Hippocampus, Associative Learning, and PTSD Prevention

Introduction

Increased attention has been brought to the issue of post-traumatic stress disorder (PTSD), particularly since veterans returning from wars in the Middle East have necessitated that attention as a result of their own mental health challenges (Vogt et al., 2017). Currently, more than 1 million veterans of these wars are at risk for suicide as a result of untreated PTSD (Kang et al., 2015). Soldiers are but one population afflicted with PTSD, however. Police officers are also at high risk for exposure to trauma and, consequently, for the effects of PTSD (Chopko & Schwartz, 2012). How to identify the signs of PTSD and how to treat it effectively are issues under ongoing debate, primarily because the neuroscience of PTSD is still being investigated. Some debate also exists over whether individuals are experiencing PTSD or traumatic brain injury (TBI) (Klimova, Korgaonkar, Whitford & Bryant, 2019). Nonetheless, neuroscientific research associated with PTSD has so far demonstrated that specific regions of the brain become smaller in people afflicted with PTSD (Tan et al., 2013). This paper discusses the neuroscience associated with PTSD and shows how brain imaging has helped researchers construct a new narrative about what happens in individuals who experience chronic PTSD.

What Is PTSD?

According to the DSM-5, PTSD is characterized by exposure to a significant stressor — such as death, the threat of death, or serious injury or violence — along with intrusive symptoms such as nightmares or flashbacks that cause the person to unwillingly relive the traumatic experience. Additional symptoms include avoidance of stimuli that could trigger unwanted memories or thoughts, negative changes in thoughts and feelings such as self-isolation or excessively negative thinking, risky behavior, hypervigilance, aggression, functional impairment, depersonalization, and derealization (Carmassi et al., 2013).

PTSD can be caused by any experience that is traumatic, even if the traumatic event is only indirectly experienced. However, PTSD is distinct from post-traumatic distress, which is commonly experienced by people who are directly or indirectly involved in a traumatic incident. PTSD is longer-lasting and increasingly destabilizing, whereas post-traumatic distress typically resolves over time (Giordano et al., 2016). Something about PTSD prevents distress from resolving. One of the clues for why this happens may be found in the field of neuroscience.

Neuroscience and PTSD

One consistent finding across PTSD literature is that individuals afflicted with PTSD lose interest in activities that previously engaged them (Feeny, Zoellner, Fitzgibbons & Foa, 2000; Nader, Pynoos, Fairbanks, Al-Ajeel & Al-Asfour, 1993). There is a neurological impact when the areas of the brain that the body is accustomed to stimulating are no longer engaged. When a person is dealing with PTSD, those parts of the brain become inactive and begin to atrophy, which creates a downward spiral in which additional brain areas cease to be engaged. A shrinking left superior parietal lobule has been associated with PTSD as evidence of this process (Tan et al., 2013).

Tan et al. (2013) found in their examination of mine disaster survivors that PTSD caused regions of the brain in both hemispheres to shrink in size and lose volume. This finding is supported by Lambert and McLaughlin (2019), who show that "smaller hippocampal volume is associated with increased risk for PTSD following trauma" (p. 729). The researchers further suggest that individuals with a propensity for PTSD also exhibit "broad impairment in hippocampus-dependent associative learning" (Lambert & McLaughlin, 2019, p. 729). In other words, not everyone is neurologically predisposed to PTSD in the same way: some individuals are more vulnerable than others based on the degree to which their hippocampus has developed. People who lack associative learning capacity are more likely to display PTSD symptoms.

An important question that emerges from this research is whether PTSD is a collection of symptoms arising from comorbidities that go unaddressed. This question is especially significant given that exposure to trauma has been found to be widespread across all populations — from children to adults — with more than half of all children and three-fourths of adults experiencing trauma at some point in their lives (Kessler, 2000; McLaughlin, 2013). Given how widespread trauma exposure is, why does only a fraction of the population develop PTSD? The answer may lie in the study of brain volume, particularly in the hippocampus (Lambert & McLaughlin, 2019).

Conclusion

The neuroscience associated with PTSD has shown that brain volume is linked both with the affliction of PTSD and with an individual's vulnerability to developing it. Because most of the population experiences trauma at some point in their lives but does not become permanently afflicted, there is reason to believe that the ability to process trauma may be connected to the development of the hippocampal region and its role in associative learning. The failure of some individuals to develop this area of the brain may put them at higher risk of PTSD — of failing to process trauma, to understand how ideas are linked to experience, and to move beyond distressing events. Instead, they are haunted by traumatic experiences because they lack the cognitive tools to process those events in a meaningful way.

The more that educators do to help individuals develop this area of the brain, the more they may be contributing to PTSD prevention. The path for educators may involve insisting on the development of grit and strength of character — fostering in learners the willingness to overcome challenges, apply critical thinking, link ideas with experiences, and find constructive solutions.

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