A developing brain is marked by its ability to be high in plasticity, indicating that the structure of the brain and its parts change depending upon the kind of experiences the individual undergoes. Neuroplasticity occurs in both positive and negative connotations. There have been many cases wherein the brain has changed its neurological structure post injuries that have affected only specific parts of the brain. For example, in the case of a stroke, the post-injury brain showed a decrease in the excitability of the motor cortex near the affected area, but after treatment and rehabilitation, the same hemisphere was observed to have better motor representations (Carey et al., 2002). This case study shows how neuroplasticity alters the structure of the brain after traumatic injuries.
Studies have also revealed that age plays an important role in the functionality of the brain after the injury, in the sense that, younger individuals have a better rate and level of full recovery after an injury as compared to adults. 37 individuals under the age of 17 who had suffered from a traumatic brain injury were studied and compared to an older sample. The comparison revealed that children have a better chance of recovery and better functioning as compared to adults. (Berger et al., 1985)
It has also been found that physical trauma isn’t the only reason behind the brain’s plasticity. Several cases reveal that prolonged sexual, emotional and traumatic stress changes the structuring of the brain. The parts of the brain most adversely affected by these stressors and traumatic events are the amygdala, prefrontal cortex and hippocampus, as they undergo structural changes, as well as changes in the grey matter volume.
Although there exists a direct correlation between the changes in the brain's structure and trauma, reducing a broad word such as ‘trauma’ to just ‘stressors’ seems imprecise. In order to have a more concrete and realistic idea of this relationship, it would be helpful to look at the brain’s plasticity through the lenses of disorders, which manifest due to prolonged trauma.
Dissociative Identity Disorder is one of the most severe conditions that follow trauma. The disorder previously termed multiple personality disorder, comprises the individual developing “alternate personalities” which switch at various moments. The disorder, after numerous research, seems to have stemmed from long-term physical, sexual or emotional abuse. (Mayoclinic, 2017). Researchers have done various case studies to find out whether dissociative identity disorder, amongst other dissociative disorders, has any effect on the brain, and discovered that not only do parts of the brain undergo functional change, but they also undergo structural changes.
Beginning by focusing on the functional changes observed, when the brain is experiencing trauma (measured by the researchers through a comparison of trauma scripts vs. neutral scripts), parts of the brain such as the amygdala discern an elevation in activity when exposed to trauma. The insula levels in the brain also increase. On the other hand, the researchers observed a decrease in the activity in the cingulate gyrus, parietal cortex, and parahippocampus, when the brain is in the simulated traumatic form.
Although functional changes are very critical to the overall functioning of the individual, we can view them as temporary effects of the stressors to which the individuals who had been exposed. However, structural changes tend to be more permanent, as the structure of specific parts of the brain is shifting as an adjustment to the trauma the individual has undergone. Individuals with Dissociative Identity disorder oftentimes have structural changes in the amygdala, hippocampus and parahippocampus, in the sense that, these parts of the brain are comparatively smaller in volume. (Vermetten et al., 2006; Ehling et al., 2008; Weniger et al., 2008). The structure of the hippocampus specifically has been associated with not just Dissociative Identity disorder, but also childhood trauma as a whole, pertaining to the idea that when childhood trauma leads to an increase in the release of cortisol, the hippocampus, which is sensitive to it, experiences cell damage and in turn reduces in volume (Bremner, 2006). Moreover, another type of dissociative disorder, Depersonalisation disorder, also leads to structural changes, specifically in areas including the right thalamus, which experiences a decrease in the grey matter volume (Daniels et al., 2015).
Looking at the plasticity of the brain, through the lens of a disorder caused because of prolonged trauma puts into perspective how the brain changes its structuring to adapt to the stimuli presented. The aforementioned arguments display that the brain’s plasticity works on both, a positive and negative level, in the sense that the brain changes its neurological structuring when a part is damaged in order to ensure that the individual functions properly regardless and to cope with traumatic instances.
Another aspect to ponder over stems from the factor of age and recovery of the brain structure. Plasticity is more easily reversed when dealing with a child as compared to when dealing with an adult. Does this mean if trauma manifests as a disorder in later parts of one's life, it is much harder to reverse that to the standard structure of the brain, and the affected parts of the brain?
References
Berger, M. S., Pitts, L. H., Lovely, M., Edwards, M. S., & Bartkowski, H. M. (1985). Outcome from severe head injury in children and adolescents. Journal of neurosurgery, 62(2), 194-199. https://doi.org/10.3171/jns.1985.62.2.0194
Bremner, D. J. (2006, December). Traumatic stress: effects on the brain. Dialogues Clin Neurosci, 8(4), 445-461. 10.31887/DCNS.2006.8.4/jbremner
Carey, J., Kimberley, T., Lewis, S., Auerbach, E., Dorsey, L., Rundquist, P., & Ugurbil, K. (2002). Analysis of fMRI and finger tracking training in subjects with chronic stroke. Brain : a journal of neurology, 125(4), 773-788. https://doi.org/10.1093/brain/awf091
Daniels, J., Gaebler, M., Lamke, J., & Walter, H. (2015, January). Grey matter alterations in patients with depersonalization disorder: a voxel-based morphometry study. Journal of Psychiatry and Neuroscience, 40(1), 19-27. 10.1503/jpn.130284
Dissociative disorders - Symptoms and causes. (2017, November 17). Mayo Clinic. Retrieved October, 2022, from https://www.mayoclinic.org/diseases-conditions/dissociative-disorders/symptoms-causes/syc-20355215
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Jeong, H. J., Durnham, L., Moore, T. M., Dupont, R. M., & Mcdowell, M. (2021, April 24). The association between latent trauma and brain structure in children. Translational Psychiatry, 11(240). https://www.nature.com/articles/s41398-021-01357-z
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