This chapter highlights the neurobiology of the whole spectrum of defense responses to threats: near or distant, immediate or potential, physical or social. It focuses on vigilance, fight, flight, freeze, hide, cringe, submit, and avoid behaviors. When survival is threatened by physical injury, death, or social exclusion, the brain has well-established responses, immediate and sequential, to promote safety. These defense responses are based in the emotion-generating regions of the brainstem but are rapidly modified and modulated by the more developed and evolved cortical capacities. The chapter focuses on clinical observations, brain imaging studies in humans, and animal studies of responses to trauma to promote testable conclusions on the likely neurochemical mediators of the key components of posttraumatic stress disorders (PTSD). Chronic characterological changes arising from alterations in self-perception with guilt and shame, self-blame, feelings of ineffectiveness, and loss of trust are part of the long-term damage caused by early trauma.
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There is a range of immediate orienting and defense responses available when a threat is perceived, and a separate but overlapping system of vigilance when there is awareness of a potential threat. Vogt, Aston-Jones, and Vogt propose that the reduced anterior cingulate functioning repeatedly demonstrated in posttraumatic stress disorder (PTSD) during emotional tasks facilitates the firing of locus coeruleus (LC) neurons to create a state of hyperarousal. The noncognitive suppression of emotions in young trauma sufferers is based in the areas of the ventral prefrontal cortex (PFC), which has outputs to the defense response and threat evaluation regions of the amygdala, the periaqueductal gray (PAG), and the nucleus accumbens, among others. Deep brain stimulation can be used clinically without activation of a fearful freeze response, so ventral areas of the PAG are also involved in physiological states of relaxation, comfort, and soothing from pain.
Safe embodiment is a concept that is at the core of successful treatment of traumatic stress syndromes and dissociation. Therapy with eye movement desensitization and reprocessing (EMDR) requires a potential patient or client to have access to an imaginary safe place to support calming if there is a danger of overwhelm. The experiences of belonging, safety, mindful awareness, and compassion for self and others create or restore the body state of security displaced by trauma, abuse, or neglect. Neuroplasticity can also promote some degree of repair to the brain, not only through altered function of specific brain areas but also through neurogenesis. The primary advanced human awareness may be that engendered in the anterior insular cortex (AIC) with the experience of one’s own existence as a sentient being. The evolution of the cortical mantle provides ample scope for the compartmentalization of areas of conscious awareness in the dissociative disorders.
This chapter focuses on educational purposes for the promotion of research. It helps the practitioners to study the available evidence and use professional discretion in their prescribing decisions, being fully aware of known potential risks as well as benefits. The literature describes the use of opioid antagonists in a number of different disorders, some of them traumatic stress and attachment-related disorders, as well as dissociative disorders. Self-injurious behavior is common in the more severe traumatic stress syndromes. It also happens to be one of the diagnostic criteria of borderline personality disorder (BPD), a diagnosis that has been associated with childhood abuse and attachment conflicts. Pathological gambling is thought to provide rewards through endogenous opioid effects on the mesolimbic dopamine system. Fibromyalgia is a chronic pain disorder that is thought to result from the type of autonomic system dysfunction to which traumatic stress disposes.
This chapter suggests neurobiological mechanisms to account for dissociative symptoms in general and structural dissociation in particular. Peritraumatic dissociation (PD) is associated with the release of endogenous opioids and other anesthetic neurochemicals that alter communication between lower and higher brain structures. MacLean's triune brain model provides a structure for the understanding of emotional functioning and dissociation. The integration of brain functioning both horizontally and vertically at different levels of the brain is at the core of information processing. The thalamus also plays a role in cortical oscillations, a phenomenon that has been related to cognitive-temporal binding and information processing, thus affecting cortical connectivity. The corpus callosum is the largest connective pathway in the human brain, constituted of nerve fibers that connect the left and right hemispheres, thus facilitating interhemispheric communication. Disruption of thalamocortical communication is a key component of anesthetic-induced unconsciousness.