AN ERP INVESTIGATION OF REWARD SIGNALS FOR DIFFERING CLASSES OF REINFORCING STIMULI

In order to successfully traverse an actively complex environment, an agent is required to learn from the consequences of their actions. For over a century, models of behavior have been developed demonstrating these consequence-based learning systems. More recently, underlying biological systems have been found to adhere to these constructs of learning. The electroencephalographic signal known as the Reward Positivity (RewP) is thought to reflect a dopamine-dependent cortical signal specific to reward receipt. Importantly, this signal has been shown to adhere to an axiomatic (rule-like) positive reward prediction error, whereby it is evoked following outcomes that are better than expected. These features of the RewP make it a candidate marker for clinical populations, such as major depressive disorder, substance use disorder, and Parkinson’s disease. Although recent experimental endeavors have highlighted key characteristics of the generation and modulation of the RewP, a major understudied feature of the RewP in humans is the link between hedonic experiences and reward processes, and how these interact to modulate learning. This dissertation aims to probe this overlooked hedonic aspect of RewP generation through the use of emotionally evocative image rewards. The first aim addresses methodological issues relating to the use of complex, ecologically valid stimuli in EEG experimentation. The second aim investigated techniques for rectifying these methodological issues. Lastly, the third aim investigated the use of emotionally salient images as rewards in a reinforcement learning paradigm

Routing Unmanned Aerial Vehicles While Considering General Restricted Operating Zones

U.S. military forces employ unmanned aerial vehicles (UAVs) to conduct intelligence-gathering missions worldwide. For a typical mission, commanders may task UAV operators to gather imagery on 100 or more sites or targets. UAV operators must quickly prepare mission plans that meet the needs of their commanders while dealing with real-world constraints such as time windows, site priorities, imagery requirements, UAVs with different capabilities (i.e. imagery equipment, speed, and range), and UAVs departing from different bases. Previous AFIT research provided the UAV Battlelab with a tool, AFIT Router, for generating high-quality routes to aid mission planning. This research enhances the AFIT Router by providing the ability to define general restricted operating zones and to build routes that consider these zones. This research also examines and compares a probabilistic tabu search heuristic and two reactive tabu search heuristics for solving vehicle routing problems

Hip Kinematics During a Stop-Jump Task in Patients With Chronic Ankle Instability

Context: Chronic ankle instability (CAI) commonly develops after lateral ankle sprain. Movement pattern differences at proximal joints may play a role in instability. Objective: To determine whether people with mechanical ankle instability (MAI) or functional ankle instability (FAI) exhibited different hip kinematics and kinetics during a stop-jump task compared with “copers.” Design: Cross-sectional study. Setting: Sports medicine research laboratory. Patients or Other Participants: Sixty-three recreational athletes, 21 (11 men, 10 women) per group, matched for sex, age, height, mass, and limb dominance. All participants reported a history of a moderate to severe ankle sprain. The participants with MAI and FAI reported 2 or more episodes of giving way at the ankle in the last year and decreased functional ability; copers did not. The MAI group demonstrated clinically positive anterior drawer and talar tilt tests, whereas the FAI group and copers did not. Intervention(s): Participants performed a maximum-speed approach run and a 2-legged stop jump followed by a maximum vertical jump. Main Outcome Measure(s): An electromagnetic tracking device synchronized with a force plate collected data during the stance phase of a 2-legged stop jump. Hip motion was measured from initial contact to takeoff into the vertical jump. Group differences in hip kinematics and kinetics were assessed. Results: The MAI group demonstrated greater hip flexion at initial contact and at maximum (P = .029 and P = .017, respectively) and greater hip external rotation at maximum (P = .035) than the coper group. The MAI group also demonstrated greater hip flexion displacement than both the FAI (P = .050) and coper groups (P = .006). No differences were noted between the FAI and coper groups in hip kinematic variables or among any of the groups in ground reaction force variables. Conclusions: The MAI group demonstrated different hip kinematics than the FAI and coper groups. Proximal joint motion may be affected by ankle joint function and laxity, and clinicians may need to assess proximal joints after repeated ankle sprains

The Short Rotation Period of Hi'iaka, Haumea's Largest Satellite

Hi'iaka is the larger outer satellite of the dwarf planet Haumea. Using relative photometry from the Hubble Space Telescope and Magellan and a phase dispersion minimization analysis, we have identified the rotation period of Hi'iaka to be ~9.8 hrs (double-peaked). This is ~120 times faster than its orbital period, creating new questions about the formation of this system and possible tidal evolution. The rapid rotation suggests that Hi'iaka could have a significant obliquity and spin precession that could be visible in light curves within a few years. We then turn to an investigation of what we learn about the (presently unclear) formation of the Haumea system and family based on this unexpectedly rapid rotation rate. We explore the importance of the initial semi-major axis and rotation period in tidal evolution theory and find they strongly influence the time required to despin to synchronous rotation, relevant to understanding a wide variety of satellite and binary systems. We find that despinning tides do not necessarily lead to synchronous spin periods for Hi'iaka, even if it formed near the Roche limit. Therefore the short rotation period of Hi'iaka does not rule out significant tidal evolution. Hi'iaka's spin period is also consistent with formation near its current location and spin up due to Haumea-centric impactors.Comment: 21 pages with 6 figures, to be published in The Astronomical Journa

Properties of the Distant Kuiper Belt: Results from the Palomar Distant Solar System Survey

We present the results of a wide-field survey using the 1.2-m Samuel Oschin Telescope at Palomar Observatory. This survey was designed to find the most distant members of the Kuiper belt and beyond. We searched ~12,000 deg2 down to a mean limiting magnitude of 21.3 in R. A total number of 52 KBOs and Centaurs have been detected, 25 of which were discovered in this survey. Except for the re-detection of Sedna, no additional Sedna-like bodies with perihelia greater than 45 AU were detected despite sensitivity out to distances of 1000 AU. We discuss the implications for a distant Sedna- like population beyond the Kuiper belt, focusing on the constraints we can place on the embedded stellar cluster environment the early Sun may be have been born in, where the location and distribution of Sedna-like orbits sculpted by multiple stellar encounters is indicative of the birth cluster size. We also report our observed latitude distribution and implications for the size of the plutino population.Comment: 40 pages, 12 figures, 3 tables Accepted by Ap

Characterization of antifungal C-type lectin receptor expression on murine epithelial and endothelial cells in mucosal tissues

Funding Information: We thank P. Asamaphan, A. Clark, and B. Kerscher for providing NIH overexpression cell lines, S. Yamasaki for the anti‐Mincle antibody, the staff of the University of Aberdeen animal facility for the care for our animals, and the Iain Fraser Cytometry Centre at the University of Aberdeen for their assistance. This work was supported by funding from the Wellcome Trust (102705, 217163), the Medical Research Council Centre for Medical Mycology, and the University of Exeter (MR/N006364/2).Peer reviewedPublisher PD

A collisional family of icy objects in the Kuiper belt

The small bodies in the Solar System are thought to have been highly affected by collisions and erosion. In the asteroid belt, direct evidence of the effects of large collisions can be seen in the existence of separate families of asteroids—a family consists of many asteroids with similar orbits and, frequently, similar surface properties, with each family being the remnant of a single catastrophic impact. In the region beyond Neptune, in contrast, no collisionally created families have hitherto been found. The third largest known Kuiper belt object, 2003 EL_(61), however, is thought to have experienced a giant impact that created its multiple satellite system, stripped away much of an overlying ice mantle, and left it with a rapid rotation. Here we report the discovery of a family of Kuiper belt objects with surface properties and orbits that are nearly identical to those of 2003 EL_(61). This family appears to be fragments of the ejected ice mantle of 2003 EL_(61)

Ethnic differences in do-not-resuscitate orders after intracerebral hemorrhage.

OBJECTIVE: To explore ethnic differences in do-not-resuscitate orders after intracerebral hemorrhage. DESIGN: Population-based surveillance. SETTING: Corpus Christi, Texas. PATIENTS: All cases of intracerebral hemorrhage in the community of Corpus Christi, TX were ascertained as part of the Brain Attack Surveillance in Corpus Christi (BASIC) project. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Medical records were reviewed for do-not-resuscitate orders. Unadjusted and multivariable logistic regression were used to test for associations between ethnicity and do-not-resuscitate orders, both overall ( any do-not-resuscitate ) and within 24 hrs of presentation ( early do-not-resuscitate ), adjusted for age, gender, Glasgow Coma Scale, intracerebral hemorrhage volume, intraventricular hemorrhage, infratentorial hemorrhage, modified Charlson Index, and admission from a nursing home. A total of 270 cases of intracerebral hemorrhage from 2000-2003 were analyzed. Mexican-Americans were younger and had a higher Glasgow Coma Scale than non-Hispanic whites. Mexican-Americans were half as likely as non-Hispanic whites to have early do-not-resuscitate orders in unadjusted analysis (odds ratio 0.45, 95% confidence interval 0.27, 0.75), although this association was not significant when adjusted for age (odds ratio 0.61, 95% confidence interval 0.35, 1.06) and in the fully adjusted model (odds ratio 0.75, 95% confidence interval 0.39, 1.46). Mexican-Americans were less likely than non-Hispanic whites to have do-not-resuscitate orders written at any time point (odds ratio 0.37, 95% confidence interval 0.23, 0.61). Adjustment for age alone attenuated this relationship although it retained significance (odds ratio 0.49, 95% confidence interval 0.29, 0.82). In the fully adjusted model, Mexican-Americans were less likely than non-Hispanic whites to use do-not-resuscitate orders at any time point, although the 95% confidence interval included one (odds ratio 0.52, 95% confidence interval 0.27, 1.00). CONCLUSIONS: Mexican-Americans were less likely than non-Hispanic whites to have do-not-resuscitate orders after intracerebral hemorrhage although the association was attenuated after adjustment for age and other confounders. The persistent trend toward less frequent use of do-not-resuscitate orders in Mexican-Americans suggests that further study is warranted

Lower Extremity Kinematics and Ground Reaction Forces After Prophylactic Lace-Up Ankle Bracing

Long-term effects of ankle bracing on lower extremity kinematics and kinetics are unknown. Ankle motion restriction may negatively affect the body's ability to attenuate ground reaction forces (GRFs)