79 results found
Castro P, Papoutselou E, Mahmoud S, et al., 2022, Priming overconfidence in belief systems reveals negative return on postural control mechanisms, GAIT & POSTURE, Vol: 94, Pages: 1-8, ISSN: 0966-6362
Arshad Q, Saman Y, Kaski D, et al., 2022, Magnitude estimates construct hierarchal maps for vestibular space and time: implications for functional dizziness, Frontiers in Neuroscience, Vol: 15, ISSN: 1662-453X
Maintaining balance necessitate an accurate perceptual map of the external world. Neuro-physiological mechanisms of locomotor control, sensory perception and anxiety systems, have been viewed as separate entities that can on occasion affect each other (i.e. walking on ice). Emerging models are more integrated, that envision sensory perception and threat assessment as a fundamental component of balance. Here we present the empirically based theoretical argument, that vestibular cortical areas construct magnitude estimates of the external world via neural integration of incoming sensory signals. In-turn these cortically derived magnitude estimates, construct context-dependent vestibulo-spatial and vestibulo-temporal representational maps of the external world, and, ensure an appropriate online scaling factor for associated action-perceptual risk. Thus, threat signals exert a continuous influence on planning movements, predicting outcomes of motion of self and surrounding objects, and adjusting tolerances for discrepancies between predicted and actual estimates. Such a process affects the degree of conscious attention directed to spatial and temporal aspects of motion stimuli, implying that maintaining balance may follow a Bayesian approach in which the relative weighting of vestibulo-spatial and vestibulo-temporal signals and tolerance for discrepancies are adjusted in accordance with the level of threat assessment. Here, we seek to mechanistically explain this process with our novel empirical concept of a Brainstem Cortical Scaling Metric (BCSM), which we developed from a series of neurophysiological studies illustrating the central role of interhemispheric vestibulo-cortical asymmetries for balance control. We conclude by using the BCSM to derive theoretical predictions of how a dysfunctional BCSM can mechanistically-account for functional dizziness.
Ibitoye RT, Desowska A, Guven O, et al., 2021, Small vessel disease disrupts EEG postural brain networks in ‘unexplained dizziness in the elderly’, Clinical Neurophysiology, Vol: 132, Pages: 2751-2762, ISSN: 1388-2457
ObjectiveTo examine the hypothesis that small vessel disease disrupts postural networks in older adults with unexplained dizziness in the elderly (UDE).MethodsSimultaneous electroencephalography and postural sway measurements were undertaken in upright, eyes closed standing, and sitting postures (as baseline) in 19 younger adults, 33 older controls and 36 older patients with UDE. Older adults underwent magnetic resonance imaging to determine whole brain white matter hyperintensity volumes, a measure of small vessel disease. Linear regression was used to estimate the effect of instability on electroencephalographic power and connectivity.ResultsAgeing increased theta and alpha desynchronisation on standing. In older controls, delta and gamma power increased, and theta and alpha power reduced with instability. Dizzy older patients had higher white matter hyperintensity volumes and more theta desynchronisation during periods of instability. White matter hyperintensity volume and delta power during periods of instability were correlated, positively in controls but negatively in dizzy older patients. Delta power correlated with subjective dizziness and instability.ConclusionsNeural resource demands of postural control increase with age, particularly in patients with UDE, driven by small vessel disease.SignificanceEEG correlates of postural control saturate in older adults with UDE, offering a basis to this common syndrome.
Ibitoye R, Castro P, Desowska A, et al., 2021, Small vessel disease disrupts EEG postural brain networks in 'unexplained dizziness in the elderly', 25th World Congress of Neurology (WCN), Publisher: ELSEVIER, ISSN: 0022-510X
Chan Y, Wong Y, Khalid N, et al., 2021, Acute dizziness and vertigo in cortical stroke: Bias of subjective recall, 25th World Congress of Neurology (WCN), Publisher: ELSEVIER, Pages: 3-3, ISSN: 0022-510X
Bonsu A, Britton Z, Asif Z, et al., 2021, Attentional network dysfunction in vestibular migraine, 25th World Congress of Neurology (WCN), Publisher: ELSEVIER, ISSN: 0022-510X
Arshad Q, Bronstein A, 2021, Motion perception in vestibular migraine, EUROPEAN JOURNAL OF NEUROLOGY, Vol: 28, Pages: E93-E94, ISSN: 1351-5101
Man Chan Y, Wong Y, Khalid N, et al., 2021, Prevalence of acute dizziness and vertigo in cortical stroke, EUROPEAN JOURNAL OF NEUROLOGY, Vol: 28, Pages: 3177-3181, ISSN: 1351-5101
Kamourieh S, Sokolska M, Akram H, et al., 2021, Miners' Nystagmus Following Visual Deprivation: A Case Report, ANNALS OF INTERNAL MEDICINE, Vol: 174, Pages: 1021-+, ISSN: 0003-4819
Bonsu A, Walker P, Edey J, et al., 2021, Time to consider the role of rationalisation in health psychology, PUBLIC HEALTH, Vol: 196, Pages: 59-61, ISSN: 0033-3506
McCarthy J, Castro P, Cottier R, et al., 2021, Multisensory contribution in visuospatial orientation: an interaction between neck and trunk proprioception, EXPERIMENTAL BRAIN RESEARCH, Vol: 239, Pages: 2501-2508, ISSN: 0014-4819
Bonsu AN, Nousi S, Lobo R, et al., 2021, Vestibulo-perceptual influences upon the vestibulo-spinal reflex, Experimental Brain Research, Vol: 239, Pages: 2141-2149, ISSN: 0014-4819
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.
Calzolari E, Chepisheva M, Smith RM, et al., 2021, Vestibular agnosia in traumatic brain injury and its link to imbalance, Brain, Vol: 144, Pages: 128-143, ISSN: 0006-8950
Vestibular dysfunction, causing dizziness and imbalance, is a common yet poorly understoodfeature in traumatic brain injury patients. Damage to the inner ear, nerve, brainstem, cerebellumand 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 thecommonest neurological feature in ambulating acute traumatic brain injury patients. We alsofrequently observe, during ward assessment of acute traumatic brain injury patients withcommon inner ear conditions and a related vigorous vestibular-ocular reflex nystagmus, a lossof vertigo sensation, suggesting a “vestibular agnosia”. Vestibular agnosia patients were alsomore unbalanced, however the link between vestibular agnosia and imbalance was confoundedby the presence of inner ear conditions. We investigated the brain mechanisms of imbalance inacute traumatic brain injury, its link with vestibular agnosia, and potential clinical impact, byprospective laboratory assessment of vestibular function, from reflex to perception, in patientswith 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 structuralneuroimaging. We prospectively screened 918 acute admissions, assessed 146 and recruited37. Compared to 37 matched controls, patients showed elevated vestibular-perceptualthresholds (patients 12.92°/s vs. 3.87°/s) but normal vestibular-ocular reflex thresholds(patients 2.52°/s vs. 1.78°/s). Patients with elevated vestibular-perceptual thresholds (3standard deviations above controls’ average), were designated as having vestibular agnosia,and displayed worse posturography than non-vestibular-agnosia patients, despite no differencein vestibular symptom sc
Patel M, Roberts E, Arshad Q, et al., 2020, The "broken escalator" phenomenon: vestibular dizziness interferes with locomotor adaptation, Journal of Vestibular Research: Equilibrium and Orientation: an international journal of experimental and clinical vestibular science, Vol: 30, Pages: 81-94, ISSN: 0957-4271
BACKGROUND: Although vestibular lesions degrade postural control we do not know the relative contributions of the magnitude of the vestibular loss and subjective vestibular symptoms to locomotor adaptation. OBJECTIVE: To study how dizzy symptoms interfere with adaptive locomotor learning. METHODS: We examined patients with contrasting peripheral vestibular deficits, vestibular neuritis in the chronic stable phase (n = 20) and strongly symptomatic unilateral Meniere's disease (n = 15), compared to age-matched healthy controls (n = 15). We measured locomotor adaptive learning using the "broken escalator" aftereffect, simulated on a motorised moving sled. RESULTS: Patients with Meniere's disease had an enhanced "broken escalator" postural aftereffect. More generally, the size of the locomotor aftereffect was related to how symptomatic patients were across both groups. Contrastingly, the degree of peripheral vestibular loss was not correlated with symptom load or locomotor aftereffect size. During the MOVING trials, both patient groups had larger levels of instability (trunk sway) and reduced adaptation than normal controls. CONCLUSION: Dizziness symptoms influence locomotor adaptation and its subsequent expression through motor aftereffects. Given that the unsteadiness experienced during the "broken escalator" paradigm is internally driven, the enhanced aftereffect found represents a new type of self-generated postural challenge for vestibular/unsteady patients.
Bednarczuk NF, Bradshaw JM, Mian SY, et al., 2020, Pathophysiological dissociation of the interaction between time pressure and trait anxiety during spatial orientation judgments, EUROPEAN JOURNAL OF NEUROSCIENCE, Vol: 52, Pages: 3215-3222, ISSN: 0953-816X
Castro P, Kaski D, Al-Fazly H, et al., 2019, Body sway during postural perturbations is mediated by the degree of vestibulo-cortical dominance, Brain Stimulation, Vol: 12, Pages: 1098-1100, ISSN: 1935-861X
Marcus HJ, Paine H, Sargeant M, et al., 2019, Vestibular dysfunction in acute traumatic brain injury, Journal of Neurology, Vol: 266, Pages: 2430-2433, ISSN: 0340-5354
Traumatic brain injury (TBI) is the commonest cause of disability in under-40-year-olds. Vestibular features of dizziness (illusory self-motion) or imbalance which affects 50% of TBI patients at 5 years, increases unemployment threefold in TBI survivors. Unfortunately, vestibular diagnoses are cryptogenic in 25% of chronic TBI cases, impeding therapy. We hypothesized that chronic adaptive brain mechanisms uncouple vestibular symptoms from signs. This predicts a masking of vestibular diagnoses chronically but not acutely. Hence, defining the spectrum of vestibular diagnoses in acute TBI should clarify vestibular diagnoses in chronic TBI. There are, however, no relevant acute TBI data. Of 111 Major Trauma Ward adult admissions screened (median 38-years-old), 96 patients (87%) had subjective dizziness (illusory self-motion) and/or objective imbalance were referred to the senior author (BMS). Symptoms included: feeling unbalanced (58%), headache (50%) and dizziness (40%). In the 47 cases assessed by BMS, gait ataxia was the commonest sign (62%) with half of these cases denying imbalance when asked. Diagnoses included BPPV (38%), acute peripheral unilateral vestibular loss (19%), and migraine phenotype headache (34%), another potential source of vestibular symptoms. In acute TBI, vestibular signs are common, with gait ataxia being the most frequent one. However, patients underreport symptoms. The uncoupling of symptoms from signs likely arises from TBI affecting perceptual mechanisms. Hence, the cryptogenic nature of vestibular symptoms in TBI (acute or chronic) relates to a complex interaction between injury (to peripheral and central vestibular structures and perceptual mechanisms) and brain-adaptation, emphasizing the need for acute prospective, mechanistic studies.
Arshad Q, Ortega MC, Goga U, et al., 2019, Interhemispheric control of sensory cue integration and self-motion perception, Neuroscience, Vol: 408, Pages: 378-387, ISSN: 0306-4522
Spatial orientation necessitates the integration of visual and vestibular sensory cues, in-turn facilitating self-motion perception. However, the neural mechanisms underpinning sensory integration remain unknown. Recently we have illustrated that spatial orientation and vestibular thresholds are influenced by interhemispheric asymmetries associated with the posterior parietal cortices (PPC) that predominantly house the vestibulo-cortical network. Given that sensory integration is a prerequisite to both spatial orientation and motion perception, we hypothesized that sensory integration is similarly subject to interhemispheric influences. Accordingly, we explored the relationship between vestibulo-cortical dominance – assessed using a biomarker, the degree of vestibular-nystagmus suppression following transcranial direct current stimulation over the PPC – with visual dependence measures obtained during performance of a sensory integration task (the rod-and-disk task). We observed that the degree of visual dependence was correlated with vestibulo-cortical dominance. Specifically, individuals with greater right hemispheric vestibulo-cortical dominance had reduced visual dependence. We proceeded to assess the significance of such dominance on behavior by correlating measures of visual dependence with self-motion perception in healthy subjects. We observed that right-handed individuals experienced illusionary self-motion (vection) quicker than left-handers and that the degree of vestibular cortical dominance was correlated with the time taken to experience vection, only during conditions that induced interhemispheric conflict. To conclude, we demonstrate that interhemispheric asymmetries associated with vestibulo-cortical processing in the PPC functionally and mechanistically link sensory integration and self-motion perception, facilitating spatial orientation. Our findings highlight the importance of dynamic interhemispheric competition upon control of vestib
Britton Z, Arshad Q, 2019, Vestibular and multi-sensory influences upon self-motion perception and the consequences for human behavior, Frontiers in Neurology, Vol: 10, ISSN: 1664-2295
In this manuscript, we comprehensively review both the human and animal literature regarding vestibular and multi-sensory contributions to self-motion perception. This covers the anatomical basis and how and where the signals are processed at all levels from the peripheral vestibular system to the brainstem and cerebellum and finally to the cortex. Further, we consider how and where these vestibular signals are integrated with other sensory cues to facilitate self-motion perception. We conclude by demonstrating the wide-ranging influences of the vestibular system and self-motion perception upon behavior, namely eye movement, postural control, and spatial awareness as well as new discoveries that such perception can impact upon numerical cognition, human affect, and bodily self-consciousness.
Castro P, Kaskia D, Schieppati M, et al., 2019, Subjective stability perception is related to postural anxiety in older subjects, GAIT & POSTURE, Vol: 68, Pages: 538-544, ISSN: 0966-6362
Kaski D, Rust HM, Ibitoye R, et al., 2019, Theoretical framework for "unexplained" dizziness in the elderly: The role of small vessel disease, Editors: Ramat, Shaikh, Publisher: ELSEVIER SCIENCE BV, Pages: 225-240
Castro P, Sena Esteves S, Lerchundi F, et al., 2018, Viewing target distance influences the vestibulo-ocular reflex gain when assessed using the video head impulse test, Audiology and Neurotology, Vol: 23, Pages: 285-289, ISSN: 1420-3030
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.
Edwards A, Guven O, Furman M, et al., 2018, Electroencephalographic correlates of continuous postural tasks of increasing difficulty, Neuroscience, Vol: 395, Pages: 35-48, ISSN: 0306-4522
Cortical involvement in postural control is well recognized, however the role of non-visual afferents remains unclear. Parietal cortical areas are strongly implicated in vestibulo-spatial functions, but topographical localization during balance tasks remains limited. Here, we use electroencephalography (EEG) during continuous balance tasks of increasing difficulty at single electrode positions. Twenty-four healthy, right-handed individuals performed four balance tasks of increasing difficulty (bipedal and unipedal) and a seated control condition with eyes closed. Subjective ratings of task difficulty were obtained. EEG was recorded from 32 electrodes; 5 overlying sensory and motor regions of interest (ROIs) were chosen for further investigation: C3, Cz, C4, P3, P4. Spectral power and coherence during balance tasks were analyzed in theta (4–8 Hz) and alpha (8–12 Hz) bands. Alpha power reduced as task difficulty increased and this reduction correlated with subjective difficulty ratings. Alpha coherence increased with task difficulty between C3–Cz–C4 electrode pairs. Differential changes in power were observed in Cz, suggestive of a distinct role at this electrode location, which captures lower limb cortical representation. Hemispheric asymmetry was observed, as reflected by greater reductions in theta and alpha power in right-sided areas. Our results demonstrate the functional importance of bilateral central and parietal cortices in continuous balance control. The hemispheric asymmetry observed implies that the non-dominant hemisphere is involved with online monitoring of postural control. Although the posterior parietal asymmetry found may relate to vestibular, somatosensory or multisensory feedback processing, we argue that the finding relates to active balance control rather than simple sensory-intake or reflex circuit activation.
Roberts R, Ahmad H, Patel M, et al., 2018, An fMRI study of visuo-vestibular interaction in Vestibular Neuritis, NeuroImage: Clinical, Vol: 20, Pages: 1010-1017, ISSN: 2213-1582
Vestibular neuritis (VN) is characterised by acute vertigo due to a sudden loss of unilateral vestibular function. A considerable proportion of VN patients proceed to develop chronic symptoms of dizziness, including visually induced dizziness, specifically during head turns. Here we investigated whether the development of such poor clinical outcomes following VN, is associated with abnormal visuo-vestibular cortical processing. Accordingly, we applied functional magnetic resonance imaging to assess brain responses of chronic VN patients and compared these to controls during both congruent (co-directional) and incongruent (opposite directions) visuo-vestibular stimulation (i.e. emulating situations that provoke symptoms in patients). We observed a focal significant difference in BOLD signal in the primary visual cortex V1 between patients and controls in the congruent condition (small volume corrected level of p < .05 FWE). Importantly, this reduced BOLD signal in V1 was negatively correlated with functional status measured with validated clinical questionnaires. Our findings suggest that central compensation and in turn clinical outcomes in VN are partly mediated by adaptive mechanisms associated with the early visual cortex.
Bednarczuk N, Arshad Q, Fluri S, et al., 2018, Vestibulo-cortical hemispheric dominance: the link between anxiety and the vestibular system?, European Journal of Neuroscience, Vol: 47, Pages: 1517-1724, ISSN: 0953-816X
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.
Patel M, Arshad Q, Seemungal BM, et al., 2018, Steroid injections through the eardrum reduce dizziness in Meniere’s disease, study finds - REPLY TO ADRION ET AL. ON PATEL ET AL., British Medical Journal, Vol: 355, ISSN: 0959-8138
Arshad Q, Nigmatullina Y, Siddiqui S, et al., 2017, Influence of biases in numerical magnitude allocation on human prosocial decision making, JOURNAL OF NEUROPHYSIOLOGY, Vol: 118, Pages: 3007-3013, ISSN: 0022-3077
Cronin T, Arshad Q, Seemungal BM, 2017, Vestibular deficits in neurodegenerative disorders: balance, dizziness, and spatial disorientation, Frontiers in Neurology, Vol: 8, ISSN: 1664-2295
The vestibular system consists of the peripheral vestibular organs in the inner ear and the associated extensive central nervous system projections—from the cerebellum and brainstem to the thalamic relays to cortical projections. This system is important for spatial orientation and balance, both of critical ecological importance, particularly for successful navigation in our environment. Balance disorders and spatial disorientation are common presenting features of neurodegenerative diseases; however, little is known regarding central vestibular processing in these diseases. A ubiquitous aspect of central vestibular processing is its promiscuity given that vestibular signals are commonly found in combination with other sensory signals. This review discusses how impaired central processing of vestibular signals—typically in combination with other sensory and motor systems—may account for the impaired balance and spatial disorientation in common neurodegenerative conditions. Such an understanding may provide for new diagnostic tests, potentially useful in detecting early disease while a mechanistic understanding of imbalance and spatial disorientation in these patients may enable a vestibular-targeted therapy for such problems in neurodegenerative diseases. Studies with state of the art central vestibular testing are now much needed to tackle this important topic.
Arshad Q, Bonsu A, Lobo R, et al., 2017, Biased numerical cognition impairs economic decision-making in Parkinson’s disease, Annals of Clinical and Translational Neurology, Vol: 4, Pages: 739-748, ISSN: 2328-9503
ObjectivePrevious findings suggest a context-dependent bihemispheric allocation of numerical magnitude. Accordingly, we predicted that lateralized motor symptoms in Parkinson's disease (PD), which reflect hemispheric asymmetries, would induce systematic lateralized biases in numerical cognition and have a subsequent influence on decision-making.MethodsIn 20 PD patients and matched healthy controls we assessed numerical cognition using a number-pair bisection and random number generation task. Decision-making was assessed using both the dictator game and a validated questionnaire.ResultsPD patients with predominant right-sided motor symptoms exhibited pathological biases toward smaller numerical magnitudes and formulated less favorable prosocial choices during a neuroeconomics task (i.e., dictator game). Conversely, patients with left-sided motor symptoms exhibited pathological biases toward larger numerical magnitudes and formulated more generous prosocial choices. Our account of context-dependent hemispheric allocation of numerical magnitude in PD was corroborated by applying our data to a pre-existing computational model and observing significant concordance. Notably, both numerical biasing and impaired decision-making were correlated with motor asymmetry.InterpretationAccordingly, motor asymmetry and functional impairment of cognitive processes in PD can be functionally intertwined. To conclude, our findings demonstrate context-dependent hemispheric allocation and encoding of numerical magnitude in PD and how biases in numerical magnitude allocation in Parkinsonian patients can correspondingly impair economic decision-making.
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