Dr. Cheng-Chang Lien’s team at the College of Life Sciences of National Yang Ming Chiao Tung University (NYCU), in collaboration with research teams from Denmark and Austria, has discovered a new mechanism in the formation of fearful memories in the brains of mice. This finding could help reduce the adverse effects of fear and is expected to provide new treatments for Post-Traumatic Stress Disorder (PTSD) in the future.
The research team led by Dr. Lien, in collaboration with Dr. Marco Capogna of Aarhus University in Denmark and Dr. Francesco Ferraguti of the Medical University of Innsbruck in Austria, has discovered that fearful experiences activate a small group of inhibitory neurons in the amygdala of the brain of mice to avoid overreacting to fearful memory. The findings, published this month (August 5) in the journal Cell Reports, enhance researchers’ understanding of the neurological basis of fearful memory formation and offer a potential solution for treating PTSD.
Dr. Wen-Hsien Hou, the first author and the Assistant Professor at the Department of Biomedicine of Aarhus University in Denmark, points out that fear plays a crucial role in helping people remember and respond more swiftly to potential dangers when faced with similar situations in the future. For example, in Taiwan, where earthquakes are a frequent concern, they are a common source of fear. Receiving a mobile phone alert about an earthquake can trigger these fearful memories, prompting individuals to take immediate precautions to protect themselves and avoid potential danger.
Dr. Lien indicates that recent literature suggests a region beneath the outer layer of the brain’s cortex, known as the cluster of neurons of the central amygdala (CeA), regulates fear-related emotions. It was previously unknown whether specific neurons in this region are responsible for forming fearful memories and regulating coping behaviors when recalling such experiences.
The research team discovered that the experience of fear chronically enhances the activity of a small group of neurons in the lateral central amygdala (CeL), which is responsible for inhibiting fear memory. The team used genetically transformed mice to mark these neurons (primarily somatostatin neurons) activated by different fearful experiences. Dr. Lien indicates, in particular, that the mice showed more fear when the labeled neurons were inhibited.
Dr. Lien pointed out that while most neuroscientists focus on how excitatory neurons in the brain contribute to memory storage and response, this research shows that the inhibitory neurons in the brain also play a role in shaping the mice’s response to fearful memories, revealing a more complex neural mechanism. This small group of inhibitory cells, located in the lateral central amygdala of the mouse brain, regulates memory, and their activation functions as a brake to prevent the mice from overreacting.
Dr. Lien also reminds us that although the mice and human brains are similar in structure, there are still differences in the neural circuits and connections between the two species. Further research is still needed to investigate whether this group of neurons in the central region of the amygdala regulates fear memories and performance of PTSD patients. Developing a specific neural cell regulation for the treatment of PTSD remains a major clinical challenge for the future.
