The neural basis of the sense of fatigue

Evidence suggests that the genesis and regulation of the sense of exertional fatigue is rooted within the same neural networks responsible for processing affective responses. One key mechanism proposed to be involved in the sense of exertional fatigue is the interaction between the cognitive inhibitory processes of the dorsolateral prefrontal cortex (DLPFC) and the interoceptive inputs to the amygdala. The primary purpose of this dissertation is to examine the development and progression of exertional fatigue during exercise by examining the interactions between the level of bodily perturbations evoked by the exercise, the activity of the DLPFC (Tissue Oxygenation Index [TOI] percentage), the amygdala (indexed by the acoustic startle eyeblink response [ASER] amplitude), and affective responses (Empirical Valence Scale [EVS] score). The secondary purpose is to modulate the interaction between the DLPFC TOI, the EVS scores, and the ASER amplitudes using transcranial direct current stimulation (tDCS), to explore its potential as a treatment for attenuating the sense of fatigue during physical exertion. Individual differences were also examined. Thirty healthy university students—12 women and 18 men—exercised on a cycle ergometer for up to 20 minutes or until volitional termination at (1) heavy-intensity exercise while receiving sham tDCS on the right and left DLPFC (H-Sham), (2) heavy-intensity exercise while receiving active tDCS (H-Active), (3) severe-intensity exercise while receiving sham tDCS (S-Sham), and (4) severe-intensity exercise while receiving active tDCS (S-Active). The rate of decline in EVS scores was significantly greater during severe-intensity exercise compared to heavy-intensity exercise. The decline in the right and left DLPFC TOI percentages was significantly greater during severe-intensity exercise compared to heavy-intensity exercise, and this decline was larger in the right DLPFC compared to the left DLPFC. During both exercise intensities, the strength of the correlations between EVS scores and the right and left DLPFC TOI percentages increased as the interoceptive cues intensified. tDCS significantly increased DLPFC TOI percentages and the pattern of the ASER amplitudes. In conjunction with the decline in EVS scores, the drop in TOI was most prominent during severe-intensity exercise when, on average, the right DLPFC TOI dropped below baseline and, therefore, the DLPFC entered a hypometabolic state. Individuals with a higher level of tolerance demonstrated a greater activation of the right DLPFC during the heavy-intensity exercise compared to individuals with lower tolerance. The findings of this dissertation suggest that affective responses during exercise were a function of both the severity of homeostatic perturbations and the level of inhibitory control exerted by the right DLPFC. These results support the model for hemispheric specialization of the right PFC in the cognitive inhibition of displeasure. The regulation of the sense of exertional fatigue is, therefore, likely controlled by the right DLPFC. Exertional fatigue emerged at a defined threshold. Accordingly, the physiological response pattern entered a non-steady-state, accompanied by feelings of greater displeasure (or less pleasure) and high perceived activation. Proximal to the point of termination, the hypometabolic state of the DLPFC and the decline in affective responses were not reversed with active tDCS. As such, near one’s physiological limits, if the deactivation of the DLPFC and the corresponding displeasure serve to protect the body from reaching dangerous levels of perturbation, then this mechanism appears to be immutable. Future work should evaluate the potential of therapies that target the modulation of DLPFC inhibitory control (top–down) or interoceptive sensitivity (bottom–up) networks in relation to types of fatigue (e.g., clinical)

Building Digital Archives

This presentation is about the steps followed in the development of the University of North Texas (UNT) Libraries' Digital Library infrastructure, the lessons learned along the way, and the opportunities that are available today

The Portal to Texas History: Harnessing Technology to Enable Collaboration with Small Museums and Libraries

This presentation discusses how The Portal to Texas History is harnessing technology to enable collaboration with small museums and libraries. This presentation includes information on the workflows, planning, metadata elements, and goals for the Portal project

Nuts & Bolts: Preserving Digital Content at the University of North Texas

This presentation discusses the preservation and digitization of content at the University of North Texas (UNT). The topics include a background of the digital initiatives at the UNT Libraries, the organization of the digital initiatives, the collaborative projects, the collections held by the UNT Libraries, and areas of research

2008 DOT GOV Harvest Preserving Access

Presentation for the 2008 Depository Library Council Annual Meeting. This presentation outlines the history, tool building, partner activities and future work for a collaborative project between the University of North Texas, the Library of Congress, the Internet Archive, the California Digital Library, and the U.S. Government Printing Office

Architecture of a Centralized Portal to Distributed Information: The Portal to Texas History

This handout discusses the development of the architecture to build The Portal to Texas History through the University of North Texas (UNT) Libraries' Digital Projects Unit

Scholarly Communication Transformation Initiative Planning Document

Report created for the University of North Texas (UNT) Libraries outlining plans for the Scholarly Communication Transformation Initiative

Curating the Southwest Region's Maps: UNT-UTA Collaborative Project

Presentation for the 2013 Cross Timbers Library Collaborative (CTLC) Conference discussing the Mapping the Southwest project. Mapping the Southwest was a 3-year project (2010-2013) funded by a National Endowment for the Humanities (NEH) We the People grant. This presentation discusses the background of the project, the goals and activities, impacts, and lessons learned

Mapping the Southwest: Final Performance Report

This report documents the Mapping the Southwest project, led by the University of North Texas (UNT) and with their partner, the University of Texas at Arlington (UTA) Libraries Special Collections. The project was supported by a grant from the National Endowment for the Humanities (NEH). This final report briefly describes the Mapping the Southwest project activities and accomplishments in six work areas, and provides a discussion of achievements, issues faced and resolved, and lessons learned that may be of benefit to others. Additional detail is provided in some areas with appendices

Development of Silica-Immobilized Vaccines for Improving Thermo-Tolerance and Shelf-Life

Introduction. It is estimated that 50% of vaccines produced annu- ally are wasted because effectivity is dependent on protein structure and heat exposure disrupts the intermolecular interactions that maintain this structure. Since 90% of vaccines require a temperature- controlled supply chain, it is necessary to create a cold chain system to minimize vaccine waste. We have developed a more sustainable technology via the adsorption of Invasion Plasmid Antigen D (IpaD) onto mesoporous silica gels, improving the thermal stability of pro- tein-based therapeutics. Methods.xThe solution depletion method using UV-Vis was uti- lized to study the adsorption of IpaD onto silica gels. The silica-IpaD complex is heated above the denaturing temperature of the protein and then the IpaD is removed using N,N-Dimethyldodecylamine N-oxide (LDAO) and their secondary structure is tested using cir- cular dichroism (CD). Results. Pore diameter, pore volume and surface area were charac- terized for seven different silica gels. Silica gels designated as 6389, 6378, and 6375 had an adsorption percentage above 95% at pore volumes of 2.2, 2.8 and 3.8 cm3 mg-1, respectively. CD analyses con- firmed that the adsorbed IpaD after the heat treatment displayed a similar “W” shape CD signal as the native IpaD, indicating the con- servation of α-helices. In contrast, the unprotected IpaD after being exposed to high temperature shows a flat CD signal, demonstrating the loss of secondary structure. Conclusion. We have successfully increased the thermo-tolerance for IpaD using mesoporous silica and continue to further optimize mesoporous silica’s physiochemical properties to improve adsorption and desorption yields