<p>The problem of spatial disorientation during flight of aircraft is briefly described, as are definitions of the phenomenon. Traditional countermeasure efforts that are often directed towards changes in the central visual field are reconsidered in favour of presentation of information in the peripheral visual field. It is proposed to use optic flow to support spatial orientation, as well as to omit such information from the central visual field. An experiment was conducted, and results showed that forward visual flow gave very important spatial information. The flow could be cropped to a certain degree in the periphery (horizontally), as well as parts of the central presentation could be omitted without decreasing effects in the experiment. Implications relevant to possible implementations in aircraft are discussed.</p>

Made available in DSpace on 2014-06-11T19:22:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-06-28Bitstream added on 2014-06-13T19:08:25Z : No. of bitstreams: 1 menuchi_mrtp_me_rcla.pdf: 321486 bytes, checksum: eb28a1ece2b065e6d1f1861d4c4f8762 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Durante a locomoção, ocorre um padrão de movimento visual referido como um campo de fluxo óptico. Para explorar como os ajustamentos locomotores são influenciados por este padrão, um paradigma experimental foi desenvolvido para anular o fluxo óptico durante a locomoção e ultrapassagem de obstáculo. O objetivo deste estudo foi investigar a contribuição de amostragens visuais estáticas e dinâmica na locomoção e ultrapassagem de obstáculos de diferentes alturas. Dez indivíduos (23,4 l 1,28 anos de idade, de ambos os gêneros) foram convidados a andar sobre uma passarela e ultrapassar um de dois obstáculos personalizados (obstáculo alto = altura do joelho e obstáculo baixo = altura do tornozelo) posicionado a 5m do ponto de partida. Diodos emissores de luz foram afixados no 5º metatarso e face lateral do calcâneo em ambos os pés e suas trajetórias foram filmados por quatro filmadoras digitais posicionadas bilateralmente à passarela. Dois blocos de tentativas foram apresentados em função das condições de amostragens visuais. No primeiro bloco, 10 tentativas com amostragem visual dinâmica (iluminação normal) foram apresentadas. No segundo bloco de tentativas, duas condições de amostragens visuais estáticas foram apresentadas de forma aleatória por meio de uma luz estroboscópica (2 flashes/segundo e 4 flashes/segundo). A duração de cada flash não ultrapassou 16ms e forneceu apenas imagens estáticas do ambiente. A altura do obstáculo foi randomizada em cada bloco de tentativas. Cinco tentativas para cada condição foram coletadas, totalizando 30 tentativas por participante. Todas as imagens foram digitalizadas e reconstruídas no plano tri-dimensional. As variáveis dependentes na fase de aproximação (comprimentos dos dois passos anteriores à ultrapassagem) e na fase de ultrapassagem... / During locomotion, a pattern of visual motion referred as an optic flow field occurs. In order to explore how the locomotor adjustments are influenced by this pattern, an experimental paradigm was developed to remove the optic flow during locomotion and obstacle avoidance. The aim of this study was to investigate the contribution of the static and dynamic visual sampling on the locomotion and obstacle avoidance of different heights. Ten individuals (23.4 l 1.28 years of age, both genders) were invited to walk on a pathway and to avoid one out of two personalized obstacles (high obstacle = knee height and low obstacle = ankle height) positioned 5m from the starting position. Light emitting diodes were fixed on the fifth metatarsal and calcaneus lateral face in both feet and their trajectories were recorded by four digital cameras bilaterally positioned related to the pathway. Two trial blocks were presented depending of the visual sampling conditions. In the first block, 10 trials with visual dynamic sampling (normal light) were presented. In the second trial block, two conditions of the static visual sampling frequencies were presented in an randomized way by means of the stroboscopic light (2 flashes/second or 4 flashes/second). Each flash duration was about 16ms and provided only environmental static images. Obstacle height was randomized for each trial block. Five trials for each experimental condition were collected totalizing 30 trials for each participant. All images were digitalized and reconstructed in the 3D plane. Dependent variables in the approach phase (last two step lengths before crossing) and in the crossing phase (horizontal toe distance to the obstacle prior crossing, obstacle toe clearance and mean horizontal velocity for each foot) were selected. The results revealed differences... (Complete abstract, access undermentioned electronic address)

The problem of spatial disorientation during flight of aircraft is briefly described, as are definitions of the phenomenon. Traditional countermeasure efforts that are often directed towards changes in the central visual field are reconsidered in favour of presentation of information in the peripheral visual field. It is proposed to use optic flow to support spatial orientation, as well as to omit such information from the central visual field. An experiment was conducted, and results showed that forward visual flow gave very important spatial information. The flow could be cropped to a certain degree in the periphery (horizontally), as well as parts of the central presentation could be omitted without decreasing effects in the experiment. Implications relevant to possible implementations in aircraft are discussed.

Spatial navigation is a cognitive skill fundamental to successful interaction with our environment. Normal aging is associated with weaknesses in this skill, with severe deficits in the context of Alzheimer's disease. Identifying mechanisms underlying how the aged brain navigates is important to understanding these age-related weaknesses and potentially strengthening or preserving spatial navigation ability in the aging population. One understudied aspect of spatial navigation is self-motion perception. Important to self-motion perception is optic flow, which is the pattern of visual motion experienced while moving through our environment. Several brain regions are optic flow-sensitive (OF-sensitive), responding more strongly to optic flow than other types of visual motion. The goal of the experiments in this dissertation was to examine the role of visual motion perception and cortical motion area dynamics in spatial navigation in cognitively intact aged adults. Visual path integration tasks were used because they highlight the use of radial and translational optic flow to keep track of one’s position and orientation, respectively. In the first experiment, a positive relationship between radial optic flow sensitivity and visual path integration accuracy that was stronger in aged adults was found. In the second experiment, brain activity was measured using functional magnetic resonance imaging (fMRI) while participants performed visual path integration (VPI) and turn counting (TC) tasks. Stronger activity in the OF-sensitive regions LMT+ and RpVIP during VPI, not TC, was associated with greater VPI accuracy in aged adults. In the third experiment, the functional connectivity between OF-sensitive regions and the rest of the brain during the VPI and TC tasks was measured using fMRI. Stronger average functional connectivity between the OF-sensitive regions LMT+, RMT+, LpVIP, RpVIP, LpV6 and right supramarginal gyrus and posterior cingulate during VPI, not TC, was associated with greater VPI task accuracy in aged adults. The results demonstrate novel relationships between visual path integration accuracy and radial motion perception, the response of OF-sensitive cortical regions during visual navigation, and the interaction strength between OF-sensitive regions and parietal cortex during visual navigation in aged adults. This work expands our knowledge of mechanisms underlying spatial navigation processes in the aged human brain.

Path integration is a navigational process that humans and animals use to track changes in their position and orientation. Animal and computational studies suggest that a spatially-tuned navigation system supports path integration, yet this system is not well understood in humans. Here, the prediction was tested that path integration mechanisms and goal-directed navigation in humans would recruit the same key brain regions within the parietal cortex and medial temporal lobes as predicted by animal and computational models. The three experiments described in this dissertation used behavioral and functional magnetic resonance imaging methods in 131 adults (18-35 years) to examine behavioral and brain correlates of navigation. In a landmark-free environment, path integration mechanisms are utilized to update position and orientation to a goal. Experiment 1 examined neural correlates of these mechanisms in the human brain. The results demonstrated that successful first and third person perspective navigation recruited the anterior hippocampus. The posterior hippocampus was found to track distance and temporal proximity to a goal location. The retrosplenial and posterior parietal cortices were additionally recruited for successful goal-directed navigation. In a landmark-rich environment, humans utilize route-based strategies to triangulate between their position, landmarks, and navigational goal. Experiment 2 contrasted path integration and landmark-based strategies by adding a solitary landmark to a sparse environment. The results demonstrated that successful navigation with and without an orienting landmark recruited the anterior hippocampus. Activity in the bilateral posterior hippocampus was modulated by larger triangulation between current position, landmark, and goal location during first person perspective navigation. The caudate nucleus was additionally recruited for landmark-based navigation. Experiment 3 used functional connectivity methods coupled with two fMRI tasks to determine whether areas responsive to optic flow, specifically V3A, V6, and the human motion complex (hMT+), are functionally connected to brain regions recruited during first person perspective navigation. The results demonstrated a functional relationship between optic flow areas and navigationally responsive regions, including the hippocampus, retrosplenial, posterior parietal, and medial prefrontal cortices. These studies demonstrate that goal-directed navigation is reliant upon a navigational system supported by hippocampal position computations and orientation calculations from the retrosplenial and posterior parietal cortices.

Self-motion perception is based on the integration of visual (optic flow) and vestibular (inertial) sensory information. Previous research has shown that the relative contribution of visual and vestibular cues can change in real time based on the reliability of that information. The present study assessed whether initial velocity and acceleration magnitude influence the relative contribution of these cues to the detection of self-acceleration. Participants performed a simple response time task with visual and vestibular self-acceleration cues as targets. Visual optic flow was presented at three possible initial velocities of 3, 9, or 15 m/s, and accelerated to result in three possible final velocities of 21, 27, or 33 m/s. Corresponding vestibular cues were presented at magnitudes between 0.01 and 0.04 g. The self-acceleration cues were presented at three possible stimulus onset asynchronies (SOAs): visual-first (by 100 ms), in-sync, and vestibular-first (by 100 ms). We found that presenting the cues in-sync resulted in the fastest responses across all velocities and acceleration magnitudes. Interestingly, presenting the visual cue first resulted in a relative advantage over vestibular-first at the slowest initial velocity of 3 m/s, and vice versa for the fastest initial velocity of 15 m/s. The fastest overall responses for visual-first and in-sync were observed at 9 m/s. The present results support the hypothesis that velocity of optic flow can alter the relative contribution of visual and vestibular cues to the detection of self-acceleration. / Thesis / Master of Science (MSc) / This thesis contributes valuable insight into the emerging literature on how visual and vestibular cues are integrated to result in reliable self-motion perception. Specifically, this thesis provides evidence that velocity of optic flow plays an important role in mediating the relative weighting of visual and vestibular cues during acceleration perception.

The quadrotor helicopter is a unique flying vehicle which uses the thrust from four motors to provide hover flight capability. The uncoupled nature of the longitudinal and lateral axes and its ability to support large payloads with respect to its size make it an attractive vehicle for autonomous vehicle research. In this thesis, the quadrotor is modeled based on first principles and a proportional-derivative control method is applied for attitude stabilization and position control. A unique means of using an optic flow sensor for velocity and position estimation in an indoor setting is presented with flight results. Reliable hover flight and hallway following capabilities are exhibited in GPS-denied indoor flight using only onboard sensors. Attitude angles can be reliably estimated in the short run by integrating the angular rates from MEMS gyros, but noise on the signal leads to drift which renders the measurement unsuitable to attitude estimation. Typical methods of providing vector attitude corrections such as accelerometers and magnetometers have inherent weaknesses on hovering vehicles. Thus, an additional vector measurement is necessary to correct attitude readings for long-term flights. Two methods of using image processing to determine vanishing points in a hallway are demonstrated. The more promising of the two uses a Hough transform to detect lines in the image and forms a histogram of the intersections to detect likely vanishing point candidates. Once the vanishing point is detected, it acts as a vector measurement to correct attitude estimates on the quadrotor vehicle. Results using onboard vision to estimate heading are demonstrated on a test stand. Together, these capabilities improve the utility of the quadrotor platform for flight without the need of any external sensing capability.

No description available.

<p>As an object approaches an observer’s eye, tau, defined as the inverse relative expansion rate of the object’s image on the retina (Lee, 1976) approximates time-to-collision (TTC). Many studies have suggested that human observers use TTC information, but evidence for the use of tau remains inconclusive. Here we present two studies that investigated the use of tau in object-motion and observer-motion situations. In Study I, we dissociated several monocular variables that potentially contributed to TTC perception, and found that participants were most sensitive to TTC information when performing a relative TTC estimation task; and less sensitive to non-time variables such as distance-to-collision, speed and object size. Additionally, when we manipulated sources of information to specify conflicting time-of-arrivals, TTC specified by tau was weighted more than TTC derived from distance and speed. Thus, we concluded that even in the presence of monocular depth information, observers strongly utilize tau when estimating TTC.</p> <p>In Study II, observers estimated TTC of a looming target in the presence or absence of background expansion. Results demonstrated that participants overestimated TTC in situations where the surroundings of the target’s contours expanded at a reduced rate. Moreover, simulated self-motion was unnecessary to induce this bias, as results were comparable in situations where this relative expansion was limited to the target’s immediate surroundings. Therefore, we also concluded that a relative tau variable, based on the relative rate of expansion, is utilized whenever expansion beyond the object’s immediate boundaries is less than the target’s absolute rate of expansion.</p> / Master of Science (MSc)

Microscopic video images of microcirculation have been used in clinical diagnosis for years, and theparameters obtained from images reveal most physiological activities and body organizations.Particularly, the blood flow speed is one of important indexes, which reflects the state ofmicrocirculation and make significant marks in diagnosis.In order to measure capillary blood velocity, a quantity of methods and instruments have beenstudied and developed. Based on the format of measurement, microscopy approaches used widely,can be grouped into two categories. One direct way applies microscopic-imaging technology forvisualization. The other way uses assistant methods such as laser-illumination [1] or labeling RBCswith fluorescein isothiocyanate [2]. In previous study, four methods (Direct Observation Method,Dual-windows Method, Single-window Method, Optical Flow Method) have been studied andanalysed in order to achieve better performance. But still there is a non-negligible deviation inmeasurement within different tries and compared to the data we retrieve from hospital.This study, inspired by previous work, aims to further investigate efficient and reliable algorithms forextracting capillary blood velocity. One possible solution is to implement feature based estimation tocalculate the blood flow speed distribution automatically, point by point along the middle line oftargeting blood vessel. We inherit the idea of generating motion vectors from Optic Flow algorithmwhich has the best accuracy performance in vehicle identification domain. But original optic flowalgorithm makes the system too sophisticated and time consuming. Moreover, its two required basicrules may not stand during the blood flow velocity detection. So a customized feature basedestimation is brought up here and supposed to be a practicable method for analysis not only inaccuracy but also in efficiency. Moreover, this report also introduces picture shifting, red blood cellmotion, and double windows marking to compare and to confirm the results. Previous work will beused as a reference for the assessment of new algorithms. / Mikroskopiska videobilder av mikrosirkulation har använts vid klinisk diagnos i flera år, och parametrarna erhållna från bilder avslöjar de flesta fysiologiska aktiviteter och kroppsorganisationer. Särskilt är blodflödeshastigheten ett av viktiga index, som återspeglar tillståndet för mikrosirkulation och gör betydande märken vid diagnosen.För att mäta kapillärblodshastighet har en mängd metoder och instrument studerats och utvecklats. Baserat på mätformatet kan mikroskopimetoder som används allmänt grupperas i två kategorier. Ett direkt sätt använder mikroskopisk bildteknologi för visualisering. Det andra sättet använder assistentmetoder som laserbelysning [1] eller märkning av RBC med fluoresceinisotiocyanat [2]. I tidigare studier har fyra metoder (Direct Observation Method, Dual-windows Method, Single-Window Method, Optical Flow Method) studerats och analyserats för att uppnå bättre prestanda. Men det finns fortfarande en icke försumbar avvikelse i mätningen inom olika försök och jämfört med de data vi hämtar från sjukhuset.Denna studie, inspirerad av tidigare arbete, syftar till att ytterligare undersöka effektiva och tillförlitliga algoritmer för att extrahera kapillärblodhastighet. En möjlig lösning är att implementera funktionsbaserad uppskattning för att beräkna blodflödeshastighetsfördelningen automatiskt, punkt för punkt längs mittlinjen för riktad blodkärl. Vi ärver idén att generera rörelsesvektorer från Optic Flow-algoritmen som har den bästa noggrannhetsprestanda inom fordonsidentifieringsdomän. Men den ursprungliga optiska flödesalgoritmen gör systemet för sofistikerat och tidskrävande. Dessutom kanske dess två nödvändiga grundregler inte gäller under detektionen av blodflödeshastighet. Så en anpassad funktionsbaserad uppskattning tas upp här och antas vara en genomförbar metod för analys inte bara i noggrannhet utan också i effektivitet. Dessutom introducerar detta papper också bildförskjutning, rörelse av röda blodkroppar och dubbla fönstermarkeringar för att jämföra och bekräfta resultaten. Tidigare arbete kommer att användas som referens förbedömning av nya algoritmer.