Presence and Cybersickness in Virtual Reality Are Negatively Related: A Review

In order to take advantage of the potential offered by the medium of virtual reality (VR), it will be essential to develop an understanding of how to maximize the desirable experience of “presence” in a virtual space (“being there”), and how to minimize the undesirable feeling of “cybersickness” (a constellation of discomfort symptoms experienced in VR). Although there have been frequent reports of a possible link between the observer’s sense of presence and the experience of bodily discomfort in VR, the amount of literature that discusses the nature of the relationship is limited. Recent research has underlined the possibility that these variables have shared causes, and that both factors may be manipulated with a single approach. This review paper summarizes the concepts of presence and cybersickness and highlights the strengths and gaps in our understanding about their relationship. We review studies that have measured the association between presence and cybersickness, and conclude that the balance of evidence favors a negative relationship between the two factors which is driven principally by sensory integration processes. We also discuss how system immersiveness might play a role in modulating both presence and cybersickness. However, we identify a serious absence of high-powered studies that aim to reveal the nature of this relationship. Based on this evidence we propose recommendations for future studies investigating presence, cybersickness, and other related factors

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

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, the estimates of the model parameters suggest that velocity storage does not influence perceptual thresholds

Neutrinos: Heralds of New Physics

The central role of neutrinos in the determination of fundamental interactions is reviewed. The recent SuperKamiokande discovery of neutrino mass gives an {\it aper\c cu} of physics at short distances, and tests theories of flavor. Quark-lepton symmetries, derived from grand unification and/or string theories, can help determine the standard model parameters in the neutrino sector.Comment: Invited Talk at TAUP99, Paris, September 1999. Latex, 10 page

Roll rate thresholds and perceived realism in driving simulation

Due to limited operational space, in dynamic driving simulators it is common practice to implement motion cueing algorithms that tilt the simulator cabin to reproduce sustained accelerations. In order to avoid conflicting inertial cues, the tilt rate is kept below drivers’ perceptual thresholds, which are typically derived from the results of classical vestibular research where additional sensory cues to self-motion are removed. Here we conduct two experiments in order to assess whether higher tilt limits can be employed to expand the user’s perceptual workspace of dynamic driving simulators. In the first experiment we measure detection thresholds for roll in conditions that closely resemble typical driving. In the second experiment we measure drivers’ perceived realism in slalom driving for sub-, near- and supra-threshold roll rates. Results show that detection threshold for roll in an active driving task is remarkably higher than the limits currently used in motion cueing algorithms to drive simulators. Supra-threshold roll rates in the slalom task are also rated as more realistic. Overall, our findings suggest that higher tilt limits can be successfully implemented in motion cueing algorithms to better optimize simulator operational space

Perceived timing of active head movement at different speeds

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.neulet.2018.09.065 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/The central nervous system must determine which sensory events occur at the same time. Actively moving the head corresponds with large changes in the relationship between the observer and the environment, sensorimotor processing, and spatiotemporal perception. Active head movement perception has been shown to be dependent on head movement velocity where participants who move their head fastest require the head to move earlier than comparison stimuli for perceived simultaneity more so than those who move their head slower. Such between-subject results cannot address whether active head movement perception changes with velocity. The present study used a within-subjects design to measure the point of subjective simultaneity (PSS) between active head movement speeds and a comparison sound stimulus to characterize the relationship between the velocity and perception of head movement onset. Our results clearly show that i) head movement perception is faster with faster head movements within-subjects, ii) active head movement onset must still precede the onset of other sensory events (average PSS: −123 ms to −52 ms; median PSS: −42 ms to −100 ms) in order to be perceived as occurring simultaneously even at the fastest speeds (average peak velocity: 76°/s–257°/s; median peak velocity 72 ms–257 ms). We conclude that head movement perception is slow, but that this delay is minimized with increased speed. These within-subject results are contrary to previous and present study between-subject results and are in agreement with literature where perception of auditory, visual and vestibular stimulus onset is less delayed with increased stimulus intensity.Natural Sciences and Engineering Research Council of Canada [RGPIN-05435-2014

Evaluation Of Sensitivity To Chemotherapeutants In Successive Generations Of Lepeoptheirus Salmonis From A Resistant Population

There are currently reports of reduced sensitivity to certain lice treatments in different parts of Scotland and world-wide, and research is on-going into the extent and mechanisms of resistance to different treatments (Denholm et al., 2002; Sevatdal & Horsberg, 2003; Sevatdal et al., 2005). In particular, increasing evidence of resistance of Lepeophtheirus salmonis to the chemotherapeutant emamectin benzoate (Lees et al., 2008; Espedal et al., 2010) poses a serious problem to commercial farms because there are few licensed and effective treatments available

Application of Otolith Chemical Signatures to Estimate Population Connectivity of Red Snapper In the Western Gulf of Mexico

Otolith chemical signatures of Red Snapper Lutjanus campechanus from six nursery regions were used to estimate the sources of recruits to four sampling regions in the western Gulf of Mexico (Gulf) and to estimate whether postsettlement mixing of Red Snapper occurs between the U.S. and Mexican portions of the western Gulf. In a previous study, region-specific otolith signatures (element : Ca ratios: Ba:Ca, Mg:Ca, Mn:Ca, Sr:Ca, and Li:Ca; stable isotope delta values: δ13C and δ18O) were developed based on age-0 Red Snapper (2005–2007 year-classes) sampled from the six nursery areas. In the present study, subadult and adult Red Snapper (ages 1–3) belonging to those same year-classes were collected from four sampling regions within the western Gulf (two regions in U.S. waters; two regions along the Mexican continental shelf) during summer in 2006–2008. Left sagittal otoliths were used to age subadults and adults to the corresponding nursery year-classes, and right sagittal otoliths were cored for chemical analysis. Off the southwestern U.S. coast, the sampled age-1–3 Red Snapper included locally derived recruits as well as recruits from the northwestern Gulf nursery region. However, analytical results were inconclusive with respect to estimating the connectivity between Red Snapper populations in U.S. and Mexican waters of the western Gulf

Perceived Object Stability Depends on Multisensory Estimates of Gravity

BACKGROUND: How does the brain estimate object stability? Objects fall over when the gravity-projected centre-of-mass lies outside the point or area of support. To estimate an object's stability visually, the brain must integrate information across the shape and compare its orientation to gravity. When observers lie on their sides, gravity is perceived as tilted toward body orientation, consistent with a representation of gravity derived from multisensory information. We exploited this to test whether vestibular and kinesthetic information affect this visual task or whether the brain estimates object stability solely from visual information. METHODOLOGY/PRINCIPAL FINDINGS: In three body orientations, participants viewed images of objects close to a table edge. We measured the critical angle at which each object appeared equally likely to fall over or right itself. Perceived gravity was measured using the subjective visual vertical. The results show that the perceived critical angle was significantly biased in the same direction as the subjective visual vertical (i.e., towards the multisensory estimate of gravity). CONCLUSIONS/SIGNIFICANCE: Our results rule out a general explanation that the brain depends solely on visual heuristics and assumptions about object stability. Instead, they suggest that multisensory estimates of gravity govern the perceived stability of objects, resulting in objects appearing more stable than they are when the head is tilted in the same direction in which they fall

Dark matter constraints on the parameter space and particle spectra in the nonminimal SUSY standard model

We investigate the dark matter constraints for the nonminimal SUSY standard model (NMSSM). The cosmologically restricted mass spectra of the NMSSM are compared to the minimal SUSY standard model (MSSM). The differences of the two models concerning the neutralino, sfermion and Higgs sector are discussed. The dark matter condition leads to cosmologically allowed mass ranges for the SUSY particles in the NMSSM: m_{\tilde{\chi}^0_1} < 300 GeV, m_{\tilde{e}_R} < 300 GeV, 300 GeV < m_{\tilde{u}_R} < 1900 GeV, 200 GeV < m_{\tilde{t}_1} < 1500 GeV, 350 GeV < m_{\tilde{g}} < 2100 GeV and for the mass of the lightest scalar Higgs m_{S_1} < 140 GeV.Comment: revised version to appear in Phys. Lett. B, 18 pages, LaTeX, 3 figures, uses epsfig.sty and amssymb.st