Belief Updating in Treatment Resistant Depression

Major depressive disorder (MDD) is characterized by a cognitive triad of negative beliefs about oneself, the future and the world. For example, depressed patients hold persistently negative expectations about the future, despite contradictory evidence, and these strong negative beliefs are thought to play an important role in the maintenance of depressive symptoms and potentially in treatment resistance. Indeed, one out of three patients with major depressive disorder does not respond to conventional, monoaminergic treatments, which has led to the concept of treatment resistant depression (TRD). It is unknown how the brain encodes the strong negative beliefs that are insensitive to positive disconfirming information in TRD patients, and how these neural underpinnings of maladaptive belief updating are altered by antidepressant treatment. The principal objective of this study is to gain insight into the brain mechanisms of belief updating about the future in TRD patients before and after starting ketamine treatment. The results of this study are expected to provide a better understanding of the neurocognitive mechanisms of belief-updating in depressed patients, and how these mechanisms contribute to clinical improvement following ketamine antidepressant treatment.