journal of Psychiatry nearly two decades ago and began with the following statement: " Functional echo planar magnetic resonance imaging (MRI) probably will be of importance in assessing brain abnormalities in psychiatric disorders " (1). The ability to observe the physiology of the living brain has been an intriguing tool for psychiatry since the development of the EEG in the early 20th century, but the value of what has actually been learned has often seemed elusive. Certainly, there is as yet little, if any, clinical use for any form of functional brain imaging. Studies typically do not generate insight into how abnormal brain function determines patients' thoughts and actions. Clinical readers have every reason to skip over yet one more set of brain images, and research colleagues from other disciplines may wonder whether anything has been learned to warrant all of the efforts put into these studies over 17 years. What may not be appreciated is the emergence of a different perspective on how imaging informs understanding of mechanisms in psychiatric illness, a development illustrated by two articles in this issue of the Journal, by Shin et al. (2) and Etkin and Schatzberg (3). These two studies demonstrate functional alterations in the cingulate gyrus within the medial prefrontal cortex in posttraumatic stress disorder (PTSD), generalized anxiety disorder, and major depression. Psychiatry has long struggled with the limitation of our investigative tools. We cannot biopsy the brain or otherwise directly observe the function of its nerve cells, except as they are revealed indirectly through patients' words and actions. We do not have animal models for most illnesses, unlike other medical specialties for which animal models are keys to therapeutic advances. Of course, this is because of mental illnesses' complex features, features not easily modeled outside the clinic: laboratory animals cannot tell us of their moods and anxieties. The Shin et al. and Etkin and Schatzberg articles—not uniquely but certainly in an exemplary way—bridge the gap separating studies in people and animals. They do so by suggesting that the medial prefrontal cortex neurons mediating an animal's response to danger are also dysfunctional in human PTSD, anxiety, and depression. Both fMRI studies relate medial prefrontal cortex function to specific behaviors by showing increased cingulate cortex engagement in the context of reaction time slowing. People respond to simple …