Conceptual Foundations of the Biological Models

When trying to understand the biology of PTSD, it can be easy to get lost in the reductionism of the brain and its various systems and biochemical processes and lose sight of the big picture. The big picture represents the ultimate behavior of reacting or responding to danger, the protection of life and limb, and the training or learning occurring within the nervous system. In this chapter, we will be looking at the various brain processes, structures, and systems that underlie these processes.

It might help to simplify things by referring to all of the various responses and underlying process that save or protect an organism and its valued cohorts as danger responses. The following list outlines some of these:

Fear—the emotional response to the perception of threat.

Memory—the knowledge and memories of what represents danger in our worlds.

Arousal—being on alert, vigilance in perception, and mobilization of resources.

Fighting, fleeing (flight), or freezing—aggression in self-defense and protection, avoidance of threat, or reducing threat you generate yourself.

Various other psychic or psychological processes involved in protection, such as dissociation and various psychoanalytic defense mechanisms. (For more on dissociation, see Chapter 8, and for more on psychoanalytic defense mechanisms, see Chapters 2 and 7.)

Restoring or returning to baseline—maintaining organismic balance.

The emotion of fear is a characteristic emotional response to danger or threat, and, in turn, our memory determines what in our internal and external environments represent danger or threat. They work hand in hand. Arousal keeps us alert and gets us going. Fighting eliminates the danger through force. Fleeing gets us away from the danger. Freezing might help us hide or communicate that we come in peace. Dissociation protects our consciousness.

Finally, restoration processes such as homeostasis and allostasis keep us balanced and capable of responding to the next danger. Homeostasis is the process of maintaining organismic balance and stability under normal stress loads. Allo-stasis, on the other hand, is the process of maintaining or restoring organismic balance under heavy stress loads, such as the fear of death or significant bodily injury. After all, what could be more allostatically stressing or loading than fear of death or significant injury? In allostasis, the body works to maintain stability when stressors place a load on the body system, challenging it to maintain adaptive biological functioning under significant demands, such as the demand for survival (Wilson, Friedman, & Lindy, 2001). When the processes involved in allostasis are not adequately activated in response, shut down after a response, or are overburdened, biological wear and tear on the body and brain occur (McEwan, 2004).

Before we get into the biological details of PTSD, something needs to be said about methodology and the issue of the "level of study." The ideas and models discussed in this chapter will address numerous neurobiological processes including neuroanatomical structures and systems, neurotransmitter systems, neurophysiology, functional brain systems, neuropsychological functions, and endocrine and hormonal functioning. Each of these reflects a different level of analysis within the brain and body, much the same way Newtonian physics represents a different level than quantum physics for the analysis of the physical reality of the universe. The differing analyses at different levels all address the biological reality of PTSD. Partly as a function of pragmatics, the brain in PTSD gets divided up and analyzed from all these different levels. But it is essential to understand that the brain is a complex system that typically defies such gross divisions, and perhaps these divisions only reflect our limited ability to grasp the complexity of the brain beyond a componential level. Nonetheless, in this chapter, we are going to discuss brain structures, circuits, and neurochemical phenomena. At the core we are talking about learned alterations in the brain, changes in brain structure, changes in brain circuitry or connectivity, and changes in brain chemistry. Brain circuits are interconnected brain areas that are connected by the synaptic patterns and neurotransmitter systems subserving them. Ultimately, the symptoms of PTSD reflect changes in the neurochemical functioning of the brain within specific circuits. Neural circuits are altered by changes in connectivity, a consequence of synaptic change. Neurochemicals are involved in the transmission and modulation of synaptic activity, which is shown in Figure 6.1.

Alterations in Neurochemicals

Alterations in Connectivity

Alterations in Circuitry

Alterations in Behavior and Mental Processes FIGURE 6.1 Neurobiological Alterations.

Confused? Let's hope not! But in case you are, perhaps psychiatrist Bessel A. van der Kolk can clarify things. Bessel A. van der Kolk (1996) proposes that PTSD can be accounted for by looking at how traumatic stress impacts multiple psychobiological systems in three critical ways:

1. Abnormal arousal (e.g., vigilance and hyperarousal).

2. Failure to appropriately monitor and regulate physiologic reactivity.

3. Emotional dysregulation.

He states that individuals with PTSD are in a state of a "chronically disordered pattern of arousal" (p. 218). Avoidance symptoms make sense from this view as attempts to manage such abnormal arousal by shutting down or shutting out stimuli. Further, individuals with PTSD are reactive to both internal stimuli (i.e., memories) and external stimuli (sounds, sights, etc.). Finally, normal emotional functioning that involves distinguishing between what is relevant and important and what is not is impaired. Krystal (1978) reports that in PTSD, emotions fail to alert us to what is relevant, with a subsequent breakdown in adaptive responding. Arousal and adaptation responding are disconnected from each other as van der Kolk (1996) proposes that emotional cues fail to modulate more reactive and primitive stimulus-response patterns. In PTSD, time is not taken to analyze, only to react! As emotions take on this disconnected and functionally useless role, they can then plague and remind the PTSD sufferer of his or her sense of being in danger and ineffectualness in gaining control and feeling safe. Sufferers of PTSD have intense reactions to specific reminders of the trauma. They also overreact to intense stimuli that have nothing to do necessarily with the initial traumatic stressor and suffer from what van der Kolk refers to as a failure in stimulus discrimination. Trigger stimuli acquire reactive status through fear conditioning.

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