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Biology 202
2002 Third Paper
On Serendip


Gavin Imperato


Throughout the course of this semester we have examined numerous issues which have all had different implications for the brain = behavior argument. Some who have been skeptical of the validity of this idea have been swayed by observations that processes and behaviors they originally thought to have a cloudy neurobiological basis in fact have a sound biological and physiological underpinning. One such phenomenon which can help elucidate the ongoing brain = behavior debate is Post-Traumatic Stress disorder, or PTSD. Most people are familiar in some sense with the phenomenon of PTSD. This phenomenon has been renamed, reworked, and redefined numerous times over the past century. The approach to understanding PTSD and the more general notion of traumatic experience has been an interdisciplinary undertaking, involving the fields of medically oriented psychiatry, psychology, sociology, history, and even literature (1). The reason for this interdisciplinary approach is that the greater perception of the phenomenon is seen as having much more than a simple biological basis. It is seen as having multiple external influences. This view is a result of the often overwhelming sense that whatever biological mechanisms are present must be unintelligibly complex. However, there are certain aspects of PTSD which, upon examination, allow one an easy foray into the neurobiology of the disorder. Cathy Caruth, a leading trauma theorist, discusses the definition of PTSD: "While the precise definition of post-traumatic stress disorder is contested, most descriptions generally agree that there is a response, sometimes delayed, to an overwhelming event or events, which takes the form of repeated, intrusive hallucinations, dreams, thoughts, or behaviors stemming from the event, along with numbing that may have begun during or after the experience, and possibly also increased arousal to (and avoidance of) stimuli recalling the events" (1) . It is the goal of this paper to demonstrate that the phenomenon of PTSD, despite the fact that its multiple emotional and psychosocial effects are constantly being debated, is soundly rooted in neurobiology, and that this aspect of PTSD lends support to the notion that brain = behavior.

The general problem in the assessment of PTSD is that "Traditional psychotherapy addresses the cognitive and emotional elements of trauma, but lacks techniques that work directly with the physiological elements, despite the fact that trauma profoundly affects the body and many symptoms of traumatized individuals are somatically based" (2). Popular belief is that traumatic events affect an individual at the level of the I-function - that is, in the part of the brain responsible for cognition, emotion, and feeling. It is indeed true that the symptoms of PTSD can affect mood and the nature of interpersonal interaction. However, there is strong evidence that responses to trauma are rooted in neurobiological processes independent of the I-function, and have a somatic basis. As the above excerpt states, most treatment modalities focus on the non-somatic elements of PTSD, neglecting to recognize the important physiological effects that the disorder entails.

Dianthe Lusk, a character in Pauline Hopkins' novel Of One Blood, is diagnosed by a physician after she has been rescued from the scene of a train accident: "As I diagnose this case, it is one of suspended animation. This woman has been long and persistently subjected to mesmeric influences, and the nervous shock induced by the excitement of the accident has thrown her into a cataleptic sleep" (3). This passage underscores much of how PTSD is configured in the public mind. It is seen as a mysterious and indefinable affliction - something more akin to being possessed by a demon or a ghost than actually having an identifiable pathology in the nervous system. Despite the tendency to view PTSD as a phenomenon that exists outside the boundaries of our known knowledge of the nervous system, there are several important observations which lend support to the idea that PTSD is soundly rooted in such a basis. This connection may be used to help elucidate the overarching notion that brain = behavior.


The role of the physical in the phenomenon of traumatic events is often overlooked because it is not entirely evident how it plays into these scenarios. If anything, it is usually recognized that "a victim may instantaneously freeze rather than act, a driver may not have time to execute the impulse to turn the car to avoid impact, or a person may be overpowered when attempting to fight off an assailant." (2). However, it is this precise lack of a physical response that can lead to subsequent psychodynamic maladjustments: "Over time, such interrupted or ineffective physical defensive movement sequences contribute to trauma symptoms" (2). The very psychological problems that most associate with PTSD are in fact, brought into existence because of these physical movement defensive sequences. This recognition enables us to see the importance of non-psychological factors in traumatic experience.


As Cathy Caruth states, "it is only in and through its inherent forgetting that [trauma] is first experienced at all" (1). Despite what may seem like a phenomenon whose biological basis is very cloudy, there is in fact a "general biological function of the process by which experience passes into the region of the unconscious" (4). The elucidation of this mechanism is made possible by "observations on the sensory changes which accompany the regeneration of a divided and reunited nerve" (4). Suppression, which is the mechanism by which memories enter into the unconscious, has been demonstrated experimentally to occur in the process of nerve regeneration. This very complex process involves demonstrating, using the modality of heating and cooling a human limb in which the nerve regeneration is taking place, that it is possible to suppress and recover different types of sensations that occur during the process of regeneration (4). The relevant message with regard to PTSD that can be drawn from this demonstration is "the special importance of suppression on the reflex and sensori-motor levels is that it reveals clearly the biological significance of the process" (4). The process of suppression is clearly rooted in physiology, and is experimentally reproducible. This all-important observation allows us to see that the brain = behavior argument plays significantly into the discussion of PTSD. The suppression of traumatic memory that occurs in the wake of such an event is "a process of reaction to the pleasures and pains" (4) of the event in question. The experiment described above helps us to see how many of the vague and imprecise terms such as "somatization", "conversion", "hysterical", "psychological", or "psychosomatic" distort the idea that what is actually happening in a patient with PTSD is a neurobiologically definable suppression which is independent of the conscious processing functions of the patient's brain (5).


Van der Kolk et al. state: "Though the biological underpinnings of response to trauma are extremely complex, forty years of research on humans and other mammals have demonstrated that trauma (particularly trauma early in the life cycle) has long term effects on the neurochemical response to stress, including the magnitude of the catecholamine response, the duration and extent of the cortisol response, as well as a number of other biological systems, such as the serotonin and endogenous opioid system" (6). Another tremendously important observation that lends support to the idea that PTSD is characterized by an objective effect on the nervous system can be seen in the manner in which traumatic situations affect humans of different ages. It is well documented that the early childhood years witness a significant amount of development with regard to the nervous system. We deduce that an objective change in the nervous system takes place as a result of a traumatic stress, because a child will experience much more substantial and long-lasting effects than an adult in response to a similar traumatic event. A considerably large body of research has shown that the effect of such stresses on the nervous system can cause deficiency in or induce the following: "capacity to modulate emotions, difficulty in learning new coping skills, alterations in immune competency, and impairment in the capacity to engage in meaningful social affiliation" (6). Children affected by trauma thus exhibit behaviors throughout the course of their subsequent lives that are owed to neurochemical and neurobiological alterations and deficiencies that are brought about by the given traumatic event. This recognition helps us to see that subsequent psychological problems in the lives of traumatized children are the direct result of neurobiological disruptions that occur during a crucial developmental phase of the child's nervous system.


Another observation in support of the link between PTSD and an objective neurobiological basis is the efficacy of certain drugs on the numerous psychological manifestations of the disorder. Studies of the effects of drugs used to treat PTSD have largely centered on antidepressants and MAO inhibitors. The results of such studies have not been convincing (6). However, "during the past few years evidence has accumulated that serotonin reuptake blockers are likely to be the most effective drugs in the treatment of chronic PTSD" (6). Animal researchers have been able to demonstrate that "serotonin receptor blockers reverse the suppression of fear-induced behavior, probably because an increase in available serotonin in the limbic system amplifies the signals necessary to distinguish punishment from reward" (7). This linkage, while it has not been completely elucidated, does speak to a significant correlation between the neurobiology of PTSD and the ability to treat its numerous psychodynamic maladjustments. We are able to see PTSD then, not solely as a mysterious psychological phenomenon, but rather as a disorder whose pathology can be traced to a sound neurobiological basis and whose symptomatology can be treated by drugs whose mode of action is to affect said neurobiology.


Numerous observations regarding PTSD lead us to the conclusion that it is a disorder whose basis in neurobiology, while largely unrecognized in the lay public, is in fact very sound. These observations include: the manner in which physical responses play into traumatic scenarios; the presence of a biological mechanism of suppression, the documented effect of trauma in early life, and the ability to remedy the symptoms of PTSD through psychopharmacologic treatment. The tendency to see PTSD as a pure psychosocial disorder distorts the notion that traumatic events do in fact result in neurochemical and neurobiological changes in the nervous system. This association lends support to the notion of brain = behavior as it shows that psychological problems subsequent to traumatic events do not simply arise because the person was somehow "affected" by the event. Such a person's neurobiology was in fact altered from the normative state, and although a complex undertaking, his or her behaviors can be traced to this objective underpinning.



1) Trauma: Explorations in Memory , by Cathy Caruth, a leading trauma theorist.

2) Sensorimotor Psychotherapy: One Method for Processing Traumatic Memory," from Traumatology , by Pat Ogden and Kekuni Minton.

3) Of One Blood , a novel by Pauline Hopkins.

4)"The Repression of War Experience" , by W.H.R. Rivers.

5) "The Neurophysiology of Dissociation and Chronic Disease," from Applied Psychophysiology and Biofeedback , by Robert C. Scaer.

6) "Approaches to the Treatment of PTSD" , by Bessel A. van der Kolk and Onno van der Hart.

7) The Psychology of Fear and Stress , by J. Gray.



Comments made prior to 2007
Thank you for this concise and very clearly laid out paper on the neurobiological core of PTSD. It fits precisely my own experiences of the condition. In particular, two responses have been problematic for me over a lifetime, especially in intimate relations: first, the exaggerated startle response to noise which used to induce in me a particularly strong fight/flight response and which has caused me immeasurable trouble and heartache - yell at me, and I'm gone; second, flight from structural circumstances that restimulated 'primitive' memories of the structural conditions of the initial trauma. Specifically, hostile behaviour towards me from men while in the presence of women with whom I was intimately involved. Even modest 'social' hostility, like being ignored or discounted, has been sufficient to restimulate my 'fear' response and thence to cause me to depart the relationship. I could go on...and I will, but not here. Thanks again ... Tony, 26 March 2007