Studies show that changes in the brain appear before the first symptoms of depression appear. The discovery could help predict who might develop the disease. Depression impairs the brain’s internal communication before symptoms of the disease appear, a recently published study revealed. Using a brain scan called fMRI, researchers found that depression rearranges an important area of the brain linked to motivation and attention.
“The main finding is that there is an expansion of the area of the cortex occupied by a brain network called the salience network. Previously it was not known that clinical conditions of depression could expand brain networks,” said Jonathan Roiser, neuroscientist and neuroscientist of depression. specialist at University College London, UK, who did not participate in the study.
The study, published in the scientific journal Nature in early September, analyzed the brain activity of 141 patients with depression and 37 without the disease. The goal was to find out how the disease changes the way brain regions communicate with each other.
“We typically look at the brain by the way its regions communicate with each other, as if they were all involved in a team phone call. The question is which other regions are you talking to and which network are you part of,” said Miriam Klein – Flügge, a cognitive neuroscientist at the University of Oxford, UK, who was not involved in the study.
The researchers found that the so-called “frontostriatal salience network” was expanded in participants with depression, compared to the group without the disease. This network is important for guiding attention, focusing on relevant stimuli entering the brain and regulating emotional responses to them.
“It is not yet known exactly what this network does, but it is already known to be important for mental health symptoms, including depression and anxiety,” Roiser said.
Salience network expansion predicts depression
The evidence of increased salience discovered in the study was considered a robust indicator that could predict whether people would develop depression later in life. The researchers found that this network had already been expanded in a group of children aged 10 to 12 who later developed depression in adolescence.
Klein-Flügge said the discovery was “exciting and very rare.” For the study, researchers measured participants’ brain activity over a long period, when they were well and also when they were sick.
The study also showed that the strength of the salience network is related to some symptoms of depression, particularly those related to loss of pleasure and motivation.
But it is not yet possible to deduce from the study data whether the changes in the salience network are linked to any particular psychological experience or depressive thoughts, according to Emily Hird, a neuroscientist at University College London.
The study did not compare brain activity to the participants’ symptoms or thoughts, but simply observed the “resting state.”
Instead, remapping the salience network can be seen as “a kind of trait, a risk marker to help identify people who are vulnerable to developing depression in the future,” Hird said.
Brain networks are remapped in depression
But if the salience network has expanded in depressed people, how exactly does it expand? According to Roiser, the network is remapped to include regions of the brain that are not normally involved in the salience network, including regions important for depression.
“They demonstrate that the salience network intrudes into other regions of the brain, including a region that we know plays a key role in the decision to exert effort,” Roiser said. “This is very interesting because we know that there is a reluctance among depressed people to engage in tasks that require effort.”
Roiser and Hird believe that ongoing research indicates that the known antidepressant effects of exercise may be related to altered activity in this exercise network. “Exercise is very effective against depression, at least as effective as antidepressant drugs or psychotherapy,” Roiser points out.
Klein-Flügge was surprised that the study did not discuss a brain region called the amygdala, which is important for processing emotions. “This area of the brain has been the focus of depression research for decades. It may seem like it’s not important, but we know from previous work that it is very important in depression.”
A new “biomarker” for depression?
Because the broadening of the salience network was so stable and predictable in people with depression, Klein-Flügge suggested that it could be used as a potential new “biomarker” for the disease in the future.
A biomarker is a measurable way for doctors to detect a disease or disorder in patients, such as the antigen test for Covid. If so, the size or “expansion” of the salience network measured in brain scans could one day become a biomarker for depression.
“To know whether this can be reliably used to predict an individual’s likelihood of developing depression, larger samples and replication of this work are needed,” Klein-Flügge said.
However, Roiser is more skeptical. He doesn’t believe scientists will ever find a biomarker for depression. “I don’t think depression is a homogeneous entity neurobiologically, so there won’t be a single biomarker for it.”
Instead, Roiser thinks of depressive symptoms as manifestations of many different brain states. “This is how doctors thought of dropsy, which was swelling of the legs. Now we know that dropsy is not a disease, but the manifestation of many different diseases,” he explains.
Roiser believes depression is similar. “Depressive symptoms likely arise from a complex interaction between different brain circuits that govern how we think, feel and behave, with different circuits generating symptoms in different individuals.”
Source: Terra
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