A brain network associated with attention is larger in people with depression

Symptoms of depression fluctuate over time, but many brain imaging studies of the condition study only one point in time. This has made it difficult to link networks of brain activity to different symptoms and mood swings. Now, a new study using long-term brain imaging data shows that a brain network involved in directing attention is nearly twice as large in depressed patients as in people who do not experience symptoms of depression, and remains great even when depressive symptoms subside.

“Honestly, when we started this project, we didn’t necessarily expect to find consistent, feature-like differences in the brain. [activity patterns] in people with depression,” says Charles Lynch, a neuroscientist at Weill Cornell Medical College. “We were more interested in looking for things that would change over time as their symptoms fluctuated.” The results, published on September 4 in Naturemay help improve various types of brain stimulation therapies for depression (SN: 21/9/23).

Lynch and his team hoped to uncover the driving forces behind mood swings in depression by mapping brain networks over time. Existing functional MRI data allowed the team to look at the brain activity of more than a hundred people, including those with and without depression, over several days. The data also included patient ratings of their depressive symptoms at the time of each scan.

The team identified networks of brain areas with the most coordinated activity and found that the salience network – known for identifying relevant stimuli and directing attention – was almost twice as large in people with depression. The network also directs the activity of two other networks; one that controls self-focused thinking and another that facilitates working memory during goal-directed tasks. Previous work hinted that the salience network may be involved in depression, but the findings were equivocal. The new study showed that although the overall shape of the network was similar in the two groups, its boundaries extended further outward in the depressed patients.

Although salient network boundaries remained stable over time and across moods, some changes in connectivity between specific network nodes corresponded to symptoms of deterioration. By analyzing network changes in two patients who were scanned over several months, the team found that the connection between the nucleus accumbens, which is involved in reward seeking, and the anterior cingulate, which plays a role in decision-making, weakened when patients reported. experiencing less joy.

Two individuals with bipolar II disorder also had enhanced salience networks, but those with autism or obsessive-compulsive disorder did not. “The specificity of salient network expansion to depression will thus be a very intriguing question to explore in future studies using transdiagnostic samples,” says Lucina Uddin, a neuroscientist at UCLA who was not involved in the study.

To investigate whether a large salience network might fully precede depression, the team analyzed a neuroimaging dataset of adolescents over time. They focused on 57 children who had no depressive symptoms when they were scanned between the ages of 10 and 12, but developed symptoms within a few years. These children had significantly larger networks than those who did not develop depression, and network size remained stable over time in both groups.

A larger salient network is not the result of depression; precedes depression, the results suggest. The authors believe the enlarged network may also be related to early life stressors or genetics, but more research needs to be done before anyone can say for sure.

A better understanding of the neural components that drive depression may lead the way to more precise therapeutic interventions, which would be particularly useful given the unreliable effectiveness of current medications.

“We think there is an opportunity to incorporate information about how functional brain networks are spatially organized in individuals with depression to inform how we administer brain stimulation therapies,” says Lynch.