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Rennig J.,University of Tubingen | Karnath H.-O.,University of Tubingen | Karnath H.-O.,University of South Carolina | Huberle E.,University of Tubingen | Huberle E.,Neurology and Neurorehabilitation Center
Frontiers in Human Neuroscience | Year: 2013

Visual perception depends on the visual context and is likely to be influenced by size constancy, which predicts a size and distance invariant perception of objects. However, size constancy can also result in optical illusions that allow the manipulation of the perceived size. We thus asked whether the integration of local elements into a global object can be influenced by manipulations of the visual context and size constancy? A set of stimuli was applied in healthy individuals that took advantage of the 'Kanizsa' illusion, in which three circles with open wedges oriented towards a center point are placed to form an illusionary perception of a triangle. In addition, a 3D-perspective view was implemented in which the global target ('Kanizsa' triangle) was placed in combination with several distractor circles either in a close or a distant position. Subjects were engaged in a global recognition task on the location of the 'Kanizsa' triangle. Global recognition of 'Kanizsa' triangles improved with a decreasing length of the illusory contour. Interestingly, recognition of 'Kanizsa' triangles decreased when they were perceived as if they were located further away. We conclude that the integration of local elements into a global object is dependent on the visual context and dominated by size constancy. © 2013 Rennig, Karnath and Huberle. Source


Rennig J.,University of Tubingen | Bilalic M.,University of Tubingen | Huberle E.,University of Tubingen | Huberle E.,Neurology and Neurorehabilitation Center | And 3 more authors.
Frontiers in Human Neuroscience | Year: 2013

In a recent neuroimaging study the comparison of intact vs. disturbed perception of global gestalt indicated a significant role of the temporo-parietal junction (TPJ) in the intact perception of global gestalt (Huberle and Karnath, 2012). This location corresponded well with the areas known to be damaged or impaired in patients with simultanagnosia after stroke or due to neurodegenerative diseases. It was concluded that the TPJ plays an important role in the integration of individual items to a holistic percept. Thus, increased BOLD signals should be found in this region whenever a task calls for the integration of multiple visual items. Behavioral experiments in chess experts suggested that their superior skills in comparison to chess novices are partly based on fast holistic processing of chess positions with multiple pieces. We thus analyzed BOLD data from four fMRI studies that compared chess experts with chess novices during the presentation of complex chess-related visual stimuli (Bilalić et al., 2010, 2011a,b, 2012). Three regions of interests were defined by significant TPJ clusters in the abovementioned study of global gestalt perception (Huberle and Karnath, 2012) and BOLD signal amplitudes in these regions were compared between chess experts and novices. These cross-paradigm ROI analyses revealed higher signals at the TPJ in chess experts in comparison to novices during presentations of complex chess positions. This difference was consistent across the different tasks in five independent experiments. Our results confirm the assumption that the TPJ region identified in previous work on global gestalt perception plays an important role in the processing of complex visual stimulus configurations. © 2013 Rennig, Bilalić, Huberle, Karnath and Himmelbach. Source


Geisseler O.,University of Zurich | Pflugshaupt T.,University of Zurich | Pflugshaupt T.,Neurology and Neurorehabilitation Center | Bezzola L.,University of Zurich | And 5 more authors.
NeuroImage: Clinical | Year: 2016

Cognitive impairment is as an important feature of Multiple Sclerosis (MS), and might be even more relevant to patients than mobility restrictions. Compared to the multitude of studies investigating memory deficits or basic cognitive slowing, executive dysfunction is a rarely studied cognitive domain in MS, and its neural correlates remain largely unexplored. Even rarer are topological studies on specific cognitive functions in MS. Here we used several structural MRI parameters - including cortical thinning and T2 lesion load - to investigate neural correlates of executive dysfunction, both on a global and a regional level by means of voxel- and vertex-wise analyses. Forty-eight patients with relapsing-remitting MS and 48 healthy controls participated in the study. Five executive functions were assessed, i.e. verbal and figural fluency, working memory, interference control and set shifting. Patients scored lower than controls in verbal and figural fluency only, and displayed widespread cortical thinning. On a global level, cortical thickness independently predicted verbal fluency performance, when controlling for lesion volume and central brain atrophy estimates. On a regional level, cortical thinning in the anterior cingulate region correlated with deficits in verbal and figural fluency and did so in a lateralised manner: Left-sided thinning was related to reduced verbal - but not figural - fluency, whereas the opposite pattern was observed for right-sided thinning. We conclude that executive dysfunction in MS patients can specifically affect verbal and figural fluency. The observed lateralised clinico-anatomical correlation has previously been described in brain-damaged patients with large focal lesions only, for example after stroke. Based on focal grey matter atrophy, we here show for the first time comparable lateralised findings in a white matter disease with widespread pathology. © 2015 The Authors. Published by Elsevier Inc. Source


Heldner M.R.,University of Bern | Vanbellingen T.,University of Bern | Bohlhalter S.,Neurology and Neurorehabilitation Center | Mattle H.P.,University of Bern | And 2 more authors.
Physical Therapy | Year: 2014

Background. Impaired manual dexterity is frequent and disabling in people with multiple sclerosis (MS). Therefore, convenient, quick, and validated tests for manual dexterity in people with MS are needed.Objective. The aim of this study was to validate the Coin Rotation Task (CRT) for examining manual dexterity in people with MS.Design. This was a cross-sectional study.Methods. A total of 101 outpatients with MS were assessed with the CRT, the Expanded Disability Status Scale (EDSS), the Scale for the Assessment and Rating of Ataxia (SARA), and the Modified Ashworth Scale (MAS); muscle strength and sensory deficits of the hands were noted. The concurrent validity and diagnostic accuracy of the CRT were determined by comparison with the 9-Hole Peg Test (9HPT). Construct validity was determined by comparison with a valid dexterity questionnaire. Multiple regression analyses were done to explore correlations of the CRT with the EDSS, SARA, MAS, muscle strength, and sensory deficits.Results. The CRT correlated significantly with the 9HPT (r=.73, P<.0001), indicating good concurrent validity. The cutoff values for the CRT relative to the 9HPT were 18.75 seconds for the dominant hand (sensitivity=81.5%, specificity=80.0%) and 19.25 seconds for the nondominant hand (sensitivity=90.3%, specificity= 81.8%); these values indicated good diagnostic accuracy. Furthermore, the CRT correlated significantly with the dexterity questionnaire (r=-.49, P<.0001), indicating moderate construct validity. Multiple regression analyses revealed that the EDSS was the strongest predictor for impaired dexterity.Limitations. Most of the people examined had relapsing-remitting MS and EDSS scores of up to 7.Conclusions. This study validated the CRT as a test that can be used easily and quickly to evaluate manual dexterity in people with MS. © 2014 American Physical Therapy Association. Source


Murphy S.C.,Humboldt University of Berlin | Murphy S.C.,University of Bern | Murphy S.C.,University of Melbourne | Palmer L.M.,University of Melbourne | And 5 more authors.
eLife | Year: 2016

One of the leading approaches to non-invasively treat a variety of brain disorders is transcranial magnetic stimulation (TMS). However, despite its clinical prevalence, very little is known about the action of TMS at the cellular level let alone what effect it might have at the subcellular level (e.g. dendrites). Here, we examine the effect of single-pulse TMS on dendritic activity in layer 5 pyramidal neurons of the somatosensory cortex using an optical fiber imaging approach. We find that TMS causes GABAB-mediated inhibition of sensory-evoked dendritic Ca2+ activity. We conclude that TMS directly activates fibers within the upper cortical layers that leads to the activation of dendrite-targeting inhibitory neurons which in turn suppress dendritic Ca2+ activity. This result implies a specificity of TMS at the dendritic level that could in principle be exploited for investigating these structures non-invasively. © Murphy et al. Source

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