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Epilepsy
(2010)
Differential modulation of valence and arousal in high-alexithymic and low-alexithymic individuals
(2010)
High-alexithymic individuals are characterized by an impaired ability to identify and communicate emotions whereas low-alexithymic individuals have a wide-ranging ability to deal with emotions. This study examined the hypothesis that valence and arousal modifications of emotional stimuli differentially modulate cortical regions in high-alexithymic and low-alexithymic individuals. To this end, 28 high-alexithymic and 25 low-alexithymic individuals were investigated with event-related fMRI using visual emotional stimuli. We found differential neural activations in the dorsal anterior cingulate, the insula and the amygdala. We suggest that these differences may account for the impaired ability of high-alexithymic individuals to appropriately handle emotional stimuli.
Background: One of the most prominent neurobiological
models of alexithymia assumes an altered function of the
anterior cingulate cortex (ACC) as the crucial neural correlate
of alexithymia. So far functional imaging studies have yielded
inconclusive results. Therefore, we tested this hypothesis
in healthy alexithymics and nonalexithymics in an event-related
fMRI study. Methods: Thirty high- and 30 low-alexithymic
right-handed male subjects (selected by the 20-item
Toronto Alexithymia Scale, TAS-20) were investigated with
event-related fMRI using a picture viewing paradigm. The
stimuli consisted of happy, fearful and neutral facial expressions
(Ekman-Friesen) as well as positive, negative and neutral
pictures from the International Affective Picture System.
Results: Contrasting the high-alexithymic with the low-alexithymic
group we observed increased activation of the supragenual
ACC for different emotional valences as well as for different emotional stimuli. Moreover, there was a positive
correlation of the ACC with the individual TAS-20 scores but
no correlations with the individual Beck Depression Inventory
scores. Additionally, there was no difference in activity
of the amygdala. Conclusions: We demonstrated that the
supragenual ACC is constantly activated more strongly in
alexithymic subjects and that this activation is related to the
symptoms of alexithymia and not to associated symptoms
such as depression. Therefore, our findings support the hypothesis
of an altered function of the ACC in alexithymia.
Following the success of PET/CT during the last decade and the recent increasing proliferation of SPECT/CT, another hybrid imaging instrument has been gaining more and more interest: MR-PET. First combined, simultaneous PET and MR studies carried out in small animals demonstrated the feasibility of the new approach. Concurrently, some prototypes of an MR-PET scanner for simultaneous human brain studies have been built, their performance is being tested and preliminary applications have already been shown. Through this pioneering work, it has become clear that advances in the detector design are necessary for further optimization.
Recently, the different issues related to the present state and future prospects of MR-PET were presented and discussed during an international 2-day workshop at the Forschungszentrum Jülich, Germany, held after, and in conjunction with, the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference in Dresden, Germany on October 27–28, 2008. The topics ranged from small animal MR-PET imaging to human MR-BrainPET imaging, new detector developments, challenges/opportunities for ultra-high field MR-PET imaging and considerations of possible future research and clinical applications. This report presents a critical summary of the contributions made to the workshop.
Design and initial performance of PlanTIS: a high-resolution positron emission tomograph for plants
(2010)
Positron emitters such as 11C, 13N and 18F and their labelled compounds are widely used in clinical diagnosis and animal studies, but can also be used to study metabolic and physiological functions in plants dynamically and in vivo. A very particular tracer molecule is 11CO2 since it can be applied to a leaf as a gas. We have developed a Plant Tomographic Imaging System (PlanTIS), a high-resolution PET scanner for plant studies. Detectors, front-end electronics and data acquisition architecture of the scanner are based on the ClearPET™ system. The detectors consist of LSO and LuYAP crystals in phoswich configuration which are coupled to position-sensitive photomultiplier tubes. Signals are continuously sampled by free running ADCs, and data are stored in a list mode format. The detectors are arranged in a horizontal plane to allow the plants to be measured in the natural upright position. Two groups of four detector modules stand face-to-face and rotate around the field-of-view. This special system geometry requires dedicated image reconstruction and normalization procedures. We present the initial performance of the detector system and first phantom and plant measurements.
Realization of a calorimetric gas sensor on polyimide foil for applications in aseptic food industry
(2010)