Página 1 dos resultados de 32 itens digitais encontrados em 0.003 segundos

Avaliação de diferentes topografias residuais na distribuição de tensões no remanescente dental por meio da análise de elementos finitos; Different residual topographic analysis in the distribution of tensions in the residual teeth by means of the finite element analysis

Vasco, Marco Antonio Amorim
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/12/2007 PT
Relevância na Pesquisa
16.07%
A presença de projeção dentinária acima da linha de término no preparo de dentes tratados endodônticamente para receber núcleos metálicos fundidos é bem fundamentada na literatura, influenciando positivamente na resistência da raiz. Entretanto, devido à destruição dental, nem sempre é possível atingir uma forma de projeção homogênea, contribuindo para deficiências no preparo que podem influenciar na resistência mecânica à fratura. Um incisivo central superior direito foi scaneado com tomografia computadorizada e reconstruído com software específico em um modelo virtual. Este modelo foi editado com diferentes projeções dentinárias, 2 mm acima da linha de término envolvendo projeções: ausente, total, vestibular, palatina e proximal e submetidas à simulação de uma carga mastigatória, no software Ansys Workbench v11, para avaliar a distribuição de tensões geradas no mesmo. As simulações demonstram que os melhores resultados foram obtidas com a projeção total, a projeção palatina obteve resultados muito próximos à total. O pior resultado foi da projeção ausente obtendo resultados muito próximos á projeção vestibular. Os autores nesta pesquisa concluíram que uma projeção dentinária entre o núcleo e a força aplicada é um importante fator para beneficiar a biomecânica do remanescente dental...

Efeito da escovação na formação in situ de biofilme dentário inicial e na rugosidade superficial em cerâmica de y-tzp após vitrificação e polimento

Pereira, Priscilla Cristoforides
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 100 f. : il.
POR
Relevância na Pesquisa
16.19%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Odontologia Restauradora - ICT; O objetivo deste estudo foi avaliar o efeito da vitrificação e do polimento na rugosidade superficial e formação in situ de biofilme dentário inicial, após simulação da escovação, em cerâmica policristalina de zircônia parcialmente estabilizada por ítrio (Cercon® Zirconia, Dentsply Ceramco). Amostras foram divididas em: (C) controle – sem tratamento; (V) vitrificadas; (PS) polidas com pontas de silicone diamantadas. Metade das amostras foi submetida à simulação de escovação (400.000 ciclos). Análises da rugosidade superficial (Ra e Rz) foram realizadas antes e após os tratamentos superficiais e escovação. Dez voluntários selecionados com adequado padrão de higiene bucal receberam dispositivos oclusais individualizados para a fixação das amostras na face vestibular. Após 8 horas em ambiente bucal, as amostras foram removidas do dispositivo e avaliadas em MEV (n=5) e MCVL (n=10). A análise em MEV foi realizada por meio da seleção aleatória de cinco campos (20 x 25 μm) para cada amostra para análise descritiva do material celular/acelular depositado e da topografia superficial. Para análise em MCVL...

Protocolo de modelagem tridimensional do primeiro pré-molar superior para o método dos elementos finitos e análise das concentrações de tensões na região cervical do esmalte

Silva, Adriana de Oliveira
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Tese de Doutorado Formato: 191 f. : il. color.
POR
Relevância na Pesquisa
16.36%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Ciências Odontológicas - FOAR; Este estudo objetivou a descrição de um protocolo para modelagem tridimensional de um primeiro pré-molar superior hígido para o método dos elementos finitos e a validação do modelo pela análise da distribuição de tensões de tração na região cervical do esmalte vestibular quando submetido à aplicação de cargas oclusais fisiológicas e não-fisiológicas, relacionando os resultados obtidos com os estudos dos mecanismos formadores das lesões de abfração descritos na literatura. Projetou-se anatomia das estruturas envolvidas a partir de referenciais arquitetônicos básicos da morfologia dental descritos na literatura científica. As dimensões anatômicas vestibular, oclusal e mesial do dente hígido e estruturas de suporte foram desenhadas em papel milimetrado, escaneados e com 3DSMax® -Autodesk, modelados tridimensionalmente. O modelo foi exportado para o NeiNastran® -Noran Engineering, Inc., onde foram definidas as propriedades das estruturas biológicas, além da geração da malha de elementos finitos e condições de contorno. Foi analisada a tensão tração presente no modelo de onde se concluiu que houve diferenças significativas na distribuição de tensão entre os grupos analisados. As simulações de oclusão não-fisiológica interferiram acentuadamente na distribuição de tensões quando comparados com a oclusão fisiológica...

Aminoglycoside Nephrotoxicity: Modeling, Simulation, and Control

Rougier, Florent; Claude, Daniel; Maurin, Michel; Sedoglavic, Alexandre; Ducher, Michel; Corvaisier, Stéphane; Jelliffe, Roger; Maire, Pascal
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /03/2003 EN
Relevância na Pesquisa
25.99%
The main constraints on the administration of aminoglycosides are the risks of nephrotoxicity and ototoxicity, which can lead to acute, renal, vestibular, and auditory toxicities. In the present study we focused on nephrotoxicity. No reliable predictor of nephrotoxicity has been found to date. We have developed a deterministic model which describes the pharmacokinetic behavior of aminoglycosides (with a two-compartment model), the kinetics of aminoglycoside accumulation in the renal cortex, the effects of aminoglycosides on renal cells, the resulting effects on renal function by tubuloglomerular feedback, and the resulting effects on serum creatinine concentrations. The pharmacokinetic parameter values were estimated by use of the NPEM program. The estimated pharmacodynamic parameter values were obtained after minimization of the least-squares objective function between the measured and the calculated serum creatinine concentrations. A simulation program assessed the influences of the dosage regimens on the occurrence of nephrotoxicity. We have also demonstrated the relevancy of modeling of the circadian rhythm of the renal function. We have shown the ability of the model to fit with 49 observed serum creatinine concentrations for a group of eight patients treated for endocarditis by comparison with 49 calculated serum creatinine concentrations (r2 = 0.988; P < 0.001). We have found that for the same daily dose...

Marker Entry into Vestibular Perilymph via the Stapes Following Applications to the Round Window Niche of Guinea Pigs

Salt, Alec N.; King, Elisha B.; Hartsock, Jared J.; Gill, Ruth M.; O’Leary, Stephen J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.07%
It has been widely believed that drug entry from the middle ear into perilymph occurs primarily via the round window (RW) membrane. Entry into scala vestibuli (SV) was thought to be dominated by local, inter-scala communication between scala tympani (ST) and SV through permeable tissues such as the spiral ligament. In the present study, the distribution of the ionic marker trimethylphenylammonium (TMPA) was compared following intracochlear injections or applications to the RW niche, with or without occlusion of the RW membrane or stapes area. Perilymph TMPA concentrations were monitored either in real time with TMPA-selective microelectrodes sealed into ST and SV, or by the collection of sequential perilymph samples from the lateral semi-circular canal. Local inter-scala communication of TMPA was confirmed by measuring SV and ST concentrations following direct injections into perilymph of ST. Application of TMPA to the RW niche also showed a predominant entry into ST, with distribution to SV presumed to occur secondarily. When the RW membrane was occluded by a silicone plug, RW niche irrigation produced higher concentrations in SV compared to ST, confirming direct TMPA entry into the vestibule in the region of the stapes. The proportion of TMPA entering by the two routes was quantified by perilymph sampling from the lateral semi-circular canal. The TMPA levels of initial samples (originating from the vestibule) were markedly lower when the stapes area was occluded with silicone. These data were interpreted using a simulation program that incorporates all the major fluid and tissue compartments of the cochlea and vestibular systems. From this analysis it was estimated that 65 % of total TMPA entered through the RW membrane and 35% entered the vestibule directly in the vicinity of the stapes. Direct entry of drugs into the vestibule is relevant to inner ear fluid pharmacokinetics and to the growing field of intratympanic drug delivery.

Modeling direction discrimination thresholds for yaw rotations around an earth-vertical axis for arbitrary motion profiles

Soyka, Florian; Giordano, Paolo Robuffo; Barnett-Cowan, Michael; Bülthoff, Heinrich H.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
16.07%
Understanding the dynamics of vestibular perception is important, for example, for improving the realism of motion simulation and virtual reality environments or for diagnosing patients suffering from vestibular problems. Previous research has found a dependence of direction discrimination thresholds for rotational motions on the period length (inverse frequency) of a transient (single cycle) sinusoidal acceleration stimulus. However, self-motion is seldom purely sinusoidal, and up to now, no models have been proposed that take into account non-sinusoidal stimuli for rotational motions. In this work, the influence of both the period length and the specific time course of an inertial stimulus is investigated. Thresholds for three acceleration profile shapes (triangular, sinusoidal, and trapezoidal) were measured for three period lengths (0.3, 1.4, and 6.7 s) in ten participants. A two-alternative forced-choice discrimination task was used where participants had to judge if a yaw rotation around an earth-vertical axis was leftward or rightward. The peak velocity of the stimulus was varied, and the threshold was defined as the stimulus yielding 75 % correct answers. In accordance with previous research, thresholds decreased with shortening period length (from ~2 deg/s for 6.7 s to ~0.8 deg/s for 0.3 s). The peak velocity was the determining factor for discrimination: Different profiles with the same period length have similar velocity thresholds. These measurements were used to fit a novel model based on a description of the firing rate of semi-circular canal neurons. In accordance with previous research...

A Methodology for Detecting Field Potentials from the External Ear Canal: NEER and EVestG

Lithgow, Brian
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
16.17%
An algorithm called the neural event extraction routine (NEER) and a method called Electrovestibulography (EVestG) for extracting field potentials (FPs) from artefact rich and noisy ear canal recordings is presented. Averaged FP waveforms can be used to aid detection of acoustic and or vestibular pathologies. FPs were recorded in the external ear canal proximal to the ear drum. These FPs were extracted using an algorithm called NEER. NEER utilises a modified complex Morlet wavelet analysis of phase change across multiple scales and a template matching (matched filter) methodology to detect FPs buried in noise and biological and environmental artefacts. Initial simulation with simulated FPs shows NEER detects FPs down to −30 dB SNR (power) but only 13–23% of those at SNR’s <−6 dB. This was deemed applicable to longer duration recordings wherein averaging could be applied as many FPs are present. NEER was applied to detect both spontaneous and whole body tilt evoked FPs. By subtracting the averaged tilt FP response from the averaged spontaneous FP response it is believed this difference is more representative of the vestibular response. Significant difference (p < 0.05) between up and down whole body (supine and sitting) movements was achieved. Pathologic and physiologic evidence in support of a vestibular and acoustic origin is also presented.

Vestibular Lesion-Induced Developmental Plasticity in Spinal Locomotor Networks during Xenopus laevis Metamorphosis

Beyeler, Anna; Rao, Guillaume; Ladepeche, Laurent; Jacques, André; Simmers, John; Le Ray, Didier
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 12/08/2013 EN
Relevância na Pesquisa
26.17%
During frog metamorphosis, the vestibular sensory system remains unchanged, while spinal motor networks undergo a massive restructuring associated with the transition from the larval to adult biomechanical system. We investigated in Xenopus laevis the impact of a pre- (tadpole stage) or post-metamorphosis (juvenile stage) unilateral labyrinthectomy (UL) on young adult swimming performance and underlying spinal locomotor circuitry. The acute disruptive effects on locomotion were similar in both tadpoles and juvenile frogs. However, animals that had metamorphosed with a preceding UL expressed restored swimming behavior at the juvenile stage, whereas animals lesioned after metamorphosis never recovered. Whilst kinematic and electrophysiological analyses of the propulsive system showed no significant differences in either juvenile group, a 3D biomechanical simulation suggested that an asymmetry in the dynamic control of posture during swimming could account for the behavioral restoration observed in animals that had been labyrinthectomized before metamorphosis. This hypothesis was subsequently supported by in vivo electromyography during free swimming and in vitro recordings from isolated brainstem/spinal cord preparations. Specifically...

Functional MR imaging of a simulated balance task

Karim, Helmet T.; Sparto, Patrick J.; Aizenstein, Howard J.; Furman, Joseph M.; Huppert, Theodore J.; Erickson, Kirk I.; Loughlin, Patrick J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
16.09%
Human postural control, which relies on information from vestibular, visual, and proprioceptive inputs, degrades with aging, and falls are the leading cause of injury in older adults. In the last decade, functional neuroimaging studies have been performed in order to gain a greater understanding of the supraspinal control of balance and walking. It is known that active balancing involves cortical and subcortical structures in the brain, but neuroimaging of the brain during these tasks has been limited. The study of the effect of aging on the functional neuroimaging of posture and gait has only recently been undertaken. In this study, an MRI-compatible force platform was developed to simulate active balance control. Eleven healthy participants (mean age 75 ± 5 yr) performed an active balance simulation task by using visual feedback to control anterior–posterior center of pressure movements generated by ankle dorsiflexor (DF) and plantarflexor (PF) movements, in a pattern consistent with upright stance control. An additional ankle DF/PF exertion task was performed. During both the active balance simulation and the ankle DF/PF tasks, the bilateral fusiform gyrus and middle temporal gyrus, right inferior, middle, and superior frontal gyrii were activated. No areas were found to be more active during the ankle DF/PF task when compared with the active balance simulation task. When compared to the ankle DF/PF task...

Interação entre as áreas funcionais do sistema visual e do sistema vestibular: estudo com RMF e EGV

Justina, Hellen Mathei Della
Fonte: Curitiba Publicador: Curitiba
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
36.47%
The static body equilibrium is controlled by three sensory systems: the vestibular system, responsible for informing the position and the movements of the head; the visual system, which informs the spatial objects position relative to the body; and the proprioceptive system, which controls posture and body movements. These three systems must always work in harmony, otherwise the individual will present balance problems. Thus, it is important to characterize the cortical regions, as well as their interactions, involved in this process. For this it is necessary to use functional neuroimaging techniques, the functional magnetic resonance imaging (fMRI) is one of the most used techniques in this field nowadays. However, a large fMRI experiments require the use of electronic devices for producing somatosensory stimulation in the human body, where the main difficulty is its hostile environment for electronic circuits. The galvanic vestibular stimulation is one of the most used methods to stimulate the vestibular system. This stimulation consist of applying a low current amplitude directly on vestibular afferents, which acts firing the primary vestibular neurons, affecting the otolithic afferents and the semicircular canals fibers. The objective of this work is to evaluate and analyze the brain areas involved with visual and galvanic vestibular stimulations and their interactions using fMRI. Therefore...

Efeito da simulação de perda óssea e contenção inter-dental na deformação do tecido de suporte: análise por extensometria

Soares, Priscilla Barbosa Ferreira
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
Relevância na Pesquisa
16.36%
Existem controvérsias em relação à influência da perda óssea e da contenção na deformação do tecido de suporte dental. O objetivo deste estudo foi analisar a influência da perda óssea e da contenção dental na deformação do tecido de suporte na região anterior da mandíbula em suas diferentes áreas. Oitenta dentes humanos (20 incisivos centrais, 20 incisivos laterais, 20 caninos, 20 primeiros pré-molares) hígidos foram selecionados e distribuídos aleatoriamente em 10 grupos. Para o ensaio de extensometria, em 10 réplicas de mandíbula em resina de poliestireno, 4 extensômetros foram fixados na região do incisivo central e lateral direito, sendo 2 na face vestibular e 2 na face lingual. Nos espécimes (n=10) foram, de forma seqüencial, aplicado as 7 condições experimentais de suporte dental: Cont, controle, sem alteração de normalidade; Po, simulando perda óssea de 5mm; PoRc, Po com contenção feita em resina composta de canino do lado direito a canino do lado esquerdo; PoFa, Po com contenção feita com fio de aço de 0,25mm; PoFaRc, Po com contenção feita com fio de aço de 0,25mm associado a resina composta; PoFvRcExt, Po com contenção realizada com fibra de vidro associado a resina composta extra-coronária e PoFvRcInt...

A LQR washout algorithm for a driving simulator equipped with a hexapod platform : the relationship of neuromuscular dynamics with the sensed illness rating

AYKENT, Baris; PAILLOT, Damien; MERIENNE, Frédéric; KEMENY, Andras
Fonte: Arts et Métiers ParisTech Publicador: Arts et Métiers ParisTech
EN
Relevância na Pesquisa
26.17%
This study proposes a method and an experimental validation to analyze dynamics response of the drivers with respect to the type of the control used in the hexapod driving simulator. In this article, two different forms of motion platform tracking control have been performed: - Classical motion cueing algorithm - LQR motion cueing algorithm For each situation, the EMG (electromyography) data have been registered from arm muscles of the drivers (flexor carpi radialis, brachioradialis). In addition, the acceleration based illness ratings (IR) have been computed. In order to process the data of the EMG and IR, the linear regression with a significance level of 0.05 has been assigned. Three cases have been evaluated: 1) Time exposure neuromuscular dynamics and vestibular–vehicle level conflict illness ratings 2) Time exposure neuromuscular dynamics and vestibular level sensed illness ratings 3) Impulse dynamics effect between the neuromuscular (EMG) and the vestibular dynamics (IR) The results have showed that: a) The vibration exposure condition: When the total RMS acceleration frequency weighted average IR increases, the EMG average total power increases too by driving the classical motion cueing algorithm. However, in contrast to this...

Modelling of the static and dynamic mechanical properties of human otoliths; Modellierung der statischen und dynamischen Eigenschaften menschlicher Otolithen

Jäger, Rudolf
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
26.43%
The aim of this study is a numerical investigation of the static and dynamic properties of the otoliths. The otoliths are a part of the vestibular system, located in the inner ears. They sense accelerations of the head. In the static case, information retrieved from them indicates the orientation of the head with respect to gravity. Under dynamic conditions, they provide information about the current direction and magnitude of head acceleration. Two important parts of the otoliths can be distinguished with respect to their function in the sensory apparatus, the otolith membrane and macula. The otolith membrane, a flat, layered filament structure is deformed by head accelerations. Though materials within the inner ear have similar densities, this membrane is subject to external accelerations because it contains higher density crystals, known as otoconia.The otolith macula contains hair cells, the sensory units of the otoliths. These cells feature small hair bundles which protrude into the otolith membrane, superimposed on the macula. If the membrane is deformed, the hair bundles are tilted and associated hair cells change their polarization. The resulting signal is subsequently reported to the brain. Up to now little work has been devoted to this sensory apparatus though it is known that it plays a important role within the vestibular system. The current investigation tries to improve the understanding of this structure by simulating the responses of the otolith membrane...

Human disorientation as a factor in spacecraft centrifuge design

Howse, Christopher E.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xvi, 128 p. : col. ill. ;
Relevância na Pesquisa
26.07%
Approved for public release, distribution is unlimited; Weightlessness is the major contributing factor behind the degradation of bone mass, muscle tone, and aerobic capacity during long-term space missions. With the loss of bone mass progressing at up to two percent per month, long duration and interplanetary missions shall remain the sole duty of robotic explorers until sufficient countermeasures are developed. Several countermeasures are either in use, or under development to alleviate this problem. Exercise is currently used to reduce the severity of bone loss and muscle atrophy. Exercise has proven ineffective despite the fact two hours of daily exercise together with elaborate apparatus have been devoted to simulating the load of Earth's gravity. Drug therapy and other, more exotic, countermeasures are also under consideration, but the side-effects of these other treatments and the fact that they do not directly address the root cause of the negative effects of weightlessness means that they may only reduce, not cure, those problems. Only artificial gravity addresses the root cause, weightlessness itself. This thesis addresses the need to balance the effects of Coriolis on human disorientation with the engineering costs of constructing a centrifuge for human occupation in space.; Lieutenant...

Simulation sickness comparison between a limited field of view virtual reality head mounted display (Oculus) and a medium range field of view static ecological driving simulator (Eco2)

AYKENT, Baris; YANG, Zhao; MERIENNE, Frédéric; KEMENY, Andras
Fonte: Society for Modeling & Simulation International Publicador: Society for Modeling & Simulation International
EN
Relevância na Pesquisa
46.36%
In this article, an experimental procedure is presented in order to evaluate the role of having HMD oculus and (Eco2 driving simulator) in terms of driving simulation sickness. The driving simulation sickness is investigated with respect to SSQ (simulator sickness questionnaire) and vestibular dynamics (head movements) of the driver participants for a specific driving scenario. The scenario of driving task is created by using open source “iiVR (institut image virtual reality)” software which is developed by Institut Image Arts et Métiers ParisTech. The experiments are executed in static mode for the driving simulators.

Motion sickness evaluation and comparison for a static driving simulator and a dynamic driving simulator

AYKENT, Baris; MERIENNE, Frédéric; GUILLET, Christophe; PAILLOT, Damien; KEMENY, Andras
Fonte: SAGE Publicador: SAGE
EN
Relevância na Pesquisa
26.3%
This paper deals with driving simulation and in particular with the important issue of motion sickness. The paper proposes a methodology to evaluate the objective illness rating metrics deduced from the motion sickness dose value and questionnaires for both a static simulator and a dynamic simulator. Accelerations of the vestibular cues (head movements) of the subjects were recorded with and without motion platform activation. In order to compare user experiences in both cases, the head-dynamics-related illness ratings were computed from the obtained accelerations and the motion sickness dose values. For the subjective analysis, the principal component analysis method was used to determine the conflict between the subjective assessment in the static condition and that in the dynamic condition. The principal component analysis method used for the subjective evaluation showed a consistent difference between the answers given in the sickness questionnaire for the static platform case from those for the dynamic platform case. The two-tailed Mann–Whitney U test shows the significance in the differences between the self-reports to the individual questions. According to the two-tailed Mann–Whitney U test, experiencing nausea (p = 0.019 < 0.05) and dizziness (p = 0.018 < 0.05) decreased significantly from the static case to the dynamic case. Also...

The Influence of the feedback control of the hexapod platform of the SAAM dynamic driving simulator on neuromuscular dynamics of the drivers

AYKENT, Baris; PAILLOT, Damien; MERIENNE, Frédéric; KEMENY, Andras
Fonte: INRETS Publicador: INRETS
EN
Relevância na Pesquisa
26.3%
Multi sensorial cues (visual, auditory, haptic, inertial, vestibular, neuromuscular) [Ang2] play important roles to represent a proper sensation (objectively) and so a perception (subjectively as cognition) in driving simulators. Driving simulator aims at giving the sensation of driving as in a real case. For a similar situation, the driver has to react in the same way as in reality in terms of ‘self motion’. To enable this behavior, the driving simulator must enhance the virtual immersion of the subject in the driving situation. The subject has to perceive the motion of his own body in the virtual scene of the virtual car as he will have in a real car. For that reason, restituting the inertial cues on driving simulators is essential to acquire a more proper functioning [Kol20]. Simulation sickness has been one of the main research topics for the driving simulators. It was assessed between dynamic and static simulators [Cur7], [Wat32]). For a braking maneuver, [Sie29] stated that if the motion platform is activated the bias in reaching increased levels of decelerations was reduced strongly comparing to inactivated platform case. However, there has been lack in publications of vehicle-vestibular cue conflict based illness rating approach and its correlation with the neuromuscular dynamics for that kind of research. In order to reduce the simulator sickness...

Influence of Inertial Stimulus on Visuo-Vestibular Cues Conflict for Lateral Dynamics at Driving Simulators

AYKENT, Baris; MERIENNE, Frédéric; PAILLOT, Damien; KEMENY, Andras
Fonte: OMICS Publishing Group Publicador: OMICS Publishing Group
EN_US
Relevância na Pesquisa
36.37%
Version éditeur de cet article : Aykent B, Merienne F, Paillot D, Kemeny A (2013) Influence of Inertial Stimulus on Visuo-Vestibular Cues Conflict for Lateral Dynamics at Driving Simulators. J Ergonomics 3: 113. doi:10.4172/2165-7556.1000113; This paper explains the effect of having an inertial stimulus (motion platform) for driving simulators on proximity to the reality for the sensed lateral dynamics with respect to the measurements and the perceptual fidelity using a questionnaire technique. To assess this objectively, the vestibular and vehicle level lateral accelerations (ay,sensed=ay_ vest, ayv =ay_veh ) were saved by using a motion tracking sensor and SCANeR studio software respectively. A confidence interval of 95% was chosen to test the correlations (Pearson’s correlation) and to fit models for the distributions of the visual-vestibular lateral accelerations with the multiple linear regression between the conditions of static (N=16) and dynamic (N=21) platform cases in terms of visuo-vestibular level lateral accelerations for the group of subjects (N=37). The results showed that the dynamic platform provides a higher lateral dynamics reality (positive correlation with an incidence of 90.48% for N=21) compared to the static configuration (negative correlation with an incidence of 50% for N=16) from Pearson’s correlation and a better fitted model and a lower visuo-vestibular cues’ conflict for the dynamic (R2 =0.429...

Model cerebellar granule cells can faithfully transmit modulated firing rate signals

Rössert, Christian; Solinas, Sergio; D'Angelo, Egidio; Dean, Paul; Porrill, John
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 13/10/2014 EN
Relevância na Pesquisa
16.17%
A crucial assumption of many high-level system models of the cerebellum is that information in the granular layer is encoded in a linear manner. However, granule cells are known for their non-linear and resonant synaptic and intrinsic properties that could potentially impede linear signal transmission. In this modeling study we analyse how electrophysiological granule cell properties and spike sampling influence information coded by firing rate modulation, assuming no signal-related, i.e., uncorrelated inhibitory feedback (open-loop mode). A detailed one-compartment granule cell model was excited in simulation by either direct current or mossy-fiber synaptic inputs. Vestibular signals were represented as tonic inputs to the flocculus modulated at frequencies up to 20 Hz (approximate upper frequency limit of vestibular-ocular reflex, VOR). Model outputs were assessed using estimates of both the transfer function, and the fidelity of input-signal reconstruction measured as variance-accounted-for. The detailed granule cell model with realistic mossy-fiber synaptic inputs could transmit information faithfully and linearly in the frequency range of the vestibular-ocular reflex. This was achieved most simply if the model neurons had a firing rate at least twice the highest required frequency of modulation...

Simulations of neuromuscular control in lamprey swimming.

Ekeberg, O; Grillner, S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 29/05/1999 EN
Relevância na Pesquisa
16.07%
The neuronal generation of vertebrate locomotion has been extensively studied in the lamprey. Models at different levels of abstraction are being used to describe this system, from abstract nonlinear oscillators to interconnected model neurons comprising multiple compartments and a Hodgkin-Huxley representation of the most relevant ion channels. To study the role of sensory feedback by simulation, it eventually also becomes necessary to incorporate the mechanical movements in the models. By using simplifying models of muscle activation, body mechanics, counteracting water forces, and sensory feedback through stretch receptors and vestibular organs, we have been able to close the feedback loop to enable studies of the interaction between the neuronal and the mechanical systems. The neuromechanical simulations reveal that the currently known network is sufficient for generating a whole repertoire of swimming patterns. Swimming at different speeds and with different wavelengths, together with the performance of lateral turns can all be achieved by simply varying the brainstem input. The neuronal mechanisms behind pitch and roll manoeuvres are less clear. We have put forward a 'crossed-oscillators' hypothesis where partly separate dorsal and ventral circuits are postulated. Neuromechanical simulations of this system show that it is also capable of generating realistic pitch turns and rolls...