Fear occupies all space: scientists explain how stress affects our memory.

Stress significantly impacts how our brain encodes and retrieves memories, particularly unpleasant ones, according to a new study from SickKids hospital. The findings shed light on the biological mechanisms underlying memory generalization in stress-related conditions such as post-traumatic stress disorder (PTSD) and propose potential therapeutic approaches to enhance memory functioning, as reported by ScienceDaily.

The research, published in the journal Cell, was led by Drs. Shina Joslin and Paul Franklin, experts in memory and neuroscience. Dr. Joslin highlighted the dual nature of stress, explaining that moderate stress can be beneficial, while excessive stress disrupts emotional and cognitive processing. Stress-induced memory generalization can result in unrelated stimuli, like fireworks or a car fire, triggering fear responses similar to those observed in PTSD patients.

Using a preclinical model, researchers demonstrated that stress preceding a traumatic event expands neural engrams—physical memory traces in the brain—making them less specific. Unlike typical sparse engrams, these generalized memories involve a significantly larger number of neurons, leading to an overly generalized fear response even in safe environments.

A key discovery of the researchers was related to the role of endocannabinoids—chemicals released by the brain during stress. It was found that elevated levels disrupt the functioning of interneurons, which typically regulate the size of the engram. By selectively blocking endocannabinoid receptors on these interneurons, researchers successfully curtailed memory generalization, suggesting a promising strategy for alleviating PTSD symptoms.

The study also drew parallels between stress-induced memory changes and alterations observed in the developing brain. Larger, generalized engrams seen in childhood may have biological foundations linked to stress effects, indicating a broader basis for understanding memory dynamics across different age periods. The research team intends to further explore how daily stressors may similarly affect positive memories, offering new insights for various mental health interventions.

In addition to clinical implications, this research demonstrates how understanding the biology of engrams can bridge fundamental neuroscience with practical treatment methods for mental disorders. The findings could lead to the development of targeted therapies that enhance memory processing without suppressing emotional experiences, thereby improving the quality of life for individuals suffering from severe conditions like PTSD.

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