Understanding Brain Reward Responses in Individuals With Major Depressive Disorder

Major depressive disorder (MDD) is a severe form of depression that can significantly interfere with an individual's thoughts, behavior, mood, and physical health. People who suffer from MDD may experience anhedonia, or the inability to gain pleasure from normally pleasurable experiences. Such individuals do not respond to motivational rewards in the same way as do individuals who are not depressed. Anhedonia has been recognized as a core symptom of depression and it is not always remedied with antidepressant medication. Abnormal brain activity and processing may be the underlying cause of depression and specifically anhedonia. A better understanding of the brain mechanisms of depression may lead to the development of new effective medications or psychological treatments. Event-related potential (ERP), which measures electrical activity in the brain, and functional magnetic resonance imaging (fMRI), which uses scanned images to illustrate changes in brain activity, are two techniques that can identify abnormal areas of brain processing. The purpose of this study is to use ERP and fMRI to compare brain activity that is related to reward processing in individuals with MDD versus individuals without MDD. This study will consist of 3 study visits; visits will be scheduled as close together as possible. At the first study visit, potential participants will be assessed with the SCID (Structured Clinical Interview for DSM-IV), which will identify individuals with the diagnostic criteria for MDD. A control group of non-depressed individuals will also be enrolled in the study. During the second and third study visits, participants will take part in a monetary reinforcement reward task followed by a signal detection reward task. Brain activity of all participants will be monitored during both tasks. During the second study visit, ERP will be used; during the third study visit, fMRI will be used. Demographic information will also be collected, and participants will complete several standardized questionnaires to assess mood. Some participants will be asked to return after eight weeks to complete the fMRI and EEG sessions again. Those who do complete all five sessions will be awarded a bonus.