Memories and Mental Health

There has been a lot of research on how the memories we make in our life have an impact on our mental health. The severity or amount of times that certain memories are activated in the brain can affect someone’s short-term and/or long-term emotional and mental state. This idea holds true for many kinds of memories, including positive and negative ones. With negative memories, in particular, having them stored and recalled in the brain a number of times can lead to forming or worsening of certain mental health conditions, including phobias, anxiety disorders, and PTSD (post-traumatic stress disorder). To improve current methods of mediating these disorders based on traumatic memories, and possibly find new methods to do so, it is crucial to learn more about the mechanism of how traumatic/negative memories affect the brain and how this effect can be reduced.

Fearful memories are usually encoded to help us identify a threat to survive, but if those memories are no longer needed and continue to be recalled even when no threat is present, it can lead to the development of certain disorders such as PTSD. To learn about the mechanisms that explain how fearful memories are kept in our brain or how they are suppressed, a group of researchers from NIH’s National Institute on Alcohol Abuse and Alcoholism and Institute for Biomedical Research tried to see what cells in the brain are responsible for suppressing or preserving negative memories and how they interact. They used in vivo calcium imaging in mice and tracked cell activity in the brain after putting the mice through fear conditioning. The researchers found that groups of neurons in the amygdala called intercalated cells compete with each other to either repress or preserve the fear-based memory and saw that after the unconditioned stimulus was taken away (a shock administered to the mice’s feet), the mice also showed less of a fearful response (Hagihara et. al., 2021). The results of this study gave more insight into the neural mechanisms that underlie the sustentation and/or extinction of fear in the brain.

  Currently, there are various methods people use to mediate the impact that negative memories have on their mental health, such as counseling or taking medication, but recent studies have introduced a new possible method to minimize negative memories, particularly those based on fear. A recent study led by Dr. Grella and her team introduced a way that negative fear-based memories can be disrupted by using optogenetics. During the reconsolidation of fear-based memories in mice after fear conditioning, positive memories were reactivated in the hippocampus. The results were that reactivating positive memories actually helped in disrupting the fear and reducing the impact they had on the mice (Grella et. al., 2021). Although the idea of using the same method on humans appears difficult, studies such as this show that in the near future, we may have more options to help people who suffer from mental health conditions such as PTSD.

Works Cited: 

Hagihara, K. M., Bukalo, O., Zeller, M., Aksoy-Aksel, A., Karalis, N., Limoges, A., Rigg, T., Campbell, T., Mendez, A., Weinholtz, C., Mahn, M., Zweifel, L. S., Palmiter, R. D., Ehrlich, I., Lüthi, A., & Holmes, A. (2021). Intercalated amygdala clusters orchestrate a switch in Fear State. Nature, 594(7863), 403–407. https://doi.org/10.1038/s41586-021-03593-1 

Grella, S. L., Fortin, A. H., Ruesch, E., Bladon, J. H., Reynolds, L. F., Gross, A., Shpokayte, M., Cincotta, C., Zaki, Y., & Ramirez, S. (2022). Reactivating hippocampal-mediated memories during reconsolidation to disrupt fear. Nature Communications, 13(1). https://doi.org/10.1038/s41467-022-32246-8