https://focus.psychiatryonline.org/doi/pdf/10.1176/foc.9.3.foc311

The Neurocircuitry of Fear, Stress, and Anxiety Disorders

The last decade of neuroimaging research has yielded important information concerning the structure, neurochemistry, and function of the amygdala, medial prefrontal cortex, and hippocampus in posttraumatic stress disorder (PTSD). Neuroimaging research reviewed in this article reveals heightened amygdala responsivity in PTSD during symptomatic states and during the processing of trauma-unrelated affective information. Importantly, amygdala responsivity is positively associated with symptom severity in PTSD. In contrast, medial prefrontal cortex appears to be volumetrically smaller and is hyporesponsive during symptomatic states and the performance of emotional cognitive tasks in PTSD. Medial prefrontal cortex responsivity is inversely associated with PTSD symptom severity. Lastly, the reviewed research suggests diminished volumes, neuronal integrity, and functional integrity of the hippocampus in PTSD. Remaining research questions and related future directions are presented.

Amygdala, medial prefrontal cortex, and hippocampal function in PTSD.

Background: The “default network” consists of a number of brain regions that exhibit correlated low-frequency activity at rest and that have been suggested to be involved in the processing of self-relevant stimuli. Activity in many of these areas has also been shown to be altered in individuals with posttraumatic stress disorder (PTSD). We hypothesized that the posterior cingulate cortex (PCC)/precuneus, part of the default network, would exhibit altered connectivity at rest with other areas of the default network and regions associated with PTSD. Methods: Seventeen medicated and unmedicated female patients with chronic posttraumatic stress disorder (PTSD) related to early-life trauma and 15 healthy female controls underwent a 5.5-minute functional magnetic resonance imaging scan with their eyes closed. We assessed areas of the brain whose activity positively and negatively correlated with that of the PCC/precuneus in both groups. Results: At rest, spontaneous low-frequency activity in the PCC/precuneus was more strongly correlated with activity in other areas of the default network in healthy controls than in patients with PTSD. Direct comparison of the 2 groups showed that PCC/ precuneus connectivity was also greater in healthy controls than in patients with PTSD in a number of areas previously associated with PTSD, including the right amygdala and the hippocampus/parahippocampal gyrus. Limitations: Because our PTSD sample comprised only women with chronic early-life trauma exposure, our results may not be generalizeable to male patients, to a population with single trauma exposure or to those who were adults when the trauma occurred. In addition, our sample included patients taking medication and it is not yet clear how altered connectivity is affected by medication. Conclusion: Spontaneous activity in the default network during rest, as measured using PCC correlations, is altered in patients with PTSD. The potential effects of psychotropic medications on default network connectivity in the present sample remain unknown. In this patient population, the observed alterations may be associated with the disturbances in self-referential processing often observed in patients with chronic PTSD related to early-life trauma.

/pdf/alterations-in-default-network-connectivity-in-posttraumatic-3wqfrc343q.pdf

Alterations in default network connectivity in posttraumatic stress disorder related to early-life trauma.

This paper reviews the major developments that have taken place during the last three years in imaging with computed tomography (CT) using X-ray, emission, and ultrasound sources. Space limitations have resulted in some selection of topics by the author. There are four major sections dealing with algorithms, X-ray CT, emission CT, and ultrosound CT. Since most of the currently used algorithms are of filtered-backprojection type, we have concentrated on these in the section on algorithms (with emphasis on their implementation aspects). In X-ray CT an important question raised during the last few years has concerned the parameter measured by a CT scanner, given the fact that the X-rays used in CT scanners are polychromatic and the fact that tissue attenuation coefficients are energy dependent. Answers to this question are reviewed in the section on X-ray CT where we have also discussed the artifacts caused by the polychromaticity of the X-ray photons. Methods for the removal of these artifacts have also been reviewed. In emission CT the biggest development of the last three years is the great interest in positron tomography, although space constraints have dictated an essentially introductory treatment and not all aspects of the single photon and positron tomography have been surveyed. Finally, we have reviewed recent developments in ultrasound CT. We have pointed out that because of the sensitivity of this technique to refraction, it is currently limited to soft tissue structures, with ultrasonic detection of tumors in the female breast a significant application.

Computerized tomography with X-ray, emission, and ultrasound sources

Post-traumatic stress disorder (PTSD) is a significant problem that can affect individuals who have been exposed to a traumatic event or events, such as combat, violent crime or childhood abuse. Over the past several years, neuroimaging studies of PTSD have focused on elucidating the brain circuits that mediate this disorder. In this article, we will briefly introduce some of the methods used in functional neuroimaging studies of PTSD. We will then review functional neuroimaging studies that have reported significant findings in the amygdala, medial prefrontal cortex, hippocampus and insula. Finally, we will suggest future directions for research.

/pdf/functional-neuroimaging-studies-of-post-traumatic-stress-nlc8tlyl4h.pdf

Functional neuroimaging studies of post-traumatic stress disorder

Objective Because of the treatment resistance and chronic affective lability of many post-traumatic stress disorder (PTSD) patients and the hypothesized association of these behaviors with temporal and limbic structures, a study was conducted to determine whether these patients would exhibit alterations in regional cerebral perfusion in the temporal and limbic regions compared with age-matched normal volunteers at rest. Method We studied 17 patients using 99mTc hexamethyl propylene amine oxime single photon emission computed tomography. Seven of the patients were on a selective serotonin reuptake inhibitor, five were on a tricyclic antidepressant, and five were on no medication at the time of the study. Patients were compared with eight age-matched normal controls. Results All PTSD patients showed a relative increase in regional cerebral perfusion in the anterior and posterior cingulate regions bilaterally, the right temporal and parietal regions, the right caudate/putamen region, and the left orbital and hippocampal regions compared with the control group. When the group of PTSD patients who were free of medication were compared with the control group, increased regional cerebral perfusion was found in the right and left caudate/putamen regions and the right orbital and anterior cingulate cortex bilaterally. Conclusions PTSD is associated with increased regional blood flow in limbic areas and the right temporal and parietal cortex compared with age-matched normal volunteers.

/pdf/increased-regional-cerebral-perfusion-by-99mtc-hexamethyl-32b5udv3kf.pdf

Increased regional cerebral perfusion by 99mTc hexamethyl propylene amine oxime single photon emission computed tomography in post-traumatic stress disorder.

Transverse axial positron annihilation coincidence detection tomography with a stationary circular ring posi tron camera system is described. A prototype constructed with 64 NaI(T1) crystal system has the capability of recording 736 - 1312 simultaneous coincidence pairs and is able to perform certain dynamic function studies.

Performance and Evaluation of the Circular Ring Transverse Axial Positron Camera (CRTAPC)

The varying tissue distribution of L-glutamic acid labelled at three different sites.

Knee joints were scanned in a group of patients with gout and rheumatoid arthritis and in a second group of patients without joint disease. 131I human serum albumin, 99mTc-albumin or 99mTc-pertechnetate were utilized. Scans performed with labeled albumin were reliable indicators of the presence or absence of active inflammation of the joint. Technetium, as the pertechnetate, not only concentrated in all inflamed joints but was also concentrated in the knee joint of 19 of 20 patients without joint disease.

M. B. Cohen

Papers

Increased regional cerebral perfusion by 99mTc hexamethyl propylene amine oxime single photon emission computed tomography in post-traumatic stress disorder.

Performance and Evaluation of the Circular Ring Transverse Axial Positron Camera (CRTAPC)

The varying tissue distribution of L-glutamic acid labelled at three different sites.

Avoiding false-positive joint scans by the use of labeled albumins.