Our experiences play a fundamental role in how our brain develops, and as an individual is exposed to a multitude of different environmental factors and situations, the mind continuously adapts and changes. One example of the impact of our experiences on mental health is PTSD, or post-traumatic stress disorder. PTSD is a psychiatric disorder characterized by intense, disturbing thoughts and emotions, flashbacks or nightmares, sadness, and anger. It affects approximately 3.5% of adults in the United States each year. PTSD may occur in those who have experienced or witnessed an extremely stressful or traumatic event, such as a natural disaster, war, or violent crime. Over the past 40 years, neuroimaging has allowed the study of PTSD to progress significantly, revealing that not all individuals with PTSD are affected with the same brain changes or symptoms. Studies have shown that PTSD is linked to the intersection of the amygdala, medial prefrontal cortex, and hippocampus in the brain. How can our understanding of these regions of the brain in relation to PTSD further treatment of the condition and scientific advancement in mental health treatment?
There are many components of the brain that come together to make up how an individual processes memories, learning, and emotions. The hippocampus oversees many aspects of episodic memories, including spatial, temporal, and contextual elements of experience, while the dorsal and ventral regions oversee cognitive aspects of experience and emotional components of learning and memory, respectively (Grella, 2019). Dr. Stephanie Grella et. al studies how the longitudinal axis of the hippocampus could drive appetite and fear-related behaviors via use of optogenetics. Furthermore, by experimenting also with fear conditioning, this study revealed that acute reactivation of tagged cells in the dorsal and ventral dentate gyrus, depending on the aversive or rewarding nature of the tagged memory could potentially drive freezing, place avoidance, and place preference. The reactivation of fear-associated cells in the dorsal or ventral hippocampus lead to distinct changes in behavior and neuronal activity. The data collected by Dr. Grella et. all indicate the importance of the entire hippocampus and dorsal and ventral dentate gyrus, as they are key parts of the activation of freezing behavior, and context-guided emotional components, specifically context-specific reductions or enhancements in fear behavior. These functions of the hippocampus and dorsal and ventral dentate gyrus in the brain in memory formation, retrieval, context specificity and emotional regulation in the brain reveals a much more expanded understanding of how fear memory is retained, enhanced, and stimulated in the brain, therefore contributing to the possibility of specific interventions for stress-related neuropsychiatric disorders such as PTSD.
As studies of the brain increase, treatment possibilities for PTSD also increase. In their studies, Dr. Noah Philip et al. explore the treatment of PTSD using theta-burst stimulation, a form of TMS, or transcranial magnetic stimulation. Within an experimental group of 50 veterans with chronic PTSD, theta-burst stimulation, which uses rhythms similar to those in the hippocampus, was applied intermittently, with breaks in the process to increase neuronal activity and therefore communication between neurons. (Philip, 2019). The treatment was applied to the dorsolateral prefrontal cortex in the brain, in areas such as the hippocampus, in order to calm down areas associated with many symptoms of PTSD, such as problems within memory, learning, and emotions. Within the study, intermittent TBS was presented as a promising new treatment for PTSD, as active intermittent TBS was significantly associated with improved social and occupational function, self-rated PTSD symptoms, and depression.
The study of PTSD and its treatment continues to drive scientific advancements. Exploring the connection between fear and memory in the brain has many implications for specific targeting methods, such as with intermittent theta-burst stimulation. There are many challenges when beginning to pinpoint in which circuits of the brain PTSD originates due to its complex and ambiguous nature, such as other challenges such as understanding social and cultural context, symptom overlap, and the impact of trauma history variability between individuals. However, identifying the specific roles of different brain regions in the pathways of PTSD and demonstrating the effectiveness of targeted therapies opens up promising possibilites for treatment. These advancements have the potential to improve quality of life and further understanding of how the brain processes trauma, neurotransmitter and hormone uptake, and novel therapeutic approaches, including brain stimulation therapies like iTBS, cognitive processing therapy, and prolonged exposure.
References
Chen BK, Murawski NJ, Cincotta C, et al. Artificially Enhancing and Suppressing Hippocampus- Mediated Memories. Curr Biol. 2019;29(11):1885-1894.e4. doi:10.1016/j.cub.2019.04.065
Philip NS, Barredo J, Aiken E, et al. Theta-Burst Transcranial Magnetic Stimulation for Posttraumatic Stress Disorder. Am J Psychiatry. 2019;176(11):939-948. doi:10.1176/appi.ajp.2019.18101160
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