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On the Initial Boundary Value Problem in Numerical Relativity
No full textThe principal goal of this thesis is to properly understand, characterize, and numerically implement initial boundary value problems in numerical relativity. Throughout the history of solving Einstein's field equations on computers, boundaries have been mostly dealt with in an approximate way. For example, boundaries might be placed far away from strongly gravitating sources, where approximations like linearized gravity are valid. It has become necessary however to place boundaries in the strong gravity regime of a dynamical spacetime to model complicated and interesting physics, which necessitates a complete understanding of the initial boundary value problem of Einstein's field equations.
One motivation for this comes from a need to simulate black hole echoes. In classical general relativity, black holes are perfectly absorbing objects, where the mass of radially incoming wavepackets of matter or gravitational waves is absorbed by the black hole. Thus conclusive evidence of modifications to general relativity, such as quantum gravity, could include partial reflections of radially incoming wavepackets, called black hole echoes. To properly understand the modifications this would bring to detectable gravitational wave signals, we require simulations where reflecting boundary conditions are imposed close to the horizon of a black hole. Another motivation comes from recent advances in Cauchy characteristic matching, which combines state of the art numerical techniques to obtain physically accurate gravitational waveforms from simulations. This can allow numerical relativists to dramatically save on the computational cost of black hole merger simulations, but only if boundaries can be placed in the strong gravity regime.
This thesis presents advances in simulating initial boundary value problems in numerical relativity. Starting with spherical symmetry, a framework for reflecting a scalar field in a fully dynamical spacetime is developed and implemented numerically using the Einstein-Christoffel formulation. The evolution of a wave packet and its numerical convergence, including when the location of a reflecting boundary is very close to the horizon of a black hole, is studied. Next, this approach is generalized to spacetimes with no symmetries and implemented numerically using the generalized harmonic formulation. The evolution equations are cast into a summation by parts scheme, which seats the numerical method closer to a class of provably numerically stable systems. State of the art numerical methods are demonstrated, including an embedded boundary numerical method that allows for arbitrarily shaped domains on a rectangular grid and even boundaries that evolve and move across the grid. As a demonstration of these frameworks, the evolution of gravitational wave scattering off of a boundary either inside or just outside the horizon of a black hole, is studied. Finally, a boundary condition framework designed to control quasi-local energy flux is proposed motivated by examples from electromagnetism
Examining Computer-Generated Aeronautical English Accent Testing and Training
No full textObjective: This thesis focused on the persisting problem of language-related issues, in pilot-air traffic controller (ATC) communication, particularly in relation to foreign accents interfering with pilots’ understanding. It examined the effect of foreign accents embedded in human and computer voice (HV, CV), as well as demographic background on the level of understanding of the participants.
Background: Studies focusing on the impacts of foreign accents in Aviation English (AE) are scant. Accents have been identified as one of the main contributors to miscommunication between pilot-ATC radiotelephony communication in the air, thereby endangering flight safety. It is necessary to examine how to train ab initio and returning pilots on extracting accurate meanings from an accented instruction coming from ATCs. This thesis introduces a Text-to-Speech (TTS) supported by artificial intelligence for such training.
Method: Multiple studies (a total of six) were conducted: 2 literature reviews, 4 empirical studies. For the empirical studies, 50 participants from the University of Waterloo who had experiences with flight or had experience in listening to pilot-ATC communications were recruited. They were put into two Voice Groups (HV and CV) one of which played only human voices and the other TTS. They completed two rounds (Round 1 and 2) of listening tests that contained both Aviation Script (AS; scripts read in foreign accents that were related to aviation context) and Neutral Scripts (NS; non-aviation scripts read in foreign accents with no contextual background). The foreign accents used in the listening tests along with native-accented English were three of the ICAO’s main languages: Arabic, Spanish, and French. Scores were analyzed according to the Script Types (NS, AS), Accents (Arabic, Spanish, French), Rounds (1 and 2), and Demographic Profiles (Age, Gender, Years of Speaking English, Flight Hours, Flight Ratings, Language Background, Familiarity with Arabic, Spanish, French, and Aviation English).
Results: For the empirical studies, in the HV group, participants improved their scores from round 1 to 2 in the AS portion of the tests. In the CV group, participants improved their scores in NS. Examination of demographic information showed that non-native English speakers (NNES) tended to perform more poorly on average than native English speakers (NES). Being familiar with Aviation English was beneficial for completing listening tests. Also, having a higher flight rating was beneficial. Having more years of speaking English was only partially advantageous. Post survey results were analyzed, and it was found that participants in the CV group found the speech mostly unnatural. Those in the HV group also expressed difficulty in understanding due to accents but mentioned that the speech was clear, and scripts were representative of real-life pilot-ATC communication. Participants expressed foreign accents interfered with their process of logical deduction when choosing answers on the tests. Participants – regardless of whether they belonged to the HV or CV group – found NS difficult and challenging due to lacking contexts when answering questions on the tests. For AS, participants were able to piece together information using contextual knowledge related to aviation.
Conclusion: Accents do interfere with pilots’ understanding in radiotelephony communication by making extracting content challenging, which in turn makes interpreting messages or instruction difficult. This is an important finding as it will affect situational awareness to a certain extent when making decisions on the fly. Pilots have to multi-task whenever possible to keep the passengers safe and to find the best route to get to a destination that maximizes fuel efficiency but minimizes passenger wait times. Communication plays a large role in deciding the fate of an aircraft’s journey. In this logic, accents can be said to be at the core of this overarching issue with language in the context of aviation. Therefore, training with a new technology such as TTS, along with other educational resources, could confer a valuable experience and exposure to pilots who are either beginning or re-starting their language training
Local Government Planning and Maintenance of Ecological Connectivity in a Fragmented Landscape
No full textWith the continued loss of species and habitat together with the recognition that parks, and protected areas are insufficient to maintain biodiversity, the role of spatial planning to address land use change and account for ecological connectivity is becoming more significant. A well-connected system of natural areas is required to address the continued loss of biodiversity and to reduce threats to human well-being. The value of local governments in providing the spatial planning needed to reduce threats and protect natural areas and ecological connectivity is recognized. The need for a collaborative approach that engages multiple actors including all level of government and non-government organizations is required to implement policy direction on ecological connectivity effectively and efficiently.
This dissertation explores the role of local government land use planning in the protection and maintenance of ecological connectivity through the control of land use change. As ecological connectivity crosses political boundaries, the coordination of local plans across the larger landscape is necessary for effective management of ecological connectivity. This case study research is placed within the Carolinian ecoregion in southwestern Ontario Canada, a recognized area of high biodiversity and intense development.
My dissertation addressed three concerns, (1) the integration of ecological connectivity in local government land use plans; (2) factors that help or hinder the planning and maintaining ecological connectivity; and (3) how local governments interact with other actors in pursuit of ecological connectivity. This is done through three methods of investigation. First a qualitative content analysis of 16 Official Plans in the Carolinian ecoregion was undertaken. Second, 24 interviews were conducted with planning practitioners with thematic analysis applied to identify influential factors to the planning and maintenance of ecological connectivity. Third intended social interactions were examined in Official Plan policy and past interactions identified from the interviews.
I found that ecological connectivity was consistently addressed in Official Plans through the identification of a natural heritage system, including linkages among natural areas. The policies were however inconsistently applied across the ecoregion with a notable variation between urban and rural areas in applying provincial direction. It was found that the integration of ecological connectivity in local government land use planning: is dependent upon clear and binding legislation from higher levels of government; benefits from an integrated policy framework; is addressed through site level development approvals and land stewardship initiatives; is less likely to be addressed across agricultural lands than urban areas; and lacks a coordinated approach across local government spatial boundaries. In the case study area, while some policy areas were readily integrated with ecological connectivity including water resources, parks and open space, and natural hazard lands, there was a lack of integration with climate change, green infrastructure and transportation polices.
Through interviews with planning practitioners, key factor theme areas were identified including the physical landscape, environmental governance, land use planning practices, sharing information, and resources. The results show that while ecological connectivity is supported by legislation, addressed in policy, with implementation mechanisms recognized and applied, local government still struggles with a natural features focus, cross border coordination, land use planning practice limitations, justification of the need for ecological connectivity, public and political resistance, and a lack of capacity and funding. Both the interviews and Official Plan review contributed to the identification of actor interactions. I found that coordination across local government boundaries to accommodate the provincially legislated and delegated natural heritage system was not occurring. Planning practitioners interviewed did not see local government as leading but rather participating in collaborative actions. The main findings are a lack of provincial involvement, a large role to be played by Conservation Authorities, and a gap between policy and implementation.
Collectively, this research advances our understanding of the role of local government land use planning in establishing and maintaining ecological connectivity through the control of land use change and management of the whole landscape involving nature conservation but also sectoral policies. Spatial land use planning has the potential to address ecological connectivity through a comprehensive multisectoral and collaborative approach. There are many limitations to local government land use planning to address ecological connectivity that will need to be addressed and this research contributes to the identification of issues as well as possible solutions to address those limitations
Bridging Technology and Therapy: Assessing the Quality and Analyzing the Impact of Human Editing on AI-Generated SOAP Notes in Pediatric Rehabilitation
No full textThis thesis explores the integration of artificial intelligence (AI) into clinical documentation, focusing on evaluating AI-generated SOAP (Subjective, Objective, Assessment, and Plan) notes in pediatric rehabilitation settings. AI-powered tools, such as Microsoft's Copilot and the University of Waterloo-developed KAUWbot, offer potential efficiencies by automating aspects of clinical documentation. However, their quality, reliability, and applicability to clinical practice have remained largely unexamined.
The research aims to assess and compare the quality of human-authored SOAP notes and AI-generated notes across five key criteria: clarity, completeness, conciseness, relevance, and organization. A dataset of 432 SOAP notes, divided into four pools, was evaluated using a custom rubric. The pools included human-authored notes, Copilot-generated notes edited by occupational therapists, unedited KAUWbot-generated notes, and KAUWbot-generated notes edited by occupational therapists. A rigorous anonymization process ensured evaluator impartiality.
Findings indicate that AI-generated notes, particularly when edited by clinicians, achieve comparable or superior quality to human-authored notes. After editing, notes generated by KAUWbot, a model fine-tuned on pediatric occupational therapy data, exhibited notable improvements in relevance and organization. Statistical analyses demonstrated some differences among note pools, with edited AI-generated notes consistently receiving the highest ratings. This highlights the importance of human oversight in enhancing AI output and tailoring it to specific clinical needs.
The research shows the potential of AI to augment clinical documentation processes, reduce clinician workload, and improve documentation quality. However, it also emphasizes the necessity of human-AI collaboration and robust training to mitigate limitations such as contextual inaccuracies and misclassifications. These findings provide a foundation for future research and practical recommendations for integrating AI into healthcare documentation workflows
Facing the Flood: Amphibious Architecture for Flood Resilience in Peguis, Manitoba
No full textFloods are Canada's most common and costly natural hazard and flood risks are increasing due to climate change. When floods affect housing, they not only inflict economic and property damage but also displace residents from their homes and affect people’s sense of safety and community.
Conventionally, settlements built in flood-prone regions are protected by flood control infrastructure, like levees, dikes, dams, and diversion channels. This infrastructure cannot easily or quickly respond to changing flood conditions and sometimes transfers flood risk rather than mitigating it equitably. We see this in Manitoba’s Interlake Region, where First Nations communities bear a disproportionate burden from water diversion to protect large urban centers.
Where conventional solutions have failed and new tools are urgently needed, amphibious construction can provide an option for mitigation. Amphibious structures sit on dry land when water levels are normal, like an ordinary building. However, there is a buoyancy system, allowing the structure to float on the water in a flood. Vertical guidance, often posts, holds the building in place laterally while floating. When flood waters recede the building returns to its original position undamaged.
Inspired by community members who wish to stay on their land despite flood risks, this thesis proposes amphibious architecture for a site in the First Nations Community of Peguis, Manitoba. Relocated to flood-prone land after a fraudulent land transfer in 1907, the community experiences chronic flooding. They faced several floods in the last two decades and had their worst flood on record in 2022, emphasizing the urgency of providing solutions for residents.
This thesis examines this history and a specific site in Peguis, identifying key considerations for implementing amphibious architecture there. Then, it assesses existing amphibious architecture precedents, looking at how these projects address common challenges. Drawing insights from this analysis, this thesis proposes a prototype design for the site in Peguis
A Multi-Phase Analysis of Gas Dynamics and Perturbations in the Galaxy Cluster Cores
No full textThis thesis provides a detailed analysis of gas kinematics and their interactions across various phases within galaxy cluster cores. It examines the processes that generate gas perturbations and the factors that contribute to the thermal stability of the intracluster medium (ICM). A focus is placed on exploring the origins of multi-phase gas and the mechanisms—particularly AGN feedback—that either couple or decouple their motions.
Radio-mechanical AGN feedback is identified as one of the most promising heating mechanisms that prevent the cooling of gas. However, the debate on the details of the heating transport processes has remained open. The atmospheres of 5 cool-core clusters, Abell 2029, Abell 2107, Abell 2151, RBS0533 and RBS0540, have short central cooling times but little evidence of cold gas, and jet-inflated bubbles. The amplitudes of gas density fluctuations were measured using a new statistical analysis of X-ray surface brightness fluctuations within the cool cores of these ‘spoil’ clusters in Chapter 2. The derived velocities of gas motions, typically around 100 - 200 km/s, are comparable to those in atmospheres around central galaxies experiencing energetic feedback, such as in the Perseus Cluster, and align well with the turbulent velocities expected in the ICM. Regardless of the mechanisms driving these perturbations, turbulent heating appears sufficient to counteract radiative losses in four of the five spoiler cluster cores. We thus suggest that other mechanisms, such as gas sloshing, may be responsible for generating turbulence, offering a plausible solution to suppress cooling in these structureless atmospheres.
Multiphase filaments, key byproducts of AGN feedback, are frequently observed near central galaxies, with their morphologies and kinematics closely linked to bubbles. In Chapter 3, we analyzed the velocity structure functions (VSFs) of warm ionized gas and cold molecular gas, identified through [OII] emission and CO emissions observed by the Keck Cosmic Web Imager (KCWI) and the Atacama Large Millimeter/submillimeter Array (ALMA), respectively, in four clusters: Abell 1835, PKS 0745-191, Abell 262, and RXJ0820.9+0752. Excluding Abell 262, where gas forms a circumnuclear disk, the remaining clusters exhibit VSFs steeper than the Kolmogorov slope. The VSFs of CO and [OII] in RXJ0820 and Abell 262 show close alignment, whereas in PKS 0745 and Abell 1835, were differentiated across most scales, likely due to the churning caused by the radio-AGN. The large-scale consistency in Abell 1835 and RXJ0820, together with scale-dependent velocity amplitudes of the hot atmospheres obtained from Chandra X-ray data, may support the idea of cold gas condensation from the hot atmospheres.
X-ray observations have previously been constrained by low energy resolution, which has impeded direct measurements of velocity fields in galaxy clusters. However, the recent release of initial data from the X-ray Imaging and Spectroscopy Mission (XRISM) provides a non-dispersive energy resolution of about 5 eV, facilitating the measurement of line broadening and shifts. In Chapter 4 of this thesis, I detail my contributions to calibrating the optical blocking filters for XRISM using synchrotron beamlines at the Canadian Light Source (CLS) and Advanced Light Source (ALS) prior to its launch, and I discuss the model-based estimation of the parameters of the calibrated filters. This capability for direct measurement of plasma velocities is expected to greatly improve our understanding of the ICM dynamics with high accuracy
An epidemiological investigation of physical-mental multimorbidity: Findings from the 2014 Ontario Child Health Study
No full textChildren living with chronic physical illnesses such as diabetes and epilepsy, are at increased risk for developing mental illness. The co-occurrence of at least one physical and at least one mental illness, known as multimorbidity, is not surprising as children living with physical illness and their families endure financial and psychosocial challenges, predisposing these children to experience mental health declines. Child multimorbidity is common. Approximately 25% of children live with physical illnesses that require long-term management and as many as 58% of these children are also diagnosed with a mental illness. The effects of multimorbidity are pervasive, burdening children, families, and the health, social and educational systems. Thus, there is a pressing need to address the mental health challenges of children living with physical illness. A proactive, preventive, public health approach requires a comprehensive understanding of child multimorbidity in a Canadian context.
Despite the underlying risk of mental illness across various physical illnesses, child mental health research often excludes childhood physical illness as a determinant of mental illness. Of the research that does exist, samples include older adolescents and young adults with chronic physical illness or include high-risk clinical samples. Research using epidemiological samples, inclusive of young children, has not been conducted since the seminal 1983 Ontario Child Health Study. As survivorship of children living with chronic physical illness has substantially increased with these children living well into adulthood, and as the designs and needs of healthcare and mental health care systems have changed since 1983, this research answers calls to the public health concern of child multimorbidity.
To address these knowledge gaps, the following dissertation identified which factors influence the association between chronic physical illness and mental illness (any, mood, anxiety, behavioural and neurodevelopmental disorders), including mediating and moderating factors, and examines differences in mental health service contact based on child health status (healthy, physical illness only, mental illness only, and multimorbid). Three distinct studies, with each study examining one of these main dissertation objectives, have been written for publication. These studies made use of data from the 2014 Ontario Child Health Study-a cross-sectional, epidemiological study of 10,802 children aged 4 to 17 years from 6,587 households from across 240 neighbourhoods.
1) Study 1 objectives included:
a. Estimating the lifetime prevalence of childhood chronic physical illness and the six-month prevalence of mental illness and multimorbidity in children;
b. Quantifying associations between physical illness and mental disorder, including number of illnesses; and
c. Examining factors associated with mental disorder, after adjusting for chronic physical illness.
2) Study 2 objectives included:
a. Examining moderating effects of child sex, age, health functioning, mental health service contact, and household income on associations between physical and mental illnesses; and
b. Exploring the potential mediating effect of family functioning on physical-mental multimorbidity.
3) Study 3 objectives included:
a. Estimating the six-month prevalence of health status and types of mental health service contact;
b. Quantifying adjusted associations between child health status and type of mental health service contact; and
c. Quantifying adjusted associations between child health status and number of different types of mental health service contacts.
In a sample of 10,303 children, the first manuscript estimated childhood chronic physical illness to be 27.8%, while 14.8% of children had mental disorder and 5.4% had multimorbidity. Physical illness was not associated with mental disorders. An ordinal regression illustrated children with two physical illnesses, as compared to no physical illnesses, had increased odds for having any, mood, and anxiety disorders. There were no associations found between children with one or three or more physical illnesses and mental disorders. Notably, health functioning demonstrated a dose-response across health status categories, with healthy children having highest scores and multimorbid children having lowest scores. These findings demonstrate the need for targeted and routine mental health screening in youth with two physical illnesses. Preventative mental health interventions should focus on preventing declines in health functioning.
The second manuscript used the subsample of index children (n=6,242). Physical illness was associated with increased odds of mood disorder. Health functioning moderated physical-mental illness associations, such that better health functioning in children with physical illness versus without physical illness, had higher odds for any mental illness, anxiety disorder, and attention-deficit hyperactivity disorder. There were no associations found in children with poorer health functioning and physical illness. No other child or household factors moderated associations and family functioning did not mediate physical-mental multimorbidity. These findings suggest physical-mental multimorbidity is nuanced, with differential effects of physical illness on childhood mental illness. Targeted mental health screening is needed for children living with chronic physical illnesses resulting in better health functioning.
The third manuscript estimated 21.4% of children had mental health service contact within the last six months. Regardless of child health status, contact was highest in school-based settings. Children with multimorbidity had higher odds for having every type of mental health service contact (any, general medicine, urgent medicine, alternative, school-based, and specialized mental health) than healthy controls. A dose-response was also observed, such that the number of types of mental health service contacts increased from physical illness to mental illness to multimorbidity. These findings support mental health resource allocation for school-based services. Further research is needed to understand barriers and facilitators of mental health service use including integrated health and mental health care for children with multimorbidity.
The findings from this dissertation fill critical knowledge gaps in child physical-mental multimorbidity research. Taken together, these findings show health functioning and not just the mere presence of physical illness is important to consider when examining the nuances and impact of physical illness on child mental health. Moreover, findings show mental health-related contact is similar across child health status. Findings also inform policy, intervention, and clinical research directions. From a policy lens, resources should be allocated to school-based mental health services. Universal mental health intervention efforts, regardless of child health status, should focus on preventing overall-health functioning declines. Regular mental health screenings for children living with chronic physical illness should occur, with early intervention efforts aimed at reducing the incidence of multimorbidity. Vigilant and routine screening is needed for children living with two physical illnesses and for children with better health functioning. Future longitudinal research is needed to elucidate mediating factors in physical-mental multimorbidity. Given proper supports within integrated health services, the incidence and impact of child multimorbidity can be reduced and children living with physical illness can have improved mental health outcomes
The Great Migration, Urban Spatial Structure, and Their Economic and Environmental Impacts in the U.S.
No full textThis thesis investigates the transformative impact of the Great Migration on urban spatial structure in the United States and its subsequent economic and environmental consequences. The Great Migration (1910-1970), marked by significant African American migration from the South to Northern and Western cities, reshaped the demographic and spatial landscape of receiving cities. Yet, the long-term spatial dynamics and their implications remain underexplored, a gap this study aims to address.
Using a novel dataset constructed through the City Clustering Algorithm (CCA), this research redefines historical urban boundaries, creating “synthetic cities” (Syncities) that more accurately reflect urban development from 1900 to 1970. The analysis reveals how demographic shifts influenced the size and shape of cities, with implications for their economic performance and environmental quality. By employing instrumental variable regression and mediation analysis, this thesis identifies the causal pathways through which these spatial transformations affected income levels and air quality, both immediately following the migration and decades later.
The findings highlight both economic growth and environmental challenges linked to urban expansion. Cities with larger and more dispersed urban forms benefited economically in the short term but faced greater environmental degradation over time. These results underscore the importance of urban spatial structure in shaping sustainable development trajectories.
By bridging historical demographic changes with contemporary urban outcomes, this study offers valuable insights for urban planning and policy, demonstrating how historical conditions continue to shape modern challenges. This work also provides a methodological foundation for future research on the interplay between migration, urban form, and sustainability.
This thesis is organized into seven chapters. Chapter 1 introduces the research goals and questions, explaining the importance of the study. Chapter 2 describes how the new urban spatial dataset was created and provides an overview of the key data. Chapter 3 looks at how urban areas in the U.S. changed between 1900 and 1970, providing background for the main analyses. Chapter 4 studies how the Great Migration affected the size and shape of cities, while Chapter 5 examines the economic and environmental effects of these changes. Chapter 6 explains how changes in urban areas connected the Great Migration to economic and environmental outcomes. Finally, Chapter 7 brings the findings together, discusses what they mean for policy, highlights limitations, and suggests ideas for future research. These chapters work together to show how the Great Migration reshaped American cities and what that means for sustainability today
Time-resolved and equilibrium resonant X-ray studies of nematicity in cuprate superconductors
No full textAttracting four decades of experimental and theoretical investigations since the discovery of high-temperature superconductivity, cuprates have become an essential benchmark for the exploration of intertwined electronic symmetry-breaking phases such as superconductivity, magnetism, nematicity, charge or spin density wave order in strongly correlated systems. Understanding how these phases are intertwined is of general and fundamental interest to a wide range of quantum materials. This doctoral work employs the element- and orbital-specific sensitivity of time-resolved and equilibrium resonant X-ray scattering to investigate electronic nematicity and charge density wave (CDW) order in cuprates. By probing their responses to photoexcitation using ultrafast laser pump-probe setups, varying hole doping levels, and applying compressive uniaxial stress, this thesis attempts to disentangle, understand, and manipulate intertwined phases in stripe-ordered cuprates
Symbols, Dynamics, and Maps: A Neurosymbolic Approach to Spatial Cognition
No full textThe discovery of various spatially sensitive neurons in the hippocampal formation, such as place, grid, and boundary cells, has provided valuable insights into the neural mechanisms underlying spatial representation and navigation. However, neural activity and connectivity data alone cannot fully reveal the brain’s algorithms. Bridging this gap requires computational models that not only explain the low-level activity of spatially sensitive cells but also link it to higher-level symbolic representations manipulable within a cognitive framework – models capable of binding spatial representations to discrete abstractions, while also supporting hierarchical and probabilistic structures that enable reasoning and decision-making.
The Semantic Pointer Architecture (SPA; Eliasmith, 2013), in combination with the Neural Engineering Framework (NEF; Eliasmith et al., 2003), provides a mathematical and computational framework to represent symbols and implement dynamical systems in spiking neural networks. Spatial Semantic Pointers (SSPs; Komer et al., 2019), an extension to the SPA, encode continuous variables, such as spatial locations, while supporting the binding of spatial information with other features – continuous or discrete – into compressed, multi-domain representations. This flexibility allows SSPs to model diverse cognitive processes, ranging from spatial memory to abstract reasoning, offering a unified theory for how continuous variables might be represented and manipulated in the brain.
In this thesis, we leverage these tools to model key components of spatial cognition, including path integration, cognitive map creation, and reinforcement learning. Our contributions include the development of SSP-PI, a SSP-based path integration model that combines velocity controlled oscillators with attractor dynamics to integrate continuous spatial variables. We also introduce SSP-SLAM, a biologically inspired spiking neural SLAM system capable of constructing semantic cognitive maps that bind and associate spatial and non spatial features. Furthermore, we propose spiking RL models that demonstrate how SSP embeddings can effectively represent successor features, reward distributions, and stochastic policies. Finally, we use the SPA and SSPs to construct state embeddings for deep RL networks, demonstrating their utility in tasks requiring mixed semantic-spatial representations.
Our findings underscore the potential of SSPs to act as a unifying framework for understanding spatial representation in the brain while advancing biologically inspired approaches to navigation and learning in artificial systems. This work bridges theoretical neuroscience and artificial intelligence, laying the groundwork for future explorations of shared principles across spatial and abstract cognition