Visually induced linear vection is enhanced by small physical accelerations

Wong & Frost (1981) showed that the onset latency of visually induced self-rotation illusions (circular vection) can be reduced by concomitant small physical motions (jerks). Here, we tested whether (a) such facilitation also applies for translations, and (b) whether the strength of the jerk (degree of visuo-vestibular cue conflict) matters. 14 naïve observers rated onset, intensity, and convincingness of forward linear vection induced by photorealistic visual stimuli of a street of houses presented on a projection screen (FOV: 75°×58°). For 2/3 of the trials, brief physical forward accelerations (jerks applied using a Stewart motion platform) accompanied the visual motion onset. Adding jerks enhanced vection significantly; Onset latency was reduced by 50, convincingness and intensity ratings increased by more than 60. Effect size was independent of visual acceleration (1.2 and 12m/s^2) and jerk size (about 0.8 and 1.6m/s^2 at participants’ head for 1 and 3cm displacement, respectively), and showed no interactions. Thus, quantitative matching between the visual and physical acceleration profiles might not be as critical as often believed as long as they match qualitatively and are temporally synchronized. These findings could be employed for improving the convincingness and effectiveness of low-cost simulators without the need for expensive, large motion platforms

Influence of Auditory Cues on the visually-induced Self-Motion Illusion (Circular Vection) in Virtual Reality

This study investigated whether the visually induced selfmotion illusion (“circular vection”) can be enhanced by adding a matching auditory cue (the sound of a fountain that is also visible in the visual stimulus). Twenty observers viewed rotating photorealistic pictures of a market place projected onto a curved projection screen (FOV: 54°x45°). Three conditions were randomized in a repeated measures within-subject design: No sound, mono sound, and spatialized sound using a generic head-related transfer function (HRTF). Adding mono sound increased convincingness ratings marginally, but did not affect any of the other measures of vection or presence. Spatializing the fountain sound, however, improved vection (convincingness and vection buildup time) and presence ratings significantly. Note that facilitation was found even though the visual stimulus was of high quality and realism, and known to be a powerful vection-inducing stimulus. Thus, HRTF-based auralization using headphones can be employed to improve visual VR simulations both in terms of self-motion perception and overall presence

How to simulate realistic forward accelerations on a 6dof motion platform

How are visual and physical motion cues integrated in self-motion perception? We performed a psychophysical study to test how forward accelerations can be realistically simulated. Participants were seated on a 6 dof Stewart motion platform and viewed a computer-generated visual scene on a projection screen (54 ×40.5 ). The visual scene consisted of a randomly structured ground plane and sky. Observers were told that eye height was always 2m above ground. In each of the 180 trials, participants experienced a brief simulated forward acceleration (4s ramp, followed by 2s of constant acceleration) that was presented both as platform motion and motion within the visual scene. After the acceleration, the screen went dark and the platform returned to zero in 6s. Participants used a joystick to indicate the realism of the forward acceleration experienced. They were explicitly told to give high ratings for trials in which they convincingly felt moving forward in accordance with the visual stimulus, and low ratings in trials in which they noticed conflicts. In each trial, stimuli were chosen randomly within fixed intervals for all six varied parameters: visual forward accelerations (0–1.5 m/s^2), platform backwards pitch (0–15 ), brief forward translations of the platform (0–0.5m in 4s), ratio of acceleration/deceleration durations for the translations (0.11–1.5), and up/down noise simulating ground roughness (0–7cm) using low-pass filtered noise (cosine window, 0.3–1s). Multiple hierarchical regression analyses performed for each subject revealed that only two parameters had a clear influence on the ratings: higher platform pitches and higher visual accelerations induced a better impression of being accelerated forward. Brief forward translations of the platform and bumps increased believability for some observers. Interestingly, during sensory conflict between canal and visual/otolith cues, the latter dominated, as predicted by a Bayesian model that holds vision as more reliable

Limited reliability of the indirect immunofluorescence technique for the detection of anti-Rib-P antibodies

Following publication of our recent article [1], we noticed the following errors: In the Results section, under the heading ‘Confirmation of anti-Rib-P reactivity in 51 samples by other methods’, in the first sentence, 39.6 % should be 41.2%. In the same section, the following sentence: The agreement between the individual methods and the IB was found at 0.57 (P < 0.0001) (ELISA), 0.71 (P < 0.0001), and 0.96 (P < 0.0001) according to the kappa method. Should read: The agreement between the individual methods and the IB was found at 0.57 (P < 0.0001) (ELISA), 0.71 (P < 0.0001) (LIA), and 0.96 (P < 0.0001) (EliA(R)) according to the kappa method. In the results section, under the heading ‘Anti-Rib-P reactivity in a systemic lupus erythematosus cohort and controls’, in the second sentence, 28 % should be 29%. Referenc

The effect of cognition on the visually-induced illusion of self-motion (vection)

INTRODUCTION: The illusion of self-motion induced by moving visual stimuli has typically been attributed to bottom-up perceptual processes. Here, we investigated whether a cognitive factor such as spatial presence can contribute to the illusion. Spatial presence was indirectly manipulated by presenting either a photorealistic image of a natural scene or modified versions of the same stimulus. Those were created by either scrambling image parts in a mosaic-like manner or by slicing the original image horizontally and randomly reassembling it. We expected scene modifications to decrease spatial presence and thus impair vection. METHODS: Twelve observers viewed stimuli projected onto a curved projection screen (FOV: 54 ×40.5 ). Dependent measures included vection onset time, vection intensity, and convincingness of the illusion (0–100 ratings). Spatial presence was assessed with presence questionnaires. RESULTS: Scene modification led to both reduced presence scores and impaired vection: Modified stimuli yielded significantly longer vection onset times, lower perceived intensity, and lower convincingness ratings than the intact market scene. No clear difference was found between the sliced and scrambled stimuli or among the number of slices or mosaics (2, 8, or 32). Results suggest that high level information (consistent reference frame for the intact market scene) dominated over the low-level information (more contrast edges in the scrambled stimulus, which are known to facilitate vection). CONCLUSIONS: Results suggest a direct relation between spatial presence and self-motion perception. We posit that stimuli depicting naturalistic scenes provide observers with a convincing reference frame for the simulated environment which enables them to feel “spatially present”. This, in turn, facilitates the self-motion illusion. This work has important implications for both self-motion perception and motion simulator design and applications

Evaluation of a Novel Rapid Test System for the Detection of Allergic Sensitization to Timothy Grass Pollen against Established Laboratory Methods and Skin Prick Test

Type I hypersensitivity is driven by allergen specific immunoglobulin E (sIgE) and thus sIgE represents a marker for modern allergy diagnosis. Recently, a rapid assay for the detection of sIgE, termed as (Allergy Lateral Flow Assay) ALFA, has been developed. The objective of our study is the evaluation of a scanner-based system for the semiquantitative interpretation of ALFA results. Agreement to Skin Prick Test (SPT, Allergopharma), ALLERG-O-LIQ System (Dr. Fooke), and ImmunoCAP (Phadia) was investigated using 50 sera tested for specific IgE to timothy grass pollen (g6). 35/50 sera were positive by SPT, ALLERG-O-LIQ, and ImmunoCAP. Excellent agreement was observed between ALFA results and SPT, ImmunoCAP, and ALLERG-O-LIQ. Area under the curve (AUC) values were found at 1.0, and 100% sensitivity and specificity was found versus all other methods. Visual- and scanner-based interpretation of the ALFA results revealed excellent agreement

Fused Traditional and Geometric Morphometrics Demonstrate Pinniped Whisker Diversity

Vibrissae (whiskers) are important components of the mammalian tactile sensory system, and primarily function as detectors of vibrotactile information from the environment. Pinnipeds possess the largest vibrissae among mammals and their vibrissal hair shafts demonstrate a diversity of shapes. The vibrissae of most phocid seals exhibit a beaded morphology with repeating sequences of crests and troughs along their length. However, there are few detailed analyses of pinniped vibrissal morphology, and these are limited to a few species. Therefore, we comparatively characterized differences in vibrissal hair shaft morphologies among phocid species with a beaded profile, phocid species with a smooth profile, and otariids with a smooth profile using traditional and geometric morphometric methods. Traditional morphometric measurements (peak-to-peak distance, crest width, trough width and total length) were collected using digital photographs. Elliptic Fourier analysis (geometric morphometrics) was used to quantify the outlines of whole vibrissae. The traditional and geometric morphometric datasets were subsequently combined by mathematically scaling each to true rank, followed by a single eigendecomposition. Quadratic discriminant function analysis demonstrated that 79.3, 97.8 and 100% of individuals could be correctly classified to their species based on vibrissal shape variables in the traditional, geometric and combined morphometric analyses, respectively. Phocids with beaded vibrissae, phocids with smooth vibrissae, and otariids each occupied distinct morphospace in the geometric morphometric and combined data analyses. Otariids split into two groups in the geometric morphometric analysis and gray seals appeared intermediate between beaded- and smooth-whiskered species in the traditional and combined analyses. Vibrissal hair shafts modulate the transduction of environmental stimuli to the mechanoreceptors in the follicle-sinus complex (F-SC), which results in vibrotactile reception, but it is currently unclear how the diversity of shapes affects environmental signal modulation