Palla
Fakultäten » Medizinische Fakultät » Neurologie, Klinik für » Prof. Dr. Dominik Straumann » Palla
Completed research project
| Title / Titel | Anisotropy of vestibular self-motion perception in human neurological disorders | ||||||
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| Abstract (PDF, 14 KB) | |||||||
| Summary / Zusammenfassung | Background: This research proposal expands our long-term interest in vestibular disorders towards conscious vestibular mechanisms in humans. The vestibular system influences a variety of perceptual and cognitive functions, such as spatial orientation, navigation and motion perception. This project focuses on the vestibular perception of self-motion. We will investigate patients with neurological disorders that asymmetrically affect neural structures of the central vestibular system, such as unilateral cerebral lesions involving the brainstem, the thalamus and areas centered on the posterior insula (e.g. strokes). In these patients, we will explore the consequences of imbalances in vestibular cortical inflow on self-motion perception. Working hypotheses: Normal spatial orientation and navigation critically rely on the isotropic perception of self-motion. Only directionally unbiased updating of self-position and self-orientation in space allows the accurate reaching of a desired location. This proposal is based on the working hypothesis that the neural encoding of vestibular self-motion within both cortical hemispheres is unilateral predominant, i.e. that the central flow of neural signals evoked by self-motion in one direction is predominantly processed in one cortical hemisphere. If the processing of vestibular self-motion signals is normal in both hemispheres, self-motion is sensed directionally uniform, i.e. isotropic. We hypothesize that in unilateral disorders of vestibulo-thalamo-cortical pathways self-motion perception becomes anisotropic. – Ascending pathways of the horizontal semicircular canals (SCC) project predominantly to the ipsilateral cortical areas. We therefore expect that a unilateral impairment of vestibulo-thalamo-cortical pathways carrying SCC signals becomes manifest as anisotropy of angular self-motion perception. We further hypothesize that anisotropy of angular self-motion perception is more pronounced for disorders affecting the vestibular cortical network of the non-dominant hemisphere (i.e. the right hemisphere in right-handers and the left hemisphere in left-handers), as suggested by recent functional neuroimaging studies with caloric vestibular stimulation (Aim 1). – From a functional point of view, it seems reasonable that the cortical hemispheres encode both angular and translational self-motion directionally congruent (e.g. the same hemisphere processes rotation and translation to the right), since anatomical, electrophysiological, and functional imaging studies suggest that SCC and otolith signals project to roughly the same cortical loci. We hypothesize that the directional predominances of cortical hemispheres for angular and translational self-motion perception match (e.g. the hemisphere that predominantly encodes rotation to one side will also predominantly encode translation to the same side). Consequently, we expect anisotropy of translational self-motion to parallel anisotropy of angular self-motion in patients with unilateral disorders of vestibulo-thalamo-cortical pathways carrying SCC and otolith signals (Aim 2). – The otolith organs, like all linear accelerometers, are unable to distinguish between forces resulting from reorientation relative to gravity and forces resulting from translational acceleration. It is the brain that integrates the otolith signal with other signals to distinguish between a head tilt relative to gravity or a translational linear acceleration. Recent findings suggest that the segregation between tilt and translation takes place within the brainstem (vestibular nuclei) and cerebellum (fastigial nuclei). We will investigate whether inter-aural translational self-motion perception differs from roll tilt relative to gravity in patients with unilateral disorders of vestibulo-thalamo-cortical pathways (Aim 3). Aim 1: Using threshold and postrotatory sensation paradigms, we will explore (1) whether patients with unilateral disorders of vestibulo-thalamo-cortical pathways show asymmetries in angular self-motion perception between ipsi- and contralateral rotations about the earth-vertical yaw axis and (2) whether the magnitudes of these asymmetries are different between right- and left-brain damaged patients (directional predominance). Aim 2: In patients with unilateral disorders of vestibulo-thalamo-cortical pathways we will analyze translational self-motion perception after inter-aural translations along the earth-horizontal axis (by measuring redirection of gaze towards a previously seen space-fixed target after the displacement). We will explore (1) whether the patients display asymmetries of self-motion perception between ipsi- and contralateral inter-aural translations, (2) whether these asymmetries directionally parallel the asymmetries found during horizontal angular vestibular stimulation, and (3) whether in some patients’ horizontal angular and horizontal translational self-motion perception can be affected differentially. Aim 3: In patients with unilateral disorders of vestibulo-thalamo-cortical pathways we will compare self-motion perception of inter-aural translational and of roll tilt relative to gravity stimuli (by adjusting a bar to the subjective earth-vertical and translating it proportionally to the perceived translational velocity). We aim to find out (1) whether the lesions can differentially affect inter-aural translational and roll tilt re gravity self-motion perception and (2) whether the direction of impaired inter-aural translational self-motion perception parallels the direction of roll tilt re gravity self-motion perception. Methods: This research uses techniques for vestibular (motion simulator, multi-axis turntable), eye movement recordings (dual search coil technique, 3D video-oculography), and psychophysical instruments (tachometer wheel for subjective velocity perception, somatosensory bar for translational and tilt relative to gravity perception). Expected value of the project: This project elucidates the central mechanisms of vestibular self-motion encoding and how they are affected by central disorders. It contributes to the better understanding of spatial disorientation and impaired navigation – both typically impaired in patients with spatial neglect – and to the development of new therapeutic strategies. |
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| Publications / Publikationen | Palla A, Straumann D, Obzina H (1999) Eye-position dependence of three-dimensional ocular rotation-axis orientation during head impulses in humans. Exp Brain Res 129(1):127-133. Marti S, Palla A, Straumann D (2002) Gravity dependence of ocular drift in patients with cerebellar downbeat nystagmus. Ann Neurol 52(6):712-721. Yakushin SB, Palla A, Haslwanter T, Bockisch CJ, Straumann D (2003) Dependence of adaptation of the human vertical angular vestibulo-ocular reflex on gravity. Exp Brain Res 152(1):137-142. Weber KP, Landau K, Palla A, Haslwanter T, Straumann D (2004) Ocular rotation axes during dynamic Bielschowsky head-tilt testing in unilateral trochlear nerve palsy. Invest Ophthalmol Vis Sci 45(2):455-465. Palla A, Straumann D (2004) Recovery of the high-acceleration vestibulo-ocular reflex after vestibular neuritis. J Assoc Res Otolaryngol. Dec;5(4):427-35. Palla A, Marti S, Straumann D (2005) Head-shaking nystagmus depends on gravity. J Assoc Res Otolaryngol. Mar;6(1):1-8. Palla A, Bockisch CJ, Bergamin O, Straumann D (2006) Dissociated hysteresis of static ocular counterroll in humans. J Neurophysiol. Apr;95(4):2222-32. Jorns-Haderli M, Straumann D, Palla A (2007) Accuracy of the bedside head-impulse test in detecting vestibular hypofunction. J Neurol Neurosurg Psychiatry. 2007 Oct;78(10):1113-8 Palla A, Hegemann S, Widmer U, Straumann D (2007) Vestibular and auditory deficits in Fabry disease and their response to enzyme replacement therapy. J Neurol. 2007 Oct;254(10):1433-42 |
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| Keywords / Suchbegriffe | self-motion perception, spatial orientation, humans, neuro-otology, rotation, translation, stroke, vestibular pathway, cortex, thalamus | ||||||
| Project leadership and contacts / Projektleitung und Kontakte |
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| Funding source(s) / Unterstützt durch |
SNF (Personen- und Projektförderung) Baasch Medicus Foundation |
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| In collaboration with / In Zusammenarbeit mit |
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| Duration of Project / Projektdauer | Jan 2007 to Sep 2011 |