What visuospatial perception has taught us about the pathophysiology of vestibular migraine.

PURPOSE OF REVIEW: A decade has passed since vestibular migraine (VM) was formally established as a clinical entity. During this time, VM has emerged amongst the most common cause of episodic vertigo. Like all forms of migraine, VM symptoms are most prominent during individual attacks, however many patients may also develop persistent symptoms that are less prominent and can still interfere with daily activities. RECENT FINDINGS: Vestibular inputs are strongly multimodal, and because of extensive convergence with other sensory information, they do not result in a distinct conscious sensation. Here we review experimental evidence that supports VM symptoms are linked to multisensory mechanisms that control body motion and position in space. SUMMARY: Multisensory integration is a key concept for understanding migraine. In this context, VM pathophysiology may involve multisensory processes critical for motion perception, spatial orientation, visuospatial attention, and spatial awareness.

Towards an explanation for 'unexplained' dizziness in older people.

BACKGROUND: Subjective unsteadiness or dizziness, usually without increase in body sway, is common in older people. The absence of mechanistic understanding of such symptoms renders clinical management difficult. Here, we explore the mechanisms behind such idiopathic dizziness (ID), focusing on postural control abnormalities. METHODS: Thirty patients with ID and 30 age-matched controls stood on a moving platform. Platform oscillations were randomly delivered at different velocities (from 0 to 0.2 m/s). Markers of postural control, including objective sway (trunk sway path, recorded via a sensor attached to vertebrae C7), stepping responses, subjective instability and anxiety ratings were obtained. MRI scans were available for correlations with levels of cerebral small vessel disease in 28 patients and 24 controls. RESULTS: We observed a significant relationship between objective and subjective instability in all groups. The slope of this fit was significantly steeper for patients than controls, indicating greater perceived instability for the same body sway. Stepwise linear regression showed that the slopes of this objective-subjective instability relationship were best explained by concerns about falling (Falls Efficacy Scale-International), clinical physical functioning (Short Physical Performance Battery) and, to some degree, by neuroimaging markers of cerebral small vessel disease. In addition, patients had a reduced stepping threshold, suggesting an overly cautious postural response. CONCLUSION: The distorted perception of instability and subtle impairments in balance control, including abnormal and overly cautious stepping responses, underlies the emergence of ID. It appears to relate to changes in postural performance, psychological functioning and disruption of postural brain networks associated with cerebral small vessel disease.

Focused Update on Migraine and Vertigo Comorbidity.

PURPOSE OF REVIEW: To provide an update on comorbidity of vestibular symptoms and migraine. RECENT FINDINGS: Multisensory processing and integration is a key concept for understanding mixed presentation of migraine and vestibular symptoms. Here, we discuss how vestibular migraine should be distinguished from a secondary migraine phenomenon in which migraine symptoms may coincide with or triggered by another vestibular disorder. We also have some updates on the diagnostic criteria of vestibular migraine, its pathophysiology, and common approaches used for its treatment. As a common clinical presentation of migraine and vestibular symptoms, vestibular migraine should be distinguished from a secondary migraine phenomenon, in which migraine symptoms may be triggered by or coincide with another vestibular disorder. Recent experimental evidence suggests vestibular symptoms in vestibular migraine are linked to multisensory mechanisms that control body motion and orientation in space.

Sex-disease dimorphism underpins enhanced motion sickness susceptibility in primary adrenal insufficiency: a cross-sectional observational study.

Environmental motion can induce physiological stress and trigger motion sickness. In these situations, lower-than-normal levels of adrenocorticotropic hormone (ACTH) have been linked with increased susceptibility to motion sickness in healthy individuals. However, whether patients with primary adrenal insufficiency, who typically have altered ACTH levels compared to the normal population, exhibit alterations in sickness susceptibility remains unknown. To address this, we recruited 78 patients with primary adrenal insufficiency and compared changes in the motion sickness susceptibility scores from 10 years prior to diagnosis (i.e. retrospective sickness rating) with the current sickness measures (post-diagnosis), using the validated motion sickness susceptibility questionnaire (MSSQ). Group analysis revealed that motion sickness susceptibility pre-diagnosis did not differ between controls and patients. We observed that following treatment, current measures of motion sickness were significantly increased in patients and subsequent analysis revealed that this increase was primarily in female patients with primary adrenal insufficiency. These observations corroborate the role of stress hormones in modulating sickness susceptibility and support the notion of a sexually dimorphic adrenal cortex as we only observed selective enhancement in females. A potential mechanism to account for our novel observation remains obscure, but we speculate that it may reflect a complex sex-disease-drug interaction.

Vestibular migraine treatment: a comprehensive practical review.

Vestibular migraine is an underdiagnosed but increasingly recognized neurological condition that causes episodic vertigo associated with other features of migraine. It is now thought to be the most common cause of spontaneous (non-positional) episodic vertigo, affecting up to 1% of the population. A meta-analysis of preventative treatments for vestibular migraine was published in 2021, but the authors were unable to establish a preferred treatment strategy due to low quality of evidence and heterogeneity of study design and outcome reporting. Therefore, there remains a clinical need for pragmatic management guidelines specific to vestibular migraine using the available evidence. Here, we provide a practical review utilizing a systematic qualitative assessment of the evidence for abortive and preventative interventions in adults. The overall evidence base for vestibular migraine treatment is of low quality. Nevertheless, we provide practical treatment recommendations based on the available evidence and our experience to help guide clinicians treating patients with vestibular migraine. We also discuss how future clinical trials could be designed to improve the quality of evidence in this condition.

Vestibular agnosia in traumatic brain injury and its link to imbalance.

Vestibular dysfunction, causing dizziness and imbalance, is a common yet poorly understood feature in patients with TBI. Damage to the inner ear, nerve, brainstem, cerebellum and cerebral hemispheres may all affect vestibular functioning, hence, a multi-level assessment-from reflex to perception-is required. In a previous report, postural instability was the commonest neurological feature in ambulating acute patients with TBI. During ward assessment, we also frequently observe a loss of vertigo sensation in patients with acute TBI, common inner ear conditions and a related vigorous vestibular-ocular reflex nystagmus, suggesting a 'vestibular agnosia'. Patients with vestibular agnosia were also more unbalanced; however, the link between vestibular agnosia and imbalance was confounded by the presence of inner ear conditions. We investigated the brain mechanisms of imbalance in acute TBI, its link with vestibular agnosia, and potential clinical impact, by prospective laboratory assessment of vestibular function, from reflex to perception, in patients with preserved peripheral vestibular function. Assessment included: vestibular reflex function, vestibular perception by participants' report of their passive yaw rotations in the dark, objective balance via posturography, subjective symptoms via questionnaires, and structural neuroimaging. We prospectively screened 918 acute admissions, assessed 146 and recruited 37. Compared to 37 matched controls, patients showed elevated vestibular-perceptual thresholds (patients 12.92°/s versus 3.87°/s) but normal vestibular-ocular reflex thresholds (patients 2.52°/s versus 1.78°/s). Patients with elevated vestibular-perceptual thresholds [3 standard deviations (SD) above controls' average], were designated as having vestibular agnosia, and displayed worse posturography than non-vestibular-agnosia patients, despite no difference in vestibular symptom scores. Only in patients with impaired postural control (3 SD above controls' mean), whole brain diffusion tensor voxel-wise analysis showed elevated mean diffusivity (and trend lower fractional anisotropy) in the inferior longitudinal fasciculus in the right temporal lobe that correlated with vestibular agnosia severity. Thus, impaired balance and vestibular agnosia are co-localized to the inferior longitudinal fasciculus in the right temporal lobe. Finally, a clinical audit showed a sevenfold reduction in clinician recognition of a common peripheral vestibular condition (benign paroxysmal positional vertigo) in acute patients with clinically apparent vestibular agnosia. That vestibular agnosia patients show worse balance, but without increased dizziness symptoms, explains why clinicians may miss treatable vestibular diagnoses in these patients. In conclusion, vestibular agnosia mediates imbalance in traumatic brain injury both directly via white matter tract damage in the right temporal lobe, and indirectly via reduced clinical recognition of common, treatable vestibular diagnoses.

Prevalence of acute dizziness and vertigo in cortical stroke.

BACKGROUND AND PURPOSE: In posterior circulation stroke, vertigo can be a presenting feature. However, whether isolated hemispheric strokes present with vertigo is less clear, despite a few single case reports in the literature. Here, (a) the prevalence of vertigo/dizziness in acute stroke is explored and (b) the cortical distribution of the lesions in relation to both the known vestibular cortex and the evolution of the symptoms, are considered. METHODS: Structured interviews were conducted in 173 consecutive unselected patients admitted to the hyperacute stroke unit at the University College London Hospitals. The interview was used to evaluate whether the patient was suffering from dizziness and/or vertigo before the onset of the stroke and at the time of the stroke (acute dizziness/vertigo), and the nature of these symptoms. RESULTS: In all, 53 patients had cortical infarcts, of which 21 patients reported acute dizziness. Out of these 21, five patients reported rotational vertigo. Seventeen of the total 53 patients had lesions in known vestibular cortical areas distributed within the insular and parietal opercular cortices. CONCLUSIONS: The prevalence of vertigo in acute cortical strokes was 9%, with no single locus of lesion overlap. There is growing evidence supporting a lateralized vestibular cortex, with speculation that cortical strokes affecting the right hemisphere are more likely to cause vestibular symptoms than left hemispheric strokes. A trend was observed for this association, with the right hemisphere affected in four of five patients who reported spinning vertigo at the onset of the stroke.

Multisensory contribution in visuospatial orientation: an interaction between neck and trunk proprioception.

A coherent perception of spatial orientation is key in maintaining postural control. To achieve this the brain must access sensory inputs encoding both the body and the head position and integrate them with incoming visual information. Here we isolated the contribution of proprioception to verticality perception and further investigated whether changing the body position without moving the head can modulate visual dependence-the extent to which an individual relies on visual cues for spatial orientation. Spatial orientation was measured in ten healthy individuals [6 female; 25-47 years (SD 7.8 years)] using a virtual reality based subjective visual vertical (SVV) task. Individuals aligned an arrow to their perceived gravitational vertical, initially against a static black background (10 trials), and then in other conditions with clockwise and counterclockwise background rotations (each 10 trials). In all conditions, subjects were seated first in the upright position, then with trunk tilted 20° to the right, followed by 20° to the left while the head was always aligned vertically. The SVV error was modulated by the trunk position, and it was greater when the trunk was tilted to the left compared to right or upright trunk positions (p < 0.001). Likewise, background rotation had an effect on SVV errors as these were greater with counterclockwise visual rotation compared to static background and clockwise roll motion (p < 0.001). Our results show that the interaction between neck and trunk proprioception can modulate how visual inputs affect spatial orientation.

Vestibulo-perceptual influences upon the vestibulo-spinal reflex.

The vestibular system facilitates gaze and postural stability via the vestibulo-ocular (VOR) and vestibulo-spinal reflexes, respectively. Cortical and perceptual mechanisms can modulate long-duration VOR responses, but little is known about whether high-order neural phenomena can modulate short-latency vestibulo-spinal responses. Here, we investigate this by assessing click-evoked cervical vestibular myogenic-evoked potentials (VEMPS) during visual roll motion that elicited an illusionary sensation of self-motion (i.e. vection). We observed that during vection, the amplitude of the VEMPs was enhanced when compared to baseline measures. This modulation in VEMP amplitude was positively correlated with the subjective reports of vection strength. That is, those subjects reporting greater subjective vection scores exhibited a greater increase in VEMP amplitude. Control experiments showed that simple arousal (cold-induced discomfort) also increased VEMP amplitude but that, unlike vection, it did not modulate VEMP amplitude linearly. In agreement, small-field visual roll motion that did not induce vection failed to increase VEMP amplitude. Taken together, our results demonstrate that vection can modify the response of vestibulo-collic reflexes. Even short-latency brainstem vestibulo-spinal reflexes are influenced by high-order mechanisms, illustrating the functional importance of perceptual mechanisms in human postural control. As VEMPs are inhibitory responses, we argue that the findings may represent a mechanism whereby high-order CNS mechanisms reduce activity levels in vestibulo-collic reflexes, necessary for instance when voluntary head movements need to be performed.

Pathophysiological dissociation of the interaction between time pressure and trait anxiety during spatial orientation judgments.

Spatial orientation is achieved by integrating visual, vestibular and proprioceptive cues. Individuals that rely strongly upon visual cues to facilitate spatial orientation are termed visually dependent. Heightened visual reliance commonly occurs in patients following vestibular dysfunction and can influence clinical outcome. Additionally, psychological factors, including anxiety, are associated with poorer clinical outcome following vestibular dysfunction. Given that visual dependency measures are affected by psychological and contextual influences, such as time pressure, we investigated the interaction between time pressure and anxiety upon visual dependency in healthy controls and vestibular migraine patients. Visual dependency was assessed using a "Rod and Disk" task at baseline and under time pressure (3 s to complete the task). Non-situational (trait) and situational (state) anxiety levels were quantified using the Spielberg State-Trait Anxiety Inventory. We calculated the change in visual dependency (VD) [∆VD = VDtime pressure  - VDbaseline ] and correlated it with participants' trait anxiety scores. We observed a significant negative correlation between trait anxiety and the change in VD (R2  = .393, p < .001) in healthy controls and a positive correlation in dizzy patients (R2  = .317, p < .001). That is, healthy individuals that were more anxious became less visually dependent under time pressure (i.e., more accurate), whereas less anxious individuals became more visually dependent. The reverse was observed in vestibular migraine patients. Our results illustrate that anxiety can differentially modulate task performance during spatial orientation judgements under time pressure in healthy individuals and dizzy patients. These findings have potential implications for individualised patient rehabilitation therapies.

Abnormal visuo-vestibular interactions in vestibular migraine: a cross sectional study.

Vestibular migraine is among the commonest causes of episodic vertigo. Chronically, patients with vestibular migraine develop abnormal responsiveness to both vestibular and visual stimuli characterized by heightened self-motion sensitivity and visually-induced dizziness. Yet, the neural mechanisms mediating such symptoms remain unknown. We postulate that such symptoms are attributable to impaired visuo-vestibular cortical interactions, which in turn disrupts normal vestibular function. To assess this, we investigated whether prolonged, full-field visual motion exposure, which has been previously shown to modulate visual cortical excitability in both healthy individuals and avestibular patients, could disrupt vestibular ocular reflex and vestibular-perceptual thresholds of self-motion during rotations. Our findings reveal that vestibular migraine patients exhibited abnormally elevated reflexive and perceptual vestibular thresholds at baseline. Following visual motion exposure, both reflex and perceptual thresholds were significantly further increased in vestibular migraine patients relative to healthy controls, migraineurs without vestibular symptoms and patients with episodic vertigo due to a peripheral inner-ear disorder. Our results provide support for the notion of altered visuo-vestibular cortical interactions in vestibular migraine, as evidenced by vestibular threshold elevation following visual motion exposure.

Vestibulo-cortical hemispheric dominance: The link between anxiety and the vestibular system?

Vestibular processing and anxiety networks are functionally intertwined, as demonstrated by reports of reciprocal influences upon each other. Yet whether there is an underlying link between these two systems remains unknown. Previous findings have highlighted the involvement of hemispheric lateralisation in processing of both anxiety and vestibular signals. Accordingly, we explored the interaction between vestibular cortical processing and anxiety by assessing the relationship between anxiety levels and the degree of hemispheric lateralisation of vestibulo-cortical processing in 64 right-handed, healthy individuals. Vestibulo-cortical hemispheric lateralisation was determined by gaging the degree of caloric-induced nystagmus suppression following modulation of cortical excitability using trans-cranial direct current stimulation targeted over the posterior parietal cortex, an area implicated in the processing of vestibular signals. The degree of nystagmus suppression yields an objective biomarker, allowing the quantification of the degree of right vestibulo-cortical hemisphere dominance. Anxiety levels were quantified using the Trait component of the Spielberger State-Trait Anxiety Questionnaire. Our findings demonstrate that the degree of an individual's vestibulo-cortical hemispheric dominance correlates with their anxiety levels. That is, those individuals with greater right hemispheric vestibulo-cortical dominance exhibited lower levels of anxiety. By extension, our results support the notion that hemispheric lateralisation determines an individual's emotional processing, thereby linking cortical circuits involved in processing anxiety and vestibular signals, respectively.

Viewing Target Distance Influences the Vestibulo-Ocular Reflex Gain when Assessed Using the Video Head Impulse Test.

Gaze stabilization during head movements is provided by the vestibulo-ocular reflex (VOR). Clinical assessment of this reflex is performed using the video Head Impulse Test (vHIT). To date, the influence of different fixation distances on VOR gain using the vHIT has not been explored. We assessed the effect of target proximity on the horizontal VOR using the vHIT. Firstly, we assessed the VOR gain in 18 healthy subjects with 5 viewing target distances (150, 40, 30, 20, and 10 cm). The gain increased significantly as the viewing target distance decreased. A second experiment on 10 subjects was performed in darkness whilst the subjects were imagining targets at different distances. There were significant inverse relationships between gain and distance for both the real and the imaginary targets. There was a statistically significant difference between light and dark gains for the 20- and 40-cm distances, but not for the 150-cm distance. Theoretical VOR gains for different target distances were calculated and compared with those found in light and darkness. The increase in gain observed for near targets was lower than predicted by geometrical calculations, implying a physiological ceiling effect on the VOR. The VOR gain in the dark, as assessed with the vHIT, demonstrates an enhancement associated with a reduced target distance.

Differential effect of visual motion adaption upon visual cortical excitability.

The objectives of this study were 1) to probe the effects of visual motion adaptation on early visual and V5/MT cortical excitability and 2) to investigate whether changes in cortical excitability following visual motion adaptation are related to the degree of visual dependency, i.e., an overreliance on visual cues compared with vestibular or proprioceptive cues. Participants were exposed to a roll motion visual stimulus before, during, and after visual motion adaptation. At these stages, 20 transcranial magnetic stimulation (TMS) pulses at phosphene threshold values were applied over early visual and V5/MT cortical areas from which the probability of eliciting a phosphene was calculated. Before and after adaptation, participants aligned the subjective visual vertical in front of the roll motion stimulus as a marker of visual dependency. During adaptation, early visual cortex excitability decreased whereas V5/MT excitability increased. After adaptation, both early visual and V5/MT excitability were increased. The roll motion-induced tilt of the subjective visual vertical (visual dependence) was not influenced by visual motion adaptation and did not correlate with phosphene threshold or visual cortex excitability. We conclude that early visual and V5/MT cortical excitability is differentially affected by visual motion adaptation. Furthermore, excitability in the early or late visual cortex is not associated with an increase in visual reliance during spatial orientation. Our findings complement earlier studies that have probed visual cortical excitability following motion adaptation and highlight the differential role of the early visual cortex and V5/MT in visual motion processing.NEW & NOTEWORTHY We examined the influence of visual motion adaptation on visual cortex excitability and found a differential effect in V1/V2 compared with V5/MT. Changes in visual excitability following motion adaptation were not related to the degree of an individual's visual dependency.

Influence of biases in numerical magnitude allocation on human prosocial decision making.

Over the past decade neuroscientific research has attempted to probe the neurobiological underpinnings of human prosocial decision making. Such research has almost ubiquitously employed tasks such as the dictator game or similar variations (i.e., ultimatum game). Considering the explicit numerical nature of such tasks, it is surprising that the influence of numerical cognition on decision making during task performance remains unknown. While performing these tasks, participants typically tend to anchor on a 50:50 split that necessitates an explicit numerical judgement (i.e., number-pair bisection). Accordingly, we hypothesize that the decision-making process during the dictator game recruits overlapping cognitive processes to those known to be engaged during number-pair bisection. We observed that biases in numerical magnitude allocation correlated with the formulation of decisions during the dictator game. That is, intrinsic biases toward smaller numerical magnitudes were associated with the formulation of less favorable decisions, whereas biases toward larger magnitudes were associated with more favorable choices. We proceeded to corroborate this relationship by subliminally and systematically inducing biases in numerical magnitude toward either higher or lower numbers using a visuo-vestibular stimulation paradigm. Such subliminal alterations in numerical magnitude allocation led to proportional and corresponding changes to an individual's decision making during the dictator game. Critically, no relationship was observed between neither intrinsic nor induced biases in numerical magnitude on decision making when assessed using a nonnumerical-based prosocial questionnaire. Our findings demonstrate numerical influences on decisions formulated during the dictator game and highlight the necessity to control for confounds associated with numerical cognition in human decision-making paradigms.NEW & NOTEWORTHY We demonstrate that intrinsic biases in numerical magnitude can directly predict the amount of money donated by an individual to an anonymous stranger during the dictator game. Furthermore, subliminally inducing perceptual biases in numerical-magnitude allocation can actively drive prosocial choices in the corresponding direction. Our findings provide evidence for numerical influences on decision making during performance of the dictator game. Accordingly, without the implementation of an adequate control for numerical influences, the dictator game and other tasks with an inherent numerical component (i.e., ultimatum game) should be employed with caution in the assessment of human behavior.

Intratympanic methylprednisolone versus gentamicin in patients with unilateral Ménière's disease: a randomised, double-blind, comparative effectiveness trial.

BACKGROUND: Ménière's disease is characterised by severe vertigo attacks and hearing loss. Intratympanic gentamicin, the standard treatment for refractory Ménière's disease, reduces vertigo, but damages vestibular function and can worsen hearing. We aimed to assess whether intratympanic administration of the corticosteroid methylprednisolone reduces vertigo compared with gentamicin. METHODS: In this double-blind comparative effectiveness trial, patients aged 18-70 years with refractory unilateral Ménière's disease were enrolled at Charing Cross Hospital (London, UK) and Leicester Royal Infirmary (Leicester, UK). Patients were randomly assigned (1:1) by a block design to two intratympanic methylprednisolone (62·5 mg/mL) or gentamicin (40 mg/mL) injections given 2 weeks apart, and were followed up for 2 years. All investigators and patients were masked to treatment allocation. The primary outcome was vertigo frequency over the final 6 months (18-24 months after injection) compared with the 6 months before the first injection. Analyses were done in the intention-to-treat population, and then per protocol. This trial is registered with ClinicalTrials.gov, number NCT00802529. FINDINGS: Between June 19, 2009, and April 15, 2013, 256 patients with Ménière's disease were screened, 60 of whom were enrolled and randomly assigned: 30 to gentamicin and 30 to methylprednisolone. In the intention-to-treat analysis (ie, all 60 patients), the mean number of vertigo attacks in the final 6 months compared with the 6 months before the first injection (primary outcome) decreased from 19·9 (SD 16·7) to 2·5 (5·8) in the gentamicin group (87% reduction) and from 16·4 (12·5) to 1·6 (3·4) in the methylprednisolone group (90% reduction; mean difference -0·9, 95% CI -3·4 to 1·6). Patients whose vertigo did not improve after injection (ie, non-responders) after being assessed by an unmasked clinician were eligible for additional injections given by a masked clinician (eight patients in the gentamicin group vs 15 in the methylprednisolone group). Two non-responders switched from methylprednisolone to gentamicin. Both drugs were well tolerated with no safety concerns. Six patients reported one adverse event each: three in the gentamicin group and three in the methylprednisolone group. The most common adverse event was minor ear infections, which was experienced by one patient in the gentamicin group and two in the methylprednisolone group. INTERPRETATION: Methylprednisolone injections are a non-ablative, effective treatment for refractory Ménière's disease. The choice between methylprednisolone and gentamicin should be made based on clinical knowledge and patient circumstances. FUNDING: Ménière's Society and National Institute for Health Research Imperial Biomedical Research Centre.

Bidirectional Modulation of Numerical Magnitude.

Numerical cognition is critical for modern life; however, the precise neural mechanisms underpinning numerical magnitude allocation in humans remain obscure. Based upon previous reports demonstrating the close behavioral and neuro-anatomical relationship between number allocation and spatial attention, we hypothesized that these systems would be subject to similar control mechanisms, namely dynamic interhemispheric competition. We employed a physiological paradigm, combining visual and vestibular stimulation, to induce interhemispheric conflict and subsequent unihemispheric inhibition, as confirmed by transcranial direct current stimulation (tDCS). This allowed us to demonstrate the first systematic bidirectional modulation of numerical magnitude toward either higher or lower numbers, independently of either eye movements or spatial attention mediated biases. We incorporated both our findings and those from the most widely accepted theoretical framework for numerical cognition to present a novel unifying computational model that describes how numerical magnitude allocation is subject to dynamic interhemispheric competition. That is, numerical allocation is continually updated in a contextual manner based upon relative magnitude, with the right hemisphere responsible for smaller magnitudes and the left hemisphere for larger magnitudes.

Vestibular and oculomotor influences on visual dependency.

The degree to which a person relies on visual stimuli for spatial orientation is termed visual dependency (VD). VD is considered a perceptual trait or cognitive style influenced by psychological factors and mediated by central reweighting of the sensory inputs involved in spatial orientation. VD is often measured with the rod-and-disk test, in which participants align a central rod to the subjective visual vertical (SVV) in the presence of a background that is either stationary or rotating around the line of sight-dynamic SVV. Although this task has been employed to assess VD in health and vestibular disease, what effect torsional nystagmic eye movements may have on individual performance is unknown. Using caloric ear irrigation, 3D video-oculography, and the rod-and-disk test, we show that caloric torsional nystagmus modulates measures of VD and demonstrate that increases in tilt after irrigation are positively correlated with changes in ocular torsional eye movements. When the direction of the slow phase of the torsional eye movement induced by the caloric is congruent with that induced by the rotating visual stimulus, there is a significant increase in tilt. When these two torsional components are in opposition, there is a decrease. These findings show that measures of VD can be influenced by oculomotor responses induced by caloric stimulation. The findings are of significance for clinical studies, as they indicate that VD, which often increases in vestibular disorders, is modulated not only by changes in cognitive style but also by eye movements, in particular nystagmus.