Neural Substrates of Posttraumatic Stress Disorder: Functional Magnetic Resonance Imaging Study Using Negative Priming Task

OBJECTIVES: Posttraumatic stress disorder(PTSD) has been primarily associated with emotional problems. Recently, however, the impact of PTSD on cognitive processes has interested a growing number of researchers. The current study is aimed at investigating the cognitive aspects of PTSD at both behavioral and neurological levels. METHODS: We recruited individuals with PTSD who survived the Daegu subway explosion in 2003 as well as non-PTSD individuals as a control group. To evaluate the inhibitory processes and the neural mechanisms, we had these individuals perform the negative priming task simultaneously with functional MRI scanning. RESULTS: Behaviorally, the negative priming effect was intact in the control group but was not evident in the PTSD group. In the imaging results, only the PTSD group showed the negative priming effect (i.e., increased activation of the negative priming condition as opposed to the neutral condition) in the dorsolateral prefrontal cortex, anterior cingulate cortex, and inferior temporal gyrus. The PTSD group also showed increased activity for the positive priming condition as opposed to the neutral condition in the claustrum. These results confirm and extend the previous findings that the integrity of the ACC is compromised in the trauma survivors due to disrupted white matter tract. CONCLUSIONS: The current results suggest that deteriorated performance of the PTSD group may be due to the functional problem as well as the structural abnormalities.

Changed Angle Deviation after Occlusion Therapy in Monocular Exotropia with Amblyopia

Changes of deviated angle in monocular exotropic patients with amblyopia were studied in 18 patients who had undergone occlusion therapy to investigate the possibility that occlusion may have an influence on the amount of preexisting exodeviation and fixation. Average follow up time was 9.7 months and average age was 6.3 years old. The size of the deviation angle was changed from 27.00 +/- 6.57 Prism diopter(PD) to 21.05 +/- 10.07 PD at near fixation, and from 28.56 +/- 8.67 PD to 22.05 +/- 10.08 PD at distance fixation(P<0.001). The size of deviation angle decreased more than 6 PD in 7 cases(38.9%) at near fixation and in 8 cases(44.4%) at distance fixation. The preference pattern was changed from monocular to alternating type in 14 cases(77.8%). After occluson in monocular exotropic patients with amblyopia, the visual acuity was improved and deviated angle was changed more than 6 PD. The changed angle was decreased or increased, but one patient was increased less than 5 PD. The remained deviation of angle after occlusion was less than 10 PD in 2 patients and fixation pattern was changed to exophoria in 1 patient. This results were not required surgical treatment in 3 patients. This result suggest that we should be attempt to treat by occlusion before surgery, because the occlusion therapy is helpful to improvement of visual acuity, deviated angle and fixation pattern.