Chapter 2: Review of Literature and Theories
2.3 Trauma associated neuro-bio-psychological approach
PTSD is directly related to traumatic experiences. However, the underlying cause of PTSD is complicated and undiscovered. This study employs a bio-psycho-social approach to illustrate the mechanisms behind PTSD symptoms, and possible causes of PTSD among the general population, specifically among children. PTSD symptoms are
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abnormal reactions to stress. In order to understand this mental disorder in a deeper way, the understanding of normal human neuro-bio-psychological reactions to stress and traumatic events is necessary.
Bruce Perry (2008, 2009) constructed a neuro-sequential model to explain trauma and treatment mechanism. The neuro-sequential model is based on the belief that
neurodevelopment starts from structurally simpler and lower brain areas (e.g. brainstem and diencephalon) that manage basic regulatory functions, rather than more complex and higher brain areas (cortex) that manage higher cognitive functions (Barfield, Dobson, Gaskill, & Perry, 2012; Perry, & Hambrick, 2008). The earlier developed areas have more neural circuits to widely communicate with other brain areas in order to send signals for further development (Perry, 2009). After experiencing trauma, the primary focus of the brain shifts from higher cognitive functioning (e.g., regulation of emotion, rationale, comprehension, communication) to more primitive lower functioning as a stress-reaction response (Perry & Hambrick, 2008; Van der Kolk, 2006). The communication between the bottom and top brain areas may be interrupted and
disconnected (Perry, 2006; Perry & Hambrick, 2008). Neuroimaging studies have proven the existence of abnormal connectivity in several brain circuits among victims of trauma (Gantt & Tinnin, 2009; Sripada et al., 2012). Dysregulations of brain functionings and disconnections among brain areas are the causes of most mental health issues,
particularly PTSD (Van der Kolk, 2006). The dysfunction can be ameliorated by utilizing
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somatosensory interventions such as visual art therapy, music, and movement through regulated, repetitive inputs and patterned neural inputs to the brainstem and diencephalon (Perry, 2009). This model supports the framework of a bottom-up (i.e., lower brain to higher brain) model of treatment (Perry & Hambrick, 2008).
La Greca and his colleagues (1996) constructed a conceptual model of how to predict children’s reactions to natural disasters. The model has shown how children’s preexisting characteristics (e.g., ethnicity, personality, social economic status) play an important role in predicting their reaction to traumatic events. Together with the nature of the traumatic events and posttraumatic recovery environment, these preexisting
characteristics are factors that can influence PTSD development. Wilson and Keane (2004) summarized PTSD development in a comprehensive psycho-biological
perspective. When experiencing a traumatic event, organismic processes will activate several stress-response systems in the human body; these processes involve the central nervous system, sympathetic nervous system, neuroendocrine system, and serotonergic system. According to all of the automatic responses and reactions, behavioral adaptations are developed as an external response to the trauma such as dysregulated emotional problems, personality change, altered interpersonal processes, psychosocial impacts, comorbidity, physical health effects, life-course trajectory and recovery. With most people, after a period of time, the alerted and fired systems will return to a normal level and stabilize.
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The important affected systems that are associated with PTSD and trauma are the central autonomic nervous system (Wilson & Keane, 2004), and the hypothalamic-
pituitary-adrenal axis (HAP axis) (Vermettent & Bremner, 2002; Wilson & Keane, 2004).
Once the brain receives signals from the outside world that there is a threatening event, the neurons in the nervous system release neurotransmitters to send messages telling the body to become ready and to alter itself (Wilson & Keane, 2004). The HAP axis is a reciprocal neuroendocrine process that controls the human response to stress. The HAP releases hormones from the brain to the kidney. The hypothalamus releases
corticotrophin-releasing hormones (CRH) that stimulate the release of
adrenocorticotropic hormones (ACTH) to the blood system; then ACTH stimulate the kidneys to release a major stress hormone—cortisol, which will increase metabolic energy to meet the demands of trauma (Wilson & Keane, 2004; Yehuda, 2002). If the stress response systems are inappropriately activated or last for an inappropriate amount of time, posttraumatic stress symptoms will occur (Wilson & Keane, 2004). Normally, after the threatening period, the fired-up systems can return to their resting levels (homeostasis), but some people develop dysregulated affective responses. The
functioning roles of the hippocampus in the brain are involved in working, declarative, episodic and verbal memories (Gilbertson et al., 2006; Turley & Obrzut, 2012).
Prolonged and extreme stress can cause damage to the hippocampal neurons (Vermetten
& Bremner, 2002). Volume decrease of the hippocampus has been observed in both
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animal and human studies by several researchers (Carrion et al., 2001; Gilbertson et al., 2002, 2006). A decreased volume of the hippocampus will cause impairment of verbal memories and episodic memory processing, which is commonly associated with
nightmares and flashbacks (Vermetten & Bremner, 2002). The amygdala is an important brain structure that is associated with the emotion of fear (Vermetten & Bremner, 2002;
Shin, Rauch, & Pitman, 2006). The amygdala plays an important role in emotion, learning, and memory, which will become activated especially during fear and fear extinction, as well as during the process of learning not to fear by appraisal and feedback (Karl et al., 2006; Wilson & Keane, 2004; Vasterling et al., 2010). The prefrontal cortex can store extinction memories and inhibit the initial stress response. In the middle part of the prefrontal cortex, social, emotion, and fear conditioning are associated with this area (Richert, Carrion, Karchemskiy, & Reiss, 2006). As an advanced, high-level processor, the prefrontal cortex will send messages via neurotransmitters to the other brain areas, especially the amygdala, about the stress situation, and then the amygdala will process fear-response reactions. Volume changes of grey matter in the medial prefrontal cortex have been detected among children with PTSD (Richert et al., 2006). Reduced volumes of prefrontal cortex have been observed in several studies (Vasterling et al., 2010;
Vermetten & Bremner, 2002). This phenomenon may explain the abnormal changes of the social, emotional functions after developing PTSD and the inability to restrain the stress response system. The two hemispheres of the brain should be symmetric, with
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there being a dominant brain side. However, in children with PTSD, the brain hemispheres are found asymmetrical in the frontal lobes, especially in the areas associated with recognition and emotion processing (Turley & Obrzut, 2012). Lack of brain symmetry can lead to a high possibility of trauma appraisal and emotional functioning problems (Turley & Obrzut, 2012). The asymmetry can also explain why children with PTSD have verbal, intrusive and attention problems.