Future challenges for vection research: definitions, functional significance, measures, and neural bases

This paper discusses four major challenges facing modern vection research. Challenge 1 (Defining Vection) outlines the different ways that vection has been defined in the literature and discusses their theoretical and experimental ramifications. The term vection is most often used to refer to visual illusions of self-motion induced in stationary observers (by moving, or simulating the motion of, the surrounding environment). However, vection is increasingly being used to also refer to non-visual illusions of self-motion, visually-mediated self-motion perceptions, and even general subjective experiences (i.e. feelings) of self-motion. The common thread in all of these definitions is the conscious subjective experience of self-motion. Thus, Challenge 2 (Significance of Vection) tackles the crucial issue of whether such conscious experiences actually serve functional roles during self-motion (e.g., in terms of controlling or guiding the self-motion). After more than 100 years of vection research there has been surprisingly little investigation into its functional significance. Challenge 3 (Vection Measures) discusses the difficulties with existing subjective self-report measures of vection (particularly in the context of contemporary research), and proposes several more objective measures of vection based on recent empirical findings. Finally, Challenge 4 (Neural Basis) reviews the recent neuroimaging literature examining the neural basis of vection and discusses the hurdles still facing these investigations

The effects of expectancy and control on the perception of ego-motion in space: a combined postural and electrophysiological study

In the beginning of this work was the scientific question: does the amount of control over visual self-motion cues influence their processing and/or perception? In Experiment 1, we tried to explore the possibility to use optic flow as a visual motion cue and see whether we can observe a sensory attenuation or modulation on the behavioural level in trials in which the optic flow was self-initiated using putative different levels of control by instructed or uninstructed button-presses compared to passive flow. This experiment, while not able to demonstrate a sensory modulation and with several important limitations (see below), was however an important basis for the planning of Experiment 2 and a proof-of-concept that this method has the potential to address our research question and is feasible given our facilities. In Experiment 2, we tried to overcome some of the limitations, further improved the re-producibility (e.g. stimuli and instructions) and extended our methodology to the measurement of neurophysiological and postural data to enquire about not only the behavioural level but also the processing on the physiological level. This experiment presented evidence that self-motion cues with the same physical properties are somehow processed differently at the cortical level depending on whether they are self-initiated or not. In addition to overcoming certain limitations in Experiment 3 (e.g. having a no optic flow control condition and using the standard EEG setup besides the mobile setup from Experiment 2), we were able to reproduce our findings in different subjects, a larger population and under a different posture. We were also able to show that our results are highly robust (e.g. removal of half the participants from the analysis did not change the pattern). Further outcomes from our study are that the scientific community can put more trust into mobile EEG setups given robust effects and diligent artifact removal. Additionally, we contributed findings on the relationship of vection and VIMS and tried to bridge the gap between the highly relevant fields of research on visual motion perception and sense of agency. This might act as an exploratory foundation for further research which will be essential for the economical and medical applicability of VR devices and for a deeper understanding of locomotion and navigation per se. The ability to perceive self-motion cues and dissociate them from cues for motion in the environment is fundamental for being able to take actions in the complex, dynamic environments which are our daily lives. In fact, it could be seen as a classical example of the dynamic coupling of action and perception to reach goals which is one of the most fundamental abilities not only for humans, but throughout the animal kingdom which may have lain the evolutionary basis for the later development of the human brain with its complexity as we see it nowadays (Godfrey-Smith 2016).Den Grundstein für diese Arbeit legte die Frage: spielt es für die Wahrnehmung und Verarbeitung von visuellem Feedback, das in Folge von Eigenbewegung im Raum entsteht, eine Rolle wie viel Kontrolle wir über die Bewegung haben? Wird das Feedback von aktiven Bewegungen anders verarbeitet als das von passiven? Im ersten Experiment explorierten wir die Möglichkeit uns dieser Fragestellung mit optic flow als visuellem Stimulus zu nähern. Wir haben dazu ein Experiment entwickelt bei dem gesunde Proband:innen unterschiedlich viel Kontrolle über den optic flow haben und sie anschließend zu ihrem Bewegungsempfinden (Vection) befragt. Während dieses Experiment keine relevante Modulation nachweisen konnte, so stellte es doch eine wichtige methodologische Grundlage für die Entwicklung der weiteren Experimente dar. Die wichtigsten Änderungen in Experiment 2 umfassten zum einen Modifikationen an den Stimuli und eine ausgeprägtere Formalisierung der Instruktionen, zum anderen die zusätzliche Erhebung von neurophysiologischen und posturalen Daten. Diese Änderungen erlaubten uns nicht nur explizite Unterschiede in der Intensität der Wahrnehmung von Vection zu erfassen, sondern auch eventuelle Modifikationen in der Verarbeitung der Stimuli messbar zu machen. Dieses Experiment lieferte Hinweise darauf, dass Stimuli mit denselben physikalischen Eigenschaften auf kortikaler Ebene anders verarbeitet werden, je nachdem ob sie selbst initiiert oder Computer-generiert sind. In Experiment 3 führten wir klassische Kontrollbedingungen wie zum Beispiel Versuche mit statischen Stimuli ein. Wir veränderten weiterhin die Körperposition, so dass Proband:innen nun saßen und die Hälfte der Versuche mit einer Kinnstütze stattfand. Damit konnten wir das Risiko, das unsere neurophysiologischen Effekte Bewegungsartefakte sind, minimieren. Insgesamt waren wir dazu in der Lage die Haupteffekte von Experiment 2 (agency-abhängige Modulation der evozierten Desynchronisation und der Amplitude der evozierten Potentiale) in Experiment 3 zu reproduzieren, obwohl wir hier eine deutlich größere Kohorte sowie andere Pro-band:innen in einer anderen Körperhaltung testeten. Diese Resultate sind sehr robust, so dass sie weiterhin deutlich erkennbar sind, auch nachdem wir ver-suchsweise die Hälfte der Proband:innen aus der Analyse ausgeschlossen hatten. Zusätzlich zu unserer ursprünglichen Fragestellung zeigten unsere Experimente, dass die wissenschaftliche Community mehr auf die Ergebnisse von Studien, die ein mobiles EEG-Setup verwenden, vertrauen kann, solange es sich um robuste Effekte handelt und ausreichend auf die Identifikation und Entfernung von Bewegungsartefakten geachtet wird. Außerdem konnten wir mit unseren Daten dazu beitragen die Zusammenhänge zwischen Vection und visuell-induzierter Bewegungskrankheit besser zu verstehen. Unsere Experimente versuchen die Brücke zu schlagen zwischen den jeweils für sich gesehen hoch relevanten Forschungsfeldern rund um die visuelle Bewegung-swahrnehmung und den Sense of Agency. Diese Felder zusammenzubringen wird eine essenzielle Rolle spielen, sowohl um das volle Potential von VR-Applikationen zu entfalten als auch um Lokomotion und Navigation umfassender zu begreifen. Die Fähigkeit Eigenbewegung von Bewegungen in der Umgebung anhand von visuellen Informationen zu unterscheiden, ist entscheidend um in der komplexen, dynamischen Umwelt unseres täglichen Lebens erfolgreich agieren und navigieren zu können. Diese Fähigkeit ist ein schönes Beispiel für die dynamische Koppelung von Handlung und Wahrnehmung zum Erreichen unserer Ziele und vermutlich eine der fundamentalsten Fähigkeiten nicht nur für Menschen, sondern auch im übrigen Tierreich. Möglicherweise so fundamental, dass sie die evolutionäre Basis für die spätere Entwicklung des menschlichen Gehirns in all seiner Komplexität und Schönheit, gelegt haben könnte (Godfrey-Smith 2016)

Explaining Self-Motion Perception using Virtual Reality in Patients with Ocular Disease

Safe mobility requires accurate object and self-motion perception. This involves processing retinal motion generated by optic flow (which change with eye and head movements) and correctly integrating this with vestibular and proprioceptive cues. Poor sensory feedback of self-motion can lead to increased risks of accidents which impacts quality of life. This is further problematic for those with visual deficits, such as central or peripheral vision loss or impaired binocular vision. The expansion of healthcare into using virtual reality (VR) has allowed the assessment of sensory and motor performance in a safe environment. An advantage of VR is its ability to generate vection (perceived illusory self-motion) and presence (sense of being ‘there’). However, a limitation is the potential to develop cybersickness. Initially, the project examined how binocular vision influences vection in a virtual environment. Observers with or without stereopsis (ability to judge depth binocularly) were asked to compare their perceptual experiences based on psychophysical judgements of magnitude estimation. The findings suggest that the absence of stereopsis impairs accurate judgement of self-motion and reduces perceived presence, however, it was protective for cybersickness. The project then examined the impact of central and peripheral vision loss on self-motion perception by comparing those with age-related macular degeneration (AMD) and glaucoma respectively. Effects of these visual deficits on sensory conflicts involving visual-vestibular interactions was then assessed. Sensory conflict was imposed by altering the gain of simulated head linear head position and angular orientation to be either compatible or incompatible with head movement in two separate experiments. Fixation was used to control gaze during changes in angular head orientation. Vection and presence was higher in those with AMD, compared with those with glaucoma, indicating the importance of regional specificity in visual deficits on self-motion perception. Across studies, vection and presence were predominantly visually mediated despite changes in visual-vestibular sensory conflict. The vestibular system, however, appeared to play a larger role in developing cybersickness. The altered perception of self-motion may worsen mobility, particularly with disease progression. We therefore provide a framework and recommendations for a multidisciplinary patient-centric model of care to maximise quality of life

How did we get there? Supporting older adults’ spatial orientation within the built environment.

Older adults exhibit marked declines in navigation skills; these difficulties become worse if individuals are showing early signs of cognitive impairment, which often results in disorientation, particularly in unfamiliar environments. Many of these individuals eventually face the challenge of having to learn their way around new surroundings e.g. with potential increased visits to hospitals or when moving into retirement housing or care-home environments. This PhD thesis aims to develop a clearer understanding of older adults’ route learning and route knowledge when learning routes through built environments. To gain a more complete understanding of the experiences typical and early atypical ageing adults encounter, I adopted a mixed- methods approach. Chapters 3, 4 and 8 report on data following a quantitative experimental psychology approach to measure route learning and route knowledge in virtual and real environments, whilst Chapters 6 and 7 report on data using a qualitative approach to data collection and analysis to gain an understanding of the lived orientation experiences people living in and visiting retirement settings encounter. The findings from the data chapters are discussed in relation to existing theory and literature surrounding the effects that typical and early atypical ageing has on the abilities to learn and remember routes. In particular this thesis contributes towards the understanding of how typical and atypical ageing affects route learning and route knowledge, and how the findings can be applied to critically improve the suggestions made in dementia friendly design guidelines. The thesis concludes that simplistic VR environments do reliably capture real world navigation performance, but are additionally beneficial in that they detect the earliest symptoms of early atypical ageing more so than real world navigation. This can have benefits in detecting and diagnosing early atypical ageing in a clinical setting