96 results found
Marcus HJ, Paine H, Sargeant M, et al., 2019, Vestibular dysfunction in acute traumatic brain injury, Journal of Neurology, Pages: 1-4, 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.
Connor TA, Clark JM, Jayamohan J, et al., 2019, Do equestrian helmets prevent concussion? A retrospective analysis of head injuries and helmet damage from real-world equestrian accidents, Sports Medicine - Open, Vol: 5, Pages: 19-19, ISSN: 2198-9761
OBJECTIVES: To collect and analyse helmets from real-world equestrian accidents. To record reported head injuries associated with those accidents. To compare damage to helmets certified to different standards and the injuries associated with them. METHODS: Two hundred sixteen equestrian helmets were collected in total. One hundred seventy-six helmets from amateur jockeys were collected via accident helmet return schemes in the UK and USA, while 40 helmets from professional jockeys were collected by The Irish Turf Club. All helmet damage was measured, and associated head injury was recorded. RESULTS: Eighty-eight percent (189) of equestrian fall accidents returned an injury report of which 70% (139) reported a head injury. Fifty-four percent (75) of head injury cases had associated helmet damage while 46% had no helmet damage. Reported head injuries consisted of 91% (126) concussion, 4% (6) skull fractures, 1 (0.7%) subdural hematoma, 1 (0.7%) cerebral edema and 5 (3.6%) diffuse axonal injury (DAI). It is also shown that helmets certified to the most severe standard are overrepresented in this undamaged group (p <0.001). CONCLUSIONS: It is clear that despite jockeys wearing a helmet, large proportions of concussion injuries still occur in the event of a jockey sustaining a fall. However, the data suggest it is likely that helmets reduce the severity of head injury as the occurrence of skull fracture is low. The proportion of undamaged helmets with an associated head injury suggests that many helmets may be too stiff relative to the surface they are impacting to reduce the risk of traumatic brain injury (TBI). It may be possible to improve helmet designs and certification tests to reduce the risk of head injury in low-severity impacts.
Bednarczuk NF, Bonsu A, Ortega MC, et al., 2019, Abnormal visuo-vestibular interactions in vestibular migraine: a cross sectional study, Brain, Vol: 142, Pages: 606-616, ISSN: 1460-2156
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.
Harris L, Hateley S, Seemungal B, 2019, PHENYTOIN VERSUS LEVETIRACETAM FOR POST TRAUMATIC BRAIN INJURY SEIZURE PROPHYLAXIS; A RETROSPECTIVE STUDY AT A UK MAJOR TRAUMA CENTRE, Joint Autumn Meeting of the Society-of-British-Neurological-Surgeons (SBNS)/Association-of-British-Neurologists (ABN), Publisher: BMJ PUBLISHING GROUP, Pages: E31-E31, ISSN: 0022-3050
Papathanasiou ES, Cronin T, Seemungal B, et al., 2018, Electrophysiological testing in concussion: A guide to clinical applications, Journal of Concussion, Vol: 2, ISSN: 2059-7002
The diagnosis of mild traumatic brain injury in concussion is difficult since it is often unwitnessed, the patient’s recall is unreliable and initial clinical examination is often unrevealing, correlating poorly with the extent of brain injury. At present, there are no objective biomarkers of mild traumatic brain injury in concussion. Thus, a sensitive gold standard test is required to enable the effective and safe triage of patients who present to the acute services. As well as triage, objective monitoring of patients’ recovery over time and separate from clinical features that patients may develop following the injury (e.g. depression and migraine) is also needed. In contrast to neuroimaging, which is widely used to investigate traumatic brain injury patients, electrophysiology is readily available, is cheap and there are internationally recognized standardised methodologies. Herein, we review the existing literature on electrophysiological testing in concussion and mild traumatic brain injury; specifically, electroencephalogram, polysomnography, brainstem auditory evoked potentials, electro- and videonystagmography, vestibular evoked myogenic potentials, visually evoked potentials, somatosensory evoked potentials and transcranial magnetic stimulation.
Sargeant M, Sykes E, Saviour M, et al., 2018, The utility of the Sports Concussion Assessment Tool in hospitalized traumatic brain injury patients, Journal of Concussion, Vol: 2, ISSN: 2059-7002
The Sports Concussion Assessment Tool 3rd version is a sports screening tool that is often used to support return to play decisions following a head injury. The Sports Concussion Assessment Tool 3rd version is presumed to identify brain dysfunction (implying a degree of brain injury); however, the Sports Concussion Assessment Tool has never been validated with patients with definite acute brain injury. In this study, we found that all three Sports Concussion Assessment Tool 3rd version domains – symptoms, cognitive and balance assessments – were sensitive in discriminating traumatic brain injury patients (all with abnormal acute neuroimaging) from healthy controls. Through a correlation matrix (Bonferroni corrected), we found no correlation between the subjective (symptoms) and objective (examination) Sports Concussion Assessment Tool 3rd version assessments, e.g. complaints of imbalance and memory dysfunction were not correlated, respectively, with performance on testing balance and memory function. When relaxing the correction for multiple comparisons we found that of all Sports Concussion Assessment Tool 3rd version symptoms, a feeling of ‘pressure in the head’ had the largest number of co-correlations (including affective symptoms) and overwhelmingly in a pattern indicative of migraine. Taken together, that objective and subjective assessments in the Sports Concussion Assessment Tool 3rd version are poorly correlated, could suggest that symptoms in the Sports Concussion Assessment Tool 3rd version poorly reflect brain injury but rather indicate non-brain injury processes such as migraine. It follows that the current prominent orthodoxy of resting athletes following a head injury until their symptoms settle for fear of exacerbating brain injury may be unfavourable for their recovery – at least in some cases. Prospective clinical studies would be required to assess patient recovery from concussion with early active investigation and t
Xiang M, Glasauer S, Seemungal BM, 2018, Quantitative postural models as biomarkers of balance in Parkinson’s disease, Brain, Vol: 141, Pages: 2824-2827, ISSN: 1460-2156
Seemungal BM, Passamonti L, 2018, Persistent postural-perceptual dizziness: a useful new syndrome, Practical Neurology, Vol: 18, Pages: 3-4, ISSN: 1474-7766
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.
Allen D, Ribeiro L, Arshad Q, et al., 2017, Age-Related Vestibular Loss: Current Understanding and Future Research Directions (vol 7, 231, 2016), FRONTIERS IN NEUROLOGY, Vol: 8, ISSN: 1664-2295
Allen D, Ribeiro L, Arshad Q, et al., 2017, Age-Related Vestibular Loss: Current Understanding and Future Research Directions, Frontiers in Neurology, Vol: 8, ISSN: 1664-2295
The vestibular system sub-serves a number of reflex and perceptual functions, comprisingthe peripheral apparatus, the vestibular nerve, the brainstem and cerebellarprocessing circuits, the thalamic relays, and the vestibular cerebral cortical network.This system provides signals of self-motion, important for gaze and postural control,and signals of traveled distance, for spatial orientation, especially in the dark. Currentevidence suggests that certain aspects of this multi-faceted system may deteriorate withage and sometimes with severe consequences, such as falls. Often the deterioration investibular functioning relates to how the signal is processed by brain circuits rather thanan impairment in the sensory transduction process. We review current data concerningage-related changes in the vestibular system, and how this may be important for cliniciansdealing with balance disorders.
Ahmad H, Roberts E, Patel M, et al., 2017, Downregulation of early visual cortex excitability mediates oscillopsia, Neurology, Vol: 89, Pages: 1179-1185, ISSN: 0028-3878
Objective; Identifying the neurophysiological mechanisms that mediate adaptation to oscillopsia in patients with bilateral-vestibular failure (BVF); an observational study. Methods; We directly probe the hypothesis that adaptive changes which mediate oscillopsia suppression implicate the early visual-cortex (V1/V2). Accordingly, we investigated (V1/V2) excitability using transcranial magnetic stimulation (TMS) in 12 avestibular patients and 12 healthy controls. Specifically, we assessed TMS-induced phosphene thresholds at baseline and cortical excitability changes whilst performing a visual-motion adaptation paradigm during the following conditions: (i) BASELINE measures (i.e. static), (ii) during visual-motion (i.e. MOTION PRE ADAPTATION) and, (iii) during visual-motion following 5 minutes of unidirectional visual-motion adaptation (i.e. MOTION ADAPTED). Results: Patients had significantly higher baseline phosphene-thresholds, reflecting an underlying adaptive mechanism. Individual thresholds were correlated with oscillopsia symptom load. During the visual-motion adaptation condition, no differences in excitability at BASELINE were observed but, during both MOTION PRE ADAPTATION and MOTION ADAPTED conditions, we observed significantly attenuated cortical excitability in patients. Again this attenuation in excitability was stronger in less symptomatic patients.Conclusion; Our findings provide neurophysiological evidence that cortically-mediated adaptive mechanisms in V1/V2 play a critical role in suppressing oscillopsia in patients with bilateral vestibular failure.
Cousins S, Kaski D, Cutfield N, et al., 2017, Predictors of clinical recovery from vestibular neuritis: a prospective study, Annals of Clinical and Translational Neurology, Vol: 4, Pages: 340-346, ISSN: 2328-9503
We sought to identify predictors of symptomatic recovery in vestibular neuritis. Forty VN patients were prospectively studied in the acute phase (median = 2 days) and 32 in the recovery phase (median = 10 weeks) with vestibulo-ocular reflex, vestibular-perceptual, and visual dependence tests and psychological questionnaires. Clinical outcome was Dizziness Handicap Inventory score at recovery phase. Acute visual dependency and autonomic arousal predicted outcome. Worse recovery was associated with a combination of increased visual dependence, autonomic arousal, anxiety/depression, and fear of bodily sensations, but not with vestibular variables. Findings highlight the importance of early identification of abnormal visual dependency and concurrent anxiety.
Arshad Q, Roberts RE, Ahmad H, et al., 2017, Patients with chronic dizziness following traumatic head injury typically have multiple diagnoses involving combined peripheral and central vestibular dysfunction, CLINICAL NEUROLOGY AND NEUROSURGERY, Vol: 155, Pages: 17-19, ISSN: 0303-8467
Roberts RE, Arshad Q, Patel M, et al., 2016, Functional neuroimaging of visuo-vestibular interaction, Brain Structure & Function, Vol: 222, Pages: 2329-2343, ISSN: 1863-2661
The brain combines visual, vestibular and proprioceptive information to distinguish between self-and world-motion. Often these signals are complementary and indicate that the individual is moving or stationary with respect to the surroundings. However, conflicting visual motion and vestibular cues can lead to ambiguous or false sensations of motion. In this study, we used functional magnetic resonance imaging to explore human brain activation when visual and vestibular cues were either complementary or in conflict. We combined a horizontally moving optokinetic stimulus with caloric irrigation of the right ear to produce conditions where the vestibular activation and visual motion indicatedthe same (congruent) or opposite directions of self-motion (incongruent). Visuo-vestibular conflict was associated with increased activation in a network of brain regions including posterior insular and transverse temporal areas, cerebellar tonsil, cingulate and medial frontal gyri. In the congruent condition there was increased activation in primary and secondary visual cortex. These findings suggest that when sensory information regarding self-motion is contradictory, there is preferential activation of multisensoryvestibular areas to resolve this ambiguity. When cues are congruent there is a bias towards visual cortical activation. The data support the view thata network of brain areas including the posterior insular cortex may play animportant role in integrating and disambiguating visual and vestibular cues.
Patel M, Agarwal K, Arshad Q, et al., 2016, Intratympanic methylprednisolone versus gentamicin in patients with unilateral Ménière's disease: a randomised, double-blind, comparative effectiveness trial, Lancet, Vol: 388, Pages: 2753-2762, ISSN: 1474-547X
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)
Ahmad H, Arshad Q, Roberts R, et al., 2016, CHRONIC DIZZINESS POST TRAUMATIC BRAIN INJURY: A CROSS-SECTIONAL STUDY, Annual Meeting of the Association-of-British-Neurologists (ABN), Publisher: BMJ PUBLISHING GROUP, ISSN: 0022-3050
Seemungal BM, Yousif N, Abou-El-Ela-Bourquin B, et al., 2016, Dopamine activation preserves visual motion perception despite noise interference of human V5/MT, Journal of Neuroscience, Vol: 36, Pages: 9303-9312, ISSN: 1529-2401
When processing sensory signals, the brain must account for noise, both noise in the stimulus and that arising from within its own neuronal circuitry. Dopamine receptor activation is known to enhance both visual cortical signal-to-noise-ratio (SNR) and visual perceptual performance; however, it is unknown whether these two dopamine-mediated phenomena are linked. To assess this, we used single-pulse transcranial magnetic stimulation (TMS) applied to visual cortical area V5/MT to reduce the SNR focally and thus disrupt visual motion discrimination performance to visual targets located in the same retinotopic space. The hypothesis that dopamine receptor activation enhances perceptual performance by improving cortical SNR predicts that dopamine activation should antagonize TMS disruption of visual perception. We assessed this hypothesis via a double-blinded, placebo-controlled study with the dopamine receptor agonists cabergoline (a D2 agonist) and pergolide (a D1/D2 agonist) administered in separate sessions (separated by 2 weeks) in 12 healthy volunteers in a William's balance-order design. TMS degraded visual motion perception when the evoked phosphene and the visual stimulus overlapped in time and space in the placebo and cabergoline conditions, but not in the pergolide condition. This suggests that dopamine D1 or combined D1 and D2 receptor activation enhances cortical SNR to boost perceptual performance. That local visual cortical excitability was unchanged across drug conditions suggests the involvement of long-range intracortical interactions in this D1 effect. Because increased internal noise (and thus lower SNR) can impair visual perceptual learning, improving visual cortical SNR via D1/D2 agonist therapy may be useful in boosting rehabilitation programs involving visual perceptual training.
Patel M, Agarwal K, Arshad Q, et al., Intratympanic steroids vs. gentamicin in unilateral Ménière's disease: a randomised double-blind comparative effectiveness trial, Lancet, ISSN: 1474-547X
Background: Ménière’s disease (MD) is characterised by severe vertigo attacks and deafness. Intratympanic gentamicin ablates vestibular function, quells vertigo and is the standard treatment for refractory MD - but it can worsen hearing. Intratympanic corticosteroids may reduce vertigo without harming hearing but no RCT comparing steroids versus gentamicin is available.Methods: In this comparative effectiveness trial, refractory unilateral MD patients, defined according to the American Academy of Otolaryngology, were double-blindly randomised (1:1 block-design) to intratympanic methylprednisolone (n=30, 62·5mg/ml) or gentamicin (n=30, 40mg/ml) and followed-up over two years at Charing Cross Hospital (Imperial NHS, London) and Leicester Royal Infirmary, Leicester, UK. Primary outcome was vertigo frequency over the final 6-months (18-24months post-injection) compared to a 6-month pre-injection baseline. Secondary outcomes were vestibular and auditory symptoms (validated questionnaires) and hearing preservation (audiometry). ClinicalTrials.gov:NCT00802529.Findings: For intention-to-treat analysis i.e., all 60 patients, number of vertigo attacks/6months (primary outcome) fell from 19·9 to 2·5 [87%] in the gentamicin arm and 16·4 to 1·6 [90%] in the steroid arm (difference in absolute number of attacks in the final 6months -0·9; 95%CI -3·4 to 1·6). Both drugs reduced the number of vertigo attacks at 2 years (P<0·0001), with equal efficacy (P=0·51). For hearing preservation (secondary outcome), there was no difference (P=0·18) between drugs for hearing thresholds (final difference -2·45decibels, 95%CI -13·4 to 8·5). Both drugs reduced auditory and vestibular symptoms equally. As protocol, patients whose vertigo did not respond post-injection (‘non-responders’) were considered for additional injections by an unblinded physician (8 patients ge
Murdin L, Seemungal BM, Bronstein AM, 2016, Dizziness, Medicine (United Kingdom), Vol: 44, Pages: 484-487, ISSN: 1357-3039
© 2016 Elsevier Ltd Dizziness and vertigo are common symptoms. Because there are effective treatments for vestibular disorders, it is always important to make an accurate diagnosis. In acute vertigo, expert clinical assessment is critically important in discerning stroke from non-stroke causes because stroke-protocol brain magnetic resonance imaging results, including diffusion-weighted imaging, can be falsely negative in the first 24 hours. It follows that acute medical services must have access to clinicians expert in assessing acute vertigo. Expertise in clinical examination and the interpretation of findings requires appropriate training, but in this article we outline the basic diagnostic and therapeutic approach to patients with dizziness.
Yousif N, Fu R, Abou-El-Ela-Bourquin B, et al., 2016, Dopamine preserves visual motion perception despite noise interference of human V5/MT, European Academy of Neurology, Publisher: WILEY, Pages: 874-874, ISSN: 1351-5101
Seemungal BM, 2016, Screening for BPPV in falls: an easy but big clinical "win", British Medical Journal, Vol: 353, ISSN: 1468-5833
Braga RM, Fu RZ, Seemungal BM, et al., 2016, Eye movements during auditory attention predict individual differences in dorsal attention network activity, Frontiers in Human Neuroscience, Vol: 10, ISSN: 1662-5161
The neural mechanisms supporting auditory attention are not fully understood. A dorsal frontoparietal network of brain regions is thought to mediate the spatial orienting of attention across all sensory modalities. Key parts of the this network, the frontal eye fields (FEF) and the superior parietal lobes (SPL), contain retinotopic maps and elicit saccades when stimulated. This suggests that their recruitment during auditory attention might reflect crossmodal oculomotor processes; however this has not been confirmed experimentally. Here we investigate whether task-evoked eye movements during an auditory task can predict the magnitude of activity within the dorsal frontoparietal network. A spatial and non-spatial listening task was used with on-line eye-tracking and functional magnetic resonance imaging. No visual stimuli or cues were used. The auditory task elicited systematic eye movements, with saccade rate and gaze position predicting attentional engagement and the cued sound location, respectively. Activity associated with these separate aspects of evoked eye-movements dissociated between the SPL and FEF. However these observed eye movements could not account for all the activation in the frontoparietal network. Our results suggest that the recruitment of the SPL and FEF during attentive listening reflects, at least partly, overt crossmodal oculomotor processes during non-visual attention. Further work is needed to establish whether the network’s remaining contribution to auditory attention is through covert crossmodal processes, or is directly involved in the manipulation of auditory information.
Yousif N, Bhatt H, Bain P, et al., 2016, The effect of Pedunculopontine nucleus deep brain stimulation on postural sway and vestibular perception, European Journal of Neurology, Vol: 23, Pages: 668-670, ISSN: 1468-1331
Background and purposeDeep brain stimulation (DBS) of the pedunculopontine nucleus (PPN) reduces the number of falls in patients with Parkinson's disease (PD). It was hypothesized that enhanced sensory processing contributes to this PPN-mediated gait improvement.MethodsFour PD patients (and eight matched controls) with implanted bilateral PPN and subthalamic nucleus DBS electrodes were assessed on postural (with/without vision) and vestibular perceptual threshold tasks.ResultsPedunculopontine nucleus ON stimulation (compared to OFF) lowered vestibular perceptual thresholds but there was a disproportionate increase in the normal sway increase on going from light to dark.ConclusionsThe disproportionate increased sway with PPN stimulation in the dark may paradoxically improve balance function since mechanoreceptor signals rapidly adapt to continuous pressure stimulation from postural akinesia. Additionally, the PPN-mediated vestibular signal enhancement also improves the monitoring of postural sway. Overall, PPN stimulation may improve sensory feedback and hence balance performance.
Kaski D, Quadir S, Nigmatullina Y, et al., 2015, Temporoparietal encoding of space and time during vestibular-guided orientation, Brain, Vol: 139, Pages: 392-403, ISSN: 0006-8950
When we walk in our environment, we readily determine our travelled distance and location using visual cues. In the dark, estimating travelled distance uses a combination of somatosensory and vestibular (i.e. inertial) cues. The observed inability of patients with complete peripheral vestibular failure to update their angular travelled distance during active or passive turns in the dark implies a privileged role for vestibular cues during human angular orientation. As vestibular signals only provide inertial cues of self-motion (e.g. velocity, °/s), the brain must convert motion information to distance information (a process called ‘path integration’) to maintain our spatial orientation during self-motion in the dark. It is unknown, however, what brain areas are involved in converting vestibular-motion signals to those that enable such vestibular-spatial orientation. Hence, using voxel-based lesion–symptom mapping techniques, we explored the effect of acute right hemisphere lesions in 18 patients on perceived angular position, velocity and motion duration during whole-body angular rotations in the dark. First, compared to healthy controls’ spatial orientation performance, we found that of the 18 acute stroke patients tested, only the four patients with damage to the temporoparietal junction showed impaired spatial orientation performance for leftward (contralesional) compared to rightward (ipsilesional) rotations. Second, only patients with temporoparietal junction damage showed a congruent underestimation in both their travelled distance (perceived as shorter) and motion duration (perceived as briefer) for leftward compared to rightward rotations. All 18 lesion patients tested showed normal self-motion perception. These data suggest that the cerebral cortical regions mediating vestibular-motion (‘am I moving?’) and vestibular-spatial perception (‘where am I?’) are distinct. Furthermore, the congruent contralesiona
Li LM, Leech R, Scott GT, et al., 2015, The effect of oppositional parietal transcranial direct current stimulation on lateralized brain functions, European Journal of Neuroscience, Vol: 42, Pages: 2904-2914, ISSN: 1460-9568
Cognitive functions such as numerical processing and spatial attention show varying degrees of lateralization. Transcranial direct current stimulation (tDCS) can be used to investigate how modulating cortical excitability affects performance of these tasks. This study investigated the effect of bi-parietal tDCS on numerical processing, spatial and sustained attention. It was hypothesized that tDCS would have distinct effects on these tasks because of varying lateralization (numerical processing left, spatial attention right) and that these effects are partly mediated by modulation of sustained attention. A single-blinded, crossover, sham-controlled study was performed. Eighteen healthy right-handed participants performed cognitive tasks during three sessions of oppositional parietal tDCS stimulation: sham; right anodal with left cathodal (RA/LC); and right cathodal with left anodal (RC/LA). Participants performed a number comparison task, a modified Posner task, a choice reaction task (CRT) and the rapid visual processing task (RVP). RA/LC tDCS impaired number comparison performance compared with sham, with slower responses to numerically close numbers pairs. RA/LC and RC/LA tDCS had distinct effects on CRT performance, specifically affecting vigilance level during the final block of the task. No effect of stimulation on the Posner task or RVP was found. It was demonstrated that oppositional parietal tDCS affected both numerical performance and vigilance level in a polarity-dependent manner. The effect of tDCS on numerical processing may partly be due to attentional effects. The behavioural effects of tDCS were specifically observed under high task demands, demonstrating the consequences of an interaction between stimulation type and cognitive load.
Li L, Leech R, Seemungal B, et al., 2015, A SENSE OF DIRECTION: BRAIN STIMULATION IN LATERALISED BRAIN FUNCTION, JOURNAL OF NEUROLOGY NEUROSURGERY AND PSYCHIATRY, Vol: 86, ISSN: 0022-3050
Seemungal B, Kaski D, Antonio Lopez-Escamez J, 2015, Early Diagnosis and Management of Acute Vertigo from Vestibular Migraine and Meniere's Disease, NEUROLOGIC CLINICS, Vol: 33, Pages: 619-+, ISSN: 0733-8619
Cousins S, Kaski D, Cutfield N, et al., 2015, Clinical recovery after acute vestibular neuritis, 1st Congress of the European-Academy-of-Neurology, Publisher: WILEY, Pages: 364-364, ISSN: 1351-5101
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