Motor injuries, such as stroke and spinal cord injury, are some of the leading causes of long-term disability and death worldwide. Patients are often left behind with debilitating consequences, such as paralysis or severe motor impairments, creating an urgent need for new therapies to be developed. A treatment option that is gaining momentum is the use of electrical stimulation to strengthen neural pathways for improving motor function of affected individuals. Towards this goal, I have investigated a novel electrical-stimulation paradigm called movement-triggered theta-burst stimulation (MT-TBS) to modulate neuronal connectivity in the motor cortex of macaque monkeys. To implement MT-TBS, a monkey is trained to perform a target-tracking task that activates wrist muscles involved in flexion and extension. While the monkey performs the task, sites in the motor cortex associated with wrist flexion or extension simultaneously receive theta burst stimulation; hence the movement triggers stimulation of cortical sites in this closed-loop system. After receiving MT-TBS, monkeys continue to perform the same target-tracking task on the days following conditioning. Early results show that 50% larger gains in cortical connectivity can be achieved on the same day of conditioning with open-loop TBS. This may indicate that MT-TBS may be an even better method for strengthening connections in the motor cortex. For my research project, I investigated the effects of MT-TBS on changes in the strength of neuronal connections in the motor cortex when coupled with repetition of the conditioned movement in the days following stimulation. In a series of experiments, MT-TBS was delivered during flexion, extension and with the muscle at rest. If successful, pairing MT-TBS with physical rehabilitation will serve as an effective strategy for aiding individuals with motor impairments.

Spinal cord injury (SCI) affects the lives of over 294,000 individuals in the United States alone. Therefore, there is an urgency for development of therapies for SCI. We are exploring the role of environmental enrichment in promoting motor recovery from chronic cervical SCI that produces partial to complete forelimb paralysis in adult rats. Novelty, a major component of our environmental enrichment, has been associated with memory consolidation which could be related to the release of plasticity-related products (PRPs). PRPs are a key component of lasting plasticity changes in vitro, which could prove to be vital to motor learning after spinal cord injury. Throughout a 6-week therapy period during which the rats are exposed to environmental enrichment, motor function of the impaired forelimb is assessed using behavioral scores on a reach-and-grasp pellet-retrieval task. Our project will utilize environmental enrichment to enhance the effectiveness of our physical training paradigm. Environmental enrichment will include access to toys that provide opportunities for physical exercise, socialization, and social learning. The toys will be changed each week to promote novelty. We predict that environmental enrichment will have an additive effect in promoting recovery of the impaired forelimb when combined with physical therapy. We hope these results will help inform how neural plasticity can be deployed for design of effective therapies for promoting motor recovery after chronic SCI.

Spinal cord injury (SCI) is a debilitating condition that impairs motor function and overall quality of life. We have previously shown that Targeted Activity-Dependent Spinal Stimulation (TADSS) improves motor function in a rodent cervical SCI model. The hypothesized mechanism underlying TADSS is Spike-Timing Dependent Plasticity (STDP). During STDP, the strength of the synapse, or connection, between two neurons depends on the spiking behavior of a presynaptic neuron (A) relative to the postsynaptic neuron (B) within an optimal delay window. A synapse strengthens if A spikes less than 50 ms before B. Conversely, a synapse weakens if A fires less than 50 ms after B. It is currently unclear if TADSS strengthens corticospinal tract (CST) input into cervical spinal cord. In this project, we investigated the efficacy of TADSS therapy in inducing STDP in the rodent CST. TADSS therapy involved behavioral retraining of injured animals, with treated animals receiving concurrent spinal stimulation and control animals receiving no stimulation. In separate weekly sessions, the synaptic strength between motor cortex and spinal cord was assessed by measuring spinal cord evoked potentials (EPs) during test electrical stimulation. Test electrical stimulation involved current application to the forelimb region of motor cortex and recording of the EP response in cervical spinal cord caudal to the site of injury. After 3 weeks of TADSS, we observed larger EPs in TADSS animals and smaller EPs in injured control animals. In the weeks that followed, TADSS animals exhibited improved motor function while control animals exhibited declined motor function. Our results indicate increased connectivity between the motor cortex and spinal cord which precedes behavioral improvement -- this possibly suggests that strengthening the synaptic connectivity of the descending CST input to spinal cord is incorporated in the mechanism of TADSS-induced motor recovery.

Euler integration is the simplest, most versatile, and underappreciated method of integrating partial differential equations (PDEs) that only involves repeated addition. Evaluating the evolution of connected dynamical systems is critical to fundamental research as well as to students’ understanding of the physical world and their classwork. The purpose of this research is to design and implement an educational tool that empowers students and faculty to understand the beautiful simplicity of the most applicable method of evaluating PDEs on a computer. Physical law is always written in the form of a PDE. Traditional physics education does not emphasize this technique. This is largely due to the lack of computers over the last six hundred years. But now, we have super computational ability at our fingertips, and it is time that everyone in the field of physics has access to this versatile and simple tool. The first educational tool is complete and has already helped students learn about this technique. Over the next few months this tool and ones like it will be sewn into existing curricula in the physics department. This technique applies to an enormous range of disciplines from fungal growth to fluid dynamics and will be a skill at every student’s disposal.

Clouds, in general, are difficult to account for in climate and numerical weather prediction models. They represent a complex mix of radiative forcings that currently aren’t fully understood or quantifiable. Especially difficult are “mixed-phase” clouds: clouds that exist below the freezing temperature of water but are composed of both ice crystals (water in the solid phase) and supercooled liquid droplets (water in the liquid phase). Hence the name “mixed-phase”. While common, the formation of ice in these clouds remains poorly understood – further observations are vital for obtaining insight into this process. Fortunately, we have new measurements that can provide much-needed insight into their behavior. So far, I have been using measurements from the Department of Energy’s Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) atmospheric observatory on Graciosa Island in the Azores archipelago which is in the northeastern Atlantic Ocean west of Portugal. The observatory is an ideal site for analyzing these clouds for several reasons, but chief among them is its Raman lidar. By measuring a phenomenon called Raman scattering and utilizing algorithms developed by a previous UW graduate student Tyler Thorsen, this instrument can detect different cloud types and aerosol sizes with high confidence up to twenty kilometers into the atmosphere. I’ve been exploring this data using the programming language Python, looking for patterns in these clouds utilizing the ground-based ENA data and verifying my findings with the lidar on the NASA satellite Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The poster will explore how the phase of clouds over the Azores varies with season and with temperature.

The number of theoretical models for particle collisions has been steadily increasing, but creating and running a new program for each analysis is time-consuming. Often the individual steps in these analyses are applicable to a wide range of models. We created Recast-workflow, a project that preserves the steps in the analyses for truth-level reinterpretations (theoretically ideal models), as a solution to this issue. Developed as a Python3 package with a command line interface, this program generates runnable yadage workflows, defined by a yaml schema with instructions for running each step of the analysis. There are three main steps in a Recast workflow - generation, selection, and statistics. The generation step or “subworkflow” we implemented used MadGraph with Pythia, which takes a particle collision and uses a given model to generate the parton shower. We used Rivet, a software for validating data produced by Monte Carlo event generators, for the selection step and Contur or pyhf are the final steps we made to be used to find statistical confidence levels. Recast-workflow runs each stage using the yadage workflow engine in a docker encapsulated environment, and the output from each stage is passed to the subsequent one. This project will help researchers gauge the potential of interesting physics results from a region of phase space by running these generated workflows quickly without the computational complexity of a full reinterpretation. In the future, this can be made more accessible through a web interface and powerful through an expanded catalogue of steps.

Primates shift their line of sight using two types of eye movement. The first type, called saccades, is used to quickly bring an object of interest to the fovea. We use saccades to move our line of sight to the next words when we read. The second type is called smooth pursuit (SP). This movement smoothly tracks a moving object to keep it on the fovea. In real life, saccades often must be coordinated with other saccades or other types of eye movements that intervene between the programming and execution of a saccade. Such interruptions dissociate the vector of the saccade to be executed from its retinotopic target vector. The brain must update the vector of the upcoming saccade by combining the retinotopic target vector with information about the intervening movement. Many studies confirm that when the intervening movement is a saccade, the saccadic system compensated for the intervening movement so that the upcoming saccade reaches the target accurately. In my project, we used SP as the intervening movement. We presented a laser target spot step-ramp stimulus (30-60°/s) for 125ms after a fixation period. At the end of the ramp, a target was flashed for 25ms at a distance of 5° or 10° from the gaze location. The target was turned OFF for 600ms after that. In the dark, the monkey responded by making a SP movement and followed by a saccade. We expected that the saccadic system would compensate for the displacement of the eyes caused by the SP to arrive at the flashed target location, but the saccades missed the target location by the amount of the SP displacements. We conclude that the saccadic system fails to update the spatial relation between the visual target and the eyes when a smooth pursuit movement distorts it.