Regular light-intensity exercise helps erase fear memories and prevent PTSD

Tsukuba, Japan—Post-traumatic stress disorder (PTSD) is a common mental disorder caused by severe stress. Recent research suggests that exercise can help prevent and treat PTSD. However, the specific effects of light-intensity exercise (LIE) on PTSD symptoms remain unclear. One hypothesis is that the brain-derived neurotrophic factor (BDNF) plays a crucial role in eliminating fear memories. This molecule's expression in the hippocampus, the region of the brain responsible for memory and learning, is known to increase with habitual exercise.

In this study, researchers used an animal treadmill exercise model specifically designed to determine exercise intensity based on lactate threshold. This model allowed them to explore whether regular exercise can erase fear memories and whether BDNF is involved in this process. In the experiment, rats were initially placed in a chamber and subjected to mild electrical stimulation to induce fear memories. Subsequently, the rats underwent LIE training for four weeks. After the training period, the rats were placed back in the chamber and their behavior was observed and compared with that of rats that did not undergo exercise training.

Typically, rats exhibit freezing behavior when experiencing fear. Initially, all rats demonstrated fear-induced freezing behavior. However, rats that were regularly exercised gradually became more active. This indicates that regular exercise facilitated the erasure of fear memories. Furthermore, when BDNF signaling was inhibited in the rats through the administration of a specific drug, the effects of exercise on fear memory erasure disappeared, indicating that BDNF signaling is involved in the erasure of fear memories via LIE.

The aforementioned findings indicate that PTSD psychiatric symptoms caused by intense stress may be alleviated via continuous LIE because LIE enhances BDNF activity in the hippocampus.

PTSD patients frequently experience concurrent depressive symptoms and struggle to maintain a consistent exercise routine. The findings of this study show that even LIE can effectively erase fear memories. Moreover, these findings may pave the way for new exercise-based treatment and prevention programs with high patient adherence.

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This work was supported in part by special funds of the Education and Research of the Ministry of Education, Culture, Sports, Science, and Technology granted to the Human High Performance Research Project (1111501004); the Japan Society for the Promotion of Science Grant-in-Aid for Scientific Research on Innovative Areas (16H06405); Grant-in-Aid for Scientific Research A (18H04081, 21H04858); the Body and Mind Integrated Sports Sciences Project (2010-2013); and the Japan Science and Technology Agency-Mirai Program Grant JPMJMI19D5.

_{Original Paper}

Title of original paper:
Accelerated Fear Extinction by Regular Light-Intensity Exercise: A Possible Role of Hippocampal BDNF-TrkB Signaling

Journal:
Medicine & Science in Sports & Exercise

DOI:
10.1249/MSS.0000000000003312

_{Correspondence}

Professor SOYA, Hideaki
Institute of Health and Sport Sciences, University of Tsukuba

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Institute of Health and Sport Sciences