The effect of GVS on path trajectory and body rotation in the absence of visual cues during a spatial navigation task

Background: The vestibular system has been shown to contribute to mechanisms of locomotion such as distance perception. Galvanic vestibular stimulation (GVS) is a tool used to perturb the vestibular system, and causes significant deviations in path trajectory during locomotion. Previous research has suggested that applying GVS during straight-line locomotion tasks is not sufficient to determine the effects of the vestibular system on locomotion. However, spatial navigation challenges one’s ability to navigate throughout the environment using idiothetic cues to constantly update one’s position. The purpose of the current study was to determine the effects of GVS on both path trajectory and body rotation during a task of spatial navigation in the absence of visual cues, and how accuracy of this task is affected by dance training. It was hypothesized that the delivery of GVS would significantly increase errors during the triangle completion task, and this increase would be more pronounced in the control participants compared to the dancers. Methods: Participants (n=34, all female, 18-30 years) were divided into two groups: controls (n=18) had no experience with sport-specific training while dancers (n=16) had previously experienced dance training (M = 15.6 years, SD = ±4.1) and were still currently training in dance (M = 11.5 hours/week, SD = ±7.3). Monofilament testing (Touch-Test Six Piece Foot Kit) was used to determine the plantar surface cutaneous sensitivity threshold and a joint angle-matching task was used to quantify the proprioceptive awareness of each individual. Participants completed trials of the triangle completion task in VR (via Oculus Rift DK2), during which they would navigate along the first two legs of one of two triangles using visual input, and then accurately navigate back to their initial position with the use of vision. GVS was delivered at three times the participant’s threshold in either the left or right direction prior to the final body rotation and until the participant reached their end position. The task was completed six times for each of the GVS conditions (with and without GVS) with the experimental GVS condition being further divided into right and left perturbation trials, for each of the two triangles, in both the right and left triangle directions, for a total of 48 trials (six trials x 2 GVS conditions x 2 triangles x 2 directions). Whole body kinematic data were collected at 60 Hz using an NDI Optotrak motion tracking system. Results: No significant differences were observed between control subjects and dancers with respect to arrival error, angular error, path variability, cutaneous sensitivity or proprioceptive awareness. However, there was a significant effect of GVS on both arrival error and angular error. Conditions without GVS had significantly smaller angular error than both conditions with GVS. In addition, GVS conditions with the perturbation in the same direction as the final body rotation had significantly greater arrival error than both the condition without GVS and with the current in the opposite direction of the final body rotation. There was no significant difference between GVS conditions in path variability during the return to the initial position. Conclusions: The significant effect of GVS on both arrival error and angular rotation demonstrates that vestibular perturbation reduced the accuracy of the triangle completion task. These findings suggest that the vestibular system plays a major role in both path trajectory and body rotation during tasks of spatial navigation in the absence of vision

The search for instantaneous vection: An oscillating visual prime reduces vection onset latency

2018 Palmisano, Riecke. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Typically it takes up to 10 seconds or more to induce a visual illusion of self-motion ( vection ). However, for this vection to be most useful in virtual reality and vehicle simulation, it needs to be induced quickly, if not immediately. This study examined whether vection onset latency could be reduced towards zero using visual display manipulations alone. In the main experiments, visual self-motion simulations were presented to observers via either a large external display or a head-mounted display (HMD). Priming observers with visually simulated viewpoint oscillation for just ten seconds before the main self-motion display was found to markedly reduce vection onset latencies (and also increase ratings of vection strength) in both experiments. As in earlier studies, incorporating this simulated viewpoint oscillation into the self-motion displays themselves was also found to improve vection. Average onset latencies were reduced from 8-9s in the no oscillating control condition to as little as 4.6 s (for external displays) or 1.7 s (for HMDs) in the combined oscillation condition (when both the visual prime and the main self-motion display were oscillating). As these display manipulations did not appear to increase the likelihood or severity of motion sickness in the current study, they could possibly be used to enhance computer generated simulation experiences and training in the future, at no additional cost

The role of non-invasive camera technology for gait analysis in patients with vestibular disorders

Purpose of the study Current balance assessments performed in clinical settings do not provide objective measurements of gait. Further, objective gait analysis typically requires expensive, large and dedicated laboratory facilities. The aim of this pilot study was to develop and assess a low-cost, non-invasive camera technology for gait analysis, to assist the clinical assessment of patients with vestibular disorders. Materials and methods used This is a prospective, case-controlled study that was developed jointly by the local Neurotology Department and the Centre for Sports Engineering Research. Eligible participants were approached and recruited at the local Neurotology Clinic. The gait assessment included two repetitions of a straight 7-metre walk. The gait analysis system, comprised of a camera (P3215-V, Axis Communications, Sweden) and analysis software was installed in an appropriately sized clinic room. Parameters extruded were walking velocity, step velocity, step length, cadence and step count per meter. The effect sizes (ESB) were calculated using the MatLab and were considered large, medium or small if >0.8, 0.5 and 0.2 respectively. This study was granted ethical approval by the Coventry and Warwickshire Research Ethics Committee (15/WM/0448). Results Six patients with vestibular dysfunction (P group) and six age-matched healthy volunteers (V group) were recruited in this study. The average velocity of gait for P group was 1189.1 ± 69.0 mm·s-1 whereas for V group it was 1351.4 ± 179.2 mm·s-1, (ESB: -0.91). The mean step velocities were 1353.1 ± 591.8 mm·s-1 and 1434.0 ± 396.5 mm·s-1 for P and V groups respectively (ESB: -0.20). The average cadence was 2.3 ± 0.9 Hz and 2.0 ± 0.5 Hz for P and V groups respectively (ESB: 0.60). The mean step length was 620.5 ± 150.7 mm for the P group and 728.5 ± 86.0 mm for the V group (ESB = -1.26). The average step count per meter was 1.7 ± 0.3 and 1.4 ± 0.1 for P and V groups respectively (ESB = 3.38). Conclusion This pilot study used a low-cost, non-invasive camera technology to identify changes in gait characteristics. Further, gait measurements were obtained without the application of markers or sensors to patients (i.e. non-invasive), thus allowing current, clinical practice to be supplemented by objective measurement, with minimal procedural impact. Further work needs to be undertaken to refine the device and produce normative data. In the future, similar technologies could be used in the community setting, providing an excellent diagnostic and monitoring tool for balance patients

Central Adaptation after Peripheral Vestibular Injury

This thesis examines how the human brain adapts after peripheral vestibular injury. Vestibular perceptual function is used as a probe of cortical vestibular function. A paradigm determining vestibular perceptual thresholds to yaw axis rotation by a method of limits is described. Asymmetry in the thresholds is induced in normal subjects with galvanic vestibular stimulation. In patients with acute vestibular neuritis, perceptual thresholds were bilaterally elevated, with less asymmetry when compared to the brainstem reflexive function. Thresholds were measured in a prospective longitudinal study in vestibular neuritis patients, assessed acutely and at follow-­‐up (n=16). Assessments comprised vestibular caloric testing, visual dependency measures, questionnaire measures of symptom load, anxiety, depression and fear of body sensations. Clinical recruitment found a low rate of correct diagnoses by referring clinicians. Symptomatic outcome at follow-up was associated with increased visual dependence, asymmetric caloric function, increased anxiety and depression. It was also associated with increased fear and anxiety of body sensations present acutely, suggesting this may be predisposing. The anatomical substrate of central compensation was investigated in patients with bilateral vestibular failure (n=12) and normal controls (n=15) using functional MRI. A novel air turbine-powered vibrating device was developed to provide high and low levels of proprioceptive stimulus to neck rotator muscles. This was combined with a horizontal visual motion paradigm in a factorial design. A lateralised interaction was found in the lateral occipital visual processing areas in the avestibular patients. In addition to the known visual-vestibular interaction, this demonstrates a visuo-proprioceptive interaction, which may reflect compensation after vestibular injury. Conclusions: Vestibular perceptual function can be measured in disease, and is elevated in patients with acute peripheral vestibulopathy. Specific psychological and physiological factors associated with clinical recovery after vestibular neuritis are proposed. Functional MRI shows that proprioceptive signals interact with visual motion signals in patients with vestibular failure

The Effects of Anxiety, Ageing, and Neurodegenerative Disease on Visual Reweighting for Postural Control

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonFor most people, the complex mechanisms of sensory reweighting and maintaining balance are effective in maintaining relative automaticity and stability. However, this optimal function can be jeopardized by a range of factors. Ageing, anxiety, changes in attention, and neurodegenerative disease are some of the factors that potentially affect sensory integration for balance. These factors are explored in this thesis over several empirical studies using visual perturbations delivered using virtual reality. First, I examined the effects of ageing and anxiety on the postural response to the erroneous visual experience of self-movement (Study 1). Secondly, I explored these effects in the context of Parkinson’s Disease with Freezing of Gait: a population with impaired non-visual sensory processing and increased anxiety related to motor control (Study 2). The final study attempts to isolate the effects of increased conscious control of movement on visual reweighting to examine the degree to which they account for the results of the previous studies (Study 3). Study 1 found that anxiety appears to relate to increased reliance on vision for balance, but it only partially accounts for greater reliance on vision in older adults. Study 2 found that people with PD+FOG take longer responding to the visual perturbation than healthy age-matched adults, and that freezing severity correlates with longer latency and possibly lower magnitude of response. Finally, Study 3 found no significant effect of increased conscious control of movement on reliance on vision for postural control. Overall, while anxiety does have the potential to increase reliance on visual input, increased visual dependency observed in older adults and people with PD is likely to have different origins, potentially related to physiological changes, rather than increased conscious control of movement. The General Discussion reviews the contribution of these findings to research on sensory integration and postural control, and discusses their implications, and directions for future research

Multimodal neuroimaging of vestibular and postural networks: Investigating the pathophysiology of idiopathic dizziness in older adults

Successful ageing - the preservation of good performance into old age, is an aspiration for many and a challenge for society. Modifiable factors which account for ageing-related functional decline should thus be identified and reduced. As life expectancy increases, brain ageing and its functional consequences become an increasingly important target for research and intervention. Cerebral small vessel disease, largely driven by vascular risk factors, has emerged as a strong contributor to cognitive and balance decline in late life. Though the early effects of cerebral small vessel disease on cognition are increasingly better understood, its symptomatic effects on other functional systems are not well characterised. In this thesis, I investigated the long recognised, but pathophysiologically enigmatic syndrome of dizziness in older adults, not accounted for by neurological disease or vestibular dysfunction. I considered the hypothesis that this ‘idiopathic dizziness’ is secondary to cerebral small vessel disease through its deleterious effects on white matter networks which subserve vestibular perceptual processes and/or the control of balance. I first defined the functional anatomy of the core human vestibular cortex by its functional connectivity (Chapter 3). I related the resulting anatomical subregions to behavioural and task neuroimaging data to define a vestibular network involved in self-motion perception. I proceeded to characterise the syndrome of idiopathic dizziness using clinical, cognitive and behavioural (vestibular function, balance and gait) data from patients and controls (Chapter 4). I combined this data with structural and diffusion magnetic resonance imaging data to investigate the pathophysiology of idiopathic dizziness. I found that frontal white matter tracts relevant to the control of balance had lower integrity in patients with idiopathic dizziness than controls. These findings occurred in the context of excess vascular risk, and markers of cerebral small vessel disease. Additionally, I found vestibular function and perception were normal in patients with idiopathic dizziness. The results suggest disrupted balance control may underpin idiopathic dizziness in cerebral small vessel disease. I proceeded to investigate whether neural correlates of balance control were altered in idiopathic dizziness as a model for mild balance impairment in cerebral small vessel disease (Chapter 5). To do this, I applied electroencephalography during quiet standing and related brain activity to spontaneous sway. I showed idiopathic dizziness was linked to altered cortical activity in relation to balance control, and this cortical activity was influenced by the burden of cerebral small vessel disease. Additionally, patients with idiopathic dizziness uniquely engaged a low frequency postural connectivity network, consistent with a different mode of postural control. Overall, the results within this thesis show a relationship between idiopathic dizziness and vascular injury to frontal tracts involved in the control of balance in cerebral small vessel disease. Small vessel disease may disrupt the cortical control of balance as a basis for symptoms in this syndrome.Open Acces

TGD Inspired View About Remote Mental Interactions and Consciousness-Related Anomalies, Part II

I have proposed a general vision about how remote mental interactions and related phenomena could be understood in TGD Universe around 2003. The progress that has taken place since then in TGD motivates the reconsideration of this vision. In this article - second part of an article - devoted to the updated vision about parapsychological phenomena and remote mental interactions, I will discuss some applications of the basic vision. First the notion of conscious hologram is discussed from the point of view of remote mental interactions. The notion of magnetic body is in decisive role as it is also in the understanding of quantum biology in TGD framework. TGD inspired model for OBEs relying on the notion of magnetic body is summarized. The idea is that OBEs could correspond to sensory experiences assignable to magnetic body rather than real body. Also the connections with the work of other researchers, such as Shnoll, Persinger, and Tiller are discussed briefly. The challenge of testing the vision is also considered

Identifying Low-Back Stabilization in Low-Back Pain and the Influence of Tactile Information

Dieen, J.H. van [Promotor]Veeger, H.E.J. [Promotor

EEG-based investigation of cortical activity during Postural Control

The postural control system regulates the ability to maintain a stable upright stance and to react to changes in the external environment. Although once believed to be dominated by low-level reflexive mechanisms, mounting evidence has highlighted a prominent role of the cortex in this process. Nevertheless, the high-level cortical mechanisms involved in postural control are still largely unexplored. The aim of this thesis is to use electroencephalography, a widely used and non-invasive neuroimaging tool, to shed light on the cortical mechanisms which regulate postural control and allow balance to be preserved in the wake of external disruptions to one’s quiet stance. EEG activity has been initially analysed during a well-established postural task - a sequence of proprioceptive stimulations applied to the calf muscles to induce postural instability – traditionally used to examine the posturographic response. Preliminary results, obtained through a spectral power analysis of the data, highlighted an increased activation in several cortical areas, as well as different activation patterns in the two tested experimental conditions: open and closed eyes. An improved experimental protocol has then been developed, allowing a more advanced data analysis based on source reconstruction and brain network analysis techniques. Using this new approach, it was possible to characterise with greater detail the topological structure of cortical functional connections during the postural task, as well as to draw a connection between quantitative network metrics and measures of postural performance. Finally, with the integration of electromyography in the experimental protocol, we were able to gain new insights into the cortico-muscular interactions which direct the muscular response to a postural challenge. Overall, the findings presented in this thesis provide further evidence of the prominent role played by the cortex in postural control. They also prove how novel EEG-based brain network analysis techniques can be a valid tool in postural research and offer promising perspectives for the integration of quantitative cortical network metrics into clinical evaluation of postural impairment.Kerfi stöðustjórnunar er afturvirkt stýrikerfi sem vinnur stöðugt að því að viðhalda uppréttri stöðu líkamans og bregðast við ójafnvægi. Vaxandi þekking á undanförnum árum hefur lýst því að úrvinnsla þessara upplýsinga á sér stað á öllum stigum miðtaugakerfisins, þá sérstaklega barkarsvæði heilahvela. Engu að síður, er nákvæmu hlutverk heilabarkar við stöðustjórnun enn óljóst að mörgu leyti. Tilgangur þessa verkefnis var að rannsaka nánar hlutverk heilabarkar við truflun og áreiti á kerfi stöðustjórnarinnar, með notkun hágæða heilarafrits (EEG). Við byrjuðum á því að mæla heilarit einstaklinga meðan á þekktri líkamsstöðu-æfingu stóð, til þess að skoða svörun líkamans við röð titringsáreita sem beitt var á kálfavöðvana til að framkalla óstöðugleika. Bráðabirgðaniðurstöður fengnar með PSD-aðferð (power spectral analysis) leiddu í ljós aukna virkni á ákveðnum svæðum í heilaberki og sérstakt viðbragðsmynstur við að framkvæma æfinguna, annars vegar með lokuð augu og hins vegar opin augu. Rannsókn okkar hélt áfram með nýrri og þróaðari tækni sem gerði okkur kleift að framkvæma fullkomnari greiningaraðferðir til að túlka, greina og skilja merki frá heilaritnu. Með fullkomnari greiningaraðferðum var hægt að lýsa með nákvæmari hætti staðfræðilega uppbyggingu starfrænna tenginga í heilaberki meðan á líkamsstöðu æfingunni stóð, sem og að draga tengsl á milli megindlegra netmælinga og mælinga á líkamsstöðu. Að lokum bætist við vöðvarafritsmæling við aðferðafræðina, sem gaf okkur innsýn inn í samskipti heilabarka og vöðvana sem stýra vöðvaviðbrögðum og viðhalda líkamsstöðu við utanaðkomandi áreiti. Á heildina litið gefa niðurstöðurnar sem settar eru fram í þessari ritgerð enn sterkari vísbendingar um það áberandi hlutverk sem heilabörkurinn gegnir við stjórnun líkamsstöðu. Niðurstöðurnar sanna einnig hvernig ný aðferð á greiningu á tengslaneti heilans sem byggir á heilariti getur verið gilt tæki í líkamsstöðu rannsóknum og er nytsamlegt tól fyrir mælingar á heilakerfisneti í klínískt mat á skerðingu líkamsstöðu