Depression causes people to perceive the world and all sensory stimuli in an overly negative manner—pleasant stimuli become less attractive and unpleasant stimuli more undesirable—and this contributes to the development and maintenance of depressive symptoms.
But the mechanisms underlying this “negative bias” were previously largely unknown. An international group of scientists tried to shed light on this issue by studying the activity of the amygdala in a mouse model of depression, reports the press service of the Pasteur Institute (France).
Like depressed bipolar human patients, the mice exhibited behavior characterized by anxiety and stress and responded negatively to olfactory stimuli (they were almost unattracted by the smell of females and strongly repulsed by the smell of predators).
Scientists have studied the amygdala and observed how it works during depressive episodes. It turned out that depression changes certain specific neural circuits, which leads to:
- decreased activity of neurons responsible for the pleasant perception of positive stimuli;
- excessive activation of neurons responsible for the perception of negative stimuli;
- Thus, depression appears to cause dysfunction in amygdala circuits involved in encoding environmental stimuli, which in turn further encourages the negative valence shift characteristic of depression.
We now know that the amygdala is not only involved in our emotional response to environmental stimuli, promoting attraction or repulsion, but also plays a role in the development of depression, the researchers note.
The scientists were also able to at least partially reverse the mice’s negative emotional bias and associated depressive behavior by over-activating neurons involved in the positive encoding of environmental stimuli.
We are now investigating in humans whether successful treatment of a depressive episode depends on the reactivation of these neural networks, the researchers note.
The discovery is expected to help develop new treatments for people with depression, as well as for people with bipolar disorder, who experience disproportionately long and severe mood swings.
From the point of view of modern science
Source: Racurs
I am David Wyatt, a professional writer and journalist for Buna Times. I specialize in the world section of news coverage, where I bring to light stories and issues that affect us globally. As a graduate of Journalism, I have always had the passion to spread knowledge through writing.