Positron emission tomography imaging in depression: a neural systems perspective

Depression is a common neurobehavioral disorder, characterized by persistent negative mood and selective deficits in cognitive, circadian, and motor functioning. This article presents a synthesis of functional neuroimaging studies, interpreted in the context of a data-driven depression model. In this neural systems model, a major depressive episode is considered the net result of maladaptive functional interactions among a highly-integrated network of limbic-cortical regions that are normally responsible for maintaining homeostatic emotional control in situations of cognitive and somatic stress. Findings in depressed patients, identified using positron emission tomography measures of regional blood flow and metabolism, are discussed in this context, emphasizing illness-state and treatment-specific effects. Strategies to further characterize scanpattern variability are also presented from the perspective of identifying potential imaging-based biomarkers that will facilitate optimal treatment selection in individual, depressed patients.