Master of Science, The Ohio State University, 2019, Vision Science

Intrinsically photosensitive retinal ganglion cells (ipRGCs) express melanopsin, a Gq-coupled photopigment, and these neurons exhibit sustained action potential firing in response to light. ipRGCs have primarily non-visual functions, including an influence on the pupillary light reflex (PLR) to which they contribute to sustained pupil constriction. Acetylcholine is released in the retina by starburst amacrine cells in response to retinal image motion, and can be stimulated by flickering light and moving gratings. Light with a flicker frequency range of 3-10 Hz, peaking near 6 Hz, is especially effective at evoking retinal acetylcholine release. It has been previously demonstrated that rat ipRGCs fire sustained action potentials in response to cholinergic agonists. Sustained ipRGC spiking was also evoked by 6 Hz flickering light, presented at an irradiance below melanopsin's activation threshold, mediated by a muscarinic acetylcholine receptor-mediated pathway. The purpose of this study is to evaluate human pupil responses during and after exposure to light of differing frequencies, hypothesizing that a 6 Hz flickering light will cause more sustained pupil constriction than other frequencies. Seven healthy subjects were exposed to blue (480 nm) and red (620 nm) light at different irradiances (1012 and 1010 photons/s/cm2) and frequencies (0, 0.1, 6 and 30 Hz) for five minutes. Light was presented to the dilated left pupil; the consensual response of the right pupil was recorded. Pupil constriction was normalized and compared amongst the different flicker frequencies within each wavelength and irradiance level. Pupil constriction during light exposure and pupil dilation after light offset were analyzed. For blue light at 1012 photons/s/cm2, the 6 Hz and 0.1 Hz light stimuli produced greater overall pupil constriction compared to the 30 Hz stimulus. For red light at 1012 photons/s/cm2, the 6 Hz and 0.1 Hz stimuli elicited greater overall pupil constriction relativ (open full item for complete abstract)

Committee: Andrew Hartwick OD, PhD (Advisor); Michael Earley OD, PhD (Committee Member); Donald Mutti OD, PhD (Committee Member) Subjects: Biochemistry; Neurobiology; Ophthalmology; Physiology

PhD, University of Cincinnati, 2019, Arts and Sciences: Biological Sciences

Divergent selective forces acting on populations as a result of varying ecological conditions, within the environments they inhabit, can lead to reproductive isolation and ultimately speciation. Host specialization in herbivorous insects provides a model to study this process as plants can vary in factors, such as abundance, flowering time, and diversity across an insect's geographic range and this variation acts as a selective pressure on an insect's ability to distinguish between available hosts. In recent years, multiple studies suggest that differences in volatile cues emitted by plants may result in differences in peripheral olfactory detection mechanisms that underlie variation in host preference behavior. The importance of this detection process, and its impacts on subsequent host preference behavior make it a useful model for examining mechanisms underlying adaptation to different ecological environments. This dissertation explores neurophysiological mechanisms, within the olfactory system, underlying host shift in cactophilic Drosophila. First, we examined variation in the olfactory system accompanying shifts to different host plants between two populations of Drosophila mojavensis, a species of fly consisting of four geographically isolated populations that each feed and breed on a different cactus species. We characterized the peripheral olfactory system and observed differences in the sensitivity and specificity of olfactory receptor neurons, as well as changes in their abundance between populations. Additionally, differential gene expression in members of the odorant receptor gene family was found between populations using RNA-seq. Variation in host plant availability and areas of host plant overlap exist within the D. mojavensis species range. Therefore, we next hypothesized that host plant availability would be associated with variation in neuronal response among localities within a given D. mojavensis population and that these differences would be as (open full item for complete abstract)

Committee: Stephanie Rollmann Ph.D. (Committee Chair); Elke Buschbeck Ph.D. (Committee Member); Brian Gebelein Ph.D. (Committee Member); Joshua Gross Ph.D. (Committee Member); John Layne Ph.D. (Committee Member) Subjects: Biology

MS, University of Cincinnati, 2017, Arts and Sciences: Biological Sciences

Distinct environmental conditions characterized by habitat, climate, resource availability, predation, and competition can result in the development of adaptive traits through natural selection. Divergence of adaptive traits can be seen in the olfactory systems of phytophagous insects with differing host plant preferences among conspecific populations. In this study, we examine the cactophilic fly, Drosophila mojavensis, which utilizes different host cacti across its range. Each cactus emits its own, unique composition of volatiles, which may serve as a primary sensory cue for host plant localization. Specifically, we study the olfactory system of these flies in attempts to elucidate mechanisms underlying the reported phenotypic divergence among populations. We observed variation in odor-evoked electrophysiological responses of acid and amine sensing olfactory sensory neurons (OSNs) of coeloconic sensilla across all sensillar types among populations. Additionally, we observed loss of expression an odorant receptor gene, Or35a in all four populations. Expansion to other Drosophila species revealed comparable absences in OSN responses to OR35a agonists in D. virilis and D. arizonae, suggesting a potential similar loss in gene expression as seen in D. mojavensis. Furthermore, responses of ac3 OSNs significantly differed to sixteen of the seventeen odorants tested across the four drosophilid species. Collectively, our results highlight evolution of acid and amine sensing in coeloconic sensilla through peripheral changes observed in Drosophila olfactory systems.

Committee: Stephanie Rollmann Ph.D. (Committee Chair); John Layne Ph.D. (Committee Member); Ann Marie Ray Ph.D. (Committee Member) Subjects: Evolution and Development

MS, University of Cincinnati, 2017, Engineering and Applied Science: Mechanical Engineering

Neurological data is the principal feedback for clinicians treating comatose patients in the Neuro-Intensive Care Unit (NICU), making this data critical in determining treatment, and hence patient outcomes. If this data is misinterpreted, patients can endure varying degrees of long term cognitive disabilities, or death. Therefore, understanding the signals themselves, their relationships to patient outcomes, and developing heterogeneous models for patient-specific modeling has become a key area of interest. This study has been conducted for 7 comatose patients, who have suffered traumatic brain injuries (TBI) and were treated in the University of Cincinnati's Neuro ICU Department. The primary signals of interest were 15 channels of cortical depth electroencephalogram (EEG) and intracranial pressure (ICP). Data was collected within 12 to 24 hours of injury and for 48 to 72 hours after, with intermittent gaps. The aim of this project was to investigate the existence of an EEG and ICP signal relationship, develop a biomedical data cleaning protocol for the inclusion of future signals and determine prominent ICP thresholds in relation to EEG variables. After extracting various EEG features such as energy in key sub bands, Hjorth parameters, wavelet features and time domain statistics, data was classified into different mean peak ICP threshold ranges. These feature data sets are then central to determining whether varying ICP changes can be quantified based on the cortical EEG recordings and whether a common data element can be identified for deeper understanding of these signal relationships. Long term, by realizing the complex causal relationships of neurological data, ICP may be assessed via surface EEG, eliminating the need to drill into the skull and its associated risks. Moreover, further neurophysiological brain mapping can create knowledge that can enable more informed decision-making in ICP-moderating intervention to reduce secondary brain injuries. The crit (open full item for complete abstract)

Committee: Jay Lee Ph.D. (Committee Chair); Brandon Foreman (Committee Member); Jay Kim Ph.D. (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 1987, Graduate School

Committee: Not Provided (Other) Subjects: Education

Doctor of Philosophy, The Ohio State University, 2016, Kinesiology

Traumatic musculoskeletal injury is associated with chronic functional deficits that may result from changes in brain function and structure. The neurological underpinnings of such maladaptive responses are unknown and clarification will likely require the use of multimodal neuroscientific techniques that perturb and measure brain activity with high temporal and spatial resolution. The purpose of this investigation was to produce a neurological map of knee function under resting and active conditions, including the identification of brain circuits affected by traumatic musculoskeletal injury. Twenty-three women (N=23, age 21±3yr, weight 65.8±8.8kg, height 165.2±6.2cm) volunteered to participate in a series of mixed methods experiments. Ten subjects experienced unilateral anterior cruciate ligament (ACL) rupture and reconstruction six months to five years prior to the study (3.1±1.1yr). Thirteen age-, height-, weight-, handedness-, and footedness-matched participants served as controls. The neurological basis of persistent functional deficits was examined on three separate occasions with transcranial magnetic stimulation, tests of physical performance, and functional magnetic resonance imaging. Comparisons of corticospinal, functional, and hemodynamic responses were made between the injured and uninjured leg of subjects with traumatic injury and controls with no history of lower body injury. At rest, leg injury was associated with a reduction in the excitability of the motor cortical circuits governing the injured leg. Injury was also associated with lower maximal force production in the injured leg and a reduction force asymmetry compared to controls. Altered sensorimotor functions included impaired development of fine motor skill and a trend of proprioceptive loss with increased reliance on visual inputs. Imagined use of the injured leg during a task that challenged executive function increased activity in the respective sensorimotor regi (open full item for complete abstract)

Committee: William Kraemer (Advisor); James Onate (Committee Member); Jeff Volek (Committee Member); Carl Maresh (Committee Member) Subjects: Anatomy and Physiology; Biology; Electromagnetism; Experiments; Health Sciences; Kinesiology; Medical Imaging; Neurobiology; Neurology; Neurosciences; Physical Therapy; Physiology; Psychobiology; Rehabilitation; Scientific Imaging; Sports Medicine

PHD, Kent State University, 2015, College of Arts and Sciences / School of Biomedical Sciences

Longenecker, Ryan J, Ph.D., December 2015 DIFFERENTIAL PATHOLOGIES RESULTING FROM SOUND EXPOSURE: TINNITUS VS HEARING LOSS (104 pp.)Director of Dissertation: Alexander V. Galazyuk, Ph.D. The first step in identifying the mechanism(s) responsible for tinnitus development would be to discover a neural correlate that is differentially expressed in tinnitus-positive compared to tinnitus negative animals. Previous research has identified several neural correlates of tinnitus in animals that have tested positive for tinnitus. However it is unknown whether all or some of these correlates are linked to tinnitus or if they are a byproduct of hearing loss, a common outcome of tinnitus induction. Abnormally high spontaneous activity has frequently been linked to tinnitus. However, while some studies demonstrate that hyperactivity positively correlates with behavioral evidence of tinnitus, others show that when all animals develop hyperactivity to sound exposure, not all exposed animals show evidence of tinnitus. My working hypothesis is that certain aspects of hyperactivity are linked to tinnitus while other aspects are linked to hearing loss. The first specific aim utilized the gap induced prepulse inhibition of the acoustic startle reflex (GIPAS) to monitor the development of tinnitus in CBA/CaJ mice during one year following sound exposure. Immediately after sound exposure, GIPAS testing revealed widespread gap detection deficits across all frequencies, which was likely due to temporary threshold shifts. However, three months after sound exposure these deficits were limited to a narrow frequency band and were consistently detected up to one year after exposure. This suggests the development of chronic tinnitus is a long lasting and highly dynamic process. The second specific aim assessed hearing loss in sound exposed mice using several techniques. Acoustic brainstem responses recorded initially after sound exposure reveal large magnitude deficits in all exposed mi (open full item for complete abstract)

Committee: Alexander Galazyuk Ph.D. (Advisor); Jeffrey Wenstrup Ph.D. (Committee Member); Yong Lu Ph.D. (Committee Member); Angelo DeLucia Ph.D. (Committee Member); Gary Koski Ph.D. (Committee Member) Subjects: Acoustics; Behavioral Sciences; Biomedical Research; Neurobiology; Neurosciences

Master of Science in Biomedical Engineering (MSBME), Wright State University, 2015, Biomedical Engineering

The biophysics of volume conduction that enable electrophysiological data acquisition also result in the mixing of data sources including possible, undesirable noise sources at the electrode interface. This work specifically focuses on improving the performance of the recursive least-squares (RLS) adaptive filtering method for removing eye movement artifact from the electroencephalogram. In biophysically-inspired simulated data, the RLS algorithm is verified to produce results that are inferior to extended infomax independent component analysis (ICA), the most widely used artifact correction approach in this problem space, due to its non-linear filter phase response and the presence of bidirectional contamination, or cross-talk, resultant of volume conduction in electroencephalographic data. The non-linear phase response of the RLS algorithm is mitigated by restricting its filter coefficients to form a linear phase, Type I finite impulse response filter. A reduced effect of cross-talk in RLS is achieved by filtering the reference noise input signal using a combination of non-local means weighting and Bayesian adaptive regression splines smoothing. When compared to extended infomax ICA, the modified RLS adaptive filtering approach meets or exceeds data source recovery accuracy while retaining highly desirable properties not afforded by blind source separation. These results support the use of a modified adaptive filtering approach for the near-ideal removal of eye artifact data from the electroencephalogram.

Committee: Ping He Ph.D. (Advisor); Julie Skipper Ph.D. (Committee Member); Nasser Kashou Ph.D. (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Biophysics; Engineering; Neurosciences

PhD, University of Cincinnati, 2002, Allied Health Sciences : Communication Sciences and Disorders

This project tests the hypothesis that full-term infants and toddlers who are deprived of oral feedings during the first 3-months (13 weeks) of life show altered physiologic responses to touch. Such children often suffer from Failure-to-Thrive of the "Mixed" type (MFTT). This hypothesis developed from a clinical conundrum—the frequent observation that although such infants may have a variety of medical diagnoses, they share a common profile of difficulty tolerating touch. Because normal oral feeding requires tolerance for the touch of a spoon or food in the mouth, along with the touch of a parent's arms, etc. touch intolerance can directly result in interference with oral feeding skills. The MFTT group of children also shares a clinical history of oral deprivation as a result of medically necessary tube feedings. Typically, this fact has not been considered significant within the medical profession. However, several converging lines of evidence in the literature of psychology, neurobiology and neonatology suggest that early oral deprivation can result in aberrant neurophysiological development. This study compares the responses to touch (firm pressure) of a group of MFTT children and a matched control group of children with a normal medical history. Children were examined for response to touch along a hierarchy of body points (e.g. legs, trunk, lips, etc.) and responses were assessed through state behavior changes and/or abnormal gag reflex responses. A chi-square analysis revealed that the group of MFTT children showed response patterns to firm pressure that significantly differed from the normal control group. These response patterns confirmed the original clinical observation and suggest that a history of early oral deprivation can result in aberrant response to touch. These findings have significant implications for the current understanding of physiologic development, the identification of specific behavioral manifestations within the feeding/swallowing populat (open full item for complete abstract)

Committee: Dr. Suzanne Boyce (Advisor) Subjects:

Master of Science in Bioengineering, University of Toledo, 2007, Bioengineering

The field of neuroscience has grown tremendously in the last twenty years due to advancements in instrumentation. It is now possible to electrically stimulate individual or groups of neurons, and record the results with electrodes and optical imaging techniques. Current methods to control instrumentation using waveform generation encounter many difficulties including cost, complexity, lack of customization, and multiple components to generate complex waveforms. Therefore, it would be advantageous to design a multichannel waveform generation device that can provide analog or digital signals with customizable on times, off times, delays, amplitudes, and number of cycles. A functional Direct Digital Synthesis (DDS) system was developed using a C programmed microcontroller. To begin, parameters were entered in Matlab, and microcontroller timers generated a TTL pulse using an internal oscillator to control the parameters of the waveform. An analog switch selected whether the signal entered a circuit to output a sine or square wave. If a sinusoid was selected the waveform was developed using a frequency divider and eighth order Bessel filter. The original digital or newly formed sine waves were amplitude adjusted using operational and programmable gain amplifiers. The signal was directed to the proper output channel by a set of eight analog switches addressed by a demultiplexer. This accuracy of the digital waveforms was compared with a function generator using an equal duty cycle with a range of times between 0.1ms and 1s, and the waveforms were found to be identical in timing characteristics and amplitude. The ability to generate irregular digital pulses was also tested, and the resolution was excellent over the same timing range. A sinusoid was generated using the Bessel filter and the signal was found to be clean and accurate in amplitude and frequency. The additional requirements of variable initial delay, finite number of pulses, and the ability to output from one o (open full item for complete abstract)

Committee: Scott Molitor (Advisor) Subjects:

Doctor of Philosophy, Case Western Reserve University, 2009, Neurosciences

The ability to recall information over a short period of time (working memory) is critically important for human cognition. The dominant model of working memory is persistent activity in subsets of neurons, but the cellular and circuit mechanisms underlying this activity are not known. Persistent activity in several cortical regions, including the dentate gyrus of the hippocampus (a region important for long-term memory formation) is apparent during working memory tasks in vivo. Using patch-clamp recordings in rat hippocampal slices, I found that dentate gyrus hilar cells become persistently active in vitro following brief perforant path inputs. Furthermore, when stimulating dentate gyrus inputs in multiple locations, activity recorded in small populations of hilar neurons is sufficiently unique to allow identification of the stimulus. In this thesis, I used electrophysiological and imaging methods to investigate the cellular basis of this persistent activity.I first examined whether persistent firing in mossy cells (the excitatory cells of the hilus) reflects reverberant activity among those neurons. I found that both mossy cells and hilar interneurons demonstrate marked target selectivity, with mossy cells almost never synapsing on other mossy cells and interneurons preferential contacting mossy cells over other interneurons by a ratio of 3:1. This connectivity is unlikely to support reverberance-based models of hilar persistent activity. Together with Phil Williams and Yuan Gao, I identified a new cell type (semilunar granule cells, SGCs) in the inner molecular layer of the dentate gyrus that have broad dendritic arbors and axon collaterals in the granule cell layer. SGCs enter states of prolonged depolarization following brief perforant path input while the nearby granule cells are strongly inhibited. Blockade of T-type calcium currents, or NMDA receptors, did not block synaptic transmission to the hilus but eliminated SGC plateau potentials and hilar persistent (open full item for complete abstract)

Committee: Ben Strowbridge (Advisor); Diana Kunze (Committee Chair); Lynn Landmesser (Committee Member); R. John Leigh (Committee Member); Chris Wilson (Committee Member) Subjects: Biomedical Research; Neurology