Scientists have uncovered a new role for astrocytes, star-shaped brain cells previously dismissed as mere structural support. A study published in the journal Nature reveals these cells actively participate in the formation, recall, and suppression of fear memories.
Researchers at the University of Arizona and the National Institutes of Health conducted the study to determine how these cells interact with neurons in the amygdala, the brain's fear-processing hub. The team found that astrocytes do not just hold the brain together; they encode and maintain neural signals responsible for fear.
“Astrocytes are interwoven among neurons in the brain, and it seemed unlikely they were there just for housekeeping,” said Lindsay Halladay, an assistant professor at the University of Arizona and one of the study’s senior authors. “We wanted to understand what they're actually doing and how they're shaping neural activity in the process.”
Rethinking the amygdala's fear circuitry
Using fluorescent sensors in mouse models, the research team observed astrocyte activity in real time. They discovered that activity levels in these cells spiked during the creation and recall of fear memories. When the researchers experimentally weakened the signals astrocytes sent to neurons, the fear responses in the subjects diminished.
This discovery challenges the traditional, neuron-centric view of how the brain processes trauma. When the scientists disrupted normal astrocyte signaling, neurons failed to form the specific activity patterns required for defensive responses. These findings suggest that astrocytes act as a regulatory bridge for how the brain interprets threats.
Beyond the amygdala, the research indicates that astrocytes also influence the prefrontal cortex, the region responsible for decision-making. This suggests the cells help the brain decide whether a situation requires a genuine fear reaction or a more measured response.
This shift in understanding could change how doctors treat anxiety-related conditions, including post-traumatic stress disorder. If clinicians can target astrocytes to help fade persistent, irrational fear memories, it may provide a new path for patient recovery.
Halladay plans to expand the research to other brain regions, such as the midbrain’s periaqueductal gray, which controls physical responses like freezing or fleeing. Pinpointing how these cells operate throughout the entire fear network is the next step toward explaining why some individuals develop chronic anxiety responses to non-threatening stimuli.
