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Association of olfactory learning with cuticular hydrocarbon discrimination in the ant Camponotus floridanus

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Communication amongst eusocial insect is key to their success. Ants rely on signaling to mediate many different functions within a colony such as policing and nest mate recognition. Camponotus floridanus uses chemosensory signaling in the form of cuticular hydrocarbons to

Communication amongst eusocial insect is key to their success. Ants rely on signaling to mediate many different functions within a colony such as policing and nest mate recognition. Camponotus floridanus uses chemosensory signaling in the form of cuticular hydrocarbons to regulate these functions. Each cuticular hydrocarbon profile contains numerous hydrocarbons, however it is yet to be seen if Camponotus floridanus can discriminate between linear hydrocarbons of similar length. Individual specimens were conditioned in three different ways: 5 conditioning with high concentration of sugar water (1;1 ratio), 1 conditioning with high concentration of sugar water, and 5 conditioning with low concentration of sugar water (1;4). Two linear hydrocarbons were use, C23 and C24, with C23 always being the conditioned stimulus. Specimens who were conditioned 5 times with high concentration of sugar water were the only group to show a significant response to the conditioned stimulus with a p-value of .008 and exhibited discrimination behavior 46% of the time. When compared 5 conditioning with high concentration to the other two testing conditioning groups, 1 conditioning with high concentration produced an insignificant p-value of .13 was obtained whereas when comparing it with 5 conditioning low concentration of sugar a significant p-value of .0132 was obtained. This indiciates that Camponotus floridanus are capable of discrimination however must be conditioned with high concentration of sugar water, while number of conditioning is insignificant.

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2014-05

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The Sensory Basis of Olfactory Detection in the Dampwood Termite, Zootermopsis Nevadensis

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ABSTRACT Communication is vital in the context of everyday life for all organisms, but particularly so in social insects, such as Z. nevadensis. The overall lifestyle and need for altruistic acts of individuals within a colony depends primarily on intracolony

ABSTRACT Communication is vital in the context of everyday life for all organisms, but particularly so in social insects, such as Z. nevadensis. The overall lifestyle and need for altruistic acts of individuals within a colony depends primarily on intracolony chemical communication, with a focus on odorants. The perception of these odorants is made possible by the chemoreceptive functions of sensilla basiconica and sensilla trichoid which exist on the antennal structure. The present study consists of both a morphological analysis and electrophysiological experiment concerning sensilla basiconica. It attempts to characterize the function of neurons present in sensilla basiconica through single sensillum recordings and contributes to existing literature by determining if a social insect, such as the dampwood termite, is able to perceive a wide spectrum of odorants despite having significantly fewer olfactory receptors than most other social insect species. Results indicated that sensilla basiconica presence significantly out-paced that of sensilla trichoid and sensilla chaetica combined, on all flagellomeres. Analysis demonstrated significant responses to all general odorants and several cuticular hydrocarbons. Combined with the knowledge of fewer olfactory receptors present in this species and their lifestyle, results may indicate a positive association between the the social complexity of an insect's lifestyle and the number of ORs the individuals within that colony possess.

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2015-05

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Repetitive mild traumatic brain injury induces ventriculomegaly and cortical thinning in juvenile rats

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Traumatic brain injury (TBI) most frequently occurs in pediatric patients and remains a leading cause of childhood death and disability. Mild TBI (mTBI) accounts for 70-90% of all TBI cases, yet its neuropathophysiology is still poorly understood. While a

Traumatic brain injury (TBI) most frequently occurs in pediatric patients and remains a leading cause of childhood death and disability. Mild TBI (mTBI) accounts for 70-90% of all TBI cases, yet its neuropathophysiology is still poorly understood. While a single mTBI injury can lead to persistent deficits, repeat injuries increase the severity and duration of both acute symptoms and long term deficits. In this study, to model pediatric repetitive mTBI (rmTBI) we subjected unrestrained juvenile animals (post-natal day 20) to repeat weight drop impact. Animals were anesthetized and subjected to sham or rmTBI once per day for 5 days. At 14 days post injury (PID), magnetic resonance imaging (MRI) revealed that rmTBI animals displayed marked cortical atrophy and ventriculomegaly. Specifically, the thickness of the cortex was reduced up to 46% beneath and the ventricles increased up to 970% beneath the impact zone. Immunostaining with the neuron specific marker NeuN revealed an overall loss of neurons within the motor cortex but no change in neuronal density. Examination of intrinsic and synaptic properties of layer II/III pyramidal neurons revealed no significant difference between sham and rmTBI animals at rest or under convulsant challenge with the potassium channel blocker, 4-Aminophyridine. Overall, our findings indicate that the neuropathological changes reported after pediatric rmTBI can be effectively modeled by repeat weight drop in juvenile animals. Developing a better understanding of how rmTBI alters the pediatric brain may help improve patient care and direct "return to game" decision making in adolescents.

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2014

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Genetic variations and associated electrophysiological and behavioral traits in children with childhood apraxia of speech

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Childhood Apraxia of Speech (CAS) is a severe motor speech disorder that is difficult to diagnose as there is currently no gold-standard measurement to differentiate between CAS and other speech disorders. In the present study, we investigate underlying biomarkers associated

Childhood Apraxia of Speech (CAS) is a severe motor speech disorder that is difficult to diagnose as there is currently no gold-standard measurement to differentiate between CAS and other speech disorders. In the present study, we investigate underlying biomarkers associated with CAS in addition to enhanced phenotyping through behavioral testing. Cortical electrophysiological measures were utilized to investigate differences in neural activation in response to native and non-native vowel contrasts between children with CAS and typically developing peers. Genetic analysis included full exome sequencing of a child with CAS and his unaffected parents in order to uncover underlying genetic variation that may be causal to the child’s severely impaired speech and language. Enhanced phenotyping was completed through extensive behavioral testing, including speech, language, reading, spelling, phonological awareness, gross/fine motor, and oral and hand motor tasks. Results from cortical electrophysiological measures are consistent with previous evidence of a heightened neural response to non-native sounds in CAS, potentially indicating over specified phonological representations in this population. Results of exome sequencing suggest multiple genetic variations contributing to the severely affected phenotype in the child and provide further evidence of heterogeneous genomic pathways associated with CAS. Finally, results of behavioral testing demonstrate significant impairments evident across tasks in CAS, suggesting underlying sequential processing deficits in multiple domains. Overall, these results have the potential to delineate functional pathways from genetic variations to the brain to observable behavioral phenotypes and motivate the development of preventative and targeted treatment approaches.

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2018

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Learning and retention of novel words in musicians and non-musicians: the impact of enriched auditory experience on behavioral performance and electrophysiologic measures

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Music training is associated with measurable physiologic changes in the auditory pathway. Benefits of music training have also been demonstrated in the areas of working memory, auditory attention, and speech perception in noise. The purpose of this study

Music training is associated with measurable physiologic changes in the auditory pathway. Benefits of music training have also been demonstrated in the areas of working memory, auditory attention, and speech perception in noise. The purpose of this study was to determine whether long-term auditory experience secondary to music training enhances the ability to detect, learn, and recall new words.

Participants consisted of 20 young adult musicians and 20 age-matched non-musicians. In addition to completing word recognition and non-word detection tasks, each participant learned 10 nonsense words in a rapid word-learning task. All tasks were completed in quiet and in multi-talker babble. Next-day retention of the learned words was examined in isolation and in context. Cortical auditory evoked responses to vowel stimuli were recorded to obtain latencies and amplitudes for the N1, P2, and P3a components. Performance was compared across groups and listening conditions. Correlations between the behavioral tasks and the cortical auditory evoked responses were also examined.

No differences were found between groups (musicians vs. non-musicians) on any of the behavioral tasks. Nor did the groups differ in cortical auditory evoked response latencies or amplitudes, with the exception of P2 latencies, which were significantly longer in musicians than in non-musicians. Performance was significantly poorer in babble than in quiet on word recognition and non-word detection, but not on word learning, learned-word retention, or learned-word detection. CAEP latencies collapsed across group were significantly longer and amplitudes were significantly smaller in babble than in quiet. P2 latencies in quiet were positively correlated with word recognition in quiet, while P3a latencies in babble were positively correlated with word recognition and learned-word detection in babble. No other significant correlations were observed between CAEPs and performance on behavioral tasks.

These results indicated that, for young normal-hearing adults, auditory experience resulting from long-term music training did not provide an advantage for learning new information in either favorable (quiet) or unfavorable (babble) listening conditions. Results of the present study suggest that the relationship between music training and the strength of cortical auditory evoked responses may be more complex or too weak to be observed in this population.

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2017

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Imaging and Targeting with Optics and Acoustics

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This thesis describes the development, characterization, and application of new biomedical technologies developed around the photoacoustic effect. The photoacoustic effect is defined as optical absorption-based generation of ultrasound and provides the foundation for a unique method of imaging and molecular

This thesis describes the development, characterization, and application of new biomedical technologies developed around the photoacoustic effect. The photoacoustic effect is defined as optical absorption-based generation of ultrasound and provides the foundation for a unique method of imaging and molecular detection. The range of applications of the photoacoustic effect have not yet been fully explored. Photoacoustic endoscopy (PAE) has emerged as a minimally invasive tool for imaging internal organs and tissues. One of the main themes of this dissertation involves the first reported dual-intrauterine photoacoustic and ultrasound deep-tissue imaging endoscope. This device was designed to enable physicians at the point-of-care to better elucidate overall gynecological health, by imaging the lining of the human uterus. Intrauterine photoacoustic endoscopy is made possible due to the small diameter of the endoscope (3mm), which allows for complete, 360-degree organ analysis from within the uterine cavity. In certain biomedical applications, however, further minimization is necessary. Sufficiently small diameter endoscopes may allow for the possibility of applying PAE in new areas. To further miniaturize the diameter of our endoscopes, alternative imaging probe designs were investigated. The proposed PAE architecture utilizes a hollow optical waveguide to allow for concentric guiding of both light and sound. This enables imaging depths of up to several millimeters into animal tissue while maintaining an outer diameter of roughly 1mm. In the final focus of this dissertation, these waveguides are further investigated for use in micropipette electrodes, common in the field of single cell electrophysiology. Pulsed light is coupled with these electrodes providing real-time photoacoustic feedback, useful in navigation towards intended targets. Lastly, fluorescence can be generated and collected at the micropipette aperture by utilizing an intra-electrode tapered optical fiber. This allows for a targeted robotic approach to labeled neurons that is independent of microscopy.

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2021

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Glycoside Hydrolase Gene Families Of Termite Hindgut Protists

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This project was completed to understand the evolution of the ability to digest wood in termite symbiotic protists. Lower termites harbor bacterial and protist symbionts which are essential to the termite ability to use wood as a nutritional source, producing

This project was completed to understand the evolution of the ability to digest wood in termite symbiotic protists. Lower termites harbor bacterial and protist symbionts which are essential to the termite ability to use wood as a nutritional source, producing glycoside hydrolases to break down the polysaccharides found in lignocellulose. Yet, only a few molecular studies have been done to confirm the protist species responsible for particular enzymes. By mining publicly available and newly generated genomic and transcriptomic data, including three transcriptomes from isolated protist cells, I identify over 200 new glycoside hydrolase sequences and compute the phylogenies of eight glycoside hydrolase families (GHFs) reported to be expressed by termite hindgut protists.

Of those families examined, the results are broadly consistent with Todaka et al. 2010, though none of the GHFs found were expressed in both termite-associated protist and non-termite-associated protist transcriptome data. This suggests that, rather than being inherited from their free-living protist ancestors, GHF genes were acquired by termite protists while within the termite gut, potentially via lateral gene transfer (LGT). For example one family, GHF10, implies a single acquisition of a bacterial xylanase into termite protists. The phylogenies from GHF5 and GHF11 each imply two distinct acquisitions in termite protist ancestors, each from bacteria. In eukaryote-dominated GHFs, GHF7 and GHF45, there are three apparent acquisitions by termite protists. Meanwhile, it appears prior reports of GHF62 in the termite gut may have been misidentified GHF43 sequences. GHF43 was the only GHF found to contain sequences from the protists not found in the termite gut. These findings generally all support the possibility termite-associated protists adapted to a lignocellulosic diet after colonization of the termite hindgut. Nonetheless, the poor resolution of GHF phylogeny and limited termite and protist sampling constrain interpretation.

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2019

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Micro-Scale In Vivo Human Electrophysiological Functional Connectivity During Simple Language Production and Parkinson’s Disease

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Information processing in the brain is mediated by network interactions between anatomically distant (centimeters apart) regions of cortex and network action is fundamental to human behavior. Disruptive activity of these networks may allow a variety of diseases to develop. Degradation

Information processing in the brain is mediated by network interactions between anatomically distant (centimeters apart) regions of cortex and network action is fundamental to human behavior. Disruptive activity of these networks may allow a variety of diseases to develop. Degradation or loss of network function in the brain can affect many aspects of the human experience; motor disorder, language difficulties, memory loss, mood swings, and more. The cortico-basal ganglia loop is a system of networks in the brain between the cortex, basal ganglia, the thalamus, and back to the cortex. It is not one singular circuit, but rather a series of parallel circuits that are relevant towards motor output, motor planning, and motivation and reward. Studying the relationship between basal ganglia neurons and cortical local field potentials may lead to insights about neurodegenerative diseases and how these diseases change the cortico-basal ganglia circuit. Speech and language are uniquely human and require the coactivation of several brain regions. The various aspects of language are spread over the temporal lobe and parts of the occipital, parietal, and frontal lobe. However, the core network for speech production involves collaboration between phonologic retrieval (encoding ideas into syllabic representations) from Wernicke’s area, and phonemic encoding (translating syllables into motor articulations) from Broca’s area. Studying the coactivation of these brain regions during a repetitive speech production task may lead to a greater understanding of their electrophysiological functional connectivity. The primary purpose of the work presented in this document is to validate the use of subdural microelectrodes in electrophysiological functional connectivity research as these devices best match the spatial and temporal scales of brain activity. Neuron populations in the cortex are organized into functional units called cortical columns. These cortical columns operate on the sub-millisecond temporal and millimeter spatial scale. The study of brain networks, both in healthy and unwell individuals, may reveal new methodologies of treatment or management for disease and injury, as well as contribute to our scientific understanding of how the brain works.

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2021