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Four Achnanthidium species (Bacillariophyta) formerly identified as Achnanthidium minutissimum from the Antarctic Region (2014)

Bart van de Vijver Kateřina Kopalová

Four taxa belonging to the complex of species around Achnanthidium minutissimum were found during the ongoing taxonomic revision of the Antarctic freshwater and limno-terrestrial diatom flora. Two taxa were previously described as Achnanthidium lailae and A. sieminskae. Two others were formerly identified as A. minutissimum but detailed light and scanning electron microscopical observations revealed sufficient morphological differences compared to the type of A. minutissimum, to justify their separation and description as new taxa: Achnanthidium indistinctum and A. maritimo-antarcticum. The morphology and ecology of all four taxa are discussed comparing the species with morphologically similar taxa. The biogeographical consequences of the splitting of the former A. minutissimum complex in the Antarctic Region are discussed.

The development of infants' action-related object knowledge : deferred imitation and eye tracking studies in 12- and 18-month-olds (2014)

Gabriella Óturai

Imitation paradigms are used in various domains of developmental psychological research to assess various cognitive processes such as memory (deferred imitation), action perception and action understanding (mainly direct imitation), as well as categorization and learning about objects (deferred imitation with a change in target objects and generalized imitation). Although these processes are most likely not independent from each other, their relations are still largely unclear. On the one hand, deferred imitation studies have shown that infants' performance improves with increasing age, resulting in the reproduction of more target actions after longer delay intervals. On the other hand, imitation studies focusing on infants' action understanding have found that infants do not necessarily imitate the model's exact actions – actions or action steps that seem to be irrational or irrelevant are omitted by infants under certain circumstances (selective imitation). Additionally, findings of imitation studies that require a transfer of the target actions to novel objects have demonstrated that infants do not only learn about actions, but also about objects, when they engage in imitation. The present dissertation aims at integrating different perspectives of imitation research by testing 12- and 18-month-old infants in deferred imitation tests consisting of functional vs. arbitrary target actions, and by combining deferred imitation with eye tracking in half of the experiments. A deferred imitation paradigm was chosen to assess memory performance. Systematic variation of target action characteristics enabled the assessment of infants' imitation pattern, i.e., if they would imitate one kind of target actions more frequently than the other. Functionality was chosen as the action characteristic in focus because function is an object's most important property, thus this variation might shed some light on infants' learning about objects in the context of an imitation test. The main goal of the eye tracking experiments was to tackle the relations between infants' visual attention to, and deferred imitation of, different kinds of target actions. The behavioral experiments revealed that both 12- and 18-month-olds imitated significantly more functional than arbitrary target actions after a delay of 30 minutes. In addition, while 12-month-olds showed a memory effect only for functional actions, 18-month-olds showed a memory effect for both kinds of actions. Thus, 12-month-olds imitated strictly selectively, and 18-month-olds imitated more exactly. This shows that the well established memory effect is modulated by target action functionality, which affects 12- and 18-month-olds' imitation differently. Furthermore, when retested after a two weeks delay, 18-month-olds' performance rates of functional and arbitrary target actions decreased parallel. This suggests that selective imitation is not affected by the duration of the retention interval, and that selection of target actions takes place at an earlier stage of action perception and memory processes. In the eye tracking experiments, both 12- and 18-month-olds' imitation patterns replicated the findings of the behavioral experiments, showing consistently higher imitation rates of functional than arbitrary target actions. Contrary to this, infants' fixation times to the target actions were not affected by target action functionality. This contrast was supported by statistical analyses that found no clear correspondence between visual attention to and deferred imitation of target actions. This suggests that selective imitation cannot be explained by selective visual attention. Nevertheless, finer-grained analyses of gaze and imitation data in the 18 months old group suggested that infants' increased attention to the social-communicative context of the imitation task was related to more exact imitation, i.e. imitation of not only functional, but also arbitrary target actions. The findings are discussed against the background of imitation theories, with regard to the relations between different cognitive processes underlying infants' imitation, such as memory, action perception and learning about objects.

Psychological compensation in attention deficit hyperactivity disorder - application of a theoretical framework (2014)

Anne Christine Julia Merkt

The term compensation is widely used in every-day language, in psychological research, and also discussed in the context of Attention Deficit Hyperactivity Disorder (ADHD). However, few studies have looked at psychological compensation in ADHD systematically and theory based. Compensation can be inferred if a deficit (i.e., a mismatch between skill and environmental demand) is counterbalanced by the investment of more effort, the utilization of latent or the acquisition of new skills. Based on the application of a theoretical framework (Bäckman & Dixon, 1992) to ADHD, I developed the following aims: (1) To reassess the awareness of deficits in ADHD and (2) to explore psychological compensation in a group with ADHD that accomplishes high achievement. The results of Study 1 showed that children with ADHD did not overestimate their own skills compared to a group matched for academic achievement. In Study 2, college students with ADHD reported higher achievement motivation compared to college students without ADHD. Furthermore, results indicated that women with ADHD compensate by adopting compensatory effort and obsessive-compulsive behavior. Study 3 showed that female college students compensate for possible deficits in solving a flanker task by being overly cautious, which may reflect more obsessive-compulsive behavior. The studies are discussed within the framework of psychological compensation. They add to the understanding of compensation in ADHD by (1) the reassessment of awareness of deficits in ADHD by including a group without ADHD but with low achievement, and by (2) suggesting that overly cautious behavior could be a form of psychological compensation in females with ADHD enabling them to enter college, leading to a late diagnosis and to good performance in cognitive tasks (i.e., flanker task). Limitations are, that I did not test all components of the theoretical framework in one study and that I did not include adults with ADHD that did not enter college in Study 2 and 3 to test if achievement motivation or overly cautious behavior explains why some adults with ADHD gain admittance to higher education and show good performance in cognitive tasks and others do not.

Cognitive flexibility and cognitive stability : neural and behavioral correlates in men and mice (2014)

Diana J. N. Armbruster-Genç

The ability to flexibly adjust behavior according to a changing environment is crucial to ensure a species' survival. However, the successful pursuit of goals also requires the stable maintenance of behavior in the face of potential distractors. Thus, cognitive flexibility and cognitive stability are important processes for the cognitive control of behavior. There is a large body of behavioral and neuroimaging research concerning cognitive control in general, but also specifically on cognitive flexibility and cognitive stability, albeit most often assessed in separate task paradigms. Nevertheless, whether cognitive flexibility and cognitive stability depend upon separate or shared neuronal bases is still a matter of debate. Complementing empirical research, computational models have become an important strategy in neuroscientific research, as they have the potential of providing mechanistic explanations of empirical observations, for example by allowing for the direct manipulation of molecular parameters in simulated neural networks. The computational model underlying the so-called Dual-State Theory contains specific hypotheses with respect to cognitive flexibility and cognitive stability. The neural networks simulated by this model exhibit multiple stable firing states, i.e., the neural network can maintain a high firing state also without continuing external input due to a network architecture consisting of recurrently connected neurons. Transitions between such network states, also called attractor states, can be induced by external input, and represent working memory contents or active task rules. Simulations showed that the stability of these attractor states, and thus of task rule representations, depend on the dopamine state of the system and can consequently vary between persons. The Dual-State Theory predicts an antagonistic relationship between cognitive flexibility and cognitive stability, as robust attractor states would facilitate the inhibition of distractors, but impair efficient task switching, while rather unstable attractor states would promote efficient transitions between representations but would also come at the cost of increased distractibility. Based on the Dual-State Theory, a task paradigm was designed allowing for the simultaneous assessment of cognitive flexibility, in the sense of rule-based task switching, and cognitive stability, in the sense of inhibiting irrelevant distractors. Furthermore, a behavioral measure was developed to assess the individual attractor state stability, named spontaneous switching rate (SSR). In the first study of this work, this paradigm was tested in a sample of healthy human subjects using functional magnetic resonance imaging (fMRI). An overlapping fronto-parietal network was activated for both cognitive flexibility and cognitive stability. Furthermore, behavioral as well as neuroimaging results are in favor of an antagonistic relationship between cognitive flexibility and cognitive stability. A specific prefrontal region, the inferior frontal junction (IFJ), was implied to potentially contain the relevant neural networks mediating the transitions between attractor states, i.e., task rule representations, as its activity was modulated by the SSR such that persons with rather unstable attractor states activated it less during task switching while showing better performance. Most importantly, functional connectivity of the IFJ was antagonistically modulated by the SSR: more flexible persons connected it less to another prefrontal area during task switching, while showing higher functional connectivity during distractor inhibition. In a second study, a larger human sample was assessed and further hypotheses derived from the Dual-State Theory on variability of neural processing were tested: we hypothesized that persons with high brain signal variability should have less stable network states and thus benefit on tasks requiring cognitive flexibility but suffer from it when the task requires a higher degree of cognitive stability. Furthermore, recent fMRI-research on brain signal variability revealed beneficial effects of higher brain signal variability on cognitive performance in general. Using a novel customized analysis pipeline to measure trial-to-trial fMRI-signal variability, we indeed found differential effects of brain signal variability: higher levels of brain signal variability were found to be beneficial for effectiveness, i.e., performance in terms of error rates, for both cognitive flexibility and stability. However, brain signal variability impaired the efficiency in terms of response times of inhibiting distractors, i.e., cognitive stability. Due to further predictions of the Dual-State Theory concerning schizophrenia and the dopaminergic system, it was considered valuable to pursue a translational approach and thus allowing for the employment of animal models of psychiatric diseases. Consequently, in a first step the human paradigm was translated for a murine population using an innovative touchscreen approach. Results showed analogous behavioral effects in wildtype mice as before in healthy humans: the antagonistic relation between cognitive flexibility and cognitive stability was replicated and also for mice, a behavioral measure for the individual attractor stability was established and validated, named the individual spontaneous switching score. To conclude, we established a novel paradigm assessing both cognitive flexibility and stability simultaneously showing an antagonistic relationship between these two cognitive functions on the behavioral level in two different species, which supports predictions from the Dual-State Theory. This was further underlined by evidence on the activation, functional connectivity and signal variability level in the human brain.

Ecological perspectives on local image statistics (2014)

Daniela Pamplona

The scope of this Thesis is to understand the position dependency phenomenon of human visual perception. First, under the ecological assumption, meaning under the assumption that animals adapt to the statistical regularities of their environment, we study the consequences of the imaging on the local statistics of the input to the human visual system. Second, we model efficient representations of these statistics and their contribution to shape the properties of eye sensory neurons. Third, we model efficient representations of the semantic context of images and the correctness of different underneath geometrical assumptions on the statistics of images. The efficient coding hypothesis posits that sensory systems are adapted to the regularities of their signal input in order to reduce redundancy in the resulting representations. It is therefore important to characterize the regularities of natural signals to gain insight into the processing of natural stimuli. While measurements of statistical regularity in vision have focused on photographic images of natural environments it has been much less investigated, how the specific imaging process embodied by the organism’s eye induces statistical dependencies on the natural input to the visual system. This has allowed using the convenient assumption that natural image data is homogeneous across the visual field. Here we give up on this assumption and show how the imaging process in a human eye model influences the local statistics of the natural input to the visual system across the entire visual field. ...

MTO1-deficient mouse model mirrors the human phenotype showing complex I defect and cardiomyopathy (2014)

Lore Becker Eva Kling Evelyn Schiller Ramona Zeh Anja Schrewe Sabine M. Hölter Ilona Mossbrugger Julia Calzada-Wack Valentina Strecker Ilka Wittig Iulia Dumitru Tina Wenz Andreas Bender Michaela Aichler Dirk Janik Frauke Neff Axel Walch Leticia Quintanilla-Fend Thomas Floss Raffi Bekeredjian Valérie Gailus-Durner Helmut Fuchs Wolfgang Wurst Thomas Meitinger Holger Prokisch Martin Hrabé de Angelis Thomas Klopstock

Recently, mutations in the mitochondrial translation optimization factor 1 gene (MTO1) were identified as causative in children with hypertrophic cardiomyopathy, lactic acidosis and respiratory chain defect. Here, we describe an MTO1-deficient mouse model generated by gene trap mutagenesis that mirrors the human phenotype remarkably well. As in patients, the most prominent signs and symptoms were cardiovascular and included bradycardia and cardiomyopathy. In addition, the mutant mice showed a marked worsening of arrhythmias during induction and reversal of anaesthesia. The detailed morphological and biochemical workup of murine hearts indicated that the myocardial damage was due to complex I deficiency and mitochondrial dysfunction. In contrast, neurological examination was largely normal in Mto1-deficient mice. A translational consequence of this mouse model may be to caution against anaesthesia-related cardiac arrhythmias which may be fatal in patients.

Art as an alternative asset class: risk and return characteristics of the Middle Eastern & Northern African art markets (2014)

Roman Kräussl

This chapter analyzes the risk and return characteristics of investments in artists from the Middle East and Northern Africa (MENA) region over the sample period 2000 to 2012. With hedonic regression modeling we create an annual index that is based on 3,544 paintings created by 663 MENA artists. Our empirical results prove that investing in such a hypothetical index provides strong financial returns. While the results show an exponential growth in sales since 2006, the geometric annual return of the MENA art index is a stable13.9 percent over the whole period. We conclude that investing in MENA paintings would have been profitable but also note that we examined the performance of an emerging art market that has only seen an upward trend without any correction, yet.

License contracts, free software and creative commons : national report Germany (2014)

Alexander Peukert Dominik König

This country report was prepared for the 19th World Congress of the International Academy of Comparative Law in Vienna in 2014. It is structured as a questionnaire and provides an overview of the legal framework for Free and Open Source Software (FOSS) and other alternative license models like (e.g.) Creative Commons under German law. The first set of questions addresses the applicable statutory provisions and the reported case law in this area. The second section concerns contractual issues, in particular with regard to the interpretation and validity of open content licenses. The third section deals with copyright aspects of open content models, for example regarding revocation rights and rights to equitable remuneration. The final set of questions pertains to patent, trademark and competition law issues of open content licenses.

Imaging-systems for localization-based super-resolution light-microscopy in physical biology : design and applications (2014)

Sebastian Malkusch

Physical Biology is a field of life sciences dealing with the extraction of quantitative data from biophysical or molecular biological experiments with different levels of complexity. Such data are further used as parameters for mathematical models of the biological system. These models allow to predict reactions on external stimuli by describing the relevant molecular interactions and are therefore used for example to generate a deeper comprehension of complex human diseases. An essential technique in biophysical research on human diseases is fluorescence microscopy. This is a constantly developed toolbox comprising a large number of specific labeling strategies, as well as a broad spectrum of fluorescent probes. It is further minimal invasive and therefore suitable for measurements in living cells or organisms. The sensitivity of modern photo-detectors even allows for the detection of a single fluorescent probe with an accuracy of approximately 10 nm. ... The model-prediction was further verified by two color SMLM experiments. In this work the development and application of imaging-systems are described which provide quantitative data with single-molecule resolution for systems biological model approaches with a low degree of abstractness. In the near future, the impact of mathematical models in the research field of complex human diseases will increase. The predictions of these models will be more exact, the more detailed and accurate the input parameters will become. This work gives an impression of how quantitative data obtained by SMLM may serve as input parameters for mathematical models at the single-cell level.

Marginalized predictive likelihood comparisons of linear Gaussian state-space models with applications to DSGE, DSGE-VAR, and VAR models (2014)

Anders Warne Günter Coenen Kai Christoffel

he predictive likelihood is of particular relevance in a Bayesian setting when the purpose is to rank models in a forecast comparison exercise. This paper discusses how the predictive likelihood can be estimated for any subset of the observable variables in linear Gaussian state-space models with Bayesian methods, and proposes to utilize a missing observations consistent Kalman filter in the process of achieving this objective. As an empirical application, we analyze euro area data and compare the density forecast performance of a DSGE model to DSGE-VARs and reduced-form linear Gaussian models.

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