1,721,068 research outputs found
Unveiling the interplay between sensory attenuation and fatigue: insights from healthy population and neurological disorders
Get PDFFatigue is a pervasive yet poorly understood phenomenon that affects both healthy individuals and patients with neurological disorders. This thesis investigates the role of predictive sensory mechanisms—particularly sensory attenuation (SA)—in the emergence and perception of fatigue. Across two parts, the work combines behavioural and clinical studies to examine how internal predictions shape body perception, effort, and movement.
In Part 1, sensory attenuation was assessed in clinical populations with Parkinson’s disease and Functional Movement Disorder, as well as in healthy individuals varying in trait and state fatigue. The results demonstrate that pathological and trait fatigue are associated with impaired SA, suggesting an alteration in the brain’s ability to predict the sensory consequences of self-generated actions. These findings support and extend the Sensory Attenuation Model of Fatigue (SAF), highlighting the relevance of prediction errors in fatigue-related experiences.
Part 2 broadens this framework by exploring how mental fatigue and multisensory integration influence body perception and predictive processes. Using a novel weight estimation task and vestibular modulation, the studies show that internal models governing body representation and sensory prediction are sensitive to both cognitive load and interoceptive signals.
Together, these findings provide robust experimental support for the SAF model, showing that fatigue, both pathological and physiological, is linked to a breakdown in sensory attenuation mechanisms. This thesis offers new insights into the neurocognitive basis of fatigue and lays the groundwork for objective measures and interventions targeting sensory prediction mechanisms
Modeling Vegetation Patterns in Semiarid Environment
No full textThe aim of this work is to deepen our understanding on the mutual relationship between climate, vegetation and soil water budget within an ecohydrological framework. To this end a coupled hydrological/ecological model is adopted to describe simultaneously vegetation pattern evolution and soil water budget in a semiarid river basin in New Mexico. This represents an ideal area to study the properties of water-controlled ecosystems. Analysis have been carried out using a recently formulated framework for the water balance at the daily level linked with a vegetation model for the description of the spatial organization of vegetation. Using this approach, we identified the dynamic water stress of vegetation during the growing season paying particular attention to the spatial distribution of solar radiation and the initial soil moisture condition at the beginning of the growing season. Several different variants of the vegetation model have been tested with the aim to identify the main drivers for the spatial organization of the vegetation. Results clearly show that vegetation patterns emerge from minimization of water stress and the maximization of water use
Effetti legati alla morfologia nella stima della Radiazione Solare globale e dell’Evapotraspirazione potenziale
Get PDFNel presente lavoro vengono messi a confronto due algoritmi per la stima della radiazione solare esoatmosferica e delle principali componenti del bilancio radiativo al suolo in funzione delle caratteristiche della vegetazione, della morfologia delle superfici considerate (pendenza ed esposizione) e in condizioni di cielo sereno. Attraverso la stima della radiazione solare netta, definita mediante gli algoritmi di calcolo presentati (Kumar et al., 1997; Allen et al., 2006), si giunge alla valutazione dell’evapotraspirazione potenziale utilizzando l’equazione di Penman-Monteith. In tal modo è possibile evidenziare gli effetti legati alla morfologia nella stima della radiazione solare e dell’evapotraspirazione potenziale. Inoltre, il confronto tra le mappe ed i profili di radiazione ottenuti mostrano le differenze tra i due approcci di calcolo, dovute fondamentalmente alla differente struttura degli algoritmi. I risultati sono stati messi a confronto con dati misurati da diverse stazioni meteorologiche distribuite sul territorio lucano fornendo una stima quantitativa dell'errore associato ai due algoritmi. Il confronto ha evidenziato che i due metodi di calcolo producono risultati simili se applicati alla scala annuale, mentre alla scala giornaliera le approssimazioni presenti nel metodo di Kumar et al. (1997) producono errori non trascurabili per cui risulta più affidabile il modello proposto da Allen et al. (2006). Le analisi evidenziano il ruolo della morfologia (pendenza ed esposizione dei versanti) nella determinazione della radiazione solare globale e conseguentemente dell'evapotraspirazione potenziale a scala locale
The role of macrophages in regulating inflammation by oxidative burst
No full textThe production of reactive oxygen species (ROS) through a process called oxidative burst is an essential defence mechanism against pathogens. In phagocytes, such as neutrophils and macrophages, the NADPH oxidase 2 (NOX2) complex is the main source of ROS. Genetic alterations in any of the components of the NOX2 complex that impair the ROS production are at the origin of a condition called chronic granulomatous disease (CGD), characterized by recurrent life threatening bacterial and fungal infections. Recently, natural occurring mutations in Ncf1, a regulatory component of the NOX2 complex, were described to compromise the protein function and to increase arthritis severity in rats and mice. Macrophages are phagocytes that express NCF1 and are able to kill pathogens. At the same time, they are antigen- presenting cells known to play an important role in arthritis. We therefore hypothesized that expression of NCF1 in macrophages would have an impact on the immune response during arthritis and bacterial infections. The aim of the studies presented in this thesis is to evaluate the influence of NCF1 expressed by macrophages on development of arthritis and resolution of bacterial infections.Using transgenic mouse models we could describe a role for macrophages in both priming and activation of arthritogenic T cells. In a first transgenic mouse, expression of functional NCF1 restricted to macrophages reduced arthritis severity, priming of Th1 T cells and T cell proliferation, therefore limiting the T cell-dependent autoimmune outbreak. In a second transgenic mouse strain, where macrophages were the only cells expressing the arthritis-prone MHC class II Aq molecule, macrophages could prime arthritogenic T cells and mediate arthritis development, but only in NCF1 deficient setting. We could conclude that ROS production by macrophages is important in determining the activation state of T cells and in regulating the severity of arthritis.As in the human CGD situation, mice carrying the Ncf1 mutation were more susceptible to spontaneous and induced bacterial infections. Using the transgenic mouse where macrophages expressed the functional NCF1, we observed that macrophage-derived ROS effectively protected mice from bacterial infections, a function believed to be executed mainly by neutrophils.Finally, we tested a new model of arthritis where the disease was induced with a peptide of a glycolytic enzyme. We found that the symptoms and pathogenesis of the disease resembled the one of the most common arthritis model, collagen-induced arthritis, which is induced with the full collagen protein. Both diseases are dependent on an intact adaptive immune system and their severity is influenced by Ncf1. We were also able to identify one of the important residues causing the peptide’s arthritogenicity.In summary, our data highlight the crucial role of NCF1, and consequently of NOX2 complex, in regulating both innate and adaptive immune responses. NCF1-dependent ROS in macrophages was important during both phagocytosis and antigen presentation, resulting in clearance of bacterial infection and suppression of chronic inflammation. These findings will facilitate further investigations of the molecular pathways through which ROS influence arthritis pathogenesis and hopefully lead to identification of new therapeutic targets.List of scientific papersI. Macrophages suppress T cell responses and arthritis development in mice by producing reactive oxygen species. Kyra A. Gelderman, Malin Hultqvist, Angela Pizzolla, Ming Zhao, Kutty Selva Nandakumar, Ragnar Mattsson, Rikard Holmdahl. Journal of Clinical Investigation. 2007; 117(10):3020-8. https://doi.org/10.1172/JCI31935 II. CD68-expressing cells can prime T cells and initiate autoimmune arthritis in the absence of reactive oxygen species. Angela Pizzolla, Kyra A. Gelderman, Malin Hultqvist, Mikael Vestberg, Kenth Gustafsson, Ragnar Mattsson, Rikard Holmdahl. European Journal of Immunology. 2011; 41(2):403-12. https://doi.org/10.1002/eji.201040598 III. Reactive Oxygen Species produced by the NOX2 Complex in Monocytes Protect from Bacterial Infections in Mice. Angela Pizzolla, Malin Hultqvist, Bo Nilson, Melissa J. Grimm, Tove Eneljung, Ing-Marie Jonsson, Margareta Verdrengh, Tiina Kelkka, Inger Gjertsson, Brahm H. Segal, Rikard Holmdahl. [Submitted]IV. A new model of arthritis induced by a glucose-6-phosphate isomerase peptide: immunological requirements and peptide characterization. Angela Pizzolla, Frida Laulund and Rikard Holmdahl. [Manuscript]</p
Calorimetric Investigation of the Solvation Process of Organic Compounds in Solvents belonging to the "Critical Quartet"
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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