A recent theory of motor control, based on optimal feedback control, posits that voluntary motor behaviour involves the sophisticated manipulation of sensory feedback. Although this theory can explain how people move in the world, it does not specifically describe how this control process is implemented by the nervous system. In this thesis, we propose and explore one physiological implication of this theory. Specifically, we hypothesize that rapid feedback responses should possess the key functional attributes of voluntary control because these two systems share a common neural pathway through motor areas of cerebral cortex. Our first four studies were designed to elaborate the functional attributes of the long-latency stretch reflex, a fast feedback response which occurs 50-100ms following the mechanical stretch of a muscle. Consistent with our hypothesis, we found that the long-latency response possesses many attributes commonly reserved for voluntary control: the long-latency response is continuously modulated by subject intent (Chapter 2), it compensates for the size-recruitment principle of the motoneuron pool (Chapter 3) and it accounts for the mechanical properties of the upper-limb (Chapter 5). Further investigation revealed that the long-latency response can be decomposed into two functionally-independent processes (Chapter 4), and that one of these components contributes all of the sophistication observed in Chapters 2 and 3. The goal of our fifth study was to investigate the neural basis of the long-latency response (Chapter 6). Our results provide strong evidence from both single-neuron recordings in non-human primates and transcranial magnetic stimulation in humans that primary motor cortex, which is known to be a critical node for voluntary control, also contributes to the sophistication of the long-latency response. Taken together, the studies presented in this thesis demonstrate that the long- latency response possesses several functional attributes typically reserved for voluntary control and that this sophistication likely arises via a transcortical pathway through primary motor cortex. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2011-01-18 09:19:24.579

Patients with an impaired reflexive cough response are at increased risk of pneumonia. This study examined the correlation between cough sensitivity to citric acid and radiographic features of airway compromise. Eighty patients referred for a radiographic assessment of swallowing at an acute hospital over an 8-month period participated in the study. Nebulised citric acid diluted in 0.9% sodium chloride was inhaled through a facemask at four concentrations to assess cough sensitivity. These data were then compared to Penetration Aspiration Scale scores based on radiographic swallowing studies. There was a statistically significant correlation between cough response/lack of response and the radiographic features of airway compromise; that is, patients who had a weak or absent response to inhalation of citric acid were also likely to aspirate silently during radiographic assessment. Sensitivity for identifying absent cough was found to be high at all 4 concentrations (0.750, 0.833, 0.941, 1.000), however specificity was consistently quite low (0.344, 0.456, 0.238, 0.078). The significant findings of this research suggest that clinicians adopting cough reflex testing into their clinical practice will have a reliable screen for silent aspiration at bedside. Clinicians will be able to identify patients who require instrumental assessment and are at high risk of pneumonia. This will likely, in turn, decrease length and cost of hospital admissions as well as decrease aspiration pneumonia related morbidities.

Cough reflex testing (CRT) is used to assess the sensory and motor components of a reflexive cough. When used as an adjunct to the clinical swallowing evaluation, it has the potential to identify individuals who are more likely to aspirate silently in the event of aspiration. It is unknown how reliable clinicians are at interpreting cough responses and the factors that influence this reliability. Therefore, this study ascertained the reliability of Speech Language Therapists in interpreting cough responses in CRT and determined how sensory perception and training influence reliability. Additionally, the study determined a relative measure of CRT interpretation validity through a comparison with ‘expert’ consensus ratings. A total of 111 clinicians completed an online survey consisting of ratings of 30 audio-, visual- and audiovisual clips over three sessions, and a final questionnaire. Reliability was substantial (κ=.76) in rating for presence of cough but only fair (κ=.25) in rating for strength of cough. Clinicians used a variety of auditory and visual cues to assist in decision making. Training did not result in higher reliability. Ratings of individual clinicians were significantly associated with consensus ratings for presence of cough (p < 0.001) and strength of cough (p < 0.05). In summary, clinicians could reliably and accurately judge presence of cough response, but were poorer at rating the strength of cough.

During rhythmic arm cycling soleus H-reflex amplitudes are reduced by modulation of group Ia presynaptic inhibition (Frigon et al, 2004). This reflex suppression is graded with the frequency of arm cycling (Loadman & Zehr 2007; Hundza & Zehr 2009) and 0.8 Hz is the minimum frequency to significantly reduce the soleus H-reflex (Hundza & Zehr 2009). Despite the data on modulation of the soleus H-reflex amplitude induced by rhythmic arm cycling, comparatively little is known about the modulation of stretch reflexes due to remote limb movement. Therefore, the present study was intended to explore the effect of arm cycling on stretch and H-reflex amplitudes in the soleus muscle. In so doing, additional information on the mechanism of action during rhythmic arm cycling would be revealed. Although both reflexes share the same afferent pathway, we hypothesized that stretch reflex amplitudes would be less suppressed by arm cycling because they are less inhibited by presynaptic inhibition (Morita et al, 1998). Failure to reject this hypothesis would add additional strength to the argument that Ia presynaptic inhibition is the mechanism modulating soleus H-reflex amplitude during rhythmic arm cycling. Participants were seated in a customized chair with feet strapped to footplates. Three motor tasks were performed: static control trials and arm cycling at 1 and 2 Hz. Soleus H-reflexes were evoked using single 1 ms pulses of electrical stimulation delivered to the tibial nerve at the popliteal fossa. A constant M-wave and ~6% MVC activation of soleus was maintained across conditions. Stretch reflexes were evoked using a vibratory shaker (ET-126; Labworks Inc). The shaker was placed over the triceps surae tendon and controlled by a custom written LabView program (single sinusoidal pulse at 100Hz). Results demonstrated that rhythmic arm cycling that was effective for conditioning soleus H-reflexes did not show a suppressive effect on the amplitude of the soleus stretch reflex. We suggest this indicates that stretch reflexes are less sensitive to conditioning by rhythmic arm movement, as compared to H-reflexes, due to the relative insensitivity of Ia presynaptic inhibition. / Graduate

Thesis (M.Eng.). / Written for the Dept. of Biomedical Engineering. Title from title page of PDF (viewed 2009/06/17). Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 194-204).

Thesis (doctoral)--Universität Bern, 1960. / Includes bibliographical references.

Thesis (Ph. D.)--Drexel University, 2006. / Includes abstract and vita. Includes bibliographical references (leaves 127-162).

Universiẗat, Diss., 2001--Bonn.

Orientador: Donizeti Cesar Honorato / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-23T19:15:40Z (GMT). No. of bitstreams: 1 Leite_JulianaValeria_M.pdf: 641050 bytes, checksum: b62398f140661279efb6ea212dc9afcf (MD5) Previous issue date: 2013 / Resumo: A avaliação do nível de consciência faz parte da rotina da equipe multiprofissional que conduz pacientes em coma. Sinais que possam representar a melhora do nível de consciência destes pacientes são constantemente buscados. Atualmente sabe-se que alguns fatores, como por exemplo, a resposta motora na escala de coma de Glasgow (ECG) e a apresentação do reflexo fotomotor apresentam valor prognóstico, porém nenhum deles é relacionado diretamente ao despertar destes pacientes. O objetivo deste estudo foi o de relacionar a presença do reflexo de piscar à ameaça visual (RPAV), com o despertar de pacientes comatosos e evidenciar o seu valor prognóstico. Para tanto foi feito um estudo retrospectivo com os dados obtidos em prontuários do serviço de arquivos médicos do Hospital das Clínicas da Universidade Estadual de Campinas (HC-UNICAMP) de pacientes internados nas enfermarias de neurologia clinica e neurocirurgia entre os períodos de abril de 2005 a abril de 2010. Foram selecionados 975 prontuários correspondentes ao diagnóstico de traumatismo cranioencefálico e acidente vascular encefálico. Destes, foram selecionados 119 prontuários de pacientes que se enquadraram nos critérios de inclusão representados pela resposta motora menor ou igual a quatro na ECG na admissão hospitalar e a descrição do RPAV durante o período de internação sendo excluídos os pacientes com resposta motora na admissão hospitalar superior a quatro, que não apresentassem a descrição da avaliação do RPAV ou que tivessem patologias neurológicas associadas às mencionadas como fator de seleção para os prontuários. Foram analisados os dados relativos ao sexo, diagnóstico clínico, resposta motora isolada e ao Glasgow total na admissão e alta hospitalar, a apresentação do RPAV durante o período de internação e a evolução clínica do paciente que foi representada pelo despertar, traduzido pela resposta motora seis ou cinco na ECG, evolução ao estado vegetativo persistente e óbito. A análise estatística demonstrou através da análise de regressão logística univariada e multivariada com critério Stepwise de seleção de variáveis uma associação entre a apresentação positiva do RPAV durante o período de internação e o despertar dos pacientes estudados (p<0.001). Todos os 51 pacientes que apresentaram o reflexo despertaram enquanto os pacientes que não apresentaram o reflexo não despertaram, evoluindo ao estado vegetativo persistente (24 pacientes) ou ao óbito (44 pacientes). Os pacientes que apresentaram o reflexo positivo durante o período de internação apresentaram uma maior possibilidade de despertar (11.685.00 vezes maior) dos que não o apresentaram adotando-se o nível de significância para os testes estatísticos de 5%, ou seja, p<0.05. O presente estudo demonstrou que o RPAV apresenta valor prognostico, estando sua apresentação positiva diretamente associada ao despertar destes pacientes / Abstract: The level of consciousness assessment is part of the hospital routine in comatose patients. Signs that may indicate cognitive improvement in these patients are constantly searched. Nowadays it is kwon that some features represent prognostic value, however, none relates directly with awakening in coma patients. The main purpose of this study was to associate the presence of the blinking reflex as a response to a visual threat with awakening in coma patients. We reviewed medical records from University of Campinas Clinical Hospital from patients diagnosed with stroke and traumatic brain injury (TBI) who stayed in the hospital neurological ward from April 2005 to April 2010. We reviewed 975 medical records. 119 patients were included; on admission they presented a score four or less for motor response in Glasgow Coma Scale (GCS) and description RPVA during hospitalization, being excluded patients with diagnoses other than those cited and motor response at admission more than four, which did not present the description of the assessment the blinking reflex or had neurological pathologies associated with those mentioned as selection factor for records. We gathered information from the charts regarding sex, disease, GCS total score, GCS motor score on admission and discharge, the presence or absence of the blinking reflex and level of consciousness on discharge, characterized as awakening, persistent vegetative state or death. Statistical analysis demonstrated through the analysis of univariate and multivariate logistic regression with stepwise selection criterion variables of a direct association between a positive blinking reflex of to visual threat during the period of hospitalization awakening in our cohort (p<0.001) . All the 51 patients with a positive reflex awoke, while patients with a negative reflex don't awakening evolved to persistent vegetative state (24) or death (44). A positive blinking reflex to visual threat during hospitalization increases the chance of awakening by 11.685.00 times when compared with patients with a negative reflex. The blinking reflex as a response to a threat has great prognostic value while its positivity is directly associated with awakening in coma patients / Mestrado / Ciencias Biomedicas / Mestra em Ciências Médicas