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School of Biological Sciences

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School of Earth and Atmospheric Sciences

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School of Mathematics

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Publication Search Results

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Representing the Effect of Multiple Alternatives and Information Strength on Confidence in Perceptual Decision Tasks

(Georgia Institute of Technology, 2020-12) Crabtree, Brooklyn

Confidence in perceptual decisions is a baseline for quantitatively measuring metacognitive processes in psychology. Most researchers limit the stimulus to two choices, assuming that the mental process summarizes the likely accuracy of all choices to determine confidence in the decision. The purpose of this study was to determine whether multiple alternative choices, with varying levels of information strength for each choice, follow the same mental statistics as similar two-alternative forced choice (2AFC) tasks. If the differences between information strengths for each of the multiple choices had a direct effect on confidence, then presenting higher and lower differences of information strength between the correct choice and the incorrect choice would result in corresponding higher and lower confidence ratings. Participants were shown multicolor clouds of dots made up of three colors, with one dot color (dominant) being more abundant than the others. Participants decided which color was the dominant color for each cloud, then indicated their confidence in that decision. The overall information strength, dominant-secondary strength difference, and dominant-tertiary strength difference all had significant main effects on both confidence and accuracy. The overall strength had the largest effect size for confidence, with more information strength resulting in higher confidence ratings. The dominant-secondary strength difference had the largest effect size for accuracy, with a larger difference between dominant and secondary color strengths resulting in higher accuracy rates. Further investigation on how the brain defines relevant stimuli in an environment and processing of multiple choices must be conducted before developing computational models for confidence.
Broad Effects of Arousal on Quasi-Periodic Patterns of Brain Activity

(Georgia Institute of Technology, 2020-12) Humm, Erek Matthew

Quasi Periodic Patterns (QPPs) are recurring patterns of brain activity found in brain imaging data that last approximately 20 seconds and occur at no regular interval. In this experiment, researchers aim to establish a link between the level of mental arousal and the strength and frequency of QPPs. It was thought that increased levels of arousal would result in an increase in the strength and frequency of QPPs. To test this, subjects from three different contrasting experimental groups conducted tasks while in a functional magnetic resonance imaging (fMRI) scanner: (1) young subjects vs. old subjects, (2) task-engaged vs. resting-state, and (3) sleep disorder vs. no disorder. QPPs were regressed from the fMRI scans using an extensive processing and analysis pipeline. It was generally found that increased arousal levels led to an increase in the incidence and strength of QPPs. Increased arousal is present in young subjects, task-engaged subjects, and subjects without sleeping disorders. These results open the door for future experiments to quantify the link between arousal and QPPs. Establishing a link between these two can be vital to future research involving therapeutic devices, diagnostic tools, and even human-computer interfaces.
Influence of Social Intention on Switch Cost in Task-Switching Paradigms

(Georgia Institute of Technology, 2020-12) Barrett, Jacquelyn Marie

Humans have built a society based upon elaborate social interactions. We have processes that enable us to interact with each other and switch between tasks. Humans often multitask especially in a social context, such as talking while working on a project, listening to someone while driving, or switching between conversations with different people. One of these processes that aids in this interaction is the intentional stance. The intentional stance is the tendency humans have to view other’s actions as driven by their own mental states, beliefs, and intentions. In this experiment, it is examined whether or not social cognition, such as inferring the beliefs or intentions of others, behaves like other cognitively dominant tasks. Cognitively dominant tasks are automatic processes that are elicited with minimal to no effort, such as reading. A task switching paradigm was used among two groups, social and non-social, where tasks in the social group invoke the intentional stance and tasks in the non-social group do not. Switch cost, the increase in reaction time when switching between tasks, may increase when switching from a hard task to an easier task. This is due to the amount of inhibition initially placed on the easier stimuli in order to attend to the cued, more difficult stimulus until the more readily available stimulus has become relevant again Based on previous research, it is believed that switching from a non-social to a social task will result in a greater switch cost due to the amount of effort needed to overcome inhibition initially placed on the more readily available stimuli, or the social stimuli. These findings would support the hypothesis that social cognitive process behave similarly to other cognitively dominant processes.
Decoding Disease Persistence in Pediatric Acute Lymphoblastic Leukemia One Single Cell at a Time

(Georgia Institute of Technology, 2020-12) Imbach, Kathleen Jane

In order to understand the biological and molecular mechanisms underlying disease resistance to therapy in pediatric acute lymphoblastic leukemia (ALL), we performed an investigation utilizing single-cell RNA-sequencing (scRNA-seq) on the 10X Genomics Chromium platform. Bone marrow samples from seven patients were collected, four of whom exhibited measurable residual disease (MRD) after induction therapy, and three patients who did not. Cells from bone marrow tissue were extracted from each patient at the time of diagnosis, prior to treatment efforts. Leukemic cells were separated from peripheral immune cells using flow cytometry and ~1000 single cells were sequenced from each patients’ cell populations. The goal of this study was to discern how the immune and leukemic cell populations and gene expression therein vary at the time of diagnosis between patients who do or do not respond to induction. Our results demonstrate a comparative increase in immune exhaustion signatures in the immune cells of MRD-positive patients, corroborating previous findings that implicate the role of exhaustion in resistant disease. We also show a discrepancy of cell cycle states in the leukemic cell compartment according to disease outcome, with an enrichment of blasts from MRD-negative patients exhibiting genetic signatures of S- and G2/M-phase.
Analysis and illustration of primary and secondary structures of ribosomal RNA and ribosomal proteins

(Georgia Institute of Technology, 2020-08) Meade, Caeden Daniel

RiboVision is a collection of applications housed on servers at the Georgia Institute of Technology which serves to facilitate the development of publication-quality diagrams of ribosomal RNA (rRNA) and ribosomal protein (rProtein) structures (Petrov et. al, 2014). In particular, RiboVision seeks to promote analysis of key properties of rRNA and rProteins in primary, secondary, and tertiary structures. As key semantides (ubiquitous macromolecules which carry genetic equivalent to the information intrinsic to DNA molecules and may be used by comparison to inform phylogenetic relationships), comparison of the primary and secondary structures of 16S and 18S RNA allows for the phylogenetic comparison of prokaryotic species and eukaryotic species, respectively (Fuerst, 2001). Sequence alignments are housed on the RiboVision server and stored in a MySQL database. Over the next two semesters, major improvements will be made to the server resulting in the newest edition, RiboVision3, which will feature improvements over the preceding RiboVision2 including the integration of XRNA, a program responsible for the generation of rRNA secondary structures and their exportation of their data into common computer-file formats (CSV, SVG, PDF, etc.) and the PDB Topology Viewer, a program responsible for production of protein secondary structures and their exportation into SVG image files. The core functionality of XRNA - demonstration and editing tools of rRNA secondary structures needs to be iterated upon to allow for a more diverse set of purposes, including processing of high-quality hand-edited images into formats which are compatible with on-server management and conversion into formats native to web browsers.
Brain mechanisms for the cognitive effects of dual task interference

(Georgia Institute of Technology, 2020-08) Heo, Yeseul

Our ability to multitask has been found to have critical limitations primarily due to the restricted available attentional resources. Although many studies have explored the phenomena of processing bottleneck using serial reaction time experimental designs, there has been a significant limitation in the current literature due to the complex nature of multiple task representations. In other words, it is difficult to relate the discrepancy in performances during one-task and two-task solely to the differences in the task representation mechanisms because of the convoluted interaction between the single task and dual task experiments. To minimize such discrepancy, Schumacher et al. (2018) introduced a novel dual-task procedure that uses constant stimuli for one-task and two-task conditions. This study expanded the work by Schumacher et al. by replicating the experimental design to observe similar performance trends that show greater effects of dual-task interference in the two-task condition compared to that in the one-task condition. This finding set the stage for functional data collection that will occur following the current study using neuroimaging techniques to identify the neural correlates responsible for the facilitation of multitasking.
The Effects of Boundary Manipulations on Navigational Abilities

(Georgia Institute of Technology, 2020-08) Han, Andrew Taekyu

The purpose of this study is to see how manipulating boundaries impact one’s spatial memory in unfamiliar spaces. To test this, after we measured our participants’ Sense of Direction (SOD) and memory capacities, they were equally divided up into three separate training conditions: an abstract environment, a translucent environment, and a control environment. Afterwards, they were evaluated using wayfinding and pointing tasks. Our results indicated that the abstract training significantly impacted those with varying SOD’s. Those with low SOD’s in the control condition outperformed their abstract counterparts in wayfinding, and those with high SOD’s in the opaque abstract condition outperformed their control counterparts in the pointing tasks. This could be due to their reliance on different navigation strategies. In this case piloting versus path integration, respectively. Regardless, this study emphasizes the need to further investigate other methods of boundary manipulation that will potentially affect people’s spatial abilities.
Basal Forebrain Degeneration and Cortisol as Biomarkers Mediating Alzheimer’s Disease Pathology: A Machine Learning Approach

(Georgia Institute of Technology, 2020-05) Nakirikanti, Anudeep Sai

The impact of Alzheimer’s Disease (AD) on today’s society and healthcare is unprecedented. As a larger portion of today’s population enters an age for which AD becomes a health concern, there is growing support among health practitioners to prevent the disease’s progression and development. Early identification of the disease may serve as a critical step towards combating the disease, allowing earlier interventions in the disease process to foster healthy aging. The focus of such interventions includes alleviating risk factors of AD, two of which include cortisol and degeneration in the basal forebrain. Importantly, increased levels of cortisol and reduced volume in the basal forebrain are attributed to higher risks of AD. In the present study, we make use of machine learning and the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database to characterize individuals with AD by using data from cortisol levels and basal forebrain degeneration. This allowed us to test whether cortisol and basal forebrain degeneration were predictively valuable for AD diagnosis. Our data partially supported our prediction—the machine learning classifier yielded significantly above chance classification accuracy for basal forebrain degeneration, but the classification accuracy for cortisol was not significantly above chance. Consequently, our results indicate that basal forebrain degeneration might serve as a diagnostically useful biomarker for AD, while cortisol’s role in AD characterization necessitates further investigation.
Synthesis of Degradable Monomers for Ring-Opening Metathesis Polymerization

(Georgia Institute of Technology, 2020-05) Crolais, Alex E.

Ring opening metathesis polymerization (ROMP) is a type of olefin metathesis chain-growth polymerization that has shown great versatility in the field of polymer chemistry. Although it allows polymerization of monomers containing a variety of functional groups, how effective it is in polymerizing degradable monomers is largely unknown. In this report, we demonstrate a novel synthetic pathway to synthesize an acetal-containing degradable monomer that is compatible with ROMP and the Grubbs 3 (G3) catalyst. Polymers made from this monomer were characterized by GPC analysis and underwent degradation studies. Acetals generally undergo hydrolysis in mildly acid conditions and even in biologically relevant pH ranges, so this new monomer will have potential applications in drug delivery systems. The monomer also has the capacity to have its functional groups modified, changing its functionality which will be further studied.
Effect of Hydrodynamic Regime on Snowflake Yeast Evolution

(Georgia Institute of Technology, 2020-05) Holt, Jacob D.

Experimental evolution of S. cerevisiae has unlocked new avenues in the study of the transition from uni- to multicellularity and how selection moves from the level of the individual cell to the multicellular-level. Selection for large size, proxied by selecting for settling speed, quickly leads to clusters of cells, coined ‘snowflake yeast’, and adaptations at the cluster level. While selecting for settling speed is a good proxy for selection of large size because it is simple to implement, settling, or sedimentation, is a complex process with the potential for unforeseen impacts on this model system. By changing the hydrodynamic regime during settling speed selection, the selection process, and its effects on the snowflake yeast system other than selection for increased size, is explored. It is found that size distributions change in response to differing hydrodynamic regimes during settling speed selection. However, the path to larger size remains relatively constant, showing that the major findings of the snowflake yeast system are robust to changes in hydrodynamic regime during settling speed selection.