can lead to the intrusive cluster of symptoms, whereas hypoarousal (affect at the bottom of the zone) can lead to dissociative and numbing symptoms. When the window of tolerance is exceeded, the higher levels of processing abilities are compromised and replaced by the lower-level brain functions of reflexive, sensorimotor responses, which are mediated by the brainstem and limbic system (Ogden & Fisher, 2015).
Figure 4-2: Window of Tolerance
Note. Adapted from Ogden, P., Minton, K., & Pain, C. (2006). Trauma and the body: A sensorimotor approach to psychotherapy. W. W. Norton & Company.
Brain Structures Related to Affect Regulation Three brain structures are central to the regulation of affect and involved in the processing of trauma: The amygdala, the hippocampus, and the prefrontal cortex (Henigsberg et al., 2019). The centrally located limbic system is thought to mediate and regulate emotion, motivation, application of meaning, and processing of social experiences. Several of the limbic centers, such as the amygdala and the hippocampus, come into play with either over- or underactivation during traumatic events and are also activated during the dream state (van der Kolk, 2014). This dream-state activation is relevant in the context of posttraumatic nightmares and the dreamwork interventions that can be employed to alleviate them. The function of the amygdala is to process, interpret, and integrate emotional memory. It compares past templates in the brain to determine the course of action (i.e., fight, flight, or freeze) and is involved in the appraisal and conditioning of fear responses. It becomes active during and while Bottom-Up/Top-Down Processing The various brain structures communicate in two significant ways. The “human brain has developed from the inside out,” starting with the primitive brain (i.e., the brainstem) responsible for basic functioning (e.g., breathing; Field et al., 2015, p. 208). After that, there is the limbic system, which coordinates emotion, reactivity, and reward behaviors essential for survival (Field et al., 2015). Finally, the distinctly human portion of the brain, the prefrontal cortex, is responsible for executive functioning (e.g., thoughts, planning, and regulatory control; Field et al., 2015). This simplistic representation of the brain hierarchy is integral to understanding and treating trauma. Typically, humans process information from the top down; that is, the higher brain (prefrontal cortex) receives information from the environment, processes and appraises that information, and then sends signals to the lower parts of the brain about how to react to the stimuli (Field et al., 2015). When faced with threats or traumas, the brain shifts into survival mode, relying on the more primitive, reactive regions to engage
remembering a traumatic event. The amygdala is the alarm bell or accelerator of the limbic system. The hippocampus is responsible for memory of facts and events. It is involved in the verbal mediation of narrative and autobiographical memory (how you know who you are and that you were in a specific place). It gives time and space context to an event. When the hippocampus is successfully processing, it recognizes a beginning, a middle, and an ending to an event and a sense of what happened first, what happened next, and so on. In contrast to the amygdala, or accelerator, the hippocampus is the brake of the limbic system. The prefrontal cortex is the last part of the brain to develop (the adult thinking brain), and it is responsible for reasoning and judgment. The left hemisphere of the prefrontal cortex is involved in sequential logic (understanding what happens next), and the right hemisphere is involved in holistic and spatial logic (the overall gestalt of an experience and where things are located in space). the fight-or-flight response, in what is termed bottom-up processing (Field et al., 2015). It is important that holistic, integrative trauma treatments target both top-down and bottom-up systems. Research suggests that trauma can result in decreased volume in the prefrontal cortex, diminishing an individual’s inhibitory control of the lower brain and resulting in more reactive and less thoughtful or regulated responses, such as aggression (Lu et al., 2019). Professionals should recognize that the prefrontal cortex may be bypassed in these individuals in deference to their more reactive brain structures. Interventions that attempt to build up self-regulation through regulatory skills and strategies may be required. Alternatively, trauma can cause impairments to structures in the limbic system (the emotional brain), which might contribute to more reactive and emotional responses or dulled responses that are not as reactive as they should be (Holochwost, 2021).
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