Érzelemszabályozás és machiavellizmus kapcsolata az agyi aktiváció tükrében: fMRI-kísérlet

A klasszikus nézet szerint a machiavellista személyek érzelmileg nem vagy kevésbé vonódnak be egy helyzetbe. Interperszonális kapcsolataikat a melegség hiánya jellemzi, kerülik mások szoros közelségét. A rájuk váró feladat kognitív aspektusára koncentrálnak, tehát egy helyzet értékelése és pontos megértése vezérli őket. Affektív távolságtartásuk következtében érzelmileg megterhelő helyzetekben is képesek hideg fejjel és logikusan gondolkodni. A kérdés az, hogy a machiavellisták érzelmi távolságtartása mögött az érzelmek megélésének hiánya áll-e, vagy a kialakuló érzelmeiket erősen kontroll alatt tartják? Kísérletünkben a résztvevők agym7ködését mértük érzelmeket előhívó feladat végrehajtása közben, ami egyúttal megkövetelte a helyzet eltérő nézőpontokból való értelmezését, a rugalmas váltás képességét is. Az eltérő (és átváltást igénylő) helyzetek egyben eltérő érzelmi állapotokat is jelentettek. Az érzelmi átkeretezési feladat során agyi aktivációt találtunk a machiavellisták hippokampuszában, az inzulában, a hátulsó cinguláris tekervény és a cuneus területén. A machiavellistákra jellemző agyi aktiváció többsége (hippokampusz, cuneus) kognitív funkciókat ellátó területeken jelentkezik. Ezek részt vesznek a figyelmi, emlékezeti folyamatok végrehajtásában, a nem releváns információk gátlásában. Ugyanakkor az érzelemszabályozás agyi folyamatai is megjelennek, melyet az inzula és a hátulsó cinguláris kéreg területeinek aktivációja bizonyít. Ezek az eredmények azt mutatják, hogy valóban jellemző rájuk egy érzelmi távolságtartás, ugyanakkor intenzív érzelmeket élnek át, amely befolyásolhatja a döntéshozatali folyamataikat

Comparison of accuracy between FSL’s FIRST and Freesurfer for caudate nucleus and putamen segmentation

AbstractAlthough several methods have been developed to automatically delineate subcortical gray matter structures from MR images, the accuracy of these algorithms has not been comprehensively examined. Most of earlier studies focused primarily on the hippocampus. Here, we assessed the accuracy of two widely used non-commercial programs (FSL-FIRST and Freesurfer) for segmenting the caudate and putamen. T1-weighted 1 mm3 isotropic resolution MR images were acquired for thirty healthy subjects (15 females). Caudate nucleus and putamen were segmented manually by two independent observers and automatically by FIRST and Freesurfer (v4.5 and v5.3). Utilizing manual labels as reference standard the following measures were studied: Dice coefficient (D), percentage volume difference (PVD), absolute volume difference as well as intraclass correlation coefficient (ICC) for consistency and absolute agreement. For putamen segmentation, FIRST achieved higher D, lower PVD and higher ICC for absolute agreement with manual tracing than either version of Freesurfer. Freesurfer overestimated the putamen, while FIRST was not statistically different from manual tracing. The ICC for consistency with manual tracing was similar between the two methods. For caudate segmentation, FIRST and Freesurfer performed more similarly. In conclusion, Freesurfer and FIRST are not equivalent when comparing to manual tracing. FIRST was superior for putaminal segmentation.</jats:p

Stress-Induced Microstructural Alterations Correlate With the Cognitive Performance of Rats: A Longitudinal in vivo Diffusion Tensor Imaging Study

Background: Stress-induced cellular changes in limbic brain structures contribute to the development of various psychopathologies. In vivo detection of these microstructural changes may help us to develop objective biomarkers for psychiatric disorders. Diffusion tensor imaging (DTI) is an advanced neuroimaging technique that enables the non-invasive examination of white matter integrity and provides insights into the microstructure of pathways connecting brain areas.Objective: Our aim was to examine the temporal dynamics of stress-induced structural changes with repeated in vivo DTI scans and correlate them with behavioral alterations.Methods: Out of 32 young adult male rats, 16 were exposed to daily immobilization stress for 3 weeks. Four DTI measurements were done: one before the stress exposure (baseline), two scans during the stress (acute and chronic phases), and a last one 2 weeks after the end of the stress protocol (recovery). We used a 4.7T small-animal MRI system and examined 18 gray and white matter structures calculating the following parameters: fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). T2-weighted images were used for volumetry. Cognitive performance and anxiety levels of the animals were assessed in the Morris water maze, novel object recognition, open field, and elevated plus maze tests.Results: Reduced FA and increased MD and RD values were found in the corpus callosum and external capsule of stressed rats. Stress increased RD in the anterior commissure and reduced MD and RD in the amygdala. We observed time-dependent changes in several DTI parameters as the rats matured, but we found no evidence of stress-induced volumetric alterations in the brains. Stressed rats displayed cognitive impairments and we found numerous correlations between the cognitive performance of the animals and between various DTI metrics of the inferior colliculus, corpus callosum, anterior commissure, and amygdala.Conclusions: Our data provide further support to the translational value of DTI studies and suggest that chronic stress exposure results in similar white matter microstructural alterations that have been documented in stress-related psychiatric disorders. These DTI findings imply microstructural abnormalities in the brain, which may underlie the cognitive deficits that are often present in stress-related mental disorders

Age-dependent changes at the blood-brain barrier. A Comparative structural and functional study in young adult and middle aged rats

Abstract Decreased beta-amyloid clearance in Alzheimer’s disease and increased blood-brain barrier permeability in aged subjects have been reported in several articles. However, morphological and functional characterization of blood-brain barrier and its membrane transporter activity have not been described in physiological aging yet. The aim of our study was to explore the structural changes in the brain microvessels and possible functional alterations of P-glycoprotein at the blood-brain barrier with aging. Our approach included MR imaging for anatomical orientation in middle aged rats, electronmicroscopy and immunohistochemistry to analyse the alterations at cellular level, dual or triple-probe microdialysis and SPECT to test P-glycoprotein functionality in young and middle aged rats. Our results indicate that the thickness of basal lamina increases, the number of tight junctions decreases and the size of astrocyte endfeet extends with advanced age. On the basis of microdialysis and SPECT results the P-gp function is reduced in old rats. With our multiparametric approach a complex regulation can be suggested which includes elements leading to increased permeability of blood-brain barrier by enhanced paracellular and transcellular transport, and factors working against it. To verify the role of P-gp pumps in brain aging further studies are warranted