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Abstract A group of highly experienced pilots performed full-motion, simulated T-38 landings before and after extended missions aboard the International Space Station (ISS). On the day of return from the ISS pilots’ performance was degraded on the initial landing attempt, with difficulty maintaining altitude during banking turns and navigational errors, which affected touchdown parameters such as touchdown speed, height over runway threshold and touchdown distance from the runway threshold. A positive result was that all pilots successfully completed a second landing attempt on the same day, suggesting a rapid recovery of performance once exposed to the task at hand. These results are consistent with a previous study that demonstrated significant deficits in post-flight driving performance, and both the pilot and driver subjects’ performance recovered to pre-flight levels within four days of return from the ISS. We propose that the primary factors underlying the post-flight performance deficits were the inability to respond appropriately to gravitational and visual tilts and a reduction in multitasking ability.

This paper is concerned mainly with the assumptions underpinning the actual testing procedure, measurement, and interpretation of the video head impulse test—vHIT. Other papers have reported in detail the artifacts which can interfere with obtaining accurate eye movement results, but here we focus not on artifacts, but on the basic questions about the assumptions and geometrical considerations by which vHIT works. These matters are crucial in understanding and appropriately interpreting the results obtained, especially as vHIT is now being applied to central disorders. The interpretation of the eye velocity responses relies on thorough knowledge of the factors which can affect the response—for example the orientation of the goggles on the head, the head pitch, and the contribution of vertical canals to the horizontal canal response. We highlight some of these issues and point to future developments and improvements. The paper assumes knowledge of how vHIT testing is conducted.

Background: Cervical VEMPs and ocular VEMPs are tests for evaluating otolith function in clinical practice. We developed a simple, portable and affordable device to record VEMP responses on patients, named μVEMP. Our aim was to validate and field test the new μVEMP device.Methods: We recorded cervical VEMPs and ocular VEMPs in response to bone conducted vibration using taps tendon hammer to the forehead (Fz) and to air conducted sounds using clicks. We simultaneously recorded VEMP responses (same subject, same electrode, same stimuli) in three healthy volunteers (2 females, age range: 29–57 years) with the μVEMP device and with a standard research grade commercial (CED) system used in clinics. We also used the μVEMP device to record VEMP responses from six patients (6 females, age mean±SD: 50.3 ± 20.8 years) with classical peripheral audio-vestibular diseases (unilateral vestibular neuritis, unilateral neurectomy, bilateral vestibular loss, unilateral superior canal dehiscence, unilateral otosclerosis).Results: The first part of this paper compared the devices using simultaneous recordings. The average of the concordance correlation coefficient was rc = 0.997 ± 0.003 showing a strong similarity between the measures. VEMP responses recorded with the μVEMP device on patients with audio-vestibular diseases were similar to those typically found in the literature.Conclusions: We developed, validated and field tested a new device to record ocular and cervical VEMPs in response to sound and vibration.This new device is portable (powered by a phone or tablet) with pocket-size dimensions (105 × 66 × 27 mm) and light weight (150 g). Although further studies and normative data are required, our μVEMP device is simpler (easier to use) and potentially more accessible than standard, commercially available equipment.

In 1988, we introduced impulsive testing of semicircular canal (SCC) function measured with scleral search coils and showed that it could accurately and reliably detect impaired function even of a single lateral canal. Later we showed that it was also possible to test individual vertical canal function in peripheral and also in central vestibular disorders and proposed a physiological mechanism for why this might be so. For the next 20 years, between 1988 and 2008, impulsive testing of individual SCC function could only be accurately done by a few aficionados with the time and money to support scleral search-coil systems—an expensive, complicated and cumbersome, semi-invasive technique that never made the transition from the research lab to the dizzy clinic. Then, in 2009 and 2013, we introduced a video method of testing function of each of the six canals individually. Since 2009, the method has been taken up by most dizzy clinics around the world, with now close to 100 refereed articles in PubMed. In many dizzy clinics around the world, video Head Impulse Testing has supplanted caloric testing as the initial and in some cases the final test of choice in patients with suspected vestibular disorders. Here, we consider seven current, interesting, and controversial aspects of video Head Impulse Testing: (1) introduction to the test; (2) the progress from the head impulse protocol (HIMPs) to the new variant—suppression head impulse protocol (SHIMPs); (3) the physiological basis for head impulse testing; (4) practical aspects and potential pitfalls of video head impulse testing; (5) problems of vestibulo-ocular reflex gain calculations; (6) head impulse testing in central vestibular disorders; and (7) to stay right up-to-date—new clinical disease patterns emerging from video head impulse testing. With thanks and appreciation we dedicate this article to our friend, colleague, and mentor, Dr Bernard Cohen of Mount Sinai Medical School, New York, who since his first article 55 years ago on compensatory eye movements induced by vertical SCC stimulation has become one of the giants of the vestibular world.

Experimental objective. To provide a safe, simple, relatively inexpensive, fast, accurate way of quantifying balance performance either in isolation, or in the face of challenges provided by 3D high definition moving visual stimuli as well as by the proprioceptive challenge from standing on a foam pad. This method uses the new technology of the Wii balance board to measure postural stability during powerful, realistic visual challenges from immersive virtual reality. Limitations of current techniques. Present computerized methods for measuring postural stability are large, complex, slow and expensive, and do not allow for testing the response to realistic visual challenges.Protocol. Subjects stand on a 6cm thick, firm, foam pad on a Wii balance board. They wear a fast, high resolution, low persistence, virtual reality head set (Oculus Rift DK2). This allows displays of varying speed, direction, depth and complexity to be delivered. The subject experiences a visual illusion of real objects fixed relative to the world, and any of these displays can be perturbed in an unpredictable fashion. A special app (Balance Rite) used the same procedures for analysing postural analysis as used by the Equitest.Power of the technique. Four simple proof of concept experiments demonstrate that this technique matches the gold standard Equitest in terms of the measurement of postural stability but goes beyond the Equitest by measuring stability in the face of visual challenges, which are so powerful that even healthy subjects fall. The response to these challenges presents an opportunity for predicting falls and for rehabilitation of seniors and patients with poor postural stability.Significance for the field. This new method provides a simpler, quicker, cheaper method of measurement than the Equitest. It may provide a new mode of training to prevent falls, by maintaining postural stability in the face of visual and proprioceptive challenges similar to those encountered in life.

Background/Hypothesis. The video Head Impulse Test (vHIT) is now widely used to test the function of each of the six semicircular canals individually by measuring the eye rotation response to an abrupt head rotation in the plane of the canal. The main measure of canal adequacy is the ratio of the eye movement response to the head movement stimulus i.e. the gain of the vestibulo-ocular reflex (VOR). However there is a need for normative data about how VOR gain is affected by age and also by head velocity, to allow the response of any particular patient to be compared to response of healthy subjects in their age range. In this study we determined for all six semicircular canals, normative values of VOR gain, for each canal across a range of head velocities, for healthy subjects in each decade of life.Study Design. The VOR gain was measured for all canals across a range of head velocities for at least 10 healthy subjects in decade age bands: 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89. Methods. The compensatory eye movement response to a small, unpredictable, abrupt head rotation (head impulse) was measured by the ICS Impulse prototype system. The same operator delivered every impulse to every subject. Results. VOR gain decreased at high head velocities, but was largely unaffected by age into the 80-89 year age group. There were some small but systematic differences between the two directions of head rotation, which appear to be largely due to the fact that in this study only the right eye was measured. The results are considered in relation to recent evidence about the effect of age on VOR performance.Conclusion. These normative values allow the results of any particular patient to be compared to the values of healthy people in their age range and so allow, for example, detection of whether a patient has a bilateral vestibular loss. VOR gain, as measured directly by the eye movement response to head rotation, seems largely unaffected by aging.

Background/Hypothesis. With the video Head Impulse Test (vHIT), the vertical VOR gain is defined as (vertical eye velocity/vertical head velocity), but compensatory eye movements to vertical canal stimulation usually have a torsional component. To minimize the contribution of torsion to the eye movement measurement, the horizontal gaze direction should be directed 40º from straight ahead so it is in the plane of the stimulated canal plane pair. Hypothesis: as gaze is systematically moved horizontally away from canal plane alignment, the measured vertical VOR gain should decrease.Study Design. 10 healthy subjects, with vHIT measuring vertical eye movement to head impulses in the plane of the left anterior-right posterior (LARP) canal plane, with gaze at one of 5 horizontal gaze positions (40º (aligned with the LARP plane), 20º, 0º, -20º, -40º).Methods. Every head impulse was in the LARP plane. The compensatory eye movement was measured by the vHIT prototype system. The one operator delivered every impulse. Results. The canal stimulus remained identical across trials, but the measured vertical VOR gain decreased as horizontal gaze angle was shifted away from alignment with the LARP canal plane.Conclusion. In measuring vertical VOR gain with vHIT the horizontal gaze angle should be aligned with the canal plane under test.

BackgroundDespite optimal medical and surgical intervention, freezing of gait commonly occurs in people with Parkinson disease. Action observation via video self-modeling, combined with physical practice, has potential as a noninvasive intervention to reduce freezing of gait. ObjectiveThe aim of this study is to determine the feasibility and acceptability of a home-based, personalized video self-modeling intervention delivered via a virtual reality head-mounted display (HMD) to reduce freezing of gait in people with Parkinson disease. The secondary aim is to investigate the potential effect of this intervention on freezing of gait, mobility, and anxiety. MethodsThe study was a single-group pre-post mixed methods pilot trial for which 10 participants with Parkinson disease and freezing of gait were recruited. A physiotherapist assessed the participants in their homes to identify person-specific triggers of freezing and developed individualized movement strategies to overcome freezing of gait. 180° videos of the participants successfully performing their movement strategies were created. Participants watched their videos using a virtual reality HMD, followed by physical practice of their strategies in their own homes over a 6-week intervention period. The primary outcome measures included the feasibility and acceptability of the intervention. Secondary outcome measures included freezing of gait physical tests and questionnaires, including the Timed Up and Go Test, 10-meter walk test, Goal Attainment Scale, and Parkinson Anxiety Scale. ResultsThe recruitment rate was 24% (10/42), and the retention rate was 90% (9/10). Adherence to the intervention was high, with participants completing a mean of 84% (SD 49%) for the prescribed video viewing and a mean of 100% (SD 56%) for the prescribed physical practice. One participant used the virtual reality HMD for 1 week and completed the rest of the intervention using a flat-screen device because of a gradual worsening of his motion sickness. No other adverse events occurred during the intervention or assessment. Most of the participants found using the HMD to view their videos interesting and enjoyable and would choose to use this intervention to manage their freezing of gait in the future. Five themes were constructed from the interview data: reflections when seeing myself, my experience of using the virtual reality system, the role of the virtual reality system in supporting my learning, developing a deeper understanding of how to manage my freezing of gait, and the impact of the intervention on my daily activities. Overall, there were minimal changes to the freezing of gait, mobility, or anxiety measures from baseline to postintervention, although there was substantial variability between participants. The intervention showed potential in reducing anxiety in participants with high levels of anxiety. ConclusionsVideo self-modeling using an immersive virtual reality HMD plus physical practice of personalized movement strategies is a feasible and acceptable method of addressing freezing of gait in people with Parkinson disease.

Body-worn video is increasingly relied upon in the criminal justice system, however it is unclear how viewing chest-mounted video may affect a police officer's statement about an event. In the present study, we asked whether reviewing footage from an experienced event could shape an individual's statement, and if so, whether reporting before reviewing may preserve an officer's original experience. Student participants (n = 97) were equipped with chest-mounted cameras as they viewed a simulated theft in virtual reality. One week later, half of the participants recalled the event in an initial statement while the other half did not. Participants then viewed either their body-worn video or a control video. Finally, participants provided their statement (no initial statement condition) or were given the opportunity to amend their original account (initial statement condition). Results revealed that viewing body-worn video enhanced the completeness and accuracy of individuals' free recall statements. However, whilst reviewing footage enabled individuals to exclude errors they had written in their initial statements, they also excluded true details that were uncorroborated by the camera footage (i.e., details which individuals experienced, but that their camera did not record). Such camera conformity is discussed in light of the debate on when an officer should access their body-worn video during an investigation and the influence of post-event information on memory.

Healthy subjects (N = 10) were exposed to 10-min cumulative pseudorandom bilateral bipolar Galvanic vestibular stimulation (GVS) on a weekly basis for 12 weeks (120 min total exposure). During each trial subjects performed computerized dynamic posturography and eye movements were measured using digital video-oculography. Follow up tests were conducted 6 weeks and 6 months after the 12-week adaptation period. Postural performance was significantly impaired during GVS at first exposure, but recovered to baseline over a period of 7-8 weeks (70-80 min GVS exposure). This postural recovery was maintained 6 months after adaptation. In contrast, the roll vestibulo-ocular reflex response to GVS was not attenuated by repeated exposure. This suggests that GVS adaptation did not occur at the vestibular end-organs or involve changes in low-level (brainstem-mediated) vestibulo-ocular or vestibulo-spinal reflexes. Faced with unreliable vestibular input, the cerebellum reweighted sensory input to emphasize veridical extra-vestibular information, such as somatosensation, vision and visceral stretch receptors, to regain postural function. After a period of recovery subjects exhibited dual adaption and the ability to rapidly switch between the perturbed (GVS) and natural vestibular state for up to 6 months.