Have you ever experienced trying to recall a certain event in your life? It may have been a special event like a specific birthday or something less ideal such as robbery and an investigator is questioning you to give an accurate description of what happened. What you are trying to access is called your episodic memory. Episodic memory consists of memories of specific events and experiences that are saved into your brain in a serial way. By the serial way, I mean that they are in chronological order. That is why when you watch crime shows on television, investigators always ask you to retrace your steps or to close your eyes to help you imagine what you were doing during a specific event. They are trying to help you access your episodic memory so that you can be able to recall what happened during that stressful event.
In a New York Times article about retaining memory, the author Henry Alford speaks about how memory is fleeting and there are various methods that he uses to strengthen his memory. One task he suggests is to make rhymes and stories about the things we are trying to remember. This task that aids recall is similar to the investigator asking questions in a crime scene. They are all serial questions. Alford speaks about using a story to help remember a string of words. He sets up a particular setting and places the list of words in that setting so that they show up one right after another. In that case, he is able to remember what is going on and recall it afterward.
In regards to more scientific research, Jelena Radulovic from Northwestern University has been studying the projections in the brain that are associated with the transportation of signals from one part of the brain, dorsal hippocampus(DH), to other parts such as the retrosplenial cortex(RSC).In her studies, she attempted to explain more about the episodic memory and its retrieval in regards to stress-related memories. Her team was able to use contextual fear conditioning in animal models to understand which projections were involved in the recall from the fear conditioning. What they came up with was that if the pathway between the DH and RSC. What they found was that vGlut1 and vGlut2 were glutaminergic neurons that connected these regions. What was even more interesting what that vGlut1 had more of an impact on memory than vGlut2 and was silenced by DREADD. DREDD has a specific ability to specifically silence receptors and prevent previously encoded memories. All in all, this research aims to be used to help treat people who have PTSD as well as people who struggle with memory deficits. From their research, they were able to distinguish that episodic memory is encoded through feedforward inhibition of the vGlut1 neurons.
Not only did the researchers find the connection between the DH- RSC important for memory, but they also were able to figure out how glutaminergic pathways are involved in recalling memories. Dopamine is mostly produced in the Ventral Tegmental Area(VTA) of the brain and travels to the DH. It was concluded by the use of optogenetics and chemical injections that this pathway is involved in the reinstatement of memories. More shockingly it was noted that in females there is a higher innervation density between the VTA and the DH in comparison to males. This information helps us understand the underlying working of episodic memories and their long lasting storage. We use our memories every day to navigate our world around us. By understanding the way that memory works we will be able to help those who have memory deficits. Research like this brings us closer every day to treating diseases such as Alzheimer's Disease along with other neurodegenerative disorders. We move forward knowing that we will be closer to helping our veterans with PTSD cope with their new environments and potentially suppress the triggers that cause them to struggle in day to day life.
Alford, H. (2018, June 8). Total Recall: A Reader's Guide to Memory Gain. Retrieved from https://www.nytimes.com/2018/01/07/books/memory-loss-books.html
Episodic Memory and Semantic Memory - Types of Memory - The Human Memory. (n.d.). Retrieved from http://www.human-memory.net/types_episodic.html
Yamawaki N, et al. (2018, June 6). Differential Contributions of Glutamatergic Hippocampal→Retrosplenial Cortical Projections to the Formation and Persistence of Context Memories. - PubMed - NCBI. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/29878069
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