Detection method for unrecognized spatial disorientation based on optical flow stimuli

BACKGROUND

Flight accidents caused by spatial disorientation (SD) greatly affect flight safety.

OBJECTIVE

Few studies have been devoted to the evaluation of SD.

METHODS

10 pilots and 10 non-pilots were recruited for the experimental induction of SD. Videos for giving optical flow stimuli were played at two different flow speeds to induce SD. Subjective judgment and center of foot pressure (CoP) data were collected from the tests. The data were combined to determine the occurrence of SD and analyze the SD types.

RESULTS

The number of self-reported SD events was slightly smaller in the pilots than in the non-pilots. The average upper bound of the confidence interval for the standard deviation of CoP was 0.32 ± 0.09 cm and 0.38 ± 0.12 cm in the pilots and non-pilots, respectively. This indicator was significantly lower in the pilots than in the non-pilots (P= 0.03). The success rate of the experimental induction of unrecognized SD was 26.7% and 45.0% in the pilots and non-pilots, respectively.

CONCLUSION

The method offered a new to analyze unrecognized SD. We could determine the occurrence unrecognized SD. This is an essential means of reducing flight accidents caused by unrecognized SD.

Attentional Tunneling in Pilots During a Visual Tracking Task With a Head Mounted Display

OBJECTIVE

We examined whether active head aiming with a Helmet Mounted Display (HMD) can draw the pilot's attention away from a primary flight task. Furthermore, we examined whether visual clutter increases this effect.

BACKGROUND

Head up display symbology can result in attentional tunneling, and clutter makes it difficult to identify objects.

METHOD

Eighteen military pilots had to simultaneously perform an attitude control task while flying in clouds and a head aiming task in a fixed-base flight simulator. The former consisted of manual compensation for roll disturbances of the aircraft, while the latter consisted of keeping a moving visual target inside a small or large head-referenced circle. A "no head aiming" condition served as a baseline. Furthermore, all conditions were performed with or without visual clutter.

RESULTS

Head aiming led to deterioration of the attitude control task performance and an increase of the amount of roll-reversal errors (RREs). This was even the case when head aiming required minimal effort. Head aiming accuracy was significantly lower when the roll disturbances in the attitude control task were large compared to when they were small. Visual clutter had no effect on both tasks.

CONCLUSION

We suggest that active head aiming of HMD symbology can cause attentional tunneling, as expressed by an increased number of RREs and less accuracy on a simultaneously performed attitude control task.

APPLICATION

This study improves our understanding in the perceptual and cognitive effects of (military) HMDs, and has implications for operational use and possibly (re)design of HMDs.

Behavioral Disorders of Spatial Cognition in Patients with Mild Cognitive Impairment due to Alzheimer's Disease: Preliminary Findings from the BDSC-MCI Project

(1) Background: Spatial cognition (SC) is one of the earliest cognitive domains to be impaired in the course of Alzheimer's disease (AD), resulting in spatial disorientation and becoming lost even in familiar surroundings as later dementia symptoms. To date, few studies have identified initial alterations of spatial navigation (SN) in the premorbid AD phase by real-world paradigms, and none have adopted an innovative technological apparatus to better detect gait alterations as well as physiological aspects correlated to spatial disorientation (SD). The present study aimed at exploring initial SN defects in patients with prodromal AD via a naturalistic task by using a sensory garment. (2) Methods: 20 community-dwelling patients with Mild Cognitive Impairment (MCI) due to AD and 20 age/education controls were assessed on their sequential egocentric and allocentric navigation abilities by using a modified version of the Detour Navigation Test (DNT-mv). (3) Results: When compared to controls, patients with MCI due to AD exhibited higher wrong turns (WT) and moments of hesitation (MsH) in the DNT-mv, reflecting difficulties both in sequential egocentric and allocentric navigation, depending on hippocampal deterioration. Moreover, they reported more complaints about their SN competencies and lower long-term visuospatial memory abilities than controls. Remarkably, WTs and MsH manifested in the allocentric naturalistic task of the DNT-mv were associated with autonomic nervous system alteration pertaining to cardiac functioning in the whole sample. (4) Conclusions: Naturalistic navigation tests of hippocampal function using a continuous non-invasive monitoring device can provide early markers of spatial disorientation in patients with MCI due to AD. Future studies should develop cognitive remediation techniques able to enhance SC residual abilities in patients at high risk of conversion into dementia and ecological paradigms to be replicated on a large scale.

Factors of significance for the ability of fighter pilots to visually indicate the magnitude of roll tilt during simulated turns in a centrifuge

During coordinated flight and centrifugation, pilots show interindividual variability in perceived roll tilt. The study explored how this variability is related to perceptual and cognitive functions. Twelve pilots underwent three 6-min centrifugations on two occasions (G levels: 1.1G, 1.8G, and 2.5G; gondola tilts: 25°, 56°, and 66°). The subjective visual horizontal (SVH) was measured with an adjustable luminous line and the pilots gave estimates of experienced G level. Afterward, they were interrogated regarding the relationship between G level and roll tilt and adjusted the line to numerically mentioned angles. Generally, the roll tilt during centrifugation was underestimated, and there was a large interindividual variability. Both knowledge on the relationship between G level and bank angle, and ability to adjust the line according to given angles contributed to the prediction of SVH in a multiple regression model. However, in most cases, SVH was substantial smaller than predictions based on specific abilities.

Orientation Comes First: Becoming Aware of Spatial Disorientation Interferes with Cognitive Performance

BACKGROUND

Previous research has shown that experiencing motion stimuli negatively impacts cognitive performance.

OBJECTIVE

In the current study, we investigate whether this impact relates to Type-II spatial disorientation (SD), to motion stimulus magnitude, or to an interaction of these factors.

METHOD

Stimuli for participants (n = 23) consisted of Earth-vertical yaw rotations on a rotating chair in a completely darkened room. In the surprise condition, the stimulus started with subthreshold acceleration, followed by suprathreshold deceleration to a non-zero velocity, inducing a sensation of rotation that is opposite to the actual rotation revealed when the lights were switched on. In the no-surprise condition, the same changes in velocity were used, but starting from (almost) zero velocity, which induced a sensation of rotation in the same direction as the actual rotation. Participants performed a self-paced arithmetic task and measurement of their cognitive performance started after the environment was revealed. Stimulus magnitude was operationalized through higher or lower peak suprathreshold deceleration.

RESULTS

The results revealed that counting speed decreased significantly when participants were surprised, constituting a large effect size. The proportion of counting errors likewise increased significantly when participants were surprised, but only in the high-magnitude condition.

APPLICATION

The findings suggest that surprise caused by the recognition of SD has an involuntary disruptive effect on cognition, which may impact performance of piloting tasks. These results are relevant when modeling motion stimuli effects on performance, and when developing SD awareness training for pilots.

Hypoxic acclimatization training improves the resistance to motion sickness

Objective

Vestibular provocation is one of the main causes of flight illusions, and its occurrence is closely related to the susceptibility of motion sickness (MS). However, existing training programs have limited effect in improving the resistance to motion sickness. In this study, we investigated the effects of hypoxia acclimatization training (HAT) on the resistance to motion sickness.

Methods

Healthy military college students were identified as subjects according to the criteria. MS model was induced by a rotary chair. Experimental groups included control, HAT, 3D roller training (3DRT), and combined training.

Results

The Graybiel scores were decreased in the HAT group and the 3DRT group and further decreased in the combined training group in MS induced by the rotary chair. Participants had a significant increase in blood pressure after the rotary chair test and a significant increase in the heart rate during the rotary chair test, but these changes disappeared in all three training groups. Additionally, LFn was increased, HFn was decreased, and LF/HF was increased accordingly during the rotary chair test in the control group, but the changes of these three parameters were completely opposite in the three training groups during the rotary chair test. Compared with the control group, the decreasing changes in pupillary contraction velocity (PCV) and pupillary minimum diameter (PMD) of the three training groups were smaller. In particular, the binocular PCV changes were further attenuated in the combined training group.

Conclusion

Our research provides a possible candidate solution for training military pilots in the resistance to motion sickness.

Vibrotactile feedback as a countermeasure for spatial disorientation

Spaceflight can make astronauts susceptible to spatial disorientation which is one of the leading causes of fatal aircraft accidents. In our experiment, blindfolded participants used a joystick to balance themselves while inside a multi-axis rotation device (MARS) in either the vertical or horizontal roll plane. On Day 1, in the vertical roll plane (Earth analog condition) participants could use gravitational cues and therefore had a good sense of their orientation. On Day 2, in the horizontal roll plane (spaceflight analog condition) participants could not use gravitational cues and rapidly became disoriented and showed minimal learning and poor performance. One potential countermeasure for spatial disorientation is vibrotactile feedback that conveys body orientation provided by small vibrating devices applied to the skin. Orientation-dependent vibrotactile feedback provided to one group enhanced performance in the spaceflight condition but the participants reported a conflict between the accurate vibrotactile cues and their erroneous perception of their orientation. Specialized vibrotactile training on Day 1 provided to another group resulted in significantly better learning and performance in the spaceflight analog task with vibrotactile cueing. In this training, participants in the Earth analog condition on Day 1 were required to disengage from the task of aligning with the gravitational vertical encoded by natural vestibular/somatosensory afference and had to align with randomized non-vertical directions of balance signaled by vibrotactile feedback. At the end of Day 2, we deactivated the vibrotactile feedback after both vibration-cued groups had practiced with it in the spaceflight analog condition. They performed as well as the group who did not have any vibrotactile feedback. We conclude that after appropriate training, vibrotactile orientation feedback augments dynamic spatial orientation and does not lead to any negative dependence.

Galvanic vestibular stimulation to counteract leans illusion: comparing step and ramped waveforms

Leans is a common type of Spatial Disorientation (SD) illusion that causes pilots to be confused about the position of the aircraft during a flight. This illusion could lead to serious adverse effects and even flight mishaps. Therefore, an effective means to deal with leans is crucial for flight safety. This study aims to investigate the effects of Galvanic Vestibular Stimulation (GVS) technology with different waveforms as a tool to mitigate the negative effects of leans. 20 Air Force pilots participated in leans-induced flight simulation experiment with three GVS conditions (without-GVS, step-GVS, ramped-GVS). Bank angle error, subjective SD, perceived strength, and annoyance were measured as the dependent variables. Analysis revealed that step-GVS and ramped-GVS yielded lower bank angle errors and subjective SD than without-GVS. In addition, annoyance ratings were lower for ramped-GVS than step-GVS. This study suggests that GVS has the potential to be utilised as a counteracting tool to cope with leans.Practitioner summary: Galvanic Vestibular Stimulation (GVS) can be utilised as a tool to counteract the detrimental effects of leans illusion, specifically the ramped style GVS, considering that it is less annoying and distracting for the pilots. In general, GVS induces a roll sensation that can offset the false sensation caused by the leans, which can potentially help maintain flight safety and avoid spatial disorientation-related accidents.Abbreviations: SD: spatial disorientation; GVS: galvanic vestibular stimulation; MSSQ: motion sickness susceptibility questionniare; SSQ: simulator sickness questionnaire; BLE: bluetooth low energy; PCB: printed circuit board; RPM: revolution per minute.

Spatial Disorientation Under Dark Conditions Across Development in an Alzheimer's Disease Mouse Model

Alzheimer's disease (AD) is associated with hippocampal neuropathology and cognitive impairments, including wandering behavior or becoming lost in a familiar environment. Wandering behavior is severe and manifests early in life for people with specific genetic mutations. Genetic mouse models of AD have been developed to characterize the onset and progression of behavioral deficits that represent human behaviors, such as wandering, to test the efficacy of therapeutics. It is not clear if current assessments of mouse models capture the onset of AD or a snapshot of its progression. Sequential analysis of open field behavior provides a robust, quick test to dissociate navigation cues that contribute to spatial disorientation, a feature of wandering. Despite potential utility in evaluating this feature of AD, little work has been reported using animal models of dementia in this task. Thus, we examined the use of different sources of information to maintain spatial orientation at two prodromal ages in female transgenic CRND8 AD (n = 17) and Control mice (n = 16). These mice exhibit amyloid plaques, a hallmark neuropathological feature of AD, that are associated with cognitive dysfunction at ∼three months of age. Spatial disorientation was observed at two months and more severely at four months under dark conditions, but performance was spared when visual environmental cues were available. This study provides documentation of impaired self-movement cue processing in AD mice, establishing the dark open field as a behavioral tool to characterize spatial disorientation associated with AD. These findings may accelerate future assessments of novel therapeutic interventions for neurological disorders.

New model of superior semicircular canal dehiscence with reversible diagnostic findings characteristic of patients with the disorder

Background

Third window syndrome is a vestibular-cochlear disorder in humans in which a third mobile window of the otic capsule creates changes to the flow of sound pressure energy through the perilymph/endolymph. The nature and location of this third mobile window can occur at many different sites (or multiple sites); however, the most common third mobile window is superior semicircular canal dehiscence (SSCD). There are two essential objective diagnostic characteristics needed to validate a model of SSCD: the creation of a pseudoconductive hearing loss and cVEMP increased amplitude and decreased threshold.

Methods

Adult Mongolian gerbils (n = 36) received surgical fenestration of the superior semicircular canal of the left inner ear. ABR and c+VEMP testing were carried out prior to surgery and over acute (small 1 mm SSCD, 1-10 days) or prolonged (large 2 mm SSCD, 28 days) recovery. Because recovery of function occurred quickly, condenser brightfield stereomicroscopic examination of the dehiscence site was carried out for the small SSCD animals post-hoc and compared to both ABRs and c+VEMPs. Micro-CT analysis was also completed with representative samples of control, day 3 and 10 post-SSCD animals.

Results

The SSCD created a significant worsening of hearing thresholds of the left ear; especially in the lower frequency domain (1-4 kHz). Left (EXP)/right (CTL) ear comparisons via ABR show significant worsening thresholds at the same frequency representations, which is a proxy for the human pseudoconductive hearing loss seen in SSCD. For the c+VEMP measurements, increased amplitude of the sound-induced response (N1 2.5 ms and P1 3.2 ms) was observed in animals that received larger fenestrations. As the bone regrew, the c+VEMP and ABR responses returned toward preoperative values. For small SSCD animals, micro-CT data show that progressive osteoneogenesis results in resurfacing of the SSCD without bony obliteration.

Conclusion

The large (2 mm) SSCD used in our gerbil model results in similar electrophysiologic findings observed in patients with SSCD. The changes observed also reverse and return to baseline as the SSCD heals by bone resurfacing (with the lumen intact). Hence, this model does not require a second surgical procedure to plug the SSCD.

Visual measures of perceived roll tilt in pilots during coordinated flight and gondola centrifugation

BACKGROUND

During a simulated coordinated turn in a gondola centrifuge, experienced pilots show a substantial inter-individual variability in visual measures of perceived roll tilt. Because of the centrifuge's small radius, the pattern of stimuli to the semicircular canals during acceleration of the centrifuge differs in certain respects from that of an aircraft entering a turn.

OBJECTIVE

To explore whether these differences may be of significance for the pilot's roll- plane orientation and whether individual characteristics revealed in the centrifuge correspond to those during real flight.

METHOD

8 fixed-wing air-force pilots were tested in a centrifuge and a high-performance aircraft. The centrifuge was accelerated to 2 G (gondola inclination 60°) within 10 s. The duration at 2 G was 6 minutes. Similar profiles were created in the aircraft. The subjective visual horizontal (SVH) was measured using an adjustable luminous line in darkness. Each pilot was tested on three occasions: centrifuge (2 runs), aircraft (2 turns), centrifuge (2 runs). For each 2-G exposure, initial and final SVH values were established via curve fitting.

RESULT

Despite a large inter-individual variability (±SD), group means were similar in the aircraft (initial: 43.0±20.6°; final: 22.5±14.8°) and centrifuge (initial: 40.6±17.0°; final: 20.5±16.0°). Further, individual peculiarities in response patterns were similar in the two conditions. For both the initial and final SVH tilt there was a high correlation between centrifuge and aircraft.

CONCLUSION

The correspondence between conditions suggests that the centrifuge is an adequate means for demonstrating the fundamental motion pattern of coordinated flight and also for establishing the individual pilot's ability to perceive an aircraft's roll attitude.Findings are discussed in connection with vestibular learning and the possibility of underlying differences between pilots in the keenness for semicircular canal and somatosensory cues.

Leans Illusion in Hexapod Simulator Facilitates Erroneous Responses to Artificial Horizon in Airline Pilots

OBJECTIVE

We tested whether a procedure in a hexapod simulator can cause incorrect assumptions of the bank angle (i.e., the "leans") in airline pilots as well as incorrect interpretations of the attitude indicator (AI).

BACKGROUND

The effect of the leans on interpretation errors has previously been demonstrated in nonpilots. In-flight, incorrect assumptions can arise due to misleading roll cues (spatial disorientation).

METHOD

Pilots (n = 18) performed 36 runs, in which they were asked to roll to wings level using only the AI. They received roll cues before the AI was shown, which matched with the AI bank angle direction in most runs, but which were toward the opposite direction in a leans-opposite condition (four runs). In a baseline condition (four runs), they received no roll cues. To test whether pilots responded to the AI, the AI sometimes showed wings level following roll cues in a leans-level condition (four runs).

RESULTS

Overall, pilots made significantly more errors in the leans-opposite (19.4%) compared to the baseline (6.9%) or leans-level condition (0.0%). There was a pronounced learning effect in the leans-opposite condition, as 38.9% of pilots made an error in the first exposure to this condition. Experience (i.e., flight hours) had no significant effects.

CONCLUSION

The leans procedure was effective in inducing AI misinterpretations and control input errors in pilots.

APPLICATION

The procedure can be used in spatial disorientation demonstrations. The results underline the importance of unambiguous displays that should be able to quickly correct incorrect assumptions due to spatial disorientation.

Generating Flight Illusions Using Galvanic Vestibular Stimulation in Virtual Reality Flight Simulations

Background

Vestibular flight illusions remain a significant source of concern for aviation training. Most fixed-based simulation training environments, including new virtual reality (VR) technology, lack the ability to recreate vestibular flight illusions as vestibular cues cannot be provided without stimulating the vestibular end organs. Galvanic vestibular stimulation (GVS) has long been used to create vestibular perception. The purpose of this study is to evaluate the ability of GVS to simulate common flight illusions by intentionally providing mismatched GVS during flight simulation scenarios in VR.

Methods

Nineteen participants performed two flight simulation tasks-take off and sustained turn-during two separate VR flight simulation sessions, with and without GVS (control). In the GVS session, specific multi-axis GVS stimulation (i.e., electric currents) was provided to induce approximate somatogravic and Coriolis illusions during the take-off and sustained turn tasks, respectively. The participants used the joystick to self-report their subjective motion perception. The angular joystick movement along the roll, yaw, and pitch axes was used to measure cumulative angular distance and peak angular velocity as continuous variables of motion perception across corresponding axes. Presence and Simulator Sickness Questionnaires were administered at the end of each session.

Results

The magnitude and variability of perceived somatogravic illusion during take-off task in the form of cumulative angular distance (p < 0.001) and peak velocity (p < 0.001) along the pitch-up axis among participants were significantly larger in the GVS session than in the NO GVS session. Similarly, during the sustained turn task, perceived Coriolis illusion in the form of cumulative angular distances (roll: p = 0.005, yaw: p = 0.015, pitch: p = 0.007) and peak velocities (roll: p = 0.003, yaw: p = 0.01, pitch: p = 0.007) across all three axes were significantly larger in the GVS session than in the NO GVS session. Subjective nausea was low overall, but significantly higher in the GVS session than in the NO GVS session (p = 0.026).

Discussion

Our findings demonstrated that intentionally mismatched GVS can significantly affect motion perception and create flight illusion perceptions during fixed-based VR flight simulation. This has the potential to enhance future training paradigms, providing pilots the ability to safely experience, identify, and learn to appropriately respond to flight illusions during ground training.

Using GPS Tracking to Investigate Outdoor Navigation Patterns in Patients With Alzheimer Disease: Cross-sectional Study

Background

Spatial disorientation is one of the earliest and most distressing symptoms seen in patients with Alzheimer disease (AD) and can lead to them getting lost in the community. Although it is a prevalent problem worldwide and is associated with various negative consequences, very little is known about the extent to which outdoor navigation patterns of patients with AD explain why spatial disorientation occurs for them even in familiar surroundings.

Objective

This study aims to understand the outdoor navigation patterns of patients with AD in different conditions (alone vs accompanied; disoriented vs not disoriented during the study) and investigate whether patients with AD experienced spatial disorientation when navigating through environments with a high outdoor landmark density and complex road network structure (road intersection density, intersection complexity, and orientation entropy).

Methods

We investigated the outdoor navigation patterns of community-dwelling patients with AD (n=15) and age-matched healthy controls (n=18) over a 2-week period using GPS tracking and trajectory mining analytical techniques. Here, for the patients, the occurrence of any spatial disorientation behavior during this tracking period was recorded. We also used a spatial buffer methodology to capture the outdoor landmark density and features of the road network in the environments that the participants visited during the tracking period.

Results

The patients with AD had outdoor navigation patterns similar to those of the controls when they were accompanied; however, when they were alone, they had significantly fewer outings per day (total outings: P<.001; day outings: P=.003; night outings: P<.001), lower time spent moving per outing (P=.001), lower total distance covered per outing (P=.009), lower walking distance per outing (P=.02), and lower mean distance from home per outing (P=.004). Our results did not identify any mobility risk factors for spatial disorientation. We also found that the environments visited by patients who experienced disorientation versus those who maintained their orientation during the tracking period did not significantly differ in outdoor landmark density (P=.60) or road network structure (road intersection density: P=.43; intersection complexity: P=.45; orientation entropy: P=.89).

Conclusions

Our findings suggest that when alone, patients with AD restrict the spatial and temporal extent of their outdoor navigation in the community to successfully reduce their perceived risk of spatial disorientation. Implications of this work highlight the importance for future research to identify which of these individuals may be at an actual high risk for spatial disorientation as well as to explore the implementation of health care measures to help maintain a balance between patients’ right to safety and autonomy when making outings alone in the community.

Spatial orientation during gondola centrifugation with subjects upright versus supine: Evidence for Gestalt psychological mechanisms in vestibular perception

BACKGROUND

Recent theories suggest that perception of complex self-motion is governed by familiarity of the motion pattern as a whole in 3D.

OBJECTIVE

To explore how familiarity determines the perceived angular displacement with respect to the Earth during a simulated coordinated turn in a gondola centrifuge.

METHOD

The centrifuge was accelerated to 2G (gondola displacement 60°) within 12.5 s. Using visual indicators in darkness, responses to the gondola displacement were recorded with subjects (n = 10) in two positions: sitting-upright, facing-forward versus lying-supine, feet-forwards. Each subject underwent 2×2 6-minute runs.

RESULT

When upright, subjects indicated a tilt of initially 18.8±11.3°, declining with T = 66±37 s. In the supine position (subject's yaw plane coinciding with the plane of gondola displacement) the indicated displacement was negligible (-0.3±4.8°).

CONCLUSION

Since the canal system is most responsive to stimuli in yaw, these findings are difficult to explain by bottom-up models. Rather, the motion pattern during acceleration would be recognized as a familiar or meaningful whole (entering a co-ordinated turn) only when the subject is upright. Presumably, the degree of familiarity is reflected in the subject's ability to discern and estimate a single stimulus component. Findings are discussed in connection with human factors in aviation and the principles of Gestalt psychology.

Effect of Spatial Disorientation in a Virtual Environment on Gait and Vital Features in Patients with Dementia: Pilot Single-Blind Randomized Control Trial

Background

Orientation deficits are among the most devastating consequences of early dementia. Digital navigation devices could overcome these deficits if adaptable to the user’s needs (ie, provide situation-aware, proactive navigation assistance). To fulfill this task, systems need to automatically detect spatial disorientation from sensors in real time. Ideally, this would require field studies consisting of real-world navigation. However, such field studies can be challenging and are not guaranteed to cover sufficient instances of disorientation due to the large variability of real-world settings and a lack of control over the environment.

Objective

Extending a foregoing field study, we aim to evaluate the feasibility of using a sophisticated virtual reality (VR) setup, which allows a more controlled observation of disorientation states and accompanying behavioral and physiological parameters in cognitively healthy older people and people with dementia.

Methods

In this feasibility study, we described the experimental design and pilot outcomes of an ongoing study aimed at investigating the effect of disorientation on gait and selected physiological features in a virtual laboratory. We transferred a real-world navigation task to a treadmill-based virtual system for gait analysis. Disorientation was induced by deliberately manipulating landmarks in the VR projection. Associated responses in motion behavior and physiological parameters were recorded by sensors. Primary outcomes were variations in motion and physiological parameters, frequency of disorientation, and questionnaire-derived usability estimates (immersion and perceived control of the gait system) for our population of interest. At this time, the included participants were 9 cognitively healthy older participants [5/9 women, 4/9 men; mean age 70 years, SD 4.40; Mini–Mental State Examination (MMSE) mean 29, SD 0.70) and 4 participants with dementia (2/4 women, 2/4 men; mean age 78 years, SD 2.30 years; MMSE mean 20.50, SD 7.54). Recruitment is ongoing, with the aim of including 30 cognitively healthy older participants and 20 participants with dementia.

Results

All 13 participants completed the experiment. Patients’ route was adapted by shortening it relative to the original route. Average instances of disorientation were 21.40, 36.50, and 37.50 for the cognitively healthy older control, cognitively healthy older experimental participants, and participants with dementia, respectively. Questionnaire outcomes indicated that participants experienced adequate usability and immersion; 4.30 for presence, 3.73 for involvement, and 3.85 for realism of 7 possible points, indicating a good overall ability to cope with the experiment. Variations were also observed in motion and physiological parameters during instances of disorientation.

Conclusions

This study presents the first feasibility outcomes of a study investigating the viability of using a sophisticated VR setup, based on an earlier real-world navigation study, to study spatial disorientation among cognitively healthy older people and people with dementia. Preliminary outcomes give confidence to the notion that our setup can be used to assess motion and physiological markers of disorientation, even in people with cognitive decline.

Trial Registration

ClinicalTrials.gov; https://clinicaltrials.gov/ct2/show/NCT04134806

Testing Navigation in Real Space: Contributions to Understanding the Physiology and Pathology of Human Navigation Control

Successful navigation relies on the flexible and appropriate use of metric representations of space or topological knowledge of the environment. Spatial dimensions (2D vs. 3D), spatial scales (vista-scale vs. large-scale environments) and the abundance of visual landmarks critically affect navigation performance and behavior in healthy human subjects. Virtual reality (VR)-based navigation paradigms in stationary position have given insight into the major navigational strategies, namely egocentric (body-centered) and allocentric (world-centered), and the cerebral control of navigation. However, VR approaches are biased towards optic flow and visual landmark processing. This major limitation can be overcome to some extent by increasingly immersive and realistic VR set-ups (including large-screen projections, eye tracking and use of head-mounted camera systems). However, the highly immersive VR settings are difficult to apply particularly to older subjects and patients with neurological disorders because of cybersickness and difficulties with learning and conducting the tasks. Therefore, a need for the development of novel spatial tasks in real space exists, which allows a synchronous analysis of navigational behavior, strategy, visual explorations and navigation-induced brain activation patterns. This review summarizes recent findings from real space navigation studies in healthy subjects and patients with different cognitive and sensory neurological disorders. Advantages and limitations of real space navigation testing and different VR-based navigation paradigms are discussed in view of potential future applications in clinical neurology.

Third Window Syndrome: Surgical Management of Cochlea-Facial Nerve Dehiscence

Objective: This communication is the first assessment of outcomes after surgical repair of cochlea-facial nerve dehiscence (CFD) in a series of patients. Pre- and post-operative quantitative measurement of validated survey instruments, symptoms, diagnostic findings and anonymous video descriptions of symptoms in a cohort of 16 patients with CFD and third window syndrome (TWS) symptoms were systematically studied.

Study design: Observational analytic case-control study.

Setting: Quaternary referral center.

Patients: Group 1 had 8 patients (5 children and 3 adults) with CFD and TWS who underwent surgical management using a previously described round window reinforcement technique. Group 2 had 8 patients (2 children and 6 adults) with CFD who did not have surgical intervention.

Interventions: The Dizziness Handicap Inventory (DHI) and Headache Impact Test (HIT-6) were administered pre-operatively and post-operatively. In addition, diagnostic findings of comprehensive audiometry, cervical vestibular evoked myogenic potential (cVEMP) thresholds and electrocochleography (ECoG) were studied. Symptoms before and after surgical intervention were compared.

Main outcome measures: Pre- vs. post-operative DHI, HIT-6, and audiometric data were compared statistically. The thresholds and amplitudes for cVEMP in symptomatic ears, ears with cochlea-facial nerve dehiscence and ears without CFD were compared statistically.

Results: There was a highly significant improvement in DHI and HIT-6 at pre- vs. post-operative (p < 0.0001 and p < 0.001, respectively). The age range was 12.8–52.9 years at the time of surgery (mean = 24.7 years). There were 6 females and 2 males. All 8 had a history of trauma before the onset of their symptoms. The mean cVEMP threshold was 75 dB nHL (SD 3.8) for the operated ear and 85.7 dB (SD 10.6) for the unoperated ear. In contrast to superior semicircular canal dehiscence, where most ears have abnormal ECoG findings suggestive of endolymphatic hydrops, only 1 of 8 operated CFD ears (1 of 16 ears) had an abnormal ECoG study.

Conclusions: Overall there was a marked improvement in DHI, HIT-6 and symptoms post-operatively. Statistically significant reduction in cVEMP thresholds was observed in patients with radiographic evidence of CFD. Surgical management with round window reinforcement in patients with CFD was associated with improved symptoms and outcomes measures.

The influence of sloping cloud in the visual field on the cognitive determinants of military pilots' behavior

OBJECTIVES

The study analyzed the effectiveness of military pilots' behavior under the influence of false horizon illusion - a false perception of the real horizon. It was assumed that visual illusion tends to cause spatial disorientation (SD). The question was asked which orientation of the sloping cloud (right/left) would have a bigger impact on SD. The effectiveness of the flight profile performance under the influence of visual illusion was analyzed in the context of the field dependence (FD), field independence (FI) or field intermediate dependence (FINT) of perception, the effectiveness of attention and operational memory.

MATERIAL AND METHODS

The study covered 66 pilots. A flight simulator was used as a measure of effectiveness in performing the flight profile in spatial disorientation conditions. The effectiveness of attention and working memory was diagnosed using 4 computer tasks.

RESULTS

It was revealed that the right sloping cloud (compared to the left sloping cloud) had a greater impact on military pilots' behavior. The cognitive style distinguishes the accuracy of the flight profile performance from the inclined cloud pointing to the right. The comparisons showed significant differences between the FI and FD pilot groups. All the pilots demonstrated the right-sided asymmetry of the flight rate. While performing tasks on the simulator, the FI pilots were characterized by a more stable rate than the FINT pilots.

CONCLUSIONS

A general conclusion is that the "correct falling cloud" had a greater impact on pilots' behavior. The presented results confirm the hypothesis that susceptibility to visual illusions is significantly increased in the pilots characterized by field dependence while the pilots with the FINT style of perception are characterized by a greater variability of the flight rate. Int J Occup Med Environ Health. 2019;32(5):653-62.

Wrist-Worn Electrodermal Activity as a Novel Neurophysiological Biomarker of Autonomic Symptoms in Spatial Disorientation

Background: Spatial disorientation is one of the most frequent causes of aircraft accidents, and is thus a major problem affecting air safety. Although a number of studies have examined spatial disorientation, the precise physiological changes occurring as a direct result of spatial disorientation and motion sickness remain unclear. The present study sought to investigate electrodermal activity (EDA) and subjective autonomic symptoms during spatial disorientation training, and to develop an indicator of physiological changes for pilot candidates. Methods: In the current study, we investigated changes in EDA measured using a wrist-worn device, and subjective autonomic nervous system symptoms during spatial disorientation training for pilot candidates. We then used the Graybiel diagnostic criteria to develop a novel physiological biomarker. Results: We found that maximum EDA change and peak amplitude were significantly increased in participants with a Graybiel score of ≥3 points compared with those who scored < 2 points. Furthermore, for symptoms of cold sweating and saliva secretion (from the seven Graybiel diagnostic criteria), the maximum EDA change in participants with scores ≥1 point was significantly higher than that of participants scoring 0 points. Conclusion: Our results indicate that EDA data measured with a wrist-worn device could provide a useful method for objective evaluation of the severity of spatial disorientation and motion sickness.

Spatial disorientation and executive dysfunction in elderly nondemented patients with Parkinson's disease

OBJECTIVES

Patients with Parkinson's disease (PD) present with a wide range of cognitive deficits. Cognitive impairment is recognized as an independent nonmotor aspect of the disorder and has a critical role in functional outcome and conversion into PD dementia. To date, everyday memory impairment in elderly patients with PD is underinvestigated and its relationship with executive dysfunction was not clearly explained. Our study aims at clarifying the neuropsychological pattern of everyday memory and executive deterioration in elderly patients with PD.

METHODS

Forty nondemented PD patients (mean age 71.2 years; M:F = 29:11) and 30 well-matched controls (mean age 70.7 years; M:F = 15:15) were assessed on everyday memory (Rivermead Behavioral Memory Test [RBMT]) and executive functioning (Frontal Assessment Battery [FAB]) measures. Mann-Whitney U-tests (Bonferroni corrected) were used to compare groups on these measures and Spearman's rank correlations were performed to highlight their associations.

RESULTS

PD patients performed worse than controls on recall for novel tasks and geographic recall (RMBT) as well as lexical fluency and mental flexibility (FAB). Particularly, spatial orientation depending on egocentric navigation seems to be altered in PD patients. The clinical group showed poorer performances than controls in mental flexibility, sensitivity to interference, and inhibitory control. Such measures were associated with immediate and delayed recall, picture recognition, prospective memory, and orientation tasks of everyday memory.

CONCLUSION

Executive-type difficulties and memory-type difficulties have an impact on cognitive performances of elderly patients with PD. We recommend using the RBMT and the FAB as part of routinely neuropsychological battery for assessing PD patients.

Using virtual reality to distinguish subjects with multiple- but not single-domain amnestic mild cognitive impairment from normal elderly subjects

AIM

Spatial disorientation is a hallmark of amnestic mild cognitive impairment (aMCI) and Alzheimer's disease. Our aim was to use virtual reality to determine the allocentric and egocentric memory deficits of subjects with single-domain aMCI (aMCIsd) and multiple-domain aMCI (aMCImd). For this purpose, we introduced an advanced virtual reality navigation task (VRNT) to distinguish these deficits in mild Alzheimer's disease (miAD), aMCIsd, and aMCImd.

METHODS

The VRNT performance of 110 subjects, including 20 with miAD, 30 with pure aMCIsd, 30 with pure aMCImd, and 30 cognitively normal controls was compared. Our newly developed VRNT consists of a virtual neighbourhood (allocentric memory) and virtual maze (egocentric memory). Verbal and visuospatial memory impairments were also examined with Rey Auditory-Verbal Learning Test and Rey-Osterrieth Complex Figure Test, respectively.

RESULTS

We found that miAD and aMCImd subjects were impaired in both allocentric and egocentric memory, but aMCIsd subjects performed similarly to the normal controls on both tasks. The miAD, aMCImd, and aMCIsd subjects performed worse on finding the target or required more time in the virtual environment than the aMCImd, aMCIsd, and normal controls, respectively. Our findings indicated the aMCImd and miAD subjects, as well as the aMCIsd subjects, were more impaired in egocentric orientation than allocentric orientation.

CONCLUSION

We concluded that VRNT can distinguish aMCImd subjects, but not aMCIsd subjects, from normal elderly subjects. The VRNT, along with the Rey Auditory-Verbal Learning Test and Rey-Osterrieth Complex Figure Test, can be used as a valid diagnostic tool for properly distinguishing different forms of aMCI.

Vestibular Deficits in Neurodegenerative Disorders: Balance, Dizziness, and Spatial Disorientation

The vestibular system consists of the peripheral vestibular organs in the inner ear and the associated extensive central nervous system projections—from the cerebellum and brainstem to the thalamic relays to cortical projections. This system is important for spatial orientation and balance, both of critical ecological importance, particularly for successful navigation in our environment. Balance disorders and spatial disorientation are common presenting features of neurodegenerative diseases; however, little is known regarding central vestibular processing in these diseases. A ubiquitous aspect of central vestibular processing is its promiscuity given that vestibular signals are commonly found in combination with other sensory signals. This review discusses how impaired central processing of vestibular signals—typically in combination with other sensory and motor systems—may account for the impaired balance and spatial disorientation in common neurodegenerative conditions. Such an understanding may provide for new diagnostic tests, potentially useful in detecting early disease while a mechanistic understanding of imbalance and spatial disorientation in these patients may enable a vestibular-targeted therapy for such problems in neurodegenerative diseases. Studies with state of the art central vestibular testing are now much needed to tackle this important topic.

Visual effects on the subjective visual vertical and subjective postural head vertical during static roll-tilt

OBJECTIVES

Tilt perception is part of the perception of spatial orientation. It is determined not only by the allocentric gravity axis, but also by a second allocentric axis induced by visual information as well as by the egocentric body (head) axis induced by somatosensory information. The aim of this study was to quantify roll-tilt perception using the subjective visual vertical (SVV) and the newly developed subjective postural head vertical (SPHV) and to investigate the visual effects on both during static roll-tilt.

STUDY DESIGN

Basic science.

METHODS

Nine male volunteers participated in this study. A flight simulator was used to create several roll-tilt environments that were then combined with visual information. SVV and SPHV were evaluated in healthy participants during static roll-tilt.

RESULTS

The SVV evaluation revealed significant differences between the dark condition (control) and other visual conditions with respect to some of the body roll-tilt environments, and between a body roll-tilt of 0° and ≥ 20°. The SPHV evaluation revealed a significant difference between the dark condition and the visual condition that was always roll-tilted 20° to the right of the body axis. However, there were no significant differences in SPHV error between a body roll-tilt of 0° and other tilt angles for every visual condition, unlike SVV error.

CONCLUSIONS

Our data indicate that human susceptibility to spatial disorientation is dependent on roll-tilt angle and visual information. They also suggest that the SPHV is not affected by roll-tilt angle, and thus differs from SVV.

LEVEL OF EVIDENCE

NA.

Decreasing spatial disorientation in care-home settings: How psychology can guide the development of dementia friendly design guidelines

Alzheimer's disease results in marked declines in navigation skills that are particularly pronounced in unfamiliar environments. However, many people with Alzheimer's disease eventually face the challenge of having to learn their way around unfamiliar environments when moving into assisted living or care-homes. People with Alzheimer's disease would have an easier transition moving to new residences if these larger, and often more institutional, environments were designed to compensate for decreasing orientation skills. However, few existing dementia friendly design guidelines specifically address orientation and wayfinding. Those that do are often based on custom, practice or intuition and not well integrated with psychological and neuroscientific knowledge or navigation research, therefore often remaining unspecific. This paper discusses current dementia friendly design guidelines, reports findings from psychological and neuropsychological experiments on navigation and evaluates their potential for informing design guidelines that decrease spatial disorientation for people with dementia.

Correlation of climbing perception and eye movements during daytime and nighttime takeoffs using a flight simulator

CONCLUSION

This study suggests that the subjective climbing perception can be quantitatively evaluated using values calculated from induced eye movements, and the findings may aid in the detection of pilots who are susceptible to spatial disorientation in a screening test.

OBJECTIVE

The climbing perception experienced by a pilot during takeoff at night is stronger than that experienced during the day. To investigate this illusion, this study assessed eye movements and analyzed their correlation with subjective climbing perception during daytime and nighttime takeoffs.

METHODS

Eight male volunteers participated in this study. A simulated aircraft takeoff environment was created using a flight simulator and the maximum slow-phase velocities and vestibulo-ocular reflex gain of vertical eye movements were calculated during takeoff simulation.

RESULTS

Four of the eight participants reported that their perception of climbing at night was stronger, while the other four reported that there was no difference between day and night. These perceptions were correlated with eye movements; participants with a small difference in the maximum slow-phase velocities of their downward eye movements between daytime and nighttime takeoffs indicated that their perception of climbing was the same under the two conditions.

Wayfinding difficulties among elders with dementia in an assisted living residence

The concerning phenomena of spatial disorientation and wayfinding difficulties among elders with Alzheimer's disease or a related dementia in assisted living residences are understudied. This qualitative study aimed to identify the types of wayfinding difficulties as experienced by residents with memory-loss in two special care units of an assisted living residence. The data collection period included participant observation complemented by semi-structured interviews with care staff and managers and review of clinical records. A wide spectrum of wayfinding difficulties was identified as experienced by six residents. The residents experienced difficulties reaching several destinations on the units. The implications of the findings to practice, architectural design, and policy are discussed.

Neural correlates of spatial navigation changes in mild cognitive impairment and Alzheimer's disease

Although the memory impairment is a hallmark of Alzheimer's disease (AD), AD has also been characterized by spatial disorientation, which is present from its early stages. Spatial disorientation in AD manifests itself in getting lost in familiar and unfamiliar places and have been characterized more specifically using spatial navigation tests in both real space and virtual environments as an impairment in multiple spatial abilities, including allocentric and egocentric navigation strategies, visuo-spatial perception, or selection of relevant information for successful navigation. Patients suffering mild cognitive impairment (MCI), who are at a high risk of development of dementia, show impairment in a subset of these abilities, mainly connected with allocentric and egocentric processing. While spatial disorientation in typical AD patients probably reflects neurodegenerative changes in medial and posterior temporal, parietal, and frontal lobes, and retrosplenial cortex, the impairment of spatial navigation in MCI seem to be connected mainly with the medial temporal and also parietal brain changes. In this review, we will summarize the signs of brain disease in most MCI and AD patients showing in various tasks of spatial memory and navigation.

Potential solutions to several vestibular challenges facing clinicians

Among other problems, patients with vestibular problems suffer imbalance, spatial disorientation, and blurred vision. These problems lead to varying degrees of disability and can be debilitating. Unfortunately, a large number of patients with vestibular complaints cannot be diagnosed with the clinical tests available today. Nor do we have treatments for all patients that we can diagnose. These clinical problems provide challenges to and opportunities for the field of vestibular research. In this paper, we discuss some new diagnostic and treatment options that could become available for tomorrow's patients. As a new diagnostic, we have begun measuring patient's perceptual direction-detection thresholds. Preliminary results appear encouraging; patients diagnosed with bilateral loss have yaw rotation thresholds almost ten times greater than normals, while patients diagnosed with migraine associated vertigo have roll tilt thresholds well below normal at 0.1 Hz. As a new treatment, we have performed animal studies looking at responses evoked by electrical stimulation provided by a vestibular prosthesis. Results measuring the VOR demonstrate promise and preliminary studies of balance and perception are also encouraging. While electrical stimulation is a standard means of stimulation, optical stimulation is also being investigated as a way to improve prosthetic stimulation specificity.

Spatial disorientation in gondola centrifuges predicted by the form of motion as a whole in 3-D

INTRODUCTION

During a coordinated turn, subjects can misperceive tilts. Subjects accelerating in tilting-gondola centrifuges without external visual reference underestimate the roll angle, and underestimate more when backward-facing than when forward-facing. In addition, during centrifuge deceleration, the perception of pitch can include tumble while paradoxically maintaining a fixed perceived pitch angle. The goal of the present research was to test two competing hypotheses: 1) that components of motion are perceived relatively independently and then combined to form a three-dimensional (3-D) perception; and 2) that perception is governed by familiarity of motions as a whole in three dimensions, with components depending more strongly on the overall shape of the motion.

METHODS

Published experimental data from existing tilting-gondola centrifuge studies were used. The two hypotheses were implemented formally in computer models, and centrifuge acceleration and deceleration were simulated.

RESULTS

The second, whole-motion oriented hypothesis better predicted subjects' perceptions, including the forward-backward asymmetry and the paradoxical tumble upon deceleration. The predominant stimulus at the beginning of the motion and the familiarity of centripetal acceleration were important factors.

CONCLUSION

Three-dimensional perception is better predicted by taking into account familiarity with the form of 3-D motion.