Quantification of gait changes in subjects with visual height intolerance when exposed to heights

Rethinking Exoskeleton Simulation-Based Design: The Effect of Using Different Cost Functions

Designing an exoskeleton that can improve user capabilities is a challenging task, and most designs rely on experiments to achieve this goal. A different approach is to use simulation-based designs to determine optimal device parameters. Most of these simulations use full trajectory tracking limb kinematics during a natural gait as a reference. However, exoskeletons typically change the natural gait kinematics of the user. Other types of simulations assume that human gait is optimized for a cost function that combines several objectives, such as the cost of transport, injury prevention, and stabilization. In this study, we use a 2D OpenSim model consisting of 10 degrees of freedom and considering 18 muscles, together with the Moco optimization tool, to investigate the differences between these two approaches with respect to running with a passive knee exoskeleton. Utilizing this model, we test the effect of a full trajectory tracking objective with different weights (representing the importance of the objective in the optimization cost function) and show that when using weights that are typically used in the literature, there is no deviation from the experimental data. Next, we develop a multi-objective cost function with foot clearance term based on peak knee angle during swing, that achieves trajectories similar (RMSE=7.4 deg) to experimental running data. Finally, we investigate the effect of different parameters in the design of a clutch-based passive knee exoskeleton (1.5 kg at each leg) and find that a design that utilizes a 2.5 Nm/deg spring achieves an improvement of up to 8% in net metabolic energy. Our results show that tracking objectives in the cost function, even with a low weight, hinders the simulation's ability to change the gait trajectory. Thus, there is a need for other predictive simulation methods for exoskeletons.

Heterogeneities of the perceptual-motor style during locomotion at height

In a recent review, we summarized the characteristics of perceptual-motor style in humans. Style can vary from individual to individual, task to task and pathology to pathology, as sensorimotor transformations demonstrate considerable adaptability and plasticity. Although the behavioral evidence for individual styles is substantial, much remains to be done to understand the neural and mechanical substrates of inter-individual differences in sensorimotor performance. In this study, we aimed to investigate the modulation of perceptual-motor style during locomotion at height in 16 persons with no history of fear of heights or acrophobia. We used an inexpensive virtual reality (VR) video game. In this VR game, Richie's Plank, the person progresses on a narrow plank placed between two buildings at the height of the 30th floor. Our first finding was that the static markers (head, trunk and limb configurations relative to the gravitational vertical) and some dynamic markers (jerk, root mean square, sample entropy and two-thirds power law at head, trunk and limb level) we had previously identified to define perceptual motor style during locomotion could account for fear modulation during VR play. Our second surprising result was the heterogeneity of this modulation in the 16 young, healthy individuals exposed to moving at a height. Finally, 56% of participants showed a persistent change in at least one variable of their skeletal configuration and 61% in one variable of their dynamic control during ground locomotion after exposure to height.

The Effects of Virtual and Physical Elevation on Physiological Stress During Virtual Reality Height Exposure

Advances in virtual reality technology have greatly benefited the acrophobia research field. Virtual reality height exposure is a reliable method of inducing stress with low variance across ages and demographics. When creating a virtual height exposure environment, researchers have often used haptic feedback elements to improve the sense of realism of a virtual environment. While the quality of the rendered for the virtual environment increases over time, the physical environment is often simplified to a conservative passive haptic feedback platform. The impact of the increasing disparity between the virtual and physical environment on the induced stress levels is unclear. This article presents an experiment that explored the effect of combining an elevated physical platform with different levels of virtual heights to induce stress. Eighteen participants experienced four different conditions of varying physical and virtual heights. The measurements included gait parameters, heart rate, heart rate variability, and electrodermal activity. The results show that the added physical elevation at a low virtual height shifts the participant's walking behaviour and increases the perception of danger. However, the virtual environment still plays an essential role in manipulating height exposure and inducing physiological stress. Another finding is that a person's behaviour always corresponds to the more significant perceived threat, whether from the physical or virtual environment.

Motor control of landing in an unsteady environment

BACKGROUND

When landing from a jump or a drop, muscles contract before touchdown to anticipate imminent collision with the ground, soften ground contact and allow to return to a stable standing position without stepping or rebounding.

RESEARCH QUESTION

This study assesses the effect of the unsteadiness of the environment on the motor control of landing. The 'unsteady environment' was induced by asking participants to perform drop landings inside an aircraft that underwent trajectories parallel to Earth's surface. The participants also performed the same task in a 'steady environment' in our laboratory.

METHODS

Ground reaction forces, lower limb joints' movements and the activity of lower limb muscles were recorded. The stability of the landing was assessed by the vertical and anterior-posterior stability indexes, center of pressure measures and by the coefficient of variation of kinetic and kinematic parameters.

RESULTS

On one hand, participants slowdown their joint movements and reduce the knee joint excursion during landing, probably to avoid excessive movements that may induce imbalance. On the other hand, the stability of the landing is reduced while the variability of the movement is increased, illustrating a less stable and less consistent landing. In addition, whatever the environment, landing parameters associated with increased stiffness (i.e., increased impact forces and decreased joint range of motion) are correlated with decreased landing stability.

SIGNIFICANCE

Overall, landings in the'unsteady environment' appear to be more cautious but less stable and less finely tuned. Since the stability of the landing is not directly influenced by the steadiness of the environment, this more cautious behavior could be, at least in part, related to the fear/apprehension induced by sudden acceleration variations of the frame of the aircraft.

The Influence of Walking Height and Width on the Gait

Walking stability is an important factor that is related to working accidents at height. The understanding of the relationship between walking stability and walking conditions remains an unmet need. Therefore, this study aimed to investigate the effect of path height, width, and asymmetric conditions on the pressure and time information of the foot-ground interaction during walking. 12 subjects were required to walk at two height, three width, and asymmetric conditions. Plantar pressures during walking were measured with the F-scan insole sensors. The total pressures were normalized with body weight, and the temporal parameters were normalized with stance time. When the walking height increased, the plantar pressure at the "heel strike" phase did not change significantly, while that at "heel rise" and "toe off" phases significantly increased, and the "heel rise" occurred earlier, indicating a greater foot-ground interaction at the forefoot part of the sole. As the path width increased from 0.6 m to 1.2 m, the foot-ground interaction as well as the asymmetric effect approached to that of overground walking. The findings could help improve the risk assessment and footwear design.

Key gait findings for diagnosing three syndromic categories of dynamic instability in patients with balance disorders

With the emergence of affordable, clinical-orientated gait analysis techniques, clinicians may benefit from a general understanding of quantitative gait analysis procedures and their clinical applications. This article provides an overview of the potential of a quantitative gait analysis for decision support in three clinically relevant scenarios of early stage gait disorders: scenario I: gait ataxia and unsteadiness; scenario II: hypokinesia and slow gait; scenario III: apparently normal gait with a specific fall tendency in complex mobility situations. In a first part, we justify the advantages of standardized data collection and analysis procedures including data normalization and dimensionality reduction techniques that facilitate clinical interpretability of instrument-based gait profiles. We then outline typical patterns of pathological gait and their modulation during different walking conditions (variation of speed, sensory perturbation, and dual tasking) and highlight key aspects that are particularly helpful to support and guide clinical decision-making.

Acrophobia and visual height intolerance: advances in epidemiology and mechanisms

Historical descriptions of fear at heights date back to Chinese and Roman antiquity. Current definitions distinguish between three different states of responses to height exposure: a physiological height imbalance that results from an impaired visual control of balance, a more or less distressing visual height intolerance, and acrophobia at the severest end of the spectrum. Epidemiological studies revealed a lifetime prevalence of visual height intolerance including acrophobia in 28% of adults (32% in women; 25% in men) and 34% among prepubertal children aged 8–10 years without gender preponderance. Visual height intolerance first occurring in adulthood usually persists throughout life, whereas an early manifestation in childhood usually shows a benign course with spontaneous relief within years. A high comorbidity was found with psychiatric disorders (e.g. anxiety and depressive syndromes) and other vertigo syndromes (e.g. vestibular migraine, Menière’s disease), but not with bilateral vestibulopathy. Neurophysiological analyses of stance, gait, and eye movements revealed an anxious control of postural stability, which entails a co-contraction of anti-gravity muscles that causes a general stiffening of the whole body including the oculomotor apparatus. Visual exploration is preferably reduced to fixation of the horizon. Gait alterations are characterized by a cautious slow walking mode with reduced stride length and increased double support phases. Anxiety is the critical factor in visual height intolerance and acrophobia leading to a motor behavior that resembles an atavistic primitive reflex of feigning death. The magnitude of anxiety and neurophysiological parameters of musculoskeletal stiffening increase with increasing height. They saturate, however, at about 20 m of absolute height above ground for postural symptoms and about 40 m for anxiety (70 m in acrophobic participants). With respect to management, a differentiation should be made between behavioral recommendations for prevention and therapy of the condition. Recommendations for coping strategies target behavioral advices on visual exploration, control of posture and locomotion as well as the role of cognition. Treatment of severely afflicted persons with distressing avoidance behavior mainly relies on behavioral therapy.

The impact of motor task and environmental constraints on gait patterns during treadmill walking in a fully immersive virtual environment

BACKGROUND

Virtual environments (VE) are increasingly used in rehabilitation settings for gait training, and positive effects are reported. However, little is known about how walking under environmental constraints and solving motor tasks in fully immersive VEs impact gait patterns.

RESEARCH QUESTION

How are gait patterns in healthy adults impacted by walking under environmental constraints and solving motor tasks on a treadmill, in a fully immersive VE?

METHODS

29 healthy adults (age: 28.9±4.8 yrs) were included. Basic gait parameters (step length, cadence, walk ratio) and gait variability in the anteroposterior, mediolateral and vertical directions were measured using an inertial sensor attached to the lower back. A familiarisation treadmill walk >2 min was performed, followed by 200 m familiarisation walk in the VE with no task or environmental constraints The participants were then exposed to height, two grabbing tasks, a balancing task and narrow-path walking. Gait patterns were captured for 15-25 seconds during each of the conditions. The Simulator Sickness Questionnaire was completed before and after the session.

RESULTS

Gait regularity decreased when solving all the motor tasks, and under all the environmental constraints, except when being familiarised to height exposure, where regularity returned to pre-exposure levels. Step length and walk ratio decreased, and cadence increased during height exposure and while performing the grabbing tasks and the balancing task. The different tasks and environments appeared to have specific impact on gait patterns. There was no increase in simulator sickness symptoms.

SIGNIFICANCE

Gait patterns were impacted by solving motor tasks, and by environmental constraints, in healthy young adults, suggesting increased need for balance control. We suggest that VE-training on a treadmill holds potential for improving gait and balance control.

Saccular function is associated with both angular and distance errors on the triangle completion test

OBJECTIVE

The present study was designed to determine whether healthy older adults with age-related vestibular loss have deficits in spatial navigation.

METHODS

154 adults participating in the Baltimore Longitudinal Study of Aging were tested for semicircular canal, saccular, and utricular function and spatial navigation ability using the blindfolded Triangle Completion Test (TCT). Multiple linear regression was used to investigate the relationships between each measure of vestibular function and performance on the TCT (angular error, end point error, and distance walked) while controlling for age and sex.

RESULTS

Individuals with abnormal saccular function made larger angular errors (β = 4.2°, p < 0.05) and larger end point errors (β = 13.6 cm, p < 0.05). Independent of vestibular function, older age was associated with larger angular (β's = 2.2-2.8°, p's < 0.005) and end point errors (β's = 7.5-9.0 cm, p's < 0.005) for each decade increment in age.

CONCLUSIONS

Saccular function appears to play a prominent role in accurate spatial navigation during a blindfolded navigation task.

SIGNIFICANCE

We hypothesize that gravitational cues detected by the saccule may be integrated into estimation of place as well as heading direction.

Behavioral realism and lifelike psychophysiological responses in virtual reality by the example of a height exposure

Virtual reality (VR) is increasingly gaining importance as a valuable methodical tool for psychological research. The greatest benefit of using VR is generating rich, complex and vivid, but still highly controllable settings. As VR has been found to elicit lifelike psychophysiological and emotional responses, we examined by means of a height exposure whether VR resembles physical reality to the necessary degree to constitute a suitable framework for investigating real-life behavior in a controlled experimental context. As hypothesized, participants behaved in VR exactly as would be appropriate in a real environment: Being exposed to great height, participants walked significantly slower across a virtual steel girder construction protruding from a high-rise building as compared to participants who traversed the very same construction on the ground level. In the height condition, this realistic behavior could be predicted on basis of the participants' trait anxiety. Aligned with the behavioral responses, they showed realistic psychophysiological responses, i.e., an elevated heart rate when exposed to height. Interestingly, participants of the height condition reported a greater sense of presence, which indicates that emotions have an elevating effect on presence. As a conclusion, our findings provide further evidence that VR evokes lifelike responses at both behavioral and psychophysiological level and therefore increases ecological validity of psychological experiments.

Clinical and automated gait analysis in patients with vestibular, cerebellar, and functional gait disorders: perspectives and limitations

This article outlines recent developments in the clinical and automated assessment of neurological gait disorders. With a primary focus on vestibular, cerebellar, and functional gait disorders, we discuss how instrumented gait examination may assist clinical decision making in these disorders with respect to the initial differential diagnosis and prognosis as well as the objective monitoring of disease progression and therapeutic interventions. We delineate strategies for data handling and analysis of quantitative gait examinations that can facilitate the clinical characterization and interpretation of walking impairments. These strategies include data normalization and dimensionality reduction procedures. We further emphasize the value of a comprehensive, standardized gait assessment protocol. Accordingly, the examination of walking conditions that challenge patients with respect to their biomechanical, sensory, or cognitive resources are particularly helpful to disclose and characterize the causes underlying their gait impairment. Finally, we provide a perspective on the emerging implementation of pattern recognition approaches within the framework of clinical management of gait disorders and discuss their potential to assist clinical decision making with respect to the differential diagnosis and the prognosis of fall risk in individual patients.

Preferred walking speed on rough terrain; is it all about energetics?

Humans have evolved the ability to walk very efficiently. Further, humans prefer to walk at speeds that approximately minimize their metabolic energy expenditure per unit distance (i.e. gross cost of transport, COT). This has been found in a variety of population groups and other species. However, these studies were mostly performed on smooth, level ground or on treadmills. We hypothesized that the objective function for walking is more complex than only minimizing the COT. To test this idea, we compared the preferred speeds and the relationships between COT and speed for people walking on both a smooth, level floor and a rough, natural terrain trail. Rough terrain presumably introduces other factors, such as stability, to the objective function. 10 healthy men walked on both a straight, flat, smooth floor and on an outdoor trail strewn with rocks and boulders. In both locations, subjects performed 5-7 trials at different speeds relative to their preferred speed. The COT-speed relationships were similarly U-shaped for both surfaces, but the COT values on rough terrain were approximately 115% greater. On the smooth surface, the preferred speed (1.24+/−0.17 m/sec) was found to be statistically not different (p-value =0.09) than the speed that minimized COT (1.34 +/− 0.03 m/sec). On rough terrain, the preferred speed (1.07+/−0.05 m/sec) was slower than the COT minimum speed (1.13 +/− 0.07 m/sec) and was statistical significant (p-value=0.02). Since near the optimum speed the COT function is very shallow, these changes in speed result in small change in COT (0.5%). It appears that the objective function for speed preference when walking on rough terrain includes COT and additional factors such as stability.

New Insights on Emotional Contributions to Human Postural Control

It has been just over 20 years since the effects of height-induced threat on human postural control were first investigated. Raising the height of the support surface on which individuals stood increased the perceived consequences of instability and generated postural control changes. Since this initial work, converging evidence has accumulated supporting the efficacy of using height-induced threat to study the effects of emotions on postural control and confirming a direct influence of threat-related changes in arousal, anxiety, and fear of falling on all aspects of postural control, including standing, anticipatory, and reactive balance. In general, threat-related postural changes promote a greater physical safety margin while maintaining upright stance. We use the static balance literature to critically examine the current state of knowledge regarding: (1) the extent to which threat-related changes in postural control are sensitive to threat-related changes in emotions; (2) the underlying neurophysiological and cognitive mechanisms that may contribute to explaining the relationship between emotions and postural control; and (3) the generalizability of threat-related changes across different populations and types of threat. These findings have important implications for understanding the neuromechanisms that control healthy balance, and highlight the need to recognize the potential contributions of psychological and physiological factors to balance deficits associated with age or pathology. We conclude with a discussion of the practical significance of this research, its impact on improving diagnosis and treatment of postural control deficits, and potential directions for future research.

Effects of virtual reality high heights exposure during beam-walking on physiological stress and cognitive loading

Virtual reality has been increasingly used in research on balance rehabilitation because it provides robust and novel sensory experiences in controlled environments. We studied 19 healthy young subjects performing a balance beam walking task in two virtual reality conditions and with unaltered view (15 minutes each) to determine if virtual reality high heights exposure induced stress. We recorded number of steps off the beam, heart rate, electrodermal activity, response time to an auditory cue, and high-density electroencephalography (EEG). We hypothesized that virtual high heights exposure would increase measures of physiological stress compared to unaltered viewing at low heights. We found that the virtual high height condition increased heart rate variability and heart rate frequency power relative to virtual low heights. Virtual reality use resulted in increased number of step-offs, heart rate, electrodermal activity, and response time compared to the unaltered viewing at low heights condition. Our results indicated that virtual reality decreased dynamic balance performance and increased physical and cognitive loading compared to unaltered viewing at low heights. In virtual reality, we found significant decreases in source-localized EEG peak amplitude relative to unaltered viewing in the anterior cingulate, which is considered important in sensing loss of balance. Our findings indicate that virtual reality provides realistic experiences that can induce physiological stress in humans during dynamic balance tasks, but virtual reality use impairs physical and cognitive performance during balance.

Susceptibility to Fear of Heights in Bilateral Vestibulopathy and Other Disorders of Vertigo and Balance

Aims: To determine the susceptibility to visual height intolerance (vHI) in patients with acquired bilateral vestibulopathy (BVP). The question was whether postural instability in BVP, which is partially compensated for by visual substitution of the impaired vestibular control of balance, leads to an increased susceptibility. This is of particular importance since fear of heights is dependent on body posture, and visual control of balance at heights can no longer substitute vestibular input. For comparison susceptibility to vHI was determined in patients with other vestibular or functional disorders. Methods: A total of 150 patients aged 18 or above who had been referred to the German Center for Vertigo and Balance Disorders and diagnosed to have BVP were surveyed with a standardized questionnaire by specifically trained neurological professionals. Further, 481 patients with other vestibular or functional disorders were included. Results: Susceptibility to vHI was reported by 29% (32 % in females, 25% in males) of the patients with BVP. Patients with vHI were slightly younger (67 vs. 71 years). Seventy percent of those with vHI reported avoidance of climbing, hiking, stairs, darkness, cycling or swimming (84% of those without vHI). Mean age for onset of vHI was 40 years. Susceptibility to vHI was higher in patients with other vertigo disorders than in those with BVP: 64% in those with phobic postural vertigo, 61% in vestibular migraine, 56% in vestibular paroxysmia, 54% in benign paroxysmal positional vertigo, 49% in unilateral vestibulopathy and 48% in Menière's disease. Conclusions: The susceptibility to vHI in BVP was not higher than that of the general population (28%).This allows two explanations that need not be alternatives but contribute to each other: (1) Patients with a bilateral peripheral vestibular deficit largely avoid exposure to heights because of their postural instability. (2) The irrational anxiety to fall from heights triggers increased susceptibility to vHI, not the objective postural instability. However, patients with BVP do not exhibit increased comorbid anxiety disorders. This view is supported by the significantly increased susceptibility to vHI in other vestibular syndromes, which are characterized by an increased comorbidity of anxiety disorders.

The development of the ICF vestibular environmental scale

People with vestibular disorders report changes in symptoms based on their environment with many situations increasing their symptoms. The purpose of this paper was to utilize the International Classification of Functioning Disability and Health (ICF) from the World Health Organization (WHO) to describe common environmental triggers for dizziness in persons living with balance and vestibular disorders. A multi-centre cross-sectional study was conducted with four different centres on three different continents, including patients from the United States (Pittsburgh), Germany (Munich), Jordan (Amman) and Saudi Arabia (Riyadh).

SUBJECTS

Three hundred eighty one persons with vestibular disorders participated.

METHODS

A 9-item questionnaire (the Vestibular Environmental Scale) was developed from existing ICF items, which were compared to Dizziness Handicap Inventory (DHI) scores. Sixty-five percent of participants reported that "quick movements in the vicinity" increased symptoms, "crowds" at 45%, and "design of buildings, e.g. narrow hallways, stairs, elevators" at 42%. The "crowds" item was a good positive predictor of psychogenic vertigo (OR 1.8, 95% Confidence Interval 1.03-3.16), while "food" (OR 0.47, 95% Confidence Interval 0.17-1.29) and "light" (OR 0.41 95% Confidence Interval 0.23-0.75) were negative predictors of psychogenic vertigo. There also was a positive correlation between the number of triggers and DHI score (Spearman correlation coefficient 0.47, p < 0.0001). Sixty-eight percent of the subjects reported an increase in symptoms with between 1 and 4 environmental triggers. In our cross cultural sample, environmental triggers affect dizziness in persons living with balance and vestibular disorders. The use of items from the ICF of the WHO may help to promote cross cultural sharing of information in persons with dizziness.

Visual height intolerance and acrophobia: distressing partners for life

The course of illness, the degree of social impairment, and the rate of help-seeking behavior was evaluated in a sample of individuals with visual height intolerance (vHI) and acrophobia. On the basis of a previously described epidemiological sample representative of the German general population, 574 individuals with vHI were identified, 128 fulfilled the DSM-5 diagnostic criteria of acrophobia. The illness of the majority of all susceptible individuals with vHI ran a year-long chronic course. Two thirds were in the category “persistent/worse”, whereas only one third was in the category “improved/remitted”. Subjects with acrophobia showed significantly more traumatic triggers of onset, more signs of generalization to other height stimuli, higher rates of increasing intensity of symptom load, higher grades of social impairment, and greater overall negative impact on the quality of life than those with pure vHI. An unfavorable course of illness in pure vHI was predicted by major depression, agoraphobia, social phobia, posttraumatic stress, initial traumatic trigger, and female sex; an unfavorable course in acrophobia was predicted by major depression, chronic fatigue, panic attacks, initial traumatic trigger, social phobia, other specific phobic fears, and female sex. Help-seeking behavior was astonishingly low in the overall sample of individuals with vHI. The consequences of therapeutic interventions if complied with at all were quite modest. In adults pure vHI and even more so acrophobia are by no means only transitionally distressing states. In contrast to their occurrence in children they are more often persisting and disabling conditions. Both the utilization of and adequacy of treatment of these illnesses pose major challenges within primary and secondary neurological and psychiatric medical care.

The Effect of Optokinetic Stimulation on Perceptual and Postural Symptoms in Visual Vestibular Mismatch Patients

Background

Vestibular patients occasionally report aggravation or triggering of their symptoms by visual stimuli, which is called visual vestibular mismatch (VVM). These patients therefore experience discomfort, disorientation, dizziness and postural unsteadiness.

Objective

Firstly, we aimed to get a better insight in the underlying mechanism of VVM by examining perceptual and postural symptoms. Secondly, we wanted to investigate whether roll-motion is a necessary trait to evoke these symptoms or whether a complex but stationary visual pattern equally provokes them.

Methods

Nine VVM patients and healthy matched control group were examined by exposing both groups to a stationary stimulus as well as an optokinetic stimulus rotating around the naso-occipital axis for a prolonged period of time. Subjective visual vertical (SVV) measurements, posturography and relevant questionnaires were assessed.

Results

No significant differences between both groups were found for SVV measurements. Patients always swayed more and reported more symptoms than healthy controls. Prolonged exposure to roll-motion caused in patients and controls an increase in postural sway and symptoms. However, only VVM patients reported significantly more symptoms after prolonged exposure to the optokinetic stimulus compared to scores after exposure to a stationary stimulus.

Conclusions

VVM patients differ from healthy controls in postural and subjective symptoms and motion is a crucial factor in provoking these symptoms. A possible explanation could be a central visual-vestibular integration deficit, which has implications for diagnostics and clinical rehabilitation purposes. Future research should focus on the underlying central mechanism of VVM and the effectiveness of optokinetic stimulation in resolving it.

Functional and psychiatric vestibular disorders

Behavioral factors have long been recognized as affecting spatial orientation and balance function. Neuroanatomic and neurophysiologic studies conducted worldwide over the last 30 years have substantially advanced our knowledge about the inherently strong connectivity among threat/anxiety, vestibular, visual, and somatosensory systems in the brain. Clinical investigations have shed greater light on the nature of functional and psychiatric disorders that manifest or magnify vestibular morbidity. Concepts of these syndromes have changed over 150 years. Even their nomenclature has had different meanings in different eras. This chapter will review functional and psychiatric vestibular disorders. Terminology will follow the International Classification of Diseases, 11th edition, beta draft and the International Classification of Vestibular Disorders. Anxiety plays a central role in behavioral vestibular morbidity. Anxiety, traumatic stress, obsessive, and depressive disorders may be primary causes of episodic and chronic vestibular symptoms or secondary complications of other vestibular disorders. These psychiatric illnesses affect 30-50% of patients who consult neurologists or otologists for vestibular symptoms. Coexisting psychiatric disorders adversely affect treatment for patients with structural vestibular diseases, especially when unrecognized. Persistent postural-perceptual dizziness is the leading cause of long-term vestibular disability. Fortunately, pharmacologic, psychotherapeutic, and rehabilitative treatments of these illnesses have improved in recent years.