Post-traumatic Stress Disorder - Essay Example

Neuro-imaging studies and post-traumatic stress disorder affiliation Neuro-imaging studies on brain abnormalities thatassociate with Post-Traumatic Stress Disorder Introduction Posttraumatic stress disorder is an anxiety disorder resulting due to neural circuitry changes that involve the limbic and frontal systems after alteration in metabolism after traumatic events. The developments in the field of neuroimaging have enabled researchers to the functional and structural properties of the brain resulting from the disorder that is very essential in medicine. Extreme stressors cause the disorder, and it is rising among the population. Examples of the stressors include natural disasters, motor vehicle accidents, childhood abuse, rape and sexual abuse. Symptoms associated with the condition include numbing emotions, flashbacks, sleep disorders, social dysfunction, intrusive memories and avoidance of traumatic stimuli. The advances made in the field of neuroimaging have enabled the researchers to uncover the neural system networks that are believed to be involved in the pathophysiology of the condition (Peterson, Thome, Frewen & Lanius, 2014). These techniques include the single-photon computed emission tomography (SPECT), the functional magnetic resonance imaging (fMRI) and the positron emission tomography (PET) that enable the visualization of the activation of brain-specific areas by measuring the blood oxygen levels, regional cerebral blood flow and the neuro-receptor density. According to the research findings, the patients with the disorder have shown an altered brain activation in various brain regions. However, the findings of the techniques, designs and methodologies have been found to vary greatly. The Neuroanatomical of Post-Traumatic Stress Disorder The pathophysiology of the disorder is linked with several neurobiological mechanisms that are related to stress. According to research studies conducted, behavioral sensitization, fear response mechanism and failure of extinction of fear play an essential role in the pathophysiology of the disorder. Patients suffering from the disorder also have demonstrated significant defects in their memory and the alterations in their brain memory can be correlated with specific functional and brain structures that are altered and therefore become dysfunctional (Bremner, 2007a). The advent of the functional techniques for imaging has opened a great window of opportunities for conducting the neurological research on humans as an effort of determining the underlying pathophysiology (Osuch et al, 2009). People suffering from the condition commonly experience intrusive and vivid recall of traumatic memory thus; frequent recall is part of diagnosis criteria of the condition. These traumatic memories can be elicited through cognitive and sensory stimuli that are paired to the traumatic events that the persons have experienced. As a result of traumatic related stimuli, the patients with the disorder will display avoidance stimuli or a numbing of their emotional reactions (Sripada et al, 2013). When an individual is exposed to normally dangerous events, such situations will elicit a smaller fear response as opposed to previous situations. However, in patients suffering from the post-traumatic stress disorder, the process will not occur efficiently and the fear of certain situations will fail to extinguish that can be identified in military veterans by the fearful response to fireworks and noisy crowds. Thus, individuals have a dysfunction in extinction of fear that is associated to be the cause of the traumatic memories (Alastair M Hull, 2002). Neuroimaging Techniques The neuroimaging techniques are important in measuring the different activities that place in the brain i.e. SPECT, PET, and fMRI that derive brain function from physiological measures such as the cerebral blood flow, energy consumption levels as well as blood oxygen levels (Nardo et al, 2013). The parameters are based on the assumption that glucose metabolism and blood flow alter when certain brain areas become inhibited or activated. When a neural cell fires, they increase their activity that will require a restoration of the energy that is used, thus the metabolic demands by the neuron result to increased blood flow in the areas. The techniques work by interpreting the physiological measures to deduce the brain activity (Bremner, 2002). Single-photon Emission Computed Tomography (SPECT) A common technique that uses the γ emitters to measure rCBF changes occurring in the brain. Radiotracers are introduced by an injection in the body as a γ camera acquires an arc of single photon projections that are emitted by the radiotracers determining the activity within a specific region. The advantages of utilizing the technique include the high availability as well as a simple methodology as compared to other techniques i.e. Position Emission Tomography (Bisson, 2007). Among the drawbacks facing the technique includes lack of positional information on the incoming photon resulting to decreased sensitivity of images and decreased accuracy as activity is measured deeper into the brain as a result of the attenuation of signals that are caused by tissues between the camera and the source (Sripada et al, 2013). Positron Emission Tomography The technique involves the production of functional images of neural activity by acquiring Coincidence events. A coincide results when two photons are registered at an angle 180 degrees by the radiation detectors with the camera. The coincidences are then utilized for generating a three-dimensional map of the radiotracer position and concentration of a given part of the brain through calculation of brain metabolism and blood flow with the aid of a computer algorithm (A M Hull, 2002). The emitters are introduced by means of an injection or gas. The disadvantage associated with the method involves financial issues that are coupled with it as the radiotracers utilized have a much shorter half-life; therefore, there is a need of production on site (Sripada et al, 2013). Functional Magnetic Resonance Imaging (fMRI) This technique does not require the introduction of a radioactive tracer to produce neural activation, but rather relies on the body abilities of producing its own tracer. The Hemoglobin in the red blood cells acts as a tracer when it is exposed to a strong magnetic field. The radio frequency pulse is then sent through a subject specific to hydrogen causing the protons to become excited, they absorb the energy, and an image is reconstructed as they return to equilibrium. The technique is advantageous, as it does not require any exposure to radiation (Lanius et al, 2005). Thus, the imaging process is very safe, and the patient can repeat the process without worry over exposure to radioactive substances. Other advantages include its lower cost; it has a high availability as well as its spatial and anatomical resolution it provides as compared to other methods. The main limitation of the method is that it results to reduced temporal resolution as it measures changes of rCBF in response to the neuronal activity of the brain and it is very noisy thus, it can be uncomfortable to the patient. Functional Neuroimaging Paradigms Various strategies can be used to measure the brain function with the most straightforward method being measuring the brains activity by observing the individual at rest. Receptors availability, cerebral blood flow and affinity are other indirect measures that can measure the activity of the brain (Liberzon & Garfinkel, 2009). The differences in the variables are also important in describing the pathophysiology of the disorder. The brains activity can also be observed by having the subject participating on an active task. Thus individuals are asked to perform certain activities that elicit a predicted response of the brain that change the neural activities in the regions hypothesized to be dysfunctional in PTSD i.e. memory recall task, emotional recall, memory encoding tasks and auditory continuous performance tasks (Whalley et al, 2013). Brain abnormalities that associate with Post-Traumatic Stress Disorder The finding among patients with post-traumatic stress disorder using PET, fMRI, and SPECT is decreased medial prefrontal cortex as well as increased amygdalar activation. Other findings have tied regions such as the hippocampus and the adjacent parahippocampal gyrus to be involved, and the inconsistencies could be as a result of the wide variation of parameters among the different studies. The altered function of the amygdala has been frequently discussed in the presentation of the disorder with an increased activation patterns as compared to a normal individual (Kar, 2011). Moreover, other studies that utilized task activity found the amygdala activation when the subjects were instructed to perform an auditory continuous performance task, active trauma recall and memory recall (Whalley et al, 2013). Another common feature among the post-traumatic stress disorder patients is hypo activation of the mPFC that involves parts of the Brodmann’s area. System provocation paradigms found the latter among patients where they used images and traumatic sounds, traumatic scripts and emotional faces. Studies using active studies have found mPFC deactivation among subjects who were instructed to perform a continuous auditory performance task (Liberzon & Garfinkel, 2009). However, there has been a suggested link or a relationship between the amygdala and the mPFC regions. Studies found a decrease in mPFC activity with a simultaneous hyperactivation of the amygdala to be occurring simultaneously among patients with post-traumatic stress disorder. It has been suggested that the mPFC provides system of negative feedback regulating the activation of the amygdala. Although a significant relationship exists between the two, some findings point out differently reported parallel between the mPFC and amygdala activity (Whalley et al, 2013). The hippocampus has a critical role in the consolidation of novel memories of events and facts. Patients with post-traumatic stress disorder have been shown to perform significantly poorly on hippocampal learning tasks and memory. However, in studies that utilized tasks with emotional content, there were inconsistent findings (Fox & Greicius, 2010). The parahippocampal gyrus is related to the hippocampus and findings related to the structure show a trend of increased activity that contradict the theory of memory deficit in PTSD. Another less documented finding in functional neuroimaging is the thalamus involvement among patients with post-traumatic stress disorder. It is an important relay station for the transmission of sensory information to different regions of the limbic system and cerebral cortex for processing. Target regions include the gyrus, frontal cortex, hippocampus and amygdala that are related to the neural networks active in a post-traumatic stress disorder patient (Bremner, 2007b). There is a decrease in the thalamic activity among the affected patients that results to various traits being displayed by the clinical presentation of PSTD. The disruptions in thalamus activity results to misinterpretation of external stimuli. This has been proven using the fMRI as opposed to other techniques (Fox & Greicius, 2010). The finding trends resulting from the functional imaging studies remain a complicated issue. These results are due to the underlying discrepancies that lies among the various studies in the design of paradigms used in measuring the neural activity in the patients with the disorder. The studies use widespread methodologies measuring and retesting brain activity, presenting a range of stimuli and using active task performance by subject. A wide range of subjects in the specific studies is another issue that complicates the studies when comparing different studies i.e. the patients broad trauma spectrum and their different sexes thus, it is important to distinguish between the trauma cases. By doing analyzes of patients with a common sex and history of trauma, it is, therefore, possible to analyze neural activity with the highest precision, as well as potential differences between the groups (Etkin & Wager, 2007) Conclusion Posttraumatic stress disorder is an anxiety disorder resulting due to neural circuitry changes that involve the limbic and frontal systems after alteration in metabolism after traumatic events. Functional neuroimaging studies have used SPECT, PET, and fMRI to open up the window of uncovering the mechanism behind post-traumatic stress disorder. From the findings, the most consistent results from the studies are the relative decrease in mPFC activity as well as increased amygdalar activation where a functional relationship between the two has been hypothesized. The role of the Parahippocampal gyrus and hippocampus is also altered despite other studies supporting the involvement of the two. The finding trends resulting from the functional imaging studies remain a complicated issue due to the underlying discrepancies that lies among the various studies in the design of paradigms used in measuring the neural activity in the patients with the disorder. Many recent advances have been made in neuroimaging field of PSTD, but future research is important to further approach neurological correlates of the diverse and complex disorder. References Bisson, J. I. (2007). Post-traumatic stress disorder. BMJ (Clinical Research Ed.), 334, 789– 793. doi:10.1136/bmj.39162.538553.80 Bremner, J. D. (2002). Neuroimaging studies in post-traumatic stress disorder. Current Psychiatry Reports, 4, 254–263. doi: 10.1007/s11920-996-0044-9 Bremner, J. D. (2007a). Functional neuroimaging in post-traumatic stress disorder. Expert Review of Neurotherapeutics, 7, 393–405. doi:10.1586/14737175.7.4.393 Bremner, J. D. (2007b). Neuroimaging in Posttraumatic Stress Disorder and Other Stress- Related Disorders. Neuroimaging Clinics of North America. doi:10.1016/j.nic.2007.07.003 Etkin, A., & Wager, T. D. (2007). Functional Neuroimaging of Anxiety: A Meta-Analysis of Emotional Processing in PTSD, Social Anxiety Disorder, and Specific Phobia. American Journal Of Psychiatry, 164(10), 1476-1488. doi:10.1176/appi.ajp.2007.07030504 Fox, M. D., & Greicius, M. (2010). Clinical applications of resting state functional connectivity. Frontiers In Systems Neuroscience, 419. doi:10.3389/fnsys.2010.00019 Hull, A. M. (2002). Neuroimaging findings in post-traumatic stress disorder. Systematic review. Br J Psychiatry, 181, 102–110. Hull, A. M. (2002). Neuroimaging findings in post-traumatic stress disorder. Systematic review. The British Journal of Psychiatry : The Journal of Mental Science, 181, 102– 110. doi:10.1192/bjp.181.2.102 Kar, N. (2011). Cognitive behavioral therapy for the treatment of post-traumatic stress disorder: A review. Neuropsychiatric Disease and Treatment. doi:10.2147/NDT.S10389 Lanius, R. A., Williamson, P. C., Bluhm, R. L., Densmore, M., Boksman, K., Neufeld, R. W., & ... Menon, R. S. (2005). Functional connectivity of dissociative responses in posttraumatic stress disorder: A functional magnetic resonance imaging investigation. Biological Psychiatry, 57(8), 873-884. doi:10.1016/j.biopsych.2005.01.011 Liberzon, I., & Garfinkel, S. N. (2009). Functional Neuroimaging in Post-Traumatic Stress Disorder. In Post-Traumatic Stress Disorder: Basic Science and Clinical Practice (pp. 1–21). Nardo, D., Högberg, G., Lanius, R. A., Jacobsson, H., Jonsson, C., Hällström, T., & Pagani, M. (2013). Gray matter volume alterations related to trait dissociation in PTSD and traumatized controls. Acta Psychiatrica Scandinavica, 128(3), 222-233. doi:10.1111/acps.12026 Osuch, E. A., Benson, B. E., Luckenbaugh, D. A., Geraci, M., Post, R. M., & McCann, U. (2009). Repetitive TMS combined with exposure therapy for PTSD: A preliminary study. Journal Of Anxiety Disorders, 23(1), 54-59. doi:10.1016/j.janxdis.2008.03.015 Peterson, A., Thome, J., Frewen, P., & Lanius, R. A. (2014). Resting-state neuroimaging studies: a new way of identifying differences and similarities among the anxiety disorders?. Canadian Journal Of Psychiatry. Revue Canadienne De Psychiatrie, 59(6), 294-300. Sripada, R. K., King, A. P., Garfinkel, S. N., Wang, X., Sripada, C. S., Welsh, R. C., & Liberzon, I. (2012). Altered resting-state amygdala functional connectivity in men with posttraumatic stress disorder. Journal Of Psychiatry & Neuroscience: JPN, 37(4), 241-249. doi:10.1503/jpn.110069 Whalley, M. G., Kroes, M. W., Huntley, Z., Rugg, M. D., Davis, S. W., & Brewin, C. R. (2013). An fMRI Investigation of Posttraumatic Flashbacks. Brain and Cognition, 81(1), 151-159. Read More