Scientists have identified specific brain circuits that appear to play a key role in anxiety, depression-like behaviors, and social withdrawal. Even more surprising, we found that restoring balance within this circuit was enough to reverse some of these behaviors in mice.
The study was led by Juan Lerma and his team from the Laboratory of Synaptic Physiology at the Institute of Neurosciences (IN), a joint center of Spain’s National Research Council (CSIC) and Universidad Miguel Hernández (UMH) in Elche. Their discovery is iscience.
Key brain regions associated with emotional disorders
The study focused on the amygdala, a region of the brain that helps regulate emotions such as fear and anxiety. Researchers have discovered that specific groups of neurons within this region can have a powerful influence on emotional and social behavior.
“We already knew that the amygdala is involved in anxiety and fear, but now we’ve identified a specific population of neurons whose unbalanced activity alone is sufficient to cause pathological behavior,” Lerma explains.
For their study, the research team used genetically engineered mice that produce abnormally high levels of the Grik4 gene. This change increased the number of GluK4 glutamate receptors, making certain neurons more excitable than normal.
This mouse model was first developed by the same laboratory in 2015. These animals exhibit behaviors similar to anxiety and social withdrawal, traits often associated with conditions such as autism and schizophrenia.
Reverse anxiety and restore balance
The scientists then targeted neurons in a part of the amygdala known as the basolateral amygdala. By normalizing Grik4 gene activity in this region, they restored communication with inhibitory neurons in the lateral central amygdala, which are normally called firing neurons.
The effect was dramatic.
“That simple adjustment was enough to reverse the socially deficient behavior associated with anxiety, which is surprising,” says Alvaro García, lead author of the study.
To measure the impact, the research team combined electrophysiological recordings with behavioral tests commonly used to assess anxiety, depression, and social interaction in rodents. These tests examine behaviors such as willingness to explore open spaces and interest in unfamiliar mice.
Researchers used genetic engineering techniques and engineered viruses to selectively correct neural imbalances in the basolateral amygdala. Improvements in both brain activity and behavior were then observed.
Discoveries extend beyond a single genetic model
The researchers also wanted to know whether the same mechanisms might also be involved in broader anxiety.
To test this, they applied the same intervention to wild-type mice, which naturally exhibited elevated anxiety levels. This treatment also reduced anxiety in these animals.
“This validates our findings and gives us confidence that the mechanisms we have identified are not limited to a particular genetic model, but may represent general principles of how these emotions are regulated in the brain,” Lerma added.
The results suggest that the neural pathways identified in the study may be part of a more universal system involved in emotion regulation.
New possibilities for targeted therapy
Not all symptoms improved after intervention. Mice continue to show defects in object recognition memory, indicating that additional brain regions may contribute to specific aspects of these deficits.
Researchers point to areas such as the hippocampus as possible culprits that were not affected by the treatment.
Still, the findings point to promising directions for future treatments.
“Targeting these specific neural circuits could be an effective and more localized strategy to treat emotional disorders,” the researchers conclude.
This research was supported by funding from the Spanish Ministry of Science, Innovation and Universities, the Spanish National Research Agency (AEI), the Severo Ochoa Excellence Program for Research Centers of the Institute of Neurosciences CSIC-UMH, the European Regional Development Fund (ERDF), and Valenciana Generalitat through the PROMETEO and CIPROM programs.
