Physiological Targets of Artificial Gravity: The Sensory-Motor System

This chapter describes the pros and cons of artificial gravity applications in relation to human sensory-motor functioning in space. Spaceflight creates a challenge for sensory-motor functions that depend on gravity, which include postural balance, locomotion, eye-hand coordination, and spatial orientation. The sensory systems, and in particular the vestibular system, must adapt to weightlessness on entering orbit, and again to normal gravity upon return to Earth. During this period of adaptation, which persists beyond the actual gravity-level transition itself the sensory-motor systems are disturbed. Although artificial gravity may prove to be beneficial for the musculoskeletal and cardiovascular systems, it may well have negative side effects for the neurovestibular system, such as spatial disorientation, malcoordination, and nausea

Physiologic responses to water immersion in man: A compendium of research

A total of 221 reports published through December 1973 in the area of physiologic responses to water immersion in man were summarized. The author's abstract or summary was used whenever possible. Otherwise, a detailed annotation was provided under the subheadings: (1) purpose, (2) procedures and methods, (3) results, and (4) conclusions. The annotations are in alphabetical order by first author; author and subject indexes are included. Additional references are provided in the selected bibliography

The vestibular system and human dynamic space orientation.

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. Thesis. 1965. Sc.D.Bibliography: leaves 178-192.Sc.D

Sensory and methodological aspects in biomechanical research of postural control and clinical fields of application

The human senses constitute a highly complex system based on various sensory organs, afferent pathways, and central processing locations, which allow us to interact with the environment, but also with ourselves. A further domain is important to achieve this interaction: the motor system, which allows linguistic communication and locomotion, for example. It becomes evident that sensory receptors work as a source of information to initiate, optimize, or cease motor activity. One generic term for such sensory sources is the somatosensory system, which is mainly based on receptors located in muscles, tendons, and the skin (cutaneous sensitivity). In this regard, it has been shown that cutaneous sensitivity contributes to human balance regulation. However, there are still debates concerning the exact role of plantar (foot sole) receptor inputs in particular, and how their isolated contribution to, e.g., balance regulation may be assessed accordingly. To investigate the interaction between plantar cutaneous sensitivity and human balance capabilities, several aspects need to be considered which are still controversial and inconclusive in the scientific community. For example, when assessing cutaneous vibration sensitivity, it is well-known that increasing vertical forces of the contactor toward the skin usually result in improved sensitivity. However, it has not been profoundly investigated whether assessing plantar vibratory sensitivity differs when comparing a standing or sitting posture, which obviously involves different contactor forces. In addition, many studies implementing cutaneous sensitivity show certain limitations with respect to adequate data analyses. A similar aspect also applies when assessing balance performance: devices allowing an investigation of dynamic balance performance (induced by unexpected platform perturbations while standing, for example) have only been partially investigated with regard to their biomechanical quality criteria, such as reliability. With these considerations in mind, the present doctoral thesis is based on five published studies. Study 1 investigates if plantar sensitivity is influenced by different body positions when collecting data. Study 2 asks how to appropriatly analze plantar sensitivity data. Study 3 examines the reliability of dynamic balance responses using the so-called Posturomed device, and Study 4 identifies the isolated role of plantar inputs on balance responses, when an acute sensory manipulation is induced that exclusively affects plantar aspects. Ultimately, clinical fields of application (based on the previous four studies) are highlighted in Study 5. The main findings of the first four studies can be summarized as follows. First, higher contact forces when standing compared to sitting did not influence plantar sensitivity. This is an important finding, as plantar sensitivity tests (often performed during sitting) may, hence, be brought into context with balance tests usually performed during standing. Second, plantar sensitivity data are shown to exhibit heteroscedasticity, meaning that the measurement error increases as the values increase. In Study 2, we provided an easy-to-follow example for how to account for heteroscedasticity by logarithmizing the raw data, and how to control whether this approach was successful in eliminating heteroscedasticity. Third, dynamic balance responses assessed via the Posturomed device exhibit an overall good reliability. Occasional significant differences were shown to be clinically non-relevant, identified by root mean square error calculations. Fourth, a permanent plantar sensory manipulation (hypothermia) was successfully achieved and maintained throughout data collection. Study 4 showed that the reduced plantar sensory input due to the hypothermic manipulation was compensated during more unchallenging balance conditions (standing still). There was no full compensation during more challenging balance conditions (unexpected platform perturbations during standing), however, with the body reacting with cautious motor behavior. This became evident by decreased outcome measures following hypothermic plantar sensory manipulation. These four studies shed further light onto investigations combining sensory and motor tests, especially with regard to physiological and methodological aspects that should be considered when analyzing and interpreting associated data. Finally, this doctoral thesis also provides an example of identifying clinical fields of application concerning sensory-focused research. In Study 5, we highlight the role of sensory research in the (early) diagnosis of diseases associated with cognitive decline. For this purpose, various instruments such as sensory tests or coordinative motor tests are implemented. Preliminary results suggest that not only classical cognitive parameters and questionnaires should be used to identify and better understand cognitive decline.Die menschlichen Sinne stellen ein sehr komplexes System dar, welches auf verschiedenen sensorischen Organen, afferenten Leitungsbahnen und zentralen Verarbeitungsstellen basiert und es uns ermöglicht, mit der Umwelt, aber auch mit uns selbst, zu interagieren. Dahingehend ist eine weitere wichtige Domäne wichtig, um diese Interaktion zu bewerkstelligen: das motorische System, welches etwa eine sprachliche Kommunikation oder auch die Fortbewegung ermöglicht. Es wird somit offensichtlich, dass sensorische Rezeptoren eine Informationsquelle darstellen, um motorische Aktivität zu initiieren, zu optimieren oder zu beenden. Ein grundlegender Terminus für solch sensorische Quellen ist das somatosensorische System, welches überwiegend auf Rezeptoren in Muskulatur, Sehnen und der Haut (kutane Sensibilität) beruht. Diesbezüglich wurde bereits aufgezeigt, dass die kutane Sensibilität einen Beitrag bei der menschlichen Gleichgewichtsregulation leistet. Allerdings existieren dabei nachwievor Diskussionen in Bezug auf die genaue Bedeutung plantarer (die Fußsohle betreffend) Rezeptor-Inputs und inwieweit deren isolierte Bedeutung bei der Gleichgewichtsregulation entsprechend ermittelt werden kann. Um die Interaktion zwischen der kutanen Sensorik der Fußsohle und der menschlichen Gleichgewichtsfähigkeit zu erforschen, sollten verschiedene Aspekte berücksichtigt werden, welche nachwievor kontrovers und nicht eindeutig in der Wissenschaft diskutiert werden. Bei Erhebungen der kutanen Vibrationssensibilität, als Beispiel, ist bereits bekannt, dass erhöhte Vertikalkräfte, mit denen der Vibrationsstößel gegen die Haut appliziert ist, generell zu einer verbesserten Sensibilität/Sensorik führen. Allerdings wurde noch nicht klar erforscht, ob sich die plantare Vibrationssensibilität zwischen einer stehenden und sitzenden Haltung der Probanden/innen unterscheidet, wobei hier natürlich unterschiedliche Vertikalkräfte der Stößel wahrscheinlich sind. Darüber hinaus zeigen viele Studien, welche die Hautsensibilität untersuchen, gewisse Limitierungen in Bezug auf eine adäquate Datenanalyse. Ein sehr ähnlicher Aspekt trifft auch auf die Evaluierung der Gleichgewichtsfähigkeit zu: Messgeräte, welche dabei eine Erfassung der dynamischen Gleichgewichtsfähigkeit zulassen (z.B. eingeleitet durch unerwartete Plattform-Perturbationen während des Stehens), wurden bisher nur teilweise auf die biomechanischen Gütekriterien hin untersucht, wie etwa die Reliabilität. Aufgrund dieser Überlegungen basiert die vorliegende Dissertation auf fünf publizierten Studien, welche folgende Aspekte untersuchten: Wird die plantare Sensibilität durch verschiedene Körperpositionen während der Datenaufnahme beeinflusst (Studie 1)? Wie können plantare Sensibilitätsdaten angemessen analysiert werden (Studie 2)? Darüber hinaus wurde ebenso untersucht, inwiefern das sogenannte 'Posturomed'-Messgerät bei der Beurteilung dynamischer Gleichgewichtsantworten reliable Messwerte liefert (Studie 3). Ferner wurde in Studie 4 untersucht, inwiefern isoliert plantare Inputsignale bei Gleichgewichtsantworten relevant sind (anhand einer akuten sensorischen Manipulation, welche ausschließlich die Fußsohle betrifft). In Studie 5 werden konkrete klinische Anwendungsbeispiele aufgrund der vier hier vorgestellten Studien aufgezeigt. Die Hauptergebnisse der ersten vier Studien können wie folgt zusammengefasst werden: Erstens, höhere vertikale Kontaktkräfte während des Stehens verglichen mit sitzenden Positionen führten zu keinen Unterschieden bzgl. der plantaren Sensibilität. Dies ist eine wichtige Erkenntnis, da plantare Sensorikmessungen (oft während des Sitzens durchgeführt) dadurch in Kontext mit Gleichgewichtstests gebracht werden können, welche normalerweise im Stehen erfolgen. Zweitens, Daten der plantaren Sensorik zeigten Heteroskedastizität, was bedeutet, dass sich der Messfehler mit Größenzunahme der Messwerte ebenso erhöht. Wir konnten in Studie 2 ein leicht zu erschließendes Beispiel aufzeigen, wie das Problem der Heteroskedastizität durch eine Logarithmierung der Rohdaten behandelt werden konnte und wie kontrolliert werden konnte, ob diese Behandlung erfolgreich war. Drittens, die dynamischen Gleichgewichtsantworten, welche mittels des 'Posturomed' ermittelt wurden, zeigen insgesamt eine gute Reliabilität. Gelegentlich auftretende signifikante Unterschiede wurden anhand von Berechnungen der Wurzel der mittleren Fehlerquadratsumme (root mean square error, RMSE) als klinisch nicht relevant eingestuft. Viertens, eine anhaltende plantar-sensorische Manipulation (Hypothermie) wurde erfolgreich eingeleitet und während der Datenerhebung aufrecht erhalten. Studie 4 zeigte ferner, dass die hypothermisch eingeleiteten reduzierten plantaren Sensorik-Inputs während der eher nicht herausfordernden quasi-statischen Gleichgewichtsbedingungen (einfaches aufrechtes Stehen) kompensiert werden konnten. Während der herausfordernden Gleichgewichtskonditionen (unerwartete Perturbationen der Plattform während des Stehens) hingegen wurde keine vollständige Kompensation erreicht. Allerdings reagierten die Probanden mit einem vorsichtigen motorischen Verhalten. Dies wurde durch die reduzierten Ergebnisparameter infolge der plantaren hypothermischen Manipulation ersichtlich. Die vier hier genannten Studien zeigen weitere Erkenntnisse in Bezug auf Forschungsaktivitäten, welche sensorische und motorische Tests vereinen. Dies trifft speziell in Hinblick auf physiologische und methodologische Aspekte zu, welche bei der Analyse und Interpretation derartiger Daten in Betracht gezogen werden sollten. Zuletzt bietet diese Arbeit auch ein Beispiel dafür, welche klinischen Anwendungsfelder im Bereich der sensorisch-fokussierten Forschung identifiziert werden können. In Studie 5 wird dafür die Bedeutung sensorischer Forschung bei der (Früh-) Diagnose von Erkrankungen aufgezeigt, welche mit kognitiven Einschränkungen in Verbindung gebracht werden. Für diesen Zweck werden verschiedene Instrumente eingebracht, wie etwa sensorische oder koordinativ-motorische Tests. Vorläufige Ergebnisse deuten dabei bereits an, dass nicht nur die klassischen kognitiven Parameter und Fragebögen bei der Identifizierung oder zum Zwecke des besseren Verstehens kognitiven Verfalls einbezogen werden sollten

Prevalence of retained primitive reflexes in patients with anxiety disorders

Anxiety is not only one of the mental health disorders most commonly referred to clinicians, but is also a research interest, producing subsequent modification in treatment approaches. However, there are suggestions in the literature that the effectiveness of some psychological treatments have not been systematically evaluated (Department of Health, 2001), or that treatment studies have employed methods unrepresentative of everyday clinical practice (World Health Organization.2000). Furthermore, from analysis of outcome studies, psychological therapies have been reported as effective for only half of those treated (Fisher & Durham, 1999). These findings suggest that there are individuals with anxiety who fail to respond to available therapies, and that alternative approaches for this group are not well studied.One biologically-based explanation for variable responses to treatment cites the possibility of anxiety as resulting from failed development of primitive and postural reflexes, necessary for processing sensory information and maintaining gravitational security. This theory is central to the work of the Institute for Neuro-Physiological Psychology (I.N.P.P.), recently applied to research which identified infantile reflexes, and failed transformation to adult responses, in a population of adults with differing sub-types of anxiety (Blythe, 1999).This study aimed to apply I.N.N.P. reflex tests to the detection of the characteristics of reflexes in a group of adult patients with Generalized Anxiety Disorder, compared to a group of non-anxious adults. A significant difference was found between patient and control group reflex test mean scores, patients achieving higher scores on all of the six iii tests employed in the study. From analysis of all individual test scores, two of these, detecting involvement of labyrinthine processes, resulted in the highest scores. The findings from analysis of resulting data are discussed in relation to implications for future study and further use of the measures with differing populations

가상현실에서 몸의 자세와 공간인지, 공간이동방법, 존재감, 사이버멀미의 상호작용에 대한 연구

학위논문 (박사) -- 서울대학교 대학원 : 인문대학 협동과정 인지과학전공, 2021. 2. 이경민.가상현실은 몸과 마음이 공간에 함께 존재한다는 일상적 경험에 대해 새로운 관점을 제시한다. 컴퓨터로 매개된 커뮤니케이션에서 많은 경우 사용자들은 몸은 배제되며 마음의 존재가 중요하다고 느끼게 된다. 이와 관련하여 가상현실은 사용자들에게 커뮤니케이션에 있어 물리적 몸의 역할과 비체화된 상호작용의 중요성에 대해 연구할 수 있는 기회를 제공한다. 기존 연구에 의하면 실행, 주의집중, 기억, 지각과 같은 인지기능들이 몸의 자세에 따라 다르게 작용한다고 한다. 하지만 이와 같은 인지기능들과 몸 자세의 상호연관성은 여전히 명확히 밝혀지고 있지 않다. 특히 가상현실에서 몸의 자세가 지각반응에 대한 인지과정에 어떤 작용을 하는지에 대한 이해는 매우 부족한 상황이다. 가상현실 연구자들은 존재감을 가상현실의 핵심 개념으로 정의하였으며 효율적인 가상현실 시스템 구성과 밀접한 관계가 있다고 한다. 존재감은 가상공간에 있다고 느끼는 의식상태를 말한다. 구체적으로 가상현실 속 경험을 실재 존재한다고 느끼는 의식상태를 말한다. 이런 존재감이 높을 수록 현실처럼 인지하기에 존재감은 가상현실 경험을 측정하는 중요한 지표이다. 따라서 가상공간에 존재하고 있다는 의식적 경험 ((거기에 있다(being there)), 즉 존재감은 매개된 가상경험들의 인지 연구에 중요한 개념이다. 가상현실은 사이버멀미를 유발하는 것으로 알려져 있다. 이 증상은 가상현실의 사용성을 제약하는 주요 요인으로 효과적인 가상현실 경험을 위해 사이버멀미에 대한 다양한 연구가 필요하다. 사이버멀미는 가상현실 시스템을 사용할때 나타나며 어지러움, 방향상실, 두통, 땀흘림, 눈피로도등의 증상을 포함한다. 이런 사이버멀미에는 개인차, 사용된 기술, 공간디자인, 수행된 업무등 매우 다양 요인들이 관여하고 있어 명확한 원인을 규정할 수 없다. 이런 배경으로 인해 사이버멀미 저감과 관련한 다양한 연구들이 필요하며 이는 가상현실 발전에 중요한 의미를 갖는다. 공간인지는 3차원 공간에서 신체 움직임과 대상과의 상호작용에 중요한 역할을 하는 인지시스템이다. 가상공간에서 신체 움직임은 네비게이션, 사물조작, 다른 에이전트들과 상호작용에 관여한다. 특히 가상공간에서 네비게이션은 자주 사용되는 중요한 상호작용 방식이다. 이에 가상공간을 네비게이션 할때 존재감에 영향을 주지 않고 멀미증상을 유발하지 않는 효과적인 공간이동 방법에 대한 다양한 연구들이 이루어지고 있다. 이전 연구들에 의하면 시점이 존재감과 체화감에 영향을 준다고 한다. 이는 시점에 따라 사용자의 행동과 대상들과의 상호작용 방식에 달라지기 때문이다. 따라서 가상공간에서 경험 또한 시점에 따라 달라진다. 이런 배경으로 몸의 자세, 공간인지, 이동방법, 존재감, 사이버멀미의 상호 연관성에 대한 연구를 시점에 따라 분류해서 연구할 필요가 있다. 이를 통해 가상현실 속 공간 네비게이션에 대한 인지과정을 보다 다각적으로 이해 할 수 있을 것이다. 그동안 존재감과 사이버 멀미에 내재된 매커니즘을 이해하기 위해 다양한 연구들이 진행되어 왔다. 하지만 몸의 자세에 따른 인지작용이 존재감과 사이버멀미에 어떤 영향을 주는지에 대한 연구는 거의 이루어지지 않았다. 이에 본 학위논문에서는 1인칭과 3인칭 시점으로 분류된 별도의 실험과 연구를 진행하여 가상현실에서 몸의 자세와 공간인지, 공간이동방법, 존재감, 사이버멀미의 상호연관성을 보다 심층적으로 이해하고자 한다. 제3장에서는 3인칭시점의 실험과 결과에 대한 내용을 기술했다. 3인칭시점 실험에서는 가상공간에서 몸의 자세와 존재감의 상호연관성 연구를 위해 세가지 몸의 자세 (서있는 자세, 앉은 자세, 다리를 펴고 앉은 자세)와 2가지 타입의 공간이동 자유도 (무한, 유한)를 상호 비교했다. 실험결과에 의하면 공간이동 자유도가 무한한 경우 서있는 자세에서 존재감이 높게 나타났다. 추가적으로 가상공간에서 몸의 자세와 존재감은 공간이동자유도와 관련이 있는 것으로 나타났으며 여러 인지기능 중 주의집중이 몸의 자세, 존재감, 공간인지의 통합적 상호작용을 이끌어 낸 것으로 파악되었다. 3인칭시점의 결과들을 종합해 보면 몸 자세의 인지적 영향은 공간이동자유도와 상관관계가 있는 것으로 추측할 수 있다. 제4장에서는 1인칭시점의 실험과 결과에 대한 내용을 기술했다. 1인칭시점 실험에서는 가상공간에서 몸의 자세, 공간이동방법, 존재감, 사이버멀미의 상호연관성 연구를 위해 두 조건의 몸의 자세 (서있는 자세, 앉아 있는 자세)와 네가지 타입의 이동방법 (스티어링 + 몸을 활용한 회전, 스티어링 + 도구를 활용한 회전, 텔레포테이션 + 몸을 이용한 회전, 텔레포테이션 + 도구를 활용한 회전)의 상호 비교가 이루어 졌다. 실험결과에 의하면 위치이동방식과 회전방식에 따른 공간이동자유도는 성공적인 네비게이션과 관련이 있으며 존재감에 영향을 주는 것으로 나타났다. 추가적으로 연속적으로 시각정보가 입력되는 스티어링 방법은 자가운동을 높여 비연속적 방법인 텔레포테이션보다 사이버멀미를 더 유발하는 것으로 나타났다. 1인칭시점의 결과들을 종합해 보면 가상공간에서 네비게이션을 할때 존재감과 사이버멀미는 공간이동방법과 관련이 있는 것으로 가정할 수 있다. 제3장의 3인칭 시점 실험결과에 의하면 몸의 자세와 존재감은 상관관계가 있는 것으로 제시되었다. 반면 제4장의 실험결과에 의하면 1인칭시점으로 가상공간을 네비게이션 할 때는 공간이동방법이 존재감과 사이버멀미에 영향을 주는 것으로 나타났다. 이 두 실험에 대한 연구 결과를 통해 가상현실에서 몸의 자세와 공간인지 (네비게이션)의 상호연관성에 대한 이해를 확대하고 존재감 및 사이버멀미와 공간이동방법의 관련성을 밝힐 수 있을 것으로 기대한다.Immersive virtual environments (VEs) can disrupt the everyday connection between where our senses tell us we are and where we are actually located. In computer-mediated communication, the user often comes to feel that their body has become irrelevant and that it is only the presence of their mind that matters. However, virtual worlds offer users an opportunity to become aware of and explore both the role of the physical body in communication, and the implications of disembodied interactions. Previous research has suggested that cognitive functions such as execution, attention, memory, and perception differ when body position changes. However, the influence of body position on these cognitive functions is still not fully understood. In particular, little is known about how physical self-positioning may affect the cognitive process of perceptual responses in a VE. Some researchers have identified presence as a guide to what constitutes an effective virtual reality (VR) system and as the defining feature of VR. Presence is a state of consciousness related to the sense of being within a VE; in particular, it is a ‘psychological state in which the virtuality of the experience is unnoticed’. Higher levels of presence are considered to be an indicator of a more successful media experience, thus the psychological experience of ‘being there’ is an important construct to consider when investigating the association between mediated experiences on cognition. VR is known to induce cybersickness, which limits its application and highlights the need for scientific strategies to optimize virtual experiences. Cybersickness refers to the sickness associated with the use of VR systems, which has a range of symptoms including nausea, disorientation, headaches, sweating and eye strain. This is a complicated problem because the experience of cybersickness varies greatly between individuals, the technology being used, the design of the environment, and the task being performed. Thus, avoiding cybersickness represents a major challenge for VR development. Spatial cognition is an invariable precursor to action because it allows the formation of the necessary mental representations that code the positions of and relationships among objects. Thus, a number of bodily actions are represented mentally within a depicted VR space, including those functionally related to navigation, the manipulation of objects, and/or interaction with other agents. Of these actions, navigation is one of the most important and frequently used interaction tasks in VR environments. Therefore, identifying an efficient locomotion technique that does not alter presence nor cause motion sickness has become the focus of numerous studies. Though the details of the results have varied, past research has revealed that viewpoint can affect the sense of presence and the sense of embodiment. VR experience differs depending on the viewpoint of a user because this vantage point affects the actions of the user and their engagement with objects. Therefore, it is necessary to investigate the association between body position, spatial cognition, locomotion method, presence, and cybersickness based on viewpoint, which may clarify the understanding of cognitive processes in VE navigation. To date, numerous detailed studies have been conducted to explore the mechanisms underlying presence and cybersickness in VR. However, few have investigated the cognitive effects of body position on presence and cybersickness. With this in mind, two separate experiments were conducted in the present study on viewpoint within VR (i.e., third-person and first-person perspectives) to further the understanding of the effects of body position in relation to spatial cognition, locomotion method, presence, and cybersickness in VEs. In Chapter 3 (Experiment 1: third-person perspective), three body positions (standing, sitting, and half-sitting) were compared in two types of VR game with a different degree of freedom in navigation (DFN; finite and infinite) to explore the association between body position and the sense of presence in VEs. The results of the analysis revealed that standing has the most significant effect on presence for the three body positions that were investigated. In addition, the outcomes of this study indicated that the cognitive effect of body position on presence is associated with the DFN in a VE. Specifically, cognitive activity related to attention orchestrates the cognitive processes associated with body position, presence, and spatial cognition, consequently leading to an integrated sense of presence in VR. It can thus be speculated that the cognitive effects of body position on presence are correlated with the DFN in a VE. In Chapter 4 (Experiment 2: first-person perspective), two body positions (standing and sitting) and four types of locomotion method (steering + embodied control [EC], steering + instrumental control [IC], teleportation + EC, and teleportation + IC) were compared to examine the relationship between body position, locomotion method, presence, and cybersickness when navigating a VE. The results of Experiment 2 suggested that the DFN for translation and rotation is related to successful navigation and affects the sense of presence when navigating a VE. In addition, steering locomotion (continuous motion) increases self-motion when navigating a VE, which results in stronger cybersickness than teleportation (non-continuous motion). Overall, it can be postulated that presence and cybersickness are associated with the method of locomotion when navigating a VE. In this dissertation, the overall results of Experiment 1 suggest that the cognitive influence of presence is body-dependent in the sense that mental and brain processes rely on or are affected by the physical body. On the other hand, the outcomes of Experiment 2 illustrate the significant effects of locomotion method on the sense of presence and cybersickness during VE navigation. Taken together, the results of this study provide new insights into the cognitive effects of body position on spatial cognition (i.e., navigation) in VR and highlight the important implications of locomotion method on presence and cybersickness in VE navigation.Chapter 1. Introduction 1 1.1. An Introductory Overview of the Conducted Research 1 1.1.1. Presence and Body Position 1 1.1.2. Navigation, Cybersickness, and Locomotion Method 3 1.2. Research Objectives 6 1.3. Research Experimental Approach 7 Chapter 2. Theoretical Background 9 2.1. Presence 9 2.1.1. Presence and Virtual Reality 9 2.1.2. Presence and Spatiality 10 2.1.3. Presence and Action 12 2.1.4. Presence and Attention 14 2.2. Body Position 16 2.2.1. Body Position and Cognitive Effects 16 2.2.2. Body Position and Postural Control 18 2.2.3. Body Position and Postural Stability 19 2.3. Spatial Cognition: Degree of Freedom in Navigation 20 2.3.1. Degree of Freedom in Navigation and Decision-Making 20 2.4. Cybersickness 22 2.4.1. Cybersickness and Virtual Reality 22 2.4.2. Sensory Conflict Theory 22 2.4.3. Postural Instability Theory 23 2.5. Self-Motion 25 2.5.1. Vection and Virtual Reality 25 2.5.2. Self-Motion and Navigation in a VE 27 2.6. Navigation in Virtual Environments 29 2.6.1. Translation and Rotation in Navigation 29 2.6.2. Spatial Orientation and Embodiment 32 2.6.3. Locomotion Methods 37 2.6.4. Steering and Teleportation 38 Chapter 3. Experiment 1: Third-Person Perspective 40 3.1. Quantification of the Degree of Freedom in Navigation 40 3.2. Experiment 3.2.1. Experimental Design and Participants 41 3.2.2. Stimulus Materials 42 3.2.2.1. First- and Third-person Perspectives in Gameplay 43 3.2.3. Experimental Setup and Process 44 3.2.4. Measurements 45 3.3. Results 45 3.3.1. Presence: two-way ANOVA 45 3.3.2. Presence: one-way ANOVA 46 3.3.2.1. Finite Navigation Freedom 46 3.3.2.2. Infinite Navigation Freedom 47 3.3.3. Summary of the Results 48 3.4. Discussion 49 3.4.1. Presence and Body Position 49 3.4.2. Degree of Freedom in Navigation and Decision-Making 50 3.4.3. Gender Difference and Gameplay 51 3.5. Limitations 52 Chapter 4. Experiment 2: First-Person Perspective 53 4.1. Experiment 53 4.1.1. Experimental Design and Participants 53 4.1.2. Stimulus Materials 54 4.1.3. Experimental Setup and Process 55 4.1.4. Measurements 56 4.2. Results 57 4.2.1. Presence: two-way ANOVA 58 4.2.2. Cybersickness: two-way ANOVA 58 4.2.3. Presence: one-way ANOVA 60 4.2.3.1. Standing Position 60 4.2.3.2. Sitting Position 60 4.2.4. Cybersickness: one-way ANOVA 62 4.2.4.1. Standing Position 62 4.2.4.2. Sitting Position 62 4.2.5. Summary of the Results 63 4.3. Discussion 65 4.3.1. Presence 4.3.1.1. Presence and Locomotion Method 66 4.3.1.2. Presence and Body Position 68 4.3.2. Cybersickness 4.3.2.1. Cybersickness and Locomotion Method 69 4.3.2.2. Cybersickness and Body Position 70 4.4. Limitations 71 Chapter 5. Conclusion 72 5.1. Summary of Findings 72 5.2. Future Research Direction 73 References 75 Appendix A 107 Appendix B 110 국문초록 111Docto