The default mode network and self-referential processes in depression

Summary & key facts

The study looked at a brain system called the default mode network, which becomes active when we think about ourselves. In healthy people this network quiets down when they do tasks that are not about themselves. People with major depression did not quiet this network when they looked at negative pictures or tried to re-think those pictures in a less negative way. The depressed group also showed bigger responses in brain areas tied to emotion and memory when viewing negative images. The researchers say this pattern could help explain why people with depression get stuck in negative, self-focused thoughts, but the study does not prove what causes what.

Key facts:

• The default mode network is a set of brain areas that work together when people think about themselves.
• Normally, activity in this network goes down when someone does goal-directed tasks that are not about the self.
• In people with major depression, several parts of this network failed to decrease activity while they looked at negative pictures or tried to re-think the pictures in a less negative way.
• When looking at negative pictures, people with depression showed larger responses in emotion- and memory-related areas of the brain, including the amygdala and hippocampus.
• The results suggest depression involves both stronger reactions to negative things and a reduced ability to turn down self-focused brain activity, but the study shows brain differences and does not prove that these differences cause depression.

Abstract

The recently discovered default mode network (DMN) is a group of areas in the human brain characterized, collectively, by functions of a self-referential nature. In normal individuals, activity in the DMN is reduced during nonself-referential goal-directed tasks, in keeping with the folk-psychological notion of losing one's self in one's work. Imaging and anatomical studies in major depression have found alterations in both the structure and function in some regions that belong to the DMN, thus, suggesting a basis for the disordered self-referential thought of depression. Here, we sought to examine DMN functionality as a network in patients with major depression, asking whether the ability to regulate its activity and, hence, its role in self-referential processing, was impaired. To do so, we asked patients and controls to examine negative pictures passively and also to reappraise them actively. In widely distributed elements of the DMN [ventromedial prefrontal cortex prefrontal cortex (BA 10), anterior cingulate (BA 24/32), lateral parietal cortex (BA 39), and lateral temporal cortex (BA 21)], depressed, but not control subjects, exhibited a failure to reduce activity while both looking at negative pictures and reappraising them. Furthermore, looking at negative pictures elicited a significantly greater increase in activity in other DMN regions (amygdala, parahippocampus, and hippocampus) in depressed than in control subjects. These data suggest depression is characterized by both stimulus-induced heightened activity and a failure to normally down-regulate activity broadly within the DMN. These findings provide a brain network framework within which to consider the pathophysiology of depression.

Topics

Functional Brain Connectivity Studies Mental Health Research Topics Neural dynamics and brain function

Categories

Cognitive Neuroscience Life Sciences Neuroscience

Tags

Amygdala Anterior cingulate cortex Brain activity and meditation Cognition Cognitive psychology Cortex (anatomy) Default mode network Depression (economics) Economics Electroencephalography Functional connectivity Macroeconomics Neuroscience Posterior cingulate Prefrontal cortex Psychology Stimulus (psychology) Ventromedial prefrontal cortex

Conditions & symptoms

Depression Lack of energy or motivation Sadness or low mood