Editorial: The Vestibular System in Cognitive and Memory Processes in Mammalians

Evaluation of the Effects of Optokinetic Stimuli and Dual-Task Performance on Vestibulo-Ocular Reflex Function in Children With Attention Deficit and Hyperactivity Disorder

OBJECTIVES

This study investigated the effects of optokinetic stimuli and dual-task performance on vestibulo-ocular reflex (VOR) function. The study primarily focused on understanding the effects of attention deficit and hyperactivity disorder (ADHD) and its subtypes.

STUDY DESIGN

A case-control study.

SETTING

Tertiary medical centre.

METHODS

Thirty-eight children diagnosed with ADHD and 40 typically developing (TD) children aged 8-18 were included in the study. According to their diagnostic reports, children diagnosed with ADHD were also examined in three subtypes: predominantly inattentive (ADHD-PI), predominantly hyperactive-impulsive (ADHD-HI) and the combined type. Functional head impulse test (fHIT) was applied to all participants in three conditions-with no additional stimulus, optokinetic stimulation and dual-task. Correct responses (CR) were determined for each group, and the conditions were compared. For the dual-task test performance, children were given a counting task.

RESULTS

The findings of the study are significant. The CR values obtained from the fHIT tests applied under three different conditions were lower in the ADHD group compared to the control group. CR values for all fHIT conditions and all semicircular canals were lower in the ADHD-PI subtype and higher in the ADHD-HI subtype compared to other subgroups.

CONCLUSION

This study has significant practical implications underscoring its relevance. fHIT, when applied with different protocols, can provide valuable information about the vestibular and cognitive states of children with ADHD. These results are particularly significant as the diagnosis of ADHD often relies on subjective interpretations, and fHIT offers a more objective and reliable method of evaluation.

Healthcare Utilization Among Adults With Vestibular Vertigo in the United States

OBJECTIVES

Vestibular vertigo has been shown to have a high lifetime prevalence. Previous studies have described the increased morbidities associated with vestibular vertigo.

DESIGN

In this cross-sectional study of the 2016 National Health Interview Study, we sought to explore whether individuals with vestibular vertigo were more likely to utilize healthcare resources compared with those without vestibular vertigo. We characterized utilization of specific healthcare resources including general doctors, specialist doctors, emergency departments, mental health professionals, and others among individuals with vestibular vertigo to better understand how individuals with vertigo interact with the US healthcare system.

RESULTS

In multivariable analyses, participants with vestibular vertigo had an increased number of nights in the hospital in the last 12 months (mean difference = 0.67 days, 95% confidence interval [CI] = 0.37 to 0.97), increased odds of receiving healthcare 10 or more times in the last 12 months (odds ratio = 2.22, 95% CI = 1.99 to 2.48) and increased number of visits to a healthcare professional in the last 2 weeks (mean difference = 0.17 visits, 95% CI = 0.14 to 0.21). In addition, participants with vestibular vertigo had increased odds of visiting both general doctors, specialist doctors, and other healthcare professionals.

CONCLUSIONS

These findings characterize how individuals with vestibular vertigo utilize and interact with healthcare resources compared with those without vestibular vertigo.

Executive functions in patients with bilateral and unilateral peripheral vestibular dysfunction

Previous research suggests that patients with peripheral vestibular dysfunction (PVD) suffer from nonspatial cognitive problems, including executive impairments. However, previous studies that assessed executive functions are conflicting, limited to single executive components, and assessments are confounded by other cognitive functions. We compared performance in a comprehensive executive test battery in a large sample of 83 patients with several conditions of PVD (34 bilateral, 29 chronic unilateral, 20 acute unilateral) to healthy controls who were pairwise matched to patients regarding age, sex, and education. We assessed basic and complex executive functions with validated neuropsychological tests. Patients with bilateral PVD performed worse than controls in verbal initiation and working memory span, while other executive functions were preserved. Patients with chronic unilateral PVD had equal executive performance as controls. Patients with acute unilateral PVD performed worse than controls in the exact same tests as patients with bilateral PVD (verbal initiation, working memory span); however, this effect in patients with acute PVD diminished after correcting for multiple comparisons. Hearing loss and affective disorders did not influence our results. Vestibular related variables (disease duration, symptoms, dizziness handicap, deafferentation degree, and compensation) did not predict verbal initiation or working memory span in patients with bilateral PVD. The results suggest that bilateral PVD not only manifests in difficulties when solving spatial tasks but leads to more general neurocognitive deficits. This understanding is important for multidisciplinary workgroups (e.g., neurotologists, neurologists, audiologists) that are involved in diagnosing and treating patients with PVD. We recommend screening patients with PVD for executive impairments and if indicated providing them with cognitive training or psychoeducational support.

Does sleep quality affect balance? The perspective from the somatosensory, vestibular, and visual systems

OBJECTIVE

Previous studies have focused on the balance system's involvement in sleep deprivation or disorders. This study investigated how daily routine sleep quality affects the balance system of people without sleep deprivation or diagnosed sleep disorders.

METHODS

The study included 45 participants with a BMI score of <25. The PSQI was used to determine sleep quality. The SOT, HS-SOT, and ADT evaluated the vestibular system's functionality.

RESULTS

In SOT, condition 3, 4, 5, and 6 composite scores, VIS and VEST composite balance scores, and HS-SOT 5 scores were lower in the HPSQI group. At the same time, there is a statistically significant negative correlation between these scores and PSQI scores.

CONCLUSION

Poor sleep quality may be a factor influencing the balance system. Sleep quality affects the visual and vestibular systems rather than the somatosensory system. The population should be made aware of this issue, and clinicians should consider the potential impact of sleep quality when evaluating the balance system.

Cellular and Molecular Mechanisms of Vestibular Ageing

While age-related auditory deficits and cochlear alterations are well described, those affecting the vestibular sensory organs and more broadly the central vestibular pathways are much less documented. Although there is inter-individual heterogeneity in the phenomenon of vestibular ageing, common tissue alterations, such as losses of sensory hair cells or primary and secondary neurons during the ageing process, can be noted. In this review, we document the cellular and molecular processes that occur during ageing in the peripheral and central vestibular system and relate them to the impact of age-related vestibular deficits based on current knowledge.

Association between Simultaneous Occurrence of Occupational Noise-Induced Hearing Loss and Noise-Induced Vestibular Dysfunction: A Systematic Review

Background

Background: Because of functional and structural similarities between the cochlea and vestibular sensory receptors, vestibular dysfunction could be accompanied by noise-induced hearing loss (NIHL) due to occupational noise exposure. We aimed to evaluate the occurrence of vestibular dysfunction (VD) in individuals with NIHL and occupational noise exposure.

Methods

A systematic literature research was carried out within the databases of PubMed, Scopus, Science Direct, and Web of Science for published articles between 1980 and Jan 5, 2023 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The methodological quality of the included systematic reviews was assessed with the Joanna Briggs Institute (JBI) checklist. Vestibular system dysfunction parameters were considered as primary outcomes in subjects with NIHL.

Results

We reviewed the evidence (from 19 eligible articles) for VD from noise-induced damage to peripheral vestibular structures. VD can occur after occupational noise exposure or concomitantly with NIHL. Furthermore, this study showed that the saccular organ has a higher susceptibility to noise damage than the vestibular organs of the utricle and semicircular canals (SCCs).

Conclusion

Our results support the role of occupational noise exposure and NIHL as risk factors for developing VD. Further research is needed to investigate the association between the occurrence of VD due to occupational noise exposure or concomitantly with NIHL.

Dizziness, psychological disorders and cognitive decline

INTRODUCTION

Dizziness is a common disorder, particularly among the elderly population. Aim of this paper was to revise the current concepts surrounding the relationship between dizziness, psychological disorders and cognitive decline.

EVIDENCE ACQUISITION

This is a PRISMA-compliant systematic review, including observational studies in people with dizziness. Database inception, Medline/Cochrane/Embase/Web of Science/Scopus/NHS evidence were searched until October 30, 2019.

EVIDENCE SYNTHESIS

Overall 22 studies, and 65,730 participants were included. Eleven studies were cross-sectional, 7 cross-sectional controlled, 2 prospective case-control, 1 retrospective case series, and 1 cohort study. The persistence of vestibular impairment (for 6 months or more) was correlated to the presence of psychological disorders affecting patient's Quality of Life and causing social anxiety, particularly in some conditions such as Ménière's disease. Interestingly, vestibular loss has been also correlated to cognitive impairment, with certain vestibular dysfunctions reported to be more prevalent in cognitive impaired individuals.

CONCLUSIONS

The current literature suggests that there is an association between vestibular function, psychological disorders and cognitive functions. The findings from this review could be useful in informing on the need for a multidimensional diagnostic and rehabilitative programs for patients with dizziness. More studies could explore the role of counseling or behavioral therapy with an aim to reduce the perceived dizziness-related disability.

Vestibular dysfunction is an important contributor to the aging of visuospatial ability in older adults–Data from a computerized test system

Background

A convergence of research supports a key role of the vestibular system in visuospatial ability. However, visuospatial ability may decline with age. This work aims to elucidate the important contribution of vestibular function to visuospatial ability in old adults through a computerized test system.

Methods

Patients with a clinical history of recurrent vertigo and at least failed one vestibular test were included in this cross-sectional study. Healthy controls of three age groups: older, middle-aged, and young adults were also involved. Visuospatial cognitive outcomes including spatial memory, spatial navigation, and mental rotation of all the groups were recorded. Comparing the performance of the visuospatial abilities between patients and age-matched controls as well as within the controls.

Results

A total of 158 individuals were enrolled. Results showed that patients performed worse than the age-matched controls, with the differences in the forward span (p &lt; 0.001), the time of the maze 8 × 8 (p = 0.009), and the time of the maze 12 × 12 (p = 0.032) being significant. For the differences in visuospatial cognitive outcomes within the controls, the younger group had a significantly better performance than the other groups. The older group and the middle-aged group had comparable performances during all the tests.

Conclusions

Older patients with vestibular dysfunction had more difficulties during visuospatial tasks than age-matched controls, especially in spatial memory and spatial navigation. Within the controls, younger adults did much better than other age groups, while older adults behaved similarly to middle-aged adults. It is a valuable attempt to computerize the administration of tests for visuospatial ability.

Simulating Extreme Environmental Conditions via Mental Imagery: The Case of Microgravity and Weight Estimation

Mental imagery can be used for recreating an extreme environment experience. Here we assessed whether microgravity effects over cognition, that typically occur during a space mission, may be reproduced via mental imagery. Participants were randomly assigned to one of two conditions in which they were guided to imagine to be (1) in outer space or (2) in a nature scenario and subsequently estimate the weight of common objects. We found that only for those who engaged in a space scenario imagery, there was a decrease in object weight estimation compared with a prior rating. This finding is the first to indicate that the effects of weightlessness on cognition can be simulated via an imagery-based technique and add to the ongoing debate about the importance of trying to disentangle the effect of microgravity alone on human performance. Moreover, our findings ultimately suggest that imagery can be used as a less expensive simulated scenario for studying the impact of extreme environmental conditions over astronauts' cognition and behavior.

The rubber hand illusion in microgravity and water immersion

Our body has evolved in terrestrial gravity and altered gravitational conditions may affect the sense of body ownership (SBO). By means of the rubber hand illusion (RHI), we investigated the SBO during water immersion and parabolic flights, where unconventional gravity is experienced. Our results show that unconventional gravity conditions remodulate the relative weights of visual, proprioceptive, and vestibular inputs favoring vision, thus inducing an increased RHI susceptibility.

The Cognitive-Vestibular Compensation Hypothesis: How Cognitive Impairments Might Be the Cost of Coping With Compensation

Previous research in vestibular cognition has clearly demonstrated a link between the vestibular system and several cognitive and emotional functions. However, the most coherent results supporting this link come from rodent models and healthy human participants artificial stimulation models. Human research with vestibular-damaged patients shows much more variability in the observed results, mostly because of the heterogeneity of vestibular loss (VL), and the interindividual differences in the natural vestibular compensation process. The link between the physiological consequences of VL (such as postural difficulties), and specific cognitive or emotional dysfunction is not clear yet. We suggest that a neuropsychological model, based on Kahneman's Capacity Model of Attention, could contribute to the understanding of the vestibular compensation process, and partially explain the variability of results observed in vestibular-damaged patients. Several findings in the literature support the idea of a limited quantity of cognitive resources that can be allocated to cognitive tasks during the compensation stages. This basic mechanism of attentional limitations may lead to different compensation profiles in patients, with or without cognitive dysfunction, depending on the compensation stage. We suggest several objective and subjective measures to evaluate this cognitive-vestibular compensation hypothesis.

Balanced Growth project: a protocol of a single-centre observational study on the involvement of the vestibular system in a child's motor and cognitive development

INTRODUCTION

The involvement of the vestibular system in the motor and higher (cognitive) performances of typically developing or vestibular-impaired children is currently unknown or has only scarcely been explored. Interestingly, arguments for an interaction between vestibular, motor and cognitive functions in children can also be supported by research on children known for their difficulties in motor and/or cognitive processing (eg, children with neurodevelopmental disorders (NDD)), as they often present with vestibular-like characteristics. Therefore, in order to elucidate this interaction, and to increase the understanding of the pathophysiology and symptomatology of vestibular disorders and NDD in children, the Balanced Growth project was developed. It includes the following objectives: (1) to understand the association between motor skills, cognitive performances and the vestibular function in typically developing school-aged children, with special focus on the added value of the vestibular system in higher cognitive skills and motor competence; (2) to investigate whether a vestibular dysfunction (with/without an additional auditory disease) has an impact on motor skills, cognitive performances and motor-cognitive interactions in children and (3) to assess if an underlying vestibular dysfunction can be identified in school-aged children with NDD, with documentation of the occurrence and characteristics of vestibular dysfunctions in this group of children using an extensive vestibular test battery.

METHODS AND ANALYSIS

In order to achieve the objectives of the observational cross-sectional Balanced Growth study, a single-task and dual-task test protocol was created, which will be performed in three groups of school-aged children (6-12 years old): (1) a typically developing group (n=140), (2) (audio) vestibular-impaired children (n=30) and (3) children with an NDD diagnosis (n=55) (ie, autism spectrum disorder, attention deficit/hyperactivity disorder and/or developmental coordination disorder). The test protocol consists of several custom-made tests and already existing validated test batteries and includes a vestibular assessment, an extensive motor assessment, eight neurocognitive tests, a cognitive-motor interaction assessment and includes also additional screenings to control for potential confounding factors (eg, hearing status, intelligence, physical activity, etc).

ETHICS AND DISSEMINATION

The current study was approved by the ethics committee of Ghent University Hospital on 4 June 2019 with registration number B670201940165 and is registered at Clinical Trials (clinicaltrials.gov) with identifier NCT04685746. All research findings will be disseminated in peer-reviewed journals and presented at vestibular as well as multidisciplinary international conferences and meetings.

TRIAL REGISTRATION NUMBER

NCT04685746.

Case Study: Depersonalization and Vestibular Impairment

BACKGROUND

 We describe herein the case of a patient whose primary complaints were episodic vertigo and "depersonalization," a sensation of detachment from his own body.

PURPOSE

 This case study aims to further clinical knowledge and insight into the clinical evaluation of vertiginous patients with complaints of depersonalization.

RESEARCH DESIGN

 This is a case study.

DATA COLLECTION AND ANALYSIS

 A retrospective chart review of vestibular function testing done on a vertiginous patient with complaints of depersonalization was performed.

RESULTS

 Vestibular function testing revealed absent cervical and ocular vestibular evoked myogenic potentials on the left side with normal vHIT or video Head Impulse Test, videonystagmography, and rotational chair results, suggesting peripheral vestibular impairment isolated to the left saccule and utricle.

CONCLUSION

 The otolith end organ impairment explains the patient's postural deviation to the left side during attempts to ambulate. We recommend that clinicians should be attentive to patient complaints of depersonalization and perform vestibular evoked myogenic potential testing to determine whether evidence of at least a unilateral peripheral otolith end organ impairment exists.

Impaired Attentional Processing During Parabolic Flight

Previous studies suggest that altered gravity levels during parabolic flight maneuvers affect spatial updating. Little is known about the impact of the experimental setting and psychological stressors associated with parabolic flight experiments on attentional processes. To address this gap, we investigated the level of alertness, selective and sustained attention in 1 and 0 g using a Go/No-Go Continuous Performance Task. We also identified several parameters associated with the experimental set-up of a parabolic flight that could be expected to affect attentional processing. These included the use of scopolamine, sleep quality prior to the flight day, participant’s stress level as well as mood and anxiety state before and after the parabolic flight. We observed a deterioration in attentional processing prior to the first parabola that was further aggravated in weightlessness and returned to baseline after the last parabola. Reaction Time, Hit and False Alarm Rate were moderately correlated with self-reported anxiety state, but not cortisol levels or emotional states. The use of scopolamine had minor effects on Reaction Time. Our results confirm previous studies reporting impairments of cognitive performance in 0 g, and highlight important aspects that should be considered for the design of behavioral research experiments in future parabolic flight campaigns.

Can a Theater Acting Intervention Enhance Inhibitory Control in Older Adults? A Brain-Behavior Investigation

Purpose: Studies of reactive and proactive modes of inhibitory control tend to show age-related declines and are accompanied by abnormalities in the prefrontal cortex. We explored which mode of inhibitory control would be more amenable to change and accrue greater benefits following engagement in a 4-week theater acting intervention in older adults. These gains were evaluated by performance on the AX-CPT task. We hypothesized that an increase in proactive control would relate to an increase in AY errors and a decrease in BX errors. In contrast, an increase in reactive control would be associated with a decrease in AY errors, no change in AY reaction time, and an increase in BX response time. Further, we posited that an increase in behavioral proactive control would accompany greater cue versus probe activity for previously identified regions in the prefrontal cortex. In contrast, an increase in behavioral reactive control would be accompanied by greater probe activation in these identified brain areas. Materials and Methods: The participants were 179 community-dwelling adults aged 60-89 years who were on average, college-educated. Participants were pseudo-randomly assigned to either an active-experiencing acting intervention condition (n = 93) or the active control condition (n = 86); participant assignment was subject to time of enrollment. Participants in both groups were trained by theater-actor researchers with expertise in acting interventions. In contrast to the active control participants who attended a course on theater acting, the acting-intervention group was required to consistently deploy proactive and reactive control mechanisms. Both groups met two times/week for 75-min for 4 weeks. Participant brain-behavioral performance on the AX-CPT task was evaluated prior to and after this four-week period. Results: No intervention effects were found in favor of proactive control. Behavioral evidence in favor of reactive control was weak. Brain-related benefits to reactive control was illustrated by greater probe-activation in Brodmann areas 6 and 8, relative to controls and pre-intervention. Conclusion: We found some evidence for improvements in reactive control via brain measures, attributed to engagement in the acting intervention.

Vestibular function and cortical and sub-cortical alterations in an aging population

While it is well known that the vestibular system is responsible for maintaining balance, posture and coordination, there is increasing evidence that it also plays an important role in cognition. Moreover, a growing number of epidemiological studies are demonstrating a link between vestibular dysfunction and cognitive deficits in older adults; however, the exact pathways through which vestibular loss may affect cognition are unknown. In this cross-sectional study, we sought to identify relationships between vestibular function and variation in morphometry in brain structures from structural neuroimaging. We used a subset of 80 participants from the Baltimore Longitudinal Study of Aging, who had both brain MRI and vestibular physiological data acquired during the same visit. Vestibular function was evaluated through the cervical vestibular-evoked myogenic potential (cVEMP). The brain structures of interest that we analyzed were the hippocampus, amygdala, thalamus, caudate nucleus, putamen, insula, entorhinal cortex (ERC), trans-entorhinal cortex (TEC) and perirhinal cortex, as these structures comprise or are connected with the putative "vestibular cortex." We modeled the volume and shape of these structures as a function of the presence/absence of cVEMP and the cVEMP amplitude, adjusting for age and sex. We observed reduced overall volumes of the hippocampus and the ERC associated with poorer vestibular function. In addition, we also found significant relationships between the shape of the hippocampus (p = 0.0008), amygdala (p = 0.01), thalamus (p = 0.008), caudate nucleus (p = 0.002), putamen (p = 0.02), and ERC-TEC complex (p = 0.008) and vestibular function. These findings provide novel insight into the multiple pathways through which vestibular loss may impact brain structures that are critically involved in spatial memory, navigation and orientation.

De Novo Synthesized Estradiol: A Role in Modulating the Cerebellar Function

The estrogen estradiol is a potent neuroactive steroid that may regulate brain structure and function. Although the effects of estradiol have been historically associated with gonadal secretion, the discovery that this steroid may be synthesized within the brain has expanded this traditional concept. Indeed, it is accepted that de novo synthesized estradiol in the nervous system (nE2) may modulate several aspects of neuronal physiology, including synaptic transmission and plasticity, thereby influencing a variety of behaviors. These modulations may be on a time scale of minutes via non-classical and often membrane-initiated mechanisms or hours and days by classical actions on gene transcription. Besides the high level, recent investigations in the cerebellum indicate that even a low aromatase expression can be related to the fast nE2 effect on brain functioning. These pieces of evidence point to the importance of an on-demand and localized nE2 synthesis to rapidly contribute to regulating the synaptic transmission. This review is geared at exploring a new scenario for the impact of estradiol on brain processes as it emerges from the nE2 action on cerebellar neurotransmission and cerebellum-dependent learning.

The Growing Evidence for the Importance of the Otoliths in Spatial Memory

Many studies have demonstrated that vestibular sensory input is important for spatial learning and memory. However, it has been unclear what contributions the different parts of the vestibular system - the semi-circular canals and otoliths - make to these processes. The advent of mutant otolith-deficient mice has made it possible to isolate the relative contributions of the otoliths, the utricle and saccule. A number of studies have now indicated that the loss of otolithic function impairs normal spatial memory and also impairs the normal function of head direction cells in the thalamus and place cells in the hippocampus. Epidemiological studies have also provided evidence that spatial memory impairment with aging, may be linked to saccular function. The otoliths may be important in spatial cognition because of their evolutionary age as a sensory detector of orientation and the fact that velocity storage is important to the way that the brain encodes its place in space.

Quantitative Assessment of Anti-Gravity Reflexes to Evaluate Vestibular Dysfunction in Rats

The tail-lift reflex and the air-righting reflex are anti-gravity reflexes in rats that depend on vestibular function. To obtain objective and quantitative measures of performance, we recorded these reflexes with slow-motion video in two experiments. In the first experiment, vestibular dysfunction was elicited by acute exposure to 0 (control), 400, 600, or 1000 mg/kg of 3,3'-iminodipropionitrile (IDPN), which causes dose-dependent hair cell degeneration. In the second, rats were exposed to sub-chronic IDPN in the drinking water for 0 (control), 4, or 8 weeks; this causes reversible or irreversible loss of vestibular function depending on exposure time. In the tail-lift test, we obtained the minimum angle defined during the lift and descent maneuver by the nose, the back of the neck, and the base of the tail. In the air-righting test, we obtained the time to right the head. We also obtained vestibular dysfunction ratings (VDRs) using a previously validated behavioral test battery. Each measure, VDR, tail-lift angle, and air-righting time demonstrated dose-dependent loss of vestibular function after acute IDPN and time-dependent loss of vestibular function after sub-chronic IDPN. All measures showed high correlations between each other, and maximal correlation coefficients were found between VDRs and tail-lift angles. In scanning electron microscopy evaluation of the vestibular sensory epithelia, the utricle and the saccule showed diverse pathological outcomes, suggesting that they have a different role in these reflexes. We conclude that these anti-gravity reflexes provide useful objective and quantitative measures of vestibular function in rats that are open to further development.

Inertial Sensing and Encoding of Self-Motion: Structural and Functional Similarities across Metazoan Taxa

To properly orient and navigate, moving animals must obtain information about the position and motion of their bodies. Animals detect inertial signals resulting from body accelerations and rotations using a variety of sensory systems. In this review, we briefly summarize current knowledge on inertial sensing across widely disparate animal taxa with an emphasis on neuronal coding and sensory transduction. We outline systems built around mechanosensory hair cells, including the chordate vestibular complex and the statocysts seen in many marine invertebrates. We next compare these to schemes employed by flying insects for managing inherently unstable aspects of flapping flight, built around comparable mechanosensory cells but taking unique advantage of the physics of rotating systems to facilitate motion encoding. Finally, we highlight fundamental similarities across taxa with respect to the partnering of inertial senses with visual senses and conclude with a discussion of the functional utility of maintaining a multiplicity of encoding schemes for self-motion information.

Vestibular Function and Beta-Amyloid Deposition in the Baltimore Longitudinal Study of Aging

Beta-amyloid (Aβ) plaque deposition is a key feature of Alzheimer’s disease (AD), and occurs years before the onset of symptoms. Aβ plaque deposition has been shown to be present in ~30% of cognitively normal older adults using amyloid C-11 labeled Pittsburgh Compound B (¹¹C-PiB) Positron Emission Tomography (PET) imaging. Prior studies have reported a link between reduced vestibular function and poorer cognition in healthy older adults. It is unknown whether vestibular impairment occurs in association with AD pathology among individuals in the preclinical phase of AD, which could contribute to the observed association between vestibular and cognitive function in healthy older adults. Using the Baltimore Longitudinal Study of Aging (BLSA), we analyzed the association between a comprehensive set of vestibular function measures and PiB status in 98 healthy participants with a mean age of 77.3 (±8.26). We did not observe a significant relationship between any vestibular function measure and PiB status in cognitively-intact older adults in the BLSA. This finding suggests that Aβ deposition does not explain the observed association between reduced vestibular function and poorer cognition in healthy older adults.

Developmental Coordination Disorder: The Importance of Grounded Assessments and Interventions

This focused review is based on earlier studies which have shown that both children and adults diagnosed as having developmental coordination disorder (DCD), benefited from sensorimotor therapy according to the method Retraining for Balance (RB). Different approaches and assessments for children and adults in regard to DCD are scrutinized and discussed in comparison to RB which mainly includes (a) vestibular assessment and stimulation (b) assessment and integration of aberrant primary reflexes and (c) assessment and stimulation of auditory and visual perception. Earlier results indicate that the process of Sensorimotor therapy using RB techniques could be described according to a conceptual Kinesthetic-Vestibular Developmental Model (KVDM) whereby the training elicited temporary physical and psychological regressions followed by transformations i.e., positive physical and psychological development. We have also seen that this recurring pattern is similar for children and adults. In our conceptual model vestibular stimulation (perceptual priming) stimulates the nervous system, which might enhance object-related priming. This perceptual priming will also assist the suppression of persistent aberrant primary reflexes. In order to develop effective methods for assessment and intervention of DCD over the life span the importance of primary reflex inhibition and vestibular stimulation as well as a combination of bottom-up and top-down approaches have to be considered.

Vestibular Function and Hippocampal Volume in the Baltimore Longitudinal Study of Aging (BLSA)

OBJECTIVE

This study evaluated whether reduced vestibular function in aging adults is associated with lower hippocampal volume.

STUDY DESIGN

Cross-sectional study.

SETTING

Baltimore Longitudinal Study of Aging, a long-running longitudinal cohort study of healthy aging.

PATIENTS

Eligible participants were aged ≥ 60 years and had both vestibular physiological testing and brain magnetic resonance imaging at the same visit.

INTERVENTION

Vestibular function testing consisted of the cervical vestibular-evoked myogenic potential (cVEMP) to assess saccular function, ocular VEMP to assess utricular function, and video head-impulse testing to assess the horizontal semicircular canal vestibulo-ocular reflex.

MAIN OUTCOME MEASURE

Hippocampal volume calculated using diffeomorphometry.

RESULTS

The study sample included 103 participants (range of 35-90 participants in subanalyses) with mean (±SD) age 77.2 years (±8.71). Multivariate linear models including age, intracranial volume, sex, and race showed that 1 μV amplitude increase of cVEMP was associated with an increase of 319.1 mm (p = 0.003) in mean hippocampal volume. We did not observe a significant relationship between ocular VEMP amplitude or vestibulo-ocular reflex gain and mean hippocampal volume.

CONCLUSIONS

Lower cVEMP amplitude (i.e., reduced saccular function) was significantly associated with lower mean hippocampal volume. This is in line with previous work demonstrating a link between saccular function and spatial cognition. Hippocampal atrophy may be a mechanism by which vestibular loss contributes to impaired spatial cognition in older adults. Future work using longitudinal data will be needed to evaluate the causal nature of the association between vestibular loss and hippocampal atrophy.

Physiological assesment of vestibular function and toxicity in humans and animals

Physiological methods that can be similarly recorded in humans and animals have a major role in sensory toxicology, as they provide a bridge between human sensory perception data and the molecular and cellular data obtained in animal studies. Vestibular toxicity research lags well behind other sensory systems in many aspects, including the availability of methods for functional assessment in animals that could be robustly translated to human significance. Here we review the methods available for the assessment of vestibular function in both humans and laboratory animals, with an emphasis on their similarity or divergence, to highlight their potential utility for the predictive assessment of vestibular toxicity.

Does Otovestibular Loss in the Autosomal Dominant Disorder DFNA9 Have an Impact of on Cognition? A Systematic Review

Background and Purpose: Cognitive impairment has been observed in patients with bilateral vestibular loss (BVL) and in patients with sensorineural hearing loss (SNHL). DFNA9 is an autosomal dominant disorder that causes a combination of both sensory deficits by the 3rd to 5th decade. We therefore hypothesize a combined detrimental effect on cognition. The aim of this systematic review was to identify studies related to DFNA9 in general and its relationship with cognitive impairment more specifically.

Materials and Methods: Several databases including Medline, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, ISI Web of Knowledge, and Web of Science were searched to accumulate information about DFNA9-mutations, including phenotype, genotype, pathophysiology, quality of life (QOL), and imaging in general and cognitive function more specifically. A qualitative analysis was performed on the 55 articles that qualified.

Results: The clinical features of DFNA9 are different along the 24 COCH mutations, described up to now. Vestibular symptoms generally present themselves a few years after SNHL onset in mutations associated with the vWFA-domain although they can precede SNHL onset in other mutations associated with the LCCL-domain. QoL has not been studied extensively in DFNA9, although scarce work is available on the positive impact of cochlear implantation to rehabilitate hearing. No studies were found evaluating cognition in DFNA9 patients.

Conclusion: Although cognitive impairment has been demonstrated in patients with hearing loss as well as in patients with BVL, no studies have been reported on the combination of both sensory deficits, such as in DFNA9. Further research is warranted to correlate otovestibular status with cognition.

Dancing with Gravity-Why the Sense of Balance Is (the) Fundamental

The sense of balance, which is usually barely noticeable in the background of each of our movements, only becomes manifest in its function during intense stimulation or in the event of illness, which may quite literally turn your world upside down. While it is true that balance is becoming a bigger issue, that is mainly because people are losing it more frequently. So why is balance not as commonly talked about in psychology, medicine or the arts as the other five traditional senses? This is partly due to its unusual multi-modal nature, whereby three sensory inputs are coordinated and integrated by the central nervous system. Without it, however, we might not have much use for the other senses. The sense of balance encompasses the bodily experience in its entirety. Not only do we act with the body, we may also think and feel through it and with it. Bodily states are not simply effects of cognition; they cause it as well. Equilibrioception is an essential sense and it is interconnected with a wide range of other areas, including cognition, perception, embodiment, the autonomic nervous system, aesthetics, the arts, and education.

Catching-up: Children with developmental coordination disorder compared to healthy children before and after sensorimotor therapy

The aims of the present study were to (a) compare healthy children in terms of sensorimotor maturity to untreated children diagnosed with developmental coordination disorder (DCD) and (b) compare healthy children to diagnosed children following completed treatment with sensorimotor therapy. Participants were 298 children, 196 boys and 102 girls, distributed into a Norm group of healthy children (n = 99) and a group of children diagnosed with DCD (n = 199) with a total mean age of 8.77 years (SD = 2.88). Participants in both groups were assessed on instruments aimed to detect sensorimotor deviations. The children in the DCD group completed, during on average 36 months, sensorimotor therapy which comprised stereotypical fetal- and infant movements, vestibular stimulation, tactile stimulation, auditory stimulation, complementary play exercises, gross motor milestones, and sports-related gross motor skills. At the final visit a full assessment was once more performed. Results showed that the Norm group performed better on all sensorimotor tests as compared to the untreated children from the DCD group, with the exception of an audiometric test where both groups performed at the same level. Girls performed better on tests assessing proprioceptive and balance abilities. Results also showed, after controls for natural maturing effects, that the children from the DCD group after sensorimotor therapy did catch up with the healthy children. The concept of "catching-up" is used within developmental medicine but has not earlier been documented with regard to children and youth in connection with DCD.

Video Head Impulse Tests with a Remote Camera System: Normative Values of Semicircular Canal Vestibulo-Ocular Reflex Gain in Infants and Children

The video head impulse test (VHIT) is widely used to identify semicircular canal function impairments in adults. But classical VHIT testing systems attach goggles tightly to the head, which is not tolerated by infants. Remote video detection of head and eye movements resolves this issue and, here, we report VHIT protocols and normative values for children. Vestibulo-ocular reflex (VOR) gain was measured for all canals of 303 healthy subjects, including 274 children (aged 2.6 months–15 years) and 26 adults (aged 16–67). We used the Synapsys^® (Marseilles, France) VHIT Ulmer system whose remote camera measures head and eye movements. HITs were performed at high velocities. Testing typically lasts 5–10 min. In infants as young as 3 months old, VHIT yielded good inter-measure replicability. VOR gain increases rapidly until about the age of 6 years (with variation among canals), then progresses more slowly to reach adult values by the age of 16. Values are more variable among very young children and for the vertical canals, but showed no difference for right versus left head rotations. Normative values of VOR gain are presented to help detect vestibular impairment in patients. VHIT testing prior to cochlear implants could help prevent total vestibular loss and the resulting grave impairments of motor and cognitive development in patients with residual unilateral vestibular function.

Vestibular Impairment in Dementia

OBJECTIVE

Recent studies suggest an association between vestibular and cognitive function. The goal of the study was to investigate whether vestibular function was impaired in individuals with mild cognitive impairment (MCI) and Alzheimer's disease (AD) compared with cognitively normal individuals.

STUDY DESIGN

Cross-sectional study.

SETTING

Outpatient memory clinic and longitudinal observational study unit.

PATIENTS

Older individuals ≥55 years with MCI or AD. Age, sex, and education-matched normal controls were drawn from the Baltimore Longitudinal Study of Aging (BLSA).

INTERVENTION

Saccular and utricular function was assessed with cervical and ocular vestibular-evoked myogenic potentials (c- and oVEMPs) respectively, and horizontal semicircular canal function was assessed with video head impulse testing.

MAIN OUTCOME MEASURES

Presence or absence of VEMP responses, VEMP amplitude, and vestibular ocular reflex (VOR) gain were measured.

RESULTS

Forty-seven individuals with cognitive impairment (MCI N = 15 and AD N = 32) underwent testing and were matched with 94 controls. In adjusted analyses, bilaterally absent cVEMPs were associated with an over three-fold odds of AD (OR 3.42, 95% CI 1.33-8.91, p = 0.011). One microvolt increases in both cVEMP and oVEMP amplitudes were associated with decreased odds of AD (OR 0.28, 95% CI 0.09-0.93, p = 0.038 and OR 0.92, 95% CI 0.85-0.99, p = 0.036, respectively). There was no significant difference in VOR gain between the groups.

CONCLUSIONS

These findings confirm and extend emerging evidence of an association between vestibular dysfunction and cognitive impairment. Further investigation is needed to determine the causal direction for the link between peripheral vestibular loss and cognitive impairment.

Effects of vestibular disorders on vestibular reflex and imagery

The aim of this study was to establish the effect of vestibular lesion on vestibular imagery. Subjects were required to estimate verbally their passively travelled rotation angles in complete darkness, i.e., to activate vestibular imagery. During motion, the vestibulo-ocular reflex (VOR) was measured. Thus, we examined the coherence between the vestibulo-ocular reflex and self-rotation imagery, with vestibular-lesioned patients and healthy participants. Unilateral acute and chronic patients, bilateral patients, and healthy subjects were compared. The stimulus was a sequence of eight successive passive rotations, with four amplitudes (from 90° to 360°) in two directions. The VOR gain was lower in patients with unilateral lesions, for ipsilateral rotations. The healthy subjects had the highest gain and the bilateral group the lowest, on both rotation sides. Thanks to vestibular compensation after acute unilateral neuritis, the VOR gain increased in lesion side and decreased in healthy side, resulting in a similar gain in both sides. A deficit of vestibular imagery was found exclusively in patients with bilateral hyporeflexia, on both sides. The performance in vestibular imagery was good in the control group and correct in the unilateral patients. Finally, we found a significant correlation between the efficiency of the VOR and that of vestibular imagery, exclusively in the bilateral patients. The present study shows the complex relationship between vestibular imagery and the VOR. This imagery test contributes to another assessment of the spatial handicap of vestibular patients. It seems particularly interesting for patients with bilateral canal paresis and could be used to confirm this diagnosis.

Effects of bilateral vestibular deafferentation in rat on hippocampal theta response to somatosensory stimulation, acetylcholine release, and cholinergic neurons in the pedunculopontine tegmental nucleus

Vestibular dysfunction has been shown to cause spatial memory impairment. Neurophysiological studies indicate that bilateral vestibular loss (BVL), in particular, is associated with an impairment of the response of hippocampal place cells and theta rhythm. However, the specific neural pathways through which vestibular information reaches the hippocampus are yet to be fully elucidated. The aim of the present study was to further investigate the hypothesised 'theta-generating pathway' from the brainstem vestibular nucleus to the hippocampus. BVL, and in some cases, unilateral vestibular loss (UVL), induced by intratympanic sodium arsanilate injections in rats, were used to investigate the effects of vestibular loss on somatosensory-induced type 2 theta rhythm, acetylcholine (ACh) release in the hippocampus, and the number of cholinergic neurons in the pedunculopontine tegmental nucleus (PPTg), an important part of the theta-generating pathway. Under urethane anaesthesia, BVL was found to cause a significant increase in the maximum power of the type 2 theta (3-6 Hz) frequency band compared to UVL and sham animals. Rats with BVL generally exhibited a lower basal level of ACh release than sham rats; however, this difference was not statistically significant. The PPTg of BVL rats exhibited significantly more choline-acetyltransferase (ChAT)-positive neurons than that of sham animals, as did the contralateral PPTg of UVL animals; however, the number of ChAT-positive neurons on the ipsilateral side of UVL animals was not significantly different from sham animals. The results of these studies indicate that parts of the theta-generating pathway undergo a significant reorganisation following vestibular loss, which suggests that this pathway is important for the interaction between the vestibular system and the hippocampus.

Cross-Modal Attention Effects in the Vestibular Cortex during Attentive Tracking of Moving Objects

The midposterior fundus of the Sylvian fissure in the human brain is central to the cortical processing of vestibular cues. At least two vestibular areas are located at this site: the parietoinsular vestibular cortex (PIVC) and the posterior insular cortex (PIC). It is now well established that activity in sensory systems is subject to cross-modal attention effects. Attending to a stimulus in one sensory modality enhances activity in the corresponding cortical sensory system, but simultaneously suppresses activity in other sensory systems. Here, we wanted to probe whether such cross-modal attention effects also target the vestibular system. To this end, we used a visual multiple-object tracking task. By parametrically varying the number of tracked targets, we could measure the effect of attentional load on the PIVC and the PIC while holding the perceptual load constant. Participants performed the tracking task during functional magnetic resonance imaging. Results show that, compared with passive viewing of object motion, activity during object tracking was suppressed in the PIVC and enhanced in the PIC. Greater attentional load, induced by increasing the number of tracked targets, was associated with a corresponding increase in the suppression of activity in the PIVC. Activity in the anterior part of the PIC decreased with increasing load, whereas load effects were absent in the posterior PIC. Results of a control experiment show that attention-induced suppression in the PIVC is stronger than any suppression evoked by the visual stimulus per se. Overall, our results suggest that attention has a cross-modal modulatory effect on the vestibular cortex during visual object tracking.

SIGNIFICANCE STATEMENT

In this study we investigate cross-modal attention effects in the human vestibular cortex. We applied the visual multiple-object tracking task because it is known to evoke attentional load effects on neural activity in visual motion-processing and attention-processing areas. Here we demonstrate a load-dependent effect of attention on the activation in the vestibular cortex, despite constant visual motion stimulation. We find that activity in the parietoinsular vestibular cortex is more strongly suppressed the greater the attentional load on the visual tracking task. These findings suggest cross-modal attentional modulation in the vestibular cortex.