Sarcopenia is a disease of muscle wasting primarily seen in older adults. Although this term was first coined over three decades ago, there is a lack of consensus on a definition, screening criteria, and treatment protocol for sarcopenia. The primary purpose of this study is to determine whether registered dietitian nutritionists (RDNs) in the United States (U.S.) screen for sarcopenia. Study participants were recruited through a randomized email list and included RDNs throughout the U.S. Respondents completed a survey questioning knowledge of sarcopenia, screening tools and company protocols in place, and the need and desire for sarcopenia education. Data revealed a lack of pre-existing protocols in place, a dissonance of validated and unvalidated screening tools used in practice, and substantial need for sarcopenia education.

Click-evoked otoacoustic emission (CEOAE) input/output (I/O) functions were measured in ears with normal hearing and in ears with sensorineural hearing loss above 2000 Hz. The low- to midfrequency CEOAEs obtained from the ears with high-frequency hearing loss were significantly reduced in level compared to the CEOAEs obtained from the ears with normal hearing even though there were no significant group differences in the 250-2000 Hz pure-tone thresholds. The findings are discussed within the context of two hypotheses that explain the low- to midfrequency reduction in transient-evoked otoacoustic emission (TEOAE) magnitude: (1) subclinical damage to the more apical regions of the cochlea not detected by behavioral audiometry, or (2) trauma to the basal region of the cochlea that affects the generation of low-frequency emissions. It is proposed that localized damage at basal cochlear sites affects the generation of low- to midfrequency CEOAE energy.

Synaptic plasticity—the ability of a synapse to change—is fundamental to basic brain function and behavioral adaptation. Studying the mechanisms of synaptic plasticity benefits our understanding of the formation of neuronal connections and circuitry, which has great implications in the field of learning and memory and the studies of numerous human diseases. The Drosophila larval neuromuscular junction (NMJ) system is a powerful system for studying synaptic plasticity. The NMJ consists of at least two different types of motorneurons innervating the body wall muscles. Type I motorneurons controls muscle contraction using glutamate as the neurotransmitter, while type II are modulatory neurons that contain octopamine. Octopamine is a potent modulator of behavior in invertebrates. Nevertheless, its function at the synapse is poorly understood. In my thesis research, I investigated the role of octopamine in synaptic plasticity using the Drosophila NMJ system. Preliminary observations indicate that increased larval locomotion during starvation results in an increase of filopodia-like structures at type II terminals. These structures, which we termed as “synaptopods” in our previous studies, contain synaptic proteins and can mature into type II synapses. I demonstrated that this outgrowth of type II terminals is dependent on activity and octopamine. Mutations and genetic manipulations affecting the production of octopamine decrease synaptopods, whereas increase of type II activity or exogenous application of octopamine increase synaptopods. Interestingly, I found that the type II octopaminergic neurons have an absolute dependence on activity for their innervation of the muscles. Blocking activity in these neurons throughout development results in no type II synapses at the NMJ, whereas blocking activity after the formation of synapses results in gradual degradation of type II terminals. Next, I examined the autoregulatory mechanism underlying the octopamine-induced synaptic growth in octopaminergic neurons. I discovered that this positive-feedback mechanism depends on an octopamine autoreceptor, Octß2R. This receptor in turn activates a cAMP- and CREB-dependent pathway that is required in the octopamine-induction of synaptopods. Furthermore, I demonstrated that this octopaminergic autoregulatory mechanism is necessary for the larva to properly increase its locomotor activity during starvation. Thirdly, I investigated the possibility that type II innervation might regulate type I synaptic growth through octopamine. We found that ablation, blocking of type II activity, or the absence of octopamine results in reduced type I outgrowth, and this paracrine signaling is mediated by Octß2R which is also present in type I motorneurons. Lastly, the function of another octopamine receptor, Octß1R, was examined. In contrast to Octß2R, Octß1R is inhibitory to synaptic growth. I demonstrated that the inhibitory effect of this receptor is likely accomplished through the inhibitory G-protein Goα. Similar to Octß2R, Octß1R also regulates the synaptic growth of both type I and type II motorneurons in a cell-autonomous manner. The inhibitory function of this receptor potentially breaks the positive feedback loop mediated by Octß2R, allowing the animal to reset its neurons when the environment is favorable. In summary, the research presented in this thesis has unraveled both autoregulatory and paracrine mechanisms in which octopamine modulates synaptic and behavior plasticity through excitatory and inhibitory receptors.

<p>Dedicated to the memory of Dr. Colin E. Webber</p> / <p>This comparative study of peripheral (p) QCT, high-resolution pQCT (hr-pQCT) and 1.0 Tesla pMRI technologies quantified short-term test-retest reproducibility, validity, one-year detection limit and clinical sensitivity of each modality’s derived bone measures. Select bone outcomes were evaluated from scans performed on Hamiltonian women above 50 years old and externally validated in a population-based cohort. In the local cohort (age: 74 ± 9 years and BMI 27.65 ± 5.74 kg/m²), Tb.Sp measured on pMRI, Ct.Th and vBMD from pQCT showed significant correlations (r²=0.52-0.85) with hr-pQCT, yielding slopes near unity. Bland-Altman analyses revealed significant relationships between pQCT and pMRI bone outcome values (Tb.Th(-), Tb.N(+), BV/TV(-)) and agreement with hr-pQCT. Short-term reproducibility was < 5% for pQCT but only BV/TV was < 5% for pMRI. Co-registration and excluding individuals with fractures mildly reduced precision error and one-year change. In the local cohort, only Ct.Th and cortical vBMD associated with fractures (OR: 1.09-3.28) using hr-pQCT, which was externally validated in the national cohort. Certain trabecular measures on pMRI and pQCT erred towards increased odds for fractures locally. For pQCT, these became significant in the national cohort (OR:1.04-3.81). This Canadian reference dataset for hr-pQCT showed larger Tb.Sp and smaller Tb.N compared to Americans but age-related decline in Ct.Th and BV/TV was faster in Europeans. This study demonstrated validity of pMRI and pQCT-derived volumetric bone outcomes and reasonable short- and long-term precision error for pQCT but not 1.0T pMRI. A single CT slice from pQCT was comparable to 110 slices from hr-pQCT in associations with fractures.</p> / Doctor of Philosophy (Medical Science)

No / PURPOSE: To estimate refractive indices used by the Lenstar biometer to translate measured optical path lengths into geometrical path lengths within the eye. METHODS: Axial lengths of model eyes were determined using the IOLMaster and Lenstar biometers; comparing those lengths gave an overall eye refractive index estimate for the Lenstar. Using the Lenstar Graphical User Interface, we noticed that boundaries between media could be manipulated and opposite changes in optical path lengths on either side of the boundary could be introduced. Those ratios were combined with the overall eye refractive index to estimate separate refractive indices. Furthermore, Haag-Streit provided us with a template to obtain 'air thicknesses' to compare with geometrical distances. RESULTS: The axial length estimates obtained using the IOLMaster and the Lenstar agreed to within 0.01 mm. Estimates of group refractive indices used in the Lenstar were 1.340, 1.341, 1.415, and 1.354 for cornea, aqueous, lens, and overall eye, respectively. Those refractive indices did not match those of schematic eyes, but were close in the cases of aqueous and lens. Linear equations relating air thicknesses to geometrical thicknesses were consistent with our findings. CONCLUSION: The Lenstar uses different refractive indices for different ocular media. Some of the refractive indices, such as that for the cornea, are not physiological; therefore, it is likely that the calibrations in the instrument correspond to instrument-specific corrections and are not the real optical path lengths.

In this paper, we investigate how controlled changes to image properties and orientation affect eye movements for repeated viewings of images of natural scenes. We make changes to images by manipulating low-level image content (such as luminance or chromaticity) and/or inverting the image. We measure the effects of these manipulations on human scanpaths (the spatial and chronological path of fixations), additionally comparing these effects to those predicted by a widely used saliency model (L. Itti & C. Koch, 2000). Firstly we find that repeated viewing of a natural image does not significantly modify the previously known repeatability (S. A. Brandt & L. W. Stark, 1997; D. Noton & L. Stark, 1971) of scanpaths. Secondly we find that manipulating image features does not necessarily change the repeatability of scanpaths, but the removal of luminance information has a measurable effect. We also find that image inversion appears to affect scene perception and recognition and may alter fixation selection (although we only find an effect on scanpaths with the additional removal of luminance information). Additionally we confirm that visual saliency as defined by L. Itti and C. Koch's (2000) model is a poor predictor of real observer scanpaths and does not predict the small effects of our image manipulations on scanpaths.

Objective: The primary purpose of this investigation was to determine the effect of multitalker babble on ASSRs in adult subjects with normal hearing (NH) and sensorineural hearing loss (HI). The secondary purpose was to investigate the relationships among ASSRs, word recognition in quiet, and word recognition in babble. Design: ASSRs were elicited by a complex mixed-modulation tonal stimulus (carrier frequencies of 500, 1500, 2500, and 4000 Hz; modulation rate of 40 or 90 Hz) presented in quiet and in babble. The level of each carrier frequency was adjusted to match the level of the multitalker babble spectrum, which was based on the long term speech spectrum average. Word recognition in noise (WIN) performance was measured and correlated to ASSR amplitude and ASSR detection rate. Study Sample: Nineteen normal-hearing adults and nineteen adults with sensorineural hearing loss were recruited. Results and Conclusions: The presence of babble significantly reduced the ASSR detection rate and ASSR amplitude for NH subjects, but had minimal effect on ASSRs for HI subjects. In addition, babble enhanced ASSR amplitude at high stimulus levels. ASSR detection rate and ASSR amplitude recorded in quiet and babble were significantly correlated with word recognition performance for NH and HI subjects. Sumario Objetivo: El objetivo fundamental de esta investigación fue determinar el efecto de balbuceo de hablantes múltiples en los ASSR de adultos jóvenes con audición normal (NH) y con pérdidas auditivas sensorineurales (HI). El objetivo secundario fue investigar las relaciones entre los ASSR, el reconocimiento de palabras en silencio y el reconocimiento de palabras con en medio de balbuceo. Diseño: Los ASSR fueron evocados por estímulo tonal de modulación mezclada compleja (frecuencias portadoras de 500, 1500, 2500 y 4000 Hz; tasa de modulación de 40 o 90 Hz) presentadas en silencio y con el balbuceo. Se ajustó el nivel de cada frecuencia portadora para emparejar el nivel del espectro del balbuceo de hablantes múltiples, el cual se basó en el promedio del espectro a largo plazo. Se midió el rendimiento para el reconocimiento de palabras en ruido (WIN) y se correlacionó con la amplitud de los ASSR y con la tasa de detección de los ASSR. Muestra Del Estudio: Se reclutaron diez y nueve adultos normoyentes y diez y nueve adultos con pérdida auditiva sensorineural. Resultados Y Conclusiones: La presencia del balbuceo reduce significativamente la tasa de detección de los ASSR y la amplitud de los ASSR en sujetos NH, pero tiene efectos mínimos en los ASSR de sujetos HI. Además, el balbuceo aumenta la amplitud de los ASSR con estímulos de niveles altos. La tasa de detección de los ASSR y la amplitud de los ASSR registrada en silencio y con balbuceo, fueron significativamente correlacionadas con el rendimiento para reconocer palabras en sujetos NH y HI.

Purpose: The purpose of this study was to evaluate the effectiveness of triaging patients with motion-provoked dizziness into a benign paroxysmal positional vertigo (BPPV) clinic. Method: A retrospective chart review was performed of veterans who were tested and treated for BPPV in a triaged BPPV clinic and veterans who were tested and treated for BPPV in a traditional vestibular clinic. Results: The BPPV triage clinic had a hit rate of 39%. On average, the triaged BPPV clinic reduced patient wait times by 23 days relative to the wait times for the traditional vestibular clinic while also reducing patient costs. Conclusion: Triaging patients with BPPV is one method to improve access to evaluation and treatment and a mechanism for the effective use of clinic time and resources.

Young adults are more likely to suffer blast injury and traumatic brain injury (TBI) than other age groups. This article reviews the literature on the vestibular consequences of blast exposure and TBI and concussion. In addition, the vestibular test findings obtained from 31 veterans with a history of blast exposure and/or mild TBI are presented. The authors discuss loss of horizontal semicircular canal function and postural instability related to head injury. Preliminary data suggest the novel theory that otolith organs are uniquely vulnerable to head injury and blast exposure.

Vestibular evoked myogenic potentials (VEMPs) are short-latency electromyograms evoked by high-level acoustic stimuli recorded from surface electrodes over the tonically contracted sternocleidomastoid (SCM) muscle. These responses are presumed to originate in the saccule. The purpose of this preliminary report is to provide an overview of our initial experience with the VEMP by describing the responses obtained in five subjects. Click-evoked VEMPs were present at short latencies in two normal-hearing subjects, one patient with profound congenital sensorineural hearing loss, and one patient with a severe sensorineural hearing loss due to Meniere's disease. Additionally, VEMPs were absent in a patient with profound sensorineural hearing loss following removal of a cerebellopontine angle tumor. The amplitude of the VEMP was influenced by the amount of background activity of the SCM muscle, stimulus level, and stimulus frequency. Tone-burst evoked responses showed an inverse relationship between stimulus frequency and response latency. VEMPs may prove to be a reliable technique in the clinical assessment of vestibular function.