Arrow Research search

Author name cluster

Thomas Stephan

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

20 papers
1 author row

Possible papers

20

YNIMG Journal 2026 Journal Article

Multimodal MRI of the reorganization of multisensory and sensorimotor networks in chronic bilateral vestibulopathy

  • Marianne Dieterich
  • Thomas Stephan
  • Lena Fabritius
  • Rainer Boegle
  • Thomas Brandt

Chronic bilateral vestibulopathy (BVP) occurs preferably in elderly patients presenting with postural imbalance and head movement induced oscillopsia. The condition is often incomplete with residual functions in both ears. Beyond the vestibular reflexive deficits, an impairment of spatial orientation and navigation has been described associated with an atrophy of the hippocampal formation. However, this finding was inconsistent in various studies on rodents and humans. In the current MRI study on 15 BVP patients and 15 healthy controls (HC) we combined analyses of whole brain voxel-based morphometry (VBM) and the resting state fMRI (rs-fMRI) on the widely distributed multisensory vestibular network and its connections to sensorimotor, cognitive, and emotional networks at rest. Major results were gray and white matter changes in conjunction with rs-fMRI changes: the left posterior insula, angular and supramarginal gyri, and left premotor cortex; as well as bilateral anterior hippocampal formation and adjacent amygdala; visual cortex V1 and V5; thalamus; prefrontal cortex; cerebellar hemispheres and uvula; and pyramidal tract. Thus, the overlap of structural (VBM) and rs-fMRI including various correlation analyses disclosed that a bilateral reduction of peripheral vestibular input affects multiple networks from the cerebellum up to the cortical hemispheres. A possible functional interpretation is that the observed specific alterations reflect compensation and substitution by other networks - handling perception, sensorimotor balance regulation, cognition, and emotions - due to deficits in one sensory system. This is consistent with anterior hippocampal atrophy's role in spatial memory deficits, as well as the involvement of the cerebellum, amygdala, and prefrontal cortex in emotional processes. It also aligns with the top-down regulation by the prefrontal cortex via the pyramidal tract for cognitive control of balance triggered by the perception of postural instability. Further, correlation analyses support this interpretation because most morphological changes were dependent on the duration of the condition.

Details DOI

YNICL Journal 2022 Journal Article

White matter volume loss drives cortical reshaping after thalamic infarcts

  • Julian Conrad
  • Maximilian Habs
  • Ria M. Ruehl
  • Rainer Bögle
  • Matthias Ertl
  • Valerie Kirsch
  • Ozan E Eren
  • Sandra Becker-Bense

OBJECTIVE: The integration of somatosensory, ocular motor and vestibular signals is necessary for self-location in space and goal-directed action. We aimed to detect remote changes in the cerebral cortex after thalamic infarcts to reveal the thalamo-cortical connections necessary for multisensory processing and ocular motor control. METHODS: Thirteen patients with unilateral ischemic thalamic infarcts presenting with vestibular, somatosensory, and ocular motor symptoms were examined longitudinally in the acute phase and after six months. Voxel- and surface-based morphometry were used to detect changes in vestibular and multisensory cortical areas and known hubs of central ocular motor processing. The results were compared with functional connectivity data in 50 healthy volunteers. RESULTS: Patients with paramedian infarcts showed impaired saccades and vestibular perception, i.e., tilts of the subjective visual vertical (SVV). The most common complaint in these patients was double vision or vertigo / dizziness. Posterolateral thalamic infarcts led to tilts of the SVV and somatosensory deficits without vertigo. Tilts of the SVV were higher in paramedian compared to posterolateral infarcts (median 11.2° vs 3.8°). Vestibular and ocular motor symptoms recovered within six months. Somatosensory deficits persisted. Structural longitudinal imaging showed significant volume reduction in subcortical structures connected to the infarcted thalamic nuclei (vestibular nuclei region, dentate nucleus region, trigeminal root entry zone, medial lemniscus, superior colliculi). Volume loss was evident in connections to the frontal, parietal and cingulate lobes. Changes were larger in the ipsilesional hemisphere but were also detected in homotopical regions contralesionally. The white matter volume reduction led to deformation of the cortical projection zones of the infarcted nuclei. CONCLUSIONS: White matter volume loss after thalamic infarcts reflects sensory input from the brainstem as well the cortical projections of the main affected nuclei for sensory and ocular motor processing. Changes in the cortical geometry seem not to reflect gray matter atrophy but rather reshaping of the cortical surface due to the underlying white matter atrophy.

Details DOI

YNICL Journal 2021 Journal Article

Structural reorganization of the cerebral cortex after vestibulo-cerebellar stroke

  • Julian Conrad
  • Maximilian Habs
  • Maxine Ruehl
  • Rainer Boegle
  • Matthias Ertl
  • Valerie Kirsch
  • Ozan Eren
  • Sandra Becker-Bense

OBJECTIVE: Structural reorganization following cerebellar infarcts is not yet known. This study aimed to demonstrate structural volumetric changes over time in the cortical vestibular and multisensory areas (i.e., brain plasticity) after acute cerebellar infarcts with vestibular and ocular motor symptoms. Additionally, we evaluated whether structural reorganization in the patients topographically correlates with cerebello-cortical connectivity that can be observed in healthy participants. METHODS: We obtained high-resolution structural imaging in seven patients with midline cerebellar infarcts at two time points. These data were compared to structural imaging of a group of healthy age-matched controls using voxel-based morphometry (2×2 ANOVA approach). The maximum overlap of the infarcts was used as a seed region for a separate resting-state functional connectivity analysis in healthy volunteers. RESULTS: Volumetric changes were detected in the multisensory cortical vestibular areas around the parieto-opercular and (retro-) insular cortex. Furthermore, structural reorganization was evident in parts of the frontal, temporal, parietal, limbic, and occipital lobes and reflected functional connections between the main infarct regions in the cerebellum and the cerebral cortex in healthy individuals. CONCLUSIONS: This study demonstrates structural reorganization in the parieto-opercular insular vestibular cortex after acute vestibulo-cerebellar infarcts. Additionally, the widely distributed structural reorganization after midline cerebellar infarcts provides additional in vivo evidence for the multifaceted contribution of cerebellar processing to cortical functions that extend beyond vestibular or ocular motor function.

Details DOI

YNIMG Journal 2018 Journal Article

Multisensory vestibular, vestibular-auditory, and auditory network effects revealed by parametric sound pressure stimulation

  • Sun-Young Oh
  • Rainer Boegle
  • Matthias Ertl
  • Thomas Stephan
  • Marianne Dieterich

Multisensory convergence and sensorimotor integration are important aspects for the mediation of higher vestibular cognitive functions at the cortical level. In contrast to the integration of vestibulo-visual or vestibulo-tactile perception, much less is known about the neural mechanism that mediates the integration of vestibular-otolith (linear acceleration/translation/gravity detection) and auditory processing. Vestibular-otolith and auditory afferents can be simultaneously activated using loud sound pressure stimulation, which is routinely used for testing cervical and ocular vestibular evoked myogenic potentials (VEMPs) in clinical neurotological testing. Due to the simultaneous activation of afferents there is always an auditory confound problem in fMRI studies of the neural topology of these systems. Here, we demonstrate that the auditory confounding problem can be overcome in a novel way that does not require the assumption of simple subtraction and additionally allows detection of non-linear changes in the response due to vestibular-otolith interference. We used a parametric sound pressure stimulation design that took each subject's vestibular stimulation threshold into account and analyzed for changes in BOLD-response below and above vestibular-otolith threshold. This approach helped to investigate the functional neuroanatomy of sound-induced auditory and vestibular integration using functional magnetic resonance imaging (fMRI). Results revealed that auditory and vestibular convergence are contained in overlapping regions of the caudal part of the superior temporal gyrus (STG) and the posterior insula. In addition, there are regions that were responsive only to suprathreshold stimulations, suggesting vestibular (otolith) signal processing in these areas. Based on these parametric analyses, we suggest that the caudal part of the STG and posterior insula could contain areas of vestibular contribution to auditory processing, i. e. , higher vestibular cortices that provide multisensory integration that is important for tasks such as spatial localization of sound.

Details DOI

YNIMG Journal 2016 Journal Article

Magnetic vestibular stimulation modulates default mode network fluctuations

  • Rainer Boegle
  • Thomas Stephan
  • Matthias Ertl
  • Stefan Glasauer
  • Marianne Dieterich

Strong magnetic fields (>1Tesla) can cause dizziness and it was recently shown that healthy subjects (resting in total darkness) developed a persistent nystagmus even when remaining completely motionless within a MR tomograph. Consequently, it was speculated that this magnetic vestibular stimulation (MVS) might influence fMRI results, as nystagmus is indicative of an imbalance in the vestibular system, potentially influencing other systems via multisensory vestibular interactions. The objective of our study was to investigate whether MVS does indeed modulate BOLD signal fluctuations. We recorded eye movements, as well as, resting-state fMRI of 30 volunteers in darkness at 1. 5T and 3. 0T to answer the question whether MVS modulated parts of the default mode resting-state network (DMN) in accordance with the Lorentz-force model for MVS, while distinguishing this from the known signal increase due to field strength related imaging effects. Our results showed that modulation of the default mode network occurred mainly in areas associated with vestibular and ocular motor function, and was in accordance with the Lorentz-force model, i. e. , double than the expected signal scaling due to field strength alone. We discuss the implications of our findings for the interpretation of studies using resting-state fMRI, especially those concerning vestibular research. We conclude that MVS needs to be considered in vestibular research to avoid biased results, but it might also offer the possibility of manipulating network dynamics and may thus help in studying the brain as a dynamical system.

Details DOI

YNIMG Journal 2009 Journal Article

Imagined locomotion in the blind: An fMRI study

  • Angela Deutschländer
  • Thomas Stephan
  • Katharina Hüfner
  • Judith Wagner
  • Martin Wiesmann
  • Michael Strupp
  • Thomas Brandt
  • Klaus Jahn

Functional magnetic resonance imaging (fMRI) in sighted individuals previously showed parahippocampal and fusiform activations during locomotor imagery, which were interpreted to reflect visuospatial navigation. Concurrent deactivations of multisensory vestibular and somatosensory cortical areas may reflect suppression of vestibular and somatosensory input, in order to prevent adverse interactions of sensory signals with the optimized automated locomotion pattern. In this fMRI study we compared blood oxygen level dependent (BOLD) activations and deactivations during the kinesthetic imagery of standing, walking, and running in seven congenitally totally blind subjects, seven sighted age-matched controls, and five subjects with age at onset of complete blindness ≥9 y or minimal residual vision. Imagined lying served as the rest condition. As opposed to their sighted controls, congenitally totally blind individuals activated multisensory vestibular areas in the posterior insula and superior temporal gyrus during imagined locomotion. Further, congenitally blind individuals did not show activations in parahippocampal and fusiform regions during locomotor tasks. In the intergroup comparisons, congenitally blind subjects exhibited higher BOLD activity levels than sighted subjects in multisensory vestibular (posterior insula and adjacent temporal sites), somatosensory (postcentral gyrus), and primary motor cortical areas, while sighted subjects showed higher activity levels in the parahippocampal and fusiform gyri. These findings indicate that blind subjects rely more on vestibular and somatosensory feedback for locomotion control than sighted subjects. This is accompanied by enhanced voluntary motor control and enhanced motor-kinesthetic processing. Thus, we provide neuroimaging evidence of distinct sensorimotor strategies in the blind for locomotor control.

Details DOI

YNIMG Journal 2008 Journal Article

Imaging human supraspinal locomotor centers in brainstem and cerebellum

  • Klaus Jahn
  • Angela Deutschländer
  • Thomas Stephan
  • Roger Kalla
  • Martin Wiesmann
  • Michael Strupp
  • Thomas Brandt

An erect posture with bipedal locomotion is a characteristic feature of humans compared to other mammals. Most of our knowledge about the hierarchical network of supraspinal locomotor centers derives from animal experiments, mainly in the cat. We posed the question of whether evolutionary transition from quadrupedal to bipedal locomotion – with associated change of foreleg function – caused reorganization of these supraspinal locomotor centers. Using functional magnetic resonance imaging, we identified separate and distinct cerebellar and brainstem BOLD signal increases related to posture and gait during mental imagery of standing, walking, and running in healthy volunteers (n =26). Comparison with the locomotion centers in the cat showed that these activations include the pacemakers for gait initiation and speed regulation in the interfastigial cerebellum and bilateral midbrain tegmentum (cerebellar and mesencephalic locomotor regions), their descending target regions in the pontine reticular formation, and the rhythm generators in the cerebellar vermis and paravermal cortex. Moreover, during mental imagery of stance, a BOLD signal increase was observed in the dorsal pons, reflecting an activation of the dorsal tegmental field, a locomotion-suppressing site in the cat. These results support the view that the organization of supraspinal locomotor centers was preserved during the transition to bipedal locomotion. The clinical relevance of these centers has so far been largely neglected. However, Parkinson's disease, for example, is associated with reduced cell counts in the pedunculopontine nucleus, a part of the mesencephalic locomotor region. This association suggests that deep brain stimulation of locomotion centers may provide new therapeutic approaches for common gait disorders.

Details DOI

YNIMG Journal 2008 Journal Article

Nicotine-induced nystagmus correlates with midpontine activation

  • Angela Deutschländer
  • Thomas Stephan
  • Eva Riedel
  • Vera C. Zingler
  • Katharina Hüfner
  • Martin Wiesmann
  • Charles Pierrot-Deseilligny
  • Michael Strupp

The pathomechanism of nicotine-induced nystagmus (NIN) is unknown. The aim of this study was to delineate brain structures that are involved in NIN generation. Eight healthy volunteers inhaled nicotine in darkness during a functional magnetic resonance imaging (fMRI) experiment; eye movements were registered using video-oculography. NIN correlated with blood oxygen level-dependent (BOLD) activity levels in a midpontine site in the posterior basis pontis. NIN-induced midpontine activation may correspond to activation of the dorsomedial pontine nuclei and the nucleus reticularis tegmenti pontis, structures known to participate in the generation of multidirectional saccades and smooth pursuit eye movements.

Details DOI

YNIMG Journal 2005 Journal Article

Functional MRI of galvanic vestibular stimulation with alternating currents at different frequencies

  • Thomas Stephan
  • Angela Deutschländer
  • Annina Nolte
  • Erich Schneider
  • Martin Wiesmann
  • Thomas Brandt
  • Marianne Dieterich

Functional MRI was performed in 28 healthy volunteers to study the effects of galvanic vestibular stimulation with alternating currents (AC-GVS) of different frequencies on brain activation patterns. The aims of this study were (1) to identify specific areas within the vestibular cortical network that are involved in the processing of frequency-specific aspects by correlation analyses, (2) to determine the optimal frequency for stimulation of the vestibular system with respect to perception, and (3) to analyze whether different frequencies of AC-GVS are mediated in different cortical areas or different sites within the vestibular cortex. AC-GVS was performed using sinusoidal stimulation currents with an amplitude of ±2. 5 mA, and frequencies of 0. 1 Hz, 0. 3 Hz, 0. 8 Hz, 1. 0 Hz, 2. 0 Hz, and 5. 0 Hz were applied. Regardless of the applied stimulation frequency, AC-GVS elicited activations within a network of multisensory areas similar to those described in earlier studies using direct currents. No mapping of different stimulation frequencies to different cortical locations was observed. Additional activations of somatosensory cortex areas were observed during stimulation with 5 Hz only. The strongest vestibular sensations were reported during stimulation with 1 Hz and 2 Hz. Correlation analyses between blood oxygenation level dependent (BOLD) signal changes and stimulation frequency revealed a positive dependency in areas of the supramarginal gyrus, posterolateral thalamus, cerebellar vermis, posterior insula, and in the hippocampal region/uncus. These regions represent areas involved in the processing of vestibular information for head and body orientation in space.

Details DOI

YNIMG Journal 2005 Journal Article

Imaging the visual autokinetic illusion with fMRI

  • Eva Riedel
  • Thomas Stephan
  • Angela Deutschländer
  • Roger Kalla
  • Martin Wiesmann
  • Marianne Dieterich
  • Thomas Brandt

During fixation of a stationary, dim light-emitting diode (LED) in complete darkness, a subtle, apparent motion is perceived which is called autokinesis. This autokinetic illusion increases with increasing fixation time. Eleven healthy subjects were examined by fMRI while fixating an LED in darkness for 35 s. BOLD signal changes of the first and the second half of the fixation period were compared. While the stimulus was the same for both periods, perception differed in that autokinesis was more pronounced in the second half. This second half of the period was associated with bilateral activations in the motion-sensitive middle occipito-temporal area known as MT/V5. Our finding suggests that area MT/V5 is involved in the mediation of autokinesis.

Details DOI

YNIMG Journal 2004 Journal Article

Brain activation patterns during imagined stance and locomotion in functional magnetic resonance imaging

  • Klaus Jahn
  • Angela Deutschländer
  • Thomas Stephan
  • Michael Strupp
  • Martin Wiesmann
  • Thomas Brandt

Posture and gait are sensorimotor actions that involve peripheral, spinal, and supraspinal structures. To investigate brain activity during stance and locomotion, 13 healthy subjects were asked to stand, walk, run, and lie down; subsequently, they were trained to imagine standing, walking, running, and lying [imagined lying as rest condition in functional magnetic resonance imaging (fMRI)]. Separate and distinct activation/deactivation patterns were found for the three imagined conditions: (1) standing imagery was associated with activation in the thalamus, basal ganglia, and cerebellar vermis; (2) walking imagery was associated with activation in the parahippocampal and fusiform gyri (areas involved in visuospatial navigation), occipital visual areas, and in the cerebellum; (3) running imagery caused a predominantly cerebellar activation in the vermis and adjacent hemispheres (six times larger than during imagination of walking or standing), but activations in the parahippocampal and fusiform gyri were smaller than during walking. Deactivations were found for walking and running, but not for standing imagery. They were located in the vestibular (posterior insula, superior temporal gyrus, supramarginal gyrus) and somatosensory (postcentral gyrus) cortex with right-hemispheric dominance. These findings support the concept of a hierarchical organization of posture and locomotion. Automated locomotion, for example, running, is based on spinal generators whose pace is driven by the cerebellar locomotor region. Deactivation in the vestibular and somatosensory cortex prevents adverse interactions with the optimized spinal pattern and sensory signals; this confirms earlier findings of a multisensory inhibition during unhindered locomotion. During slow walking, spatial navigation, mediated by the parahippocampal cortex, becomes more important. Postural control during standing involves a low intensity cerebellar activity and sensorimotor control via the thalamus and basal ganglia.

Details DOI

YNIMG Journal 2004 Journal Article

Eyes open and eyes closed as rest conditions: impact on brain activation patterns

  • Esther Marx
  • Angela Deutschländer
  • Thomas Stephan
  • Marianne Dieterich
  • Martin Wiesmann
  • Thomas Brandt

The patterns of associated brain activations during eyes-open and eyes-closed states in complete darkness considerably differ in fMRI. An “interoceptive” state with the eyes closed is characterized by visual cortex activation, while an “exteroceptive” state with the eyes open is characterized by ocular motor system activity. The impact of the chosen rest condition (eyes open or eyes closed in complete darkness) on the pattern of brain activations during visual stimulation was evaluated in 14 healthy volunteers. During fixation or dim light room illumination, the activation of the visual cortex was larger with the eyes-open rest condition than with the eyes-closed rest condition; however, activation of the lateral geniculate nucleus was smaller. Activations that can be attributed to ocular motor structures, such as the prefrontal cortex, parietal and frontal eye fields, cerebellar vermis, the thalamus, and basal ganglia were larger with the eyes-closed rest condition than with the eyes-open rest condition. BOLD signal decreases of cortical areas that represent visual, somatosensory, auditory, and vestibular functions were seen in the comparison fixation of light emitting diode (LED) minus eyes closed. Thus, the choice of rest condition (either eyes closed or eyes open) is critical for stimulus-induced brain activation patterns. Activity of the ocular motor system as well as deactivation of sensory cortical areas may go undetected with eyes open as rest condition.

Details DOI

YNIMG Journal 2003 Journal Article

Eye closure in darkness animates sensory systems

  • Esther Marx
  • Thomas Stephan
  • Annina Nolte
  • Angela Deutschländer
  • Klaus C Seelos
  • Marianne Dieterich
  • Thomas Brandt

Single subject and group analyses (n = 12) showed that the eyes-open and eyes-closed states in complete darkness considerably and consistently differ in the patterns of associated brain activation in fMRI. During nonchanging external stimulation, ocular motor and attentional systems were activated when the eyes were open; the visual, somatosensory, vestibular, and auditory systems were activated when the eyes were closed. These data suggest that there are two different states of mental activity: with the eyes closed, an “interoceptive” state characterized by imagination and multisensory activity and with the eyes open, an “exteroceptive” state characterized by attention and ocular motor activity. Our study also shows that the chosen baseline condition may have a considerable impact on activation patterns and on the interpretation of brain activation studies.

Details DOI

YNIMG Journal 2003 Journal Article

Performing allocentric visuospatial judgments with induced distortion of the egocentric reference frame: an fMRI study with clinical implications

  • Gereon R Fink
  • John C Marshall
  • Peter H Weiss
  • Thomas Stephan
  • Christian Grefkes
  • Nadim J Shah
  • Karl Zilles
  • Marianne Dieterich

The temporary improvement of visuospatial neglect during galvanic vestibular stimulation (Scand. J. Rehabil. Med. 31 (1999)117) may result from correction of the spatial reference frame distorted by the responsible lesion. Prior to an investigation of the neural basis of this effect in neurological patients, exploration of the neural mechanisms underlying such procedures in normals is required to provide insight into the physiological basis thereof. Despite their clinical impact, the neural mechanisms underlying the interaction of galvanic (and other) vestibular manipulations with visuospatial processing (and indeed the neural bases of how spatial reference frames are computed in man) remain to be clarified. We accordingly used fMRI in normal volunteers to investigate the effect of galvanically induced interference with the egocentric spatial reference frame on the neural processes underlying allocentric visuospatial (line bisection) judgments. A significant specific interaction of galvanic vestibular stimulation with the neural mechanisms underlying allocentric visuospatial judgments was observed in right posterior parietal and ventral premotor cortex only. Activation of these areas previously found to be damaged in visuospatial neglect suggests that these effects reflect the increased processing demands when compensating for the distorted egocentric spatial reference frame while maintaining accurate performance during the allocentric spatial task. These results thus implicate right posterior parietal and right ventral premotor cortex in the computation of spatial reference frames. Furthermore, our data imply a specific physiological basis for the temporary improvement of visuospatial neglect in patients with right hemisphere lesions during galvanic vestibular stimulation and may thus impact upon the rehabilitation of neglect: understanding the interaction of galvanic vestibular stimulation with allocentric visuospatial judgments in healthy volunteers may lead to the more effective deployment of such techniques in neurological patients.

Details DOI