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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

The impact of shore types on benthic macroinvertebrate community structure and functioning in a large lowland river

Brabender, Marian 23 March 2015 (has links)
Shore zones of large rivers are hot spots of biodiversity and contribute significantly to riverine ecosystem functioning. Today, shore degradation and other structural impair-ments like river straightening and channelization are strong impact factors on river ecosystem health. However, we still lack a thorough understanding of how structural shore zone degradation affects benthic community composition and their inherent ecosystem functions. In this thesis I tested the influence of training structure induced environmental factors on benthic macroinvertebrate community composition and the share of non-native species. Moreover, I assessed the community-associated ecosystem functions in terms of secondary production and resource utilization. In the main channel, communities were composed of only a few specialized taxa with low abundances, which contributed little to riverine secondary production. This is probably due to the harsh conditions produced by constantly high flow velocities and relocation of the fine sandy sediment. Main channel habitats were hardly affected by the adjacent training structure. Hence, species compositions and productivities were similar at all investigated main channel sites. By contrast, each of the shore communities was diverse, highly abundant and productive in comparison to the main channel. However, variations between shore structure communities and their ecosystem functions were prominent. One particular training structure, i.e. the off-bankline revetment, bore the most diverse and by far most productive benthic community, which utilized vast total amounts of basal resources (1,323 g DM m-² y-1). Varying sediment compositions, availability of macrophytes and diverse flow velocities, including lentic conditions, were revealed as key factors for increasing biodiversity, secondary production and resource utilization. Allochthonous boulder habitats were generally highly prone to non-native species invasion. Neozoa proved less productive than many native community members and consumed minor relative and total amounts of the prevailing resource pelagic algae. The present quantitative comparison of shore type specific effects on biodiversity, biomass and productivity provides managers with a tool to improve the ecological attributes of large river ecosystems with an unchangeable, impaired macrostructure. In its entirety, this thesis constitutes a sound basis to increase the mechanistic understanding of the way in which shore zone manipulation can affect riverine benthic communities and their associated ecosystem functions. / Die Uferbereiche großer Flüsse sind für die Biodiversität und Funktion dieser Ökosys-teme von enormer Bedeutung. Uferdegradierung und Kanalisierung gehören zu wichti-gen Faktoren, die Flussökosysteme nachhaltig beeinträchtigen. Wie sich anthropogene Umstrukturierungen der Uferbereiche auf die Zusammensetzung benthischer Ge-meinschaften und deren Ökosystemfunktion auswirken ist jedoch weitestgehend unbe-kannt. In dieser Arbeit werden die Effekte von uferspezifischen Habitatfaktoren auf die Komposition des Makrozoobenthos und den Anteil an Neozoen getestet. Zudem wurden die gemeinschaftsassoziierten Ökosystemfunktionen in Bezug auf Sekundärproduktion und Ressourcennutzung erfasst und bewertet. Die benthische Gemeinschaft des Hauptstroms bestand lediglich aus wenigen spezialisierten Arten, welche nur geringfügig zur Gesamtsekundärproduktion des Flusses beitrugen. Dies war vermutlich auf die rauen Bedingungen im Hauptstrom (insbesondere hohe Strömungsgeschwindigkeiten und damit verbundener Sedimenttransport) zurückzuführen. Die Makrozoobenthosgemeinschaften des Hauptroms wurden von den jeweils angrenzenden Ufertypen nicht beeinflusst. Im Gegensatz zum Hauptstrom zeigte jeder der untersuchten Ufertypen hohe Dichten an benthischen Invertebraten wobei sich Zusammensetzung und Funktion der Artengemeinschaften zwischen den Ufertypen stark unterschieden. Dabei brachte das Parallelwerk die diverseste und produktivste Makroinvertebratenfauna hervor, welche enorme Mengen basaler Ressourcen ingestierte (1,323 g DM m-2y-1). Hauptfaktoren für eine Erhöhung von Biodiversität, Sekundärproduktion und Ressourcennutzung waren neben variablen Sedimentzusammensetzungen und Makrophytenbeständen sich oft ändernde Fließgeschwindigkeiten mit lentischen Phasen. Allochthone Steinhabitate waren generell anfällig für die Invasion nicht heimischer Arten. Diese Neozoen waren weniger produktiv als viele heimische Taxa und nutzten nur geringe Mengen pelagischer Algen, welche die meist verfügbare Ressource darstellten. Aus dem ökologischen Vergleich der verschiedenen Ufertypen lassen sich Managementempfehlungen zur Verbesserung des ökologischen Zustandes in Bezug auf Biodiversität und Ökosystemfunktionen ableiten, welche für große Flüsse mit degradierter und unveränderbarer Makrostruktur in Betracht gezogen werden können. In ihrer Gesamtheit liefert diese Arbeit ein fundiertes mechanistisches Verständnis über die Effekte von Ufermanipulationen auf benthische Gemeinschaften und deren assoziierte Ökosystemfunktionen in großen Flüssen.
132

Hydrocarbons as food contaminants:: Studies on the migration of mineral oil and synthetic hydrocarbons from food contact materials

Lommatzsch, Martin 19 October 2017 (has links)
The contamination of foods with hydrocarbon mixtures migrating from food contact materials (FCM) was first observed for jute and sisal bags treated with batching oil in the 1990s. Since the millennium, the focus has shifted to printing inks and recycled cardboard packaging as most recognized sources for hydrocarbon contamination from FCM. Mineral oil containing printing inks can either release hydrocarbons directly from the printing of folding boxes into food or indirectly entering the recycling chain of cardboard material by printed products, such as newspapers. The contamination of dry foods with mineral oil hydrocarbons (MOH) from recycled fiber packaging has been reported to reach up to 100 mg/kg [1]. Using LC-GC-FID technique the MOH were categorized into mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH). The molecular mass, which is assumed to be toxicological relevant, is derived from the GC retention times of accumulated MOSH in human tissues and is limited to n C16 to n-C35 [2]. MOSH is the most significant contaminant of the human body reaching 1-10 g per person, which is of particular concern since a formation of microgranulomas (causing inflammatory reactions) in the liver was observed in rats fed with saturated hydrocarbons [3]. Furthermore, some MOAH are assumed to be genotoxic analogous to polycyclic aromatic hydrocarbons [3]. In the latest draft of a German ‘Mineral Oil Regulation’ the following limits for the migration of MOH from recycled fiber are proposed: for MOSH C16-20 4.0 mg/kg, MOSH C21-35 2.0 mg/kg and for MOAH 0.5 mg per kg food [4]. Functional barriers reducing the migration of undesirable compounds from recycled cardboards (such as MOH and other contaminants) could be a part of the solution for this issue. Supporting that approach in this study, the boxes of recycled cardboard featuring a barrier layer on the internal surface or an integrated adsorbent available early in 2014 were investigated for their efficiency in reducing migration of mineral oil hydrocarbons into dry food. A practice-oriented one-year storage test was performed with wheat flakes in seven configurations: a box of virgin fibers, two boxes of unprotected recycled cardboard, three cardboards with barrier layers (a flexo-printed polyacrylate layer, a polyvinyl alcohol coating and a multilayer involving polyester) and a cardboard containing activated carbon. The highest migration of MOH (C16-24) was observed in the boxes of unprotected recycled cardboard (MOSH: 11.4 mg/kg, MOAH: 2.4 mg/kg). Of the three investigated barrier layers only two reduced migration of MOH into food below the limits of the 3rd draft of the German mineral oil ordinance (2014) until the end of shelf life. The cardboard box involving active carbon as adsorbent prevented detectable migration of mineral oil hydrocarbons (<0.1 mg/kg). In the case of virgin fiber, which was virtually free of MOH (<1 mg/kg), migration close to the proposed limits was detected (C16-24, MOSH: 1.5 mg/kg, MOAH: 0.4 mg/kg). Therefore, it has been proven that the transport box (corrugated board) substantially contributed to the transfer of MOH into food. Plastic FCM can also release hydrocarbons, such as polyolefin oligomeric hydrocarbons (POH), into food. These POH are of synthetic nature and are formed during the polymerization process of polyolefins (150 – 3000 mg/kg in granulates of homo/hetero polymers involving ethylene and propylene). This group of synthetic contaminants contain also saturated hydrocarbons (POSH) analogous to mineral oils, but contrary no aromatic hydrocarbons. Further, a significant amount (10 – 50%) of monounsaturated hydrocarbons (POMH) was determined in the oligomeric fraction of polyolefins, which are not detectable in mineral oil products. Therefore, these POMH can be used as a marker for POH migration. A method based on two-dimensional high performance liquid chromatography on-line coupled to gas chromatography (on-line HPLC-HPLC-GC) was developed to enable the separate analysis of saturated, monounsaturated and aromatic hydrocarbons in extracts of packaging materials like polyolefins or paperboard and foods, repectively. It is an extension of the HPLC-GC method for MOSH and MOAH [1] using an additional argentation HPLC column, since normal-phase HPLC on silica gel did not preseparate saturated from monounsaturated hydrocarbons. Further, this method and comprehensive two-dimensional GC (GCxGC) was used to investigate the concentration of different oligomer types in polypropylene (PP) and polyethylene (PE) based sealing layers as well as their corresponding granulates. The analyzed sealing layers contained 180-995 mg/kg POSH and 90-435 mg/kg POMH (C16-35). Only in sealing layers involving low-density PE, oxidized polyolefin oligomers as well as cyclic oligomers (alkylated cyclopentanes and hexanes) have been detected. The transfer of POH (C16-35) from the investigated sealing layers into food can be substantial (>50%) and can reach more than 2 mg per kg food. The level of contamination depends on the oligomer content of the sealing layer, the fat content of the food, the processing temperature and the surface-volume ratio. Hot melt adhesives are widely utilized to glue cardboard boxes used as food packaging material. The analysed raw materials of hot melts mainly consisted of paraffinic waxes, hydrocarbon resins and polyolefins. The hydrocarbon resins, functioning as tackifiers, were the predominant source of hydrocarbons of sufficient volatility to migrate via gaseous phase into dry foods. The 18 hydrocarbon resins analyzed contained 8.2-118 g/kg saturated and up to 59 g/kg aromatic hydrocarbons (C16-24). These synthetic tackfier resins, especially the oligomers ≤C24, have been characterized structurally and migration into food was estimated using a food simulant and by the analysis of real food samples. About 0.5-1.5 % of the potentially migrating substances (C16 24) of a hot melt were found to be transferred into food under storage conditions, which can result in a food contamination of approximately 1 mg/kg food in this case. The order of magnitude depends on the absolute amount of potentially migrating substances from the hot melt, the hot melt surface, contact time, amount and type of foods.
133

Effects of Cognitive Behavioral Therapy on Neural Processing of Agoraphobia-Specific Stimuli in Panic Disorder and Agoraphobia

Wittmann, André, Schlagenhauf, Florian, Guhn, Anne, Lueken, Ulrike, Elle, Manja, Stoy, Meline, Liebscher, Carolin, Bermpohl, Felix, Fydrich, Thomas, Pfleiderer, Bettina, Bruhn, Harald, Gerlach, Alexander L., Straube, Benjamin, Wittchen, Hans-Ulrich, Arolt, Volker, Heinz, Andreas, Ströhle, Andreas, Kircher, Tilo 19 May 2020 (has links)
Background: Patients suffering from panic disorder and agoraphobia are significantly impaired in daily life due to anxiety about getting into a situation due to apprehension about experiencing a panic attack, especially if escape may be difficult. Dysfunctional beliefs and behavior can be changed with cognitive behavioral therapy; however, the neurobiological effects of such an intervention on the anticipation and observation of agoraphobia-specific stimuli are unknown. Methods: We compared changes in neural activation by measuring the blood oxygen level-dependent signal of 51 patients and 51 healthy controls between scans before and those after treatment (group by time interaction) during anticipation and observation of agoraphobia-specific compared to neutral pictures using 3-T fMRI. Results: A significant group by time interaction was observed in the ventral striatum during anticipation and in the right amygdala during observation of agoraphobia-specific pictures; the patients displayed a decrease in ventral striatal activation during anticipation from pre- to posttreatment scans, which correlated with clinical improvement measured with the Mobility Inventory. During observation, the patients displayed decreased activation in the amygdala. These activational changes were not observed in the matched healthy controls. Conclusions: For the first time, neural effects of cognitive behavioral therapy were shown in patients suffering from panic disorder and agoraphobia using disorderspecific stimuli. The decrease in activation in the ventral striatum indicates that cognitive behavioral therapy modifies anticipatory anxiety and may ameliorate abnormally heightened salience attribution to expected threatening stimuli. The decreased amygdala activation in response to agoraphobia-specific stimuli indicates that cognitive behavioral therapy can alter the basal processing of agoraphobia-specific stimuli in a core region of the fear network.
134

Mechanismus zur Erzeugung von Infrarotimpulsen mit funktionellen Keramiken: Erz kann 10 x effizienter mit IR.C aufbereitet werden

Rachimov, Rustam Ch., John, Peter 14 March 2014 (has links)
Es wird aufgezeigt, wie mit funktionellen Keramiken hochenergetische elektromagnetische Impulse bis zu 320 W/cm² und kurze Zeiten, beispielsweise innerhalb von 10 Mikrosekunden, erzeugt und nachgewiesen werden können.
135

Anwendung funktioneller Keramiken für Technologien des Trocknens mit Impuls-Infrarot

Rachimov, Rustam Ch., Ermakov, Vladimir P., John, Peter, Rachimov, Murod R. 29 August 2014 (has links)
Das Trocknen von feuchten Gütern mit Impuls-Infrarot auf Basis funktioneller Keramiken (IR.C) ist eine neue und hocheffektive Technologie, die von den Autoren entwickelt wurde. Im Unterschied zum klassischen marktüblichen Infrarot dringt IR.C dank seiner Eigenschaften mit Lichtgeschwindigkeit tief und schonend in das Gut ein und regt dort von innen heraus das Wasser zum Verdunsten an. Die Eindringtiefe kann sowohl mit unterschiedlichen Keramiken als auch mit unterschiedlicher Impulsstärke eingestellt werden. Es wird an einer großen Zahl verschiedener Trocknungsgüter, angefangen von sensiblen landwirtschaftlichen Erzeugnissen bis hin zu robusten technischen Produkten nachgewiesen, dass mit IR.C im Vergleich zur verbreiteten konvektiven Trocknung die Effizienz nach Zeit und Energie um das 4- bis 10-fache verbessert werden kann. Gegenüber dem klassischen Infrarot ist IR.C oft 2 bis 4 x effizienter. IR.C kann mit verschiedenen primären Energiearten, auch mit thermosolarer Energie, angeregt und in unterschiedliche Trocknerarten integriert werden.
136

Functional genomic analysis of cell cycle progression in human tissue culture cells

Kittler, Ralf 18 October 2006 (has links)
The eukaryotic cell cycle orchestrates the precise duplication and distribution of the genetic material, cytoplasm and membranes to daughter cells. In multicellular eukaryotes, cell cycle regulation also governs various organisatorial processes ranging from gametogenesis over multicellular development to tissue formation and repair. Consequently, defects in cell cycle regulation provoke a variety of human cancers. A global view of genes and pathways governing the human cell cycle would advance many research areas and may also deliver novel cancer targets. Therefore this work aimed on the genome-wide identification and systematic characterisation of genes required for cell cycle progression in human cells. I developed a highly specific and efficient RNA interference (RNAi) technology to realize the potential of RNAi for genome-wide screening of the genes essential for cell cycle progression in human tissue culture cells. This approach is based on the large-scale enzymatic digestion of long dsRNAs for the rapid and cost-efficient generation of libraries of highly complex pools of endoribonuclease-prepared siRNAs (esiRNAs). The analysis of the silencing efficiency and specificity of esiRNAs and siRNAs revealed that esiRNAs are as efficient for mRNA degradation as chemically synthesized siRNA designed with state-of-the-art design algorithms, while exhibiting a markedly reduced number of off-target effects. After demonstrating the effectiveness of this approach in a proof-of-concept study, I screened a genome-wide esiRNA library and used three assays to generate a quantitative and reproducible multi-parameter profile for the 1389 identified genes. The resulting phenotypic signatures were used to assign novel cell cycle functions to genes by combining hierarchical clustering, bioinformatics and proteomic data mining. This global perspective on gene functions in the human cell cycle presents a framework for the systematic documentation necessary for the understanding of cell cycle progression and its misregulation in diseases. The identification of novel genes with a role in human cell cycle progression is a starting point for an in-depth analysis of their specific functions, which requires the validation of the observed RNAi phenotype by genetic rescue, the study of the subcellular localisation and the identification of interaction partners of the expressed protein. One strategy to achieve these experimental goals is the expression of RNAi resistant and/or tagged transgenes. A major obstacle for transgenesis in mammalian tissue culture cells is the lack of efficient homologous recombination limiting the use of cultured mammalian cells as a real genetic system like yeast. I developed a technology circumventing this problem by expressing an orthologous gene from a closely related species including its regulatory sequences carried on a bacterial artificial chromosome (BAC). This technology allows physiological expression of the transgene, which cannot be achieved with conventional cDNA expression constructs. The use of the orthologous gene from a closely related species confers RNAi resistance to the transgene allowing the depletion of the endogenous gene by RNAi. Thus, this technology mimics homologous recombination by replacing an endogenous gene with a transgene while maintaining normal gene expression. In combination with recombineering strategies this technology is useful for RNAi rescue experiments, protein localisation and the identification of protein interaction partners in mammalian tissue culture cells. In summary, this thesis presents a major technical advance for large-scale functional genomic studies in mammalian tissue culture cells and provides novel insights into various aspects of cell cycle progression. (Die Druckexemplare enthalten jeweils eine CD-ROM als Anlagenteil: 217 MB: Movies, Rohdaten - Nutzung: Referat Informationsvermittlung der SLUB)
137

Bildung funktioneller Typgruppen des Phytoplanktons: Integration von Modell-, Freiland - und Laborarbeiten

König-Rinke, Marie Rita 10 March 2008 (has links)
Phytoplankter sind die bedeutendsten Primärproduzenten in aquatischen Ökosystemen und leisten ca. 45 % der globalen Primärproduktion. Sie weisen eine hohe taxonomische Diversität mit vielfältigen morphologischen und physiologischen Eigenschaften auf. Funktionelle Eigenschaften, die das licht-, temperatur- und nährstoffabhängige Wachstum sowie Verlustgrößen (Fraß, Sedimentation) beschreiben, sind eine Möglichkeit Phytoplankter zu klassifizieren. Diese Einteilung gewinnt für das Verständnis und die Modellierung der Phytoplanktonsukzession (z.B. in Wassergütemodellen) immer mehr an Bedeutung, da nicht taxonomische, sondern funktionelle Eigenschaften das Vorkommen der Phytoplankter im Gewässer bestimmen. Das Wassergütemodell SALMO ist ein mechanistisches, dynamisches, vertikales 1D-Modell, welches Nährstoffe, Sauerstoff, Detritus, 4 funktionelle Phytoplanktontypen und eine Zooplanktonmischgruppe simuliert. Bei der Modellanwendung wurde ersichtlich, dass die vorhandenen funktionellen Typgruppen teilweise nicht ausreichen, um die funktionelle Diversität der realen Phytoplanktongemeinschaften adäquat widerzuspiegeln. Deshalb wird eine Erweiterung der funktionellen Typgruppen in SALMO angestrebt. Eine empirische Freilanddatenanalyse an zwei morphologisch und trophisch verschiedenen Talsperren ergab insgesamt 10 funktionelle Phytoplanktontypen (Typgruppen 1, 2 und 4 bereits in SALMO vorhanden). Die bestehenden funktionellen Eigenschaften wurden erweitert und teilweise verändert (insgesamt 10 funktionelle Eigenschaften). Die neue funktionelle Typgruppe 6 (unbewegliche, koloniale, gelatinöse Chlorophyceen) wurde in lichtabhängigen Wachstumsversuchen und Fraßversuchen mit Daphnia galeata × hyalina genauer untersucht. Als stellvertretende Art für diese Typgruppe wurde Sphaerocystis schroeteri gewählt. Die Wachstumsversuche bei 20 °C kennzeichneten Sphaerocystis als Starklichtart mit einer relativ hohen Wachstumsrate (Iopt = 250 µmol m-2 s-1; µmax = 0.96 d-1; 12:12 h Hell-Dunkelzyklus). Eigene Nährmediumsversuche wiesen auf eine Abhängigkeit von freiem CO2 hin. Dies bietet eine Erklärung für ihr häufiges Auftreten in oligo- bis mesotrophen Gewässern. Bei Anwesenheit von Daphnia konnte nach 96 h Versuchsdauer eine signifikante Erhöhung der Koloniegröße (Anteil nicht fressbarer Kolonien 3-74 %), im Vergleich zur Kontrolle (Anteil nicht fressbarer Kolonien 0-5 %), festgestellt werden. Dies stellt einen effektiven Fraßschutz gegen größenselektiv filtrierendes Zooplankton wie z.B. Daphnia dar und kann bei hohem Fraßdruck zur Dominanz der Typgruppe führen (z.B. Klarwasserphase in eutrophen Gewässern). Der Effekt war nicht durch Infochemikalien induzierbar. Aus Literaturdaten wurde eine relativ hohes Topt von 27 °C, eine nur mäßige Konkurrentstärke um Phosphor (mittlerer KP-Wert) sowie eine Brutto-Sinkgeschwindigkeit von 1.5 m d-1 entnommen werden. / Phytoplankter are the most important primary producer in aquatic ecosystems and contribute about 45 % to global primary production. Phytoplankton communities usually show an enormous taxonomical diversity. However, besides taxonomical diversity, a phytoplankton can also be characterised by its functional diversity by means of functional traits like resource-dependent growth characteristics (e.g. KI-, KP-, KN-values) or sensitivity to zooplankton grazing and sedimentation. Since functional, and not taxonomic, traits drive the phytoplankton succession, a functional classification of phytoplankton is recognised to be increasingly important for the ecological understanding and modelling of plankton succession (e.g. in water quality models). The mechanistic, dynamic, vertical 1D water quality model SALMO simulates the dynamics of nutrient concentrations (P, N), oxygen, detritus, 4 functional phytoplankton types and 1 mixed zooplankton group. Different model applications showed that the number of phytoplankton types in SALMO was sometimes not sufficient for accounting for the observed functional diversity in phytoplankton communities. Therefore, the aim of this thesis is to extend the functional diversity of phytoplankton types in SALMO. After careful evaluation of empirical data from two reservoirs with different morphology and trophic state 10 functional phytoplankton types are proposed (types 1, 2 and 4 remained unchanged). Existing functional traits in SALMO were extended and partly changed (in total 10 functional traits). For the new functional phytoplankton type 6 (non motile, colonial gelatinous green algae) light-dependent growth rates were measured and grazing experiments with Daphnia galeata × hyalina were carried out in the laboratory. For these experiments, Sphaerocystis schroeteri was chosen as representative species for this group. It is characterised by high light demand and relative high growth rates at 20 °C (µmax = 0.96 d-1, Iopt = 250 µmol m-2 s-1, 12:12 h light-dark cycle). Their growth depends on the availability of free CO2. This explains the common occurrence in oligo-mesotrophic water bodies. The range of the colony sizes of Sphaerocystis increased in the presence of Daphnia significantly (portion of inedible colonies 3-74 %) in contrast to the control (portion of inedible colonies 0-5 %). This was induced by direct size-selective grazing and not by infochemicals. Thus, Sphaerocystis has evolved an effective defence mechanism against size-selective filter-feeding zooplankton and is competitive superior at high zooplankton grazing pressure (e.g. clear water stage in eutrophic waters). The lack of experimentally derived parameters for temperature- and phosphorus-depending growth (Tmin, Topt, KP-value) as well as gross sinking velocity was complemented with literature data. The alga is only moderately competitive for phosphorus and exhibits relatively high minimal and optimal growth temperatures (Tmin = 7 °C, Topt = 27 °C). Since type 6 consists of large, non motile species, gross sinking velocity was estimated to be about 1.5 m d-1.
138

No evidence for the involvement of serotonin or the 5-HTTLPR genotype in intertemporal choice in a larger community sample

Neukam, Philipp T., Deza-Araujo, Yacila I., Marxen, Michael, Pooseh, Shakoor, Rietschel, Marcella, Schwarzenbolz, Uwe, Smolka, Michael N. 02 September 2020 (has links)
Background: Serotonin has been implicated in impulsive behaviours such as temporal discounting. While animal studies and theoretical approaches suggest that reduced tonic serotonin levels increase temporal discounting rates and vice versa, evidence from human studies is scarce and inconclusive. Furthermore, an important modulator of serotonin signalling, a genetic variation in the promoter region of the serotonin transporter gene (5-HTTLPR), has not been investigated for temporal discounting so far. Objective: First, the purpose of this study was to test for a significant association between 5-HTTLPR and temporal discounting. Second, we wished to investigate the effect of high/low tonic serotonin levels on intertemporal choice and blood oxygen-level-dependent response, controlling for 5-HTTLPR. Methods: We tested the association of 5-HTTLPR with temporal discounting rates using an intertemporal choice task in 611 individuals. We then manipulated tonic serotonin levels with acute tryptophan interventions (depletion, loading, balanced) in a subsample of 45 short (S)-allele and 45 long (L)/L-allele carriers in a randomised double-blind crossover design using functional magnetic resonance imaging and an intertemporal choice task. Results: Overall, we did not find any effect of serotonin and 5-HTTLPR on temporal discounting rates or the brain networks associated with valuation and cognitive control. Conclusion: Our findings indicate that serotonin may not be directly involved in choices including delays on longer timescales such as days, weeks or months. We speculate that serotonin plays a stronger role in dynamic intertemporal choice tasks where the delays are on a timescale of seconds and hence are therefore directly experienced during the experiment.
139

Effect of Cognitive-Behavioral Therapy on Neural Correlates of Fear Conditioning in Panic Disorder

Kircher, Tilo, Arolt, Volker, Jansen, Andreas, Pyka, Martin, Reinhardt, Isabelle, Kellermann, Thilo, Konrad, Carsten, Lüken, Ulrike, Gloster, Andrew T., Gerlach, Alexander L., Ströhle, Andreas, Wittmann, André, Pfleiderer, Bettina, Wittchen, Hans-Ulrich, Straube, Benjamin January 2013 (has links)
Background: Learning by conditioning is a key ability of animals and humans for acquiring novel behavior necessary for survival in a changing environment. Aberrant conditioning has been considered a crucial factor in the etiology and maintenance of panic disorder with agoraphobia (PD/A). Cognitive-behavioral therapy (CBT) is an effective treatment for PD/A. However, the neural mechanisms underlying the effects of CBT on conditioning processes in PD/A are unknown. Methods: In a randomized, controlled, multicenter clinical trial in medication-free patients with PD/A who were treated with 12 sessions of manualized CBT, functional magnetic resonance imaging (fMRI) was used during fear conditioning before and after CBT. Quality-controlled fMRI data from 42 patients and 42 healthy subjects were obtained. Results: After CBT, patients compared to control subjects revealed reduced activation for the conditioned response (CS+ > CS–) in the left inferior frontal gyrus (IFG). This activation reduction was correlated with reduction in agoraphobic symptoms from t1 to t2. Patients compared to control subjects also demonstrated increased connectivity between the IFG and regions of the “fear network” (amygdalae, insulae, anterior cingulate cortex) across time. Conclusions: This study demonstrates the link between cerebral correlates of cognitive (IFG) and emotional (“fear network”) processing during symptom improvement across time in PD/A. Further research along this line has promising potential to support the development and further optimization of targeted treatments.
140

Topographic Mapping of the Primary Sensory Cortex Using Intraoperative Optical Imaging and Tactile Irritation

Polanski, Witold H., Oelschlägel, Martin, Juratli, Tareq A., Wahl, Hannes, Krukowski, Pawel M., Morgenstern, Ute, Koch, Edmund, Steiner, Gerald, Schackert, Gabriele, Sobottka, Stephan B. 19 March 2024 (has links)
The determination of exact tumor boundaries within eloquent brain regions is essential to maximize the extent of resection. Recent studies showed that intraoperative optical imaging (IOI) combined with median nerve stimulation is a helpful tool for visualization of the primary sensory cortex (PSC). In this technical note, we describe a novel approach of using IOI with painless tactile irritation to demonstrate the feasibility of topographic mapping of different body regions within the PSC. In addition, we compared the IOI results with preoperative functional MRI (fMRI) findings. In five patients with tumors located near the PSC who received tumor removal, IOI with tactile irritation of different body parts and fMRI was applied. We showed that tactile irritation of the hand in local and general anesthesia leads to reliable changes of cerebral blood volume during IOI. Hereby, we observed comparable IOI activation maps regarding the median nerve stimulation, fMRI and tactile irritation of the hand. The tactile irritation of different body areas revealed a plausible topographic distribution along the PSC. With this approach, IOI is also suitable for awake surgeries, since the tactile irritation is painless compared with median nerve stimulation and is congruent to fMRI findings. Further studies are ongoing to standardize this method to enable a broad application within the neurosurgical community.

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