Please use this identifier to cite or link to this item: doi:10.22028/D291-23407
Title: Multimodal deficits in right brain damaged patients with and without neglect and their modulation by sensory stimulation techniques
Other Titles: Multimodale Defizite rechtshemisphärisch geschädigter Patienten mit und ohne Neglect und deren Modulation mithilfe sensorischer Stimulationstechniken
Author(s): Rosenthal, Alisha
Language: English
Year of Publication: 2015
SWD key words: Neglect
Sensorische Stimulation
Free key words: neglect
right brain damage
sensory stimulation
DDC notations: 150 Psychology
Publikation type: Dissertation
Abstract: Spatial neglect is a neurological disorder most often caused by vascular, right hemispheric brain damage. It is mainly characterized by a failure to attend, orient to or react to stimuli presented in the contralesional hemispace. By definition, neglect is seen as a higher order spatial disorder not merely caused by a sensory (e.g. hemianopia) or motor (e.g. hemiplegia) deficit. This definition includes the aspect of multimodality, which plays a central role in the assessment and therapy of the syndrome. Neglect may affect any sensory modality (visual, auditory, olfactory, tactile) or motor as well as representational aspects, leading to deficits in daily life, such as spatial orientation and navigation, visual exploration or auditory localization. Several studies in the last decade addressed the assessment and modulation of those neglect associated deficits using sensory, bottom-up stimulation techniques like galvanic vestibular stimulation or neck-proprioceptive stimulation (e.g. varying head-on-trunk-orientation), which are regarded as promising techniques to ameliorate the syndrome. Interestingly, in these studies, it was observed that not only neglect patients, but also right brain damaged patients without spatial neglect, serving as patient control groups have peculiarities in performing those tasks, and show associations (e.g. disorganized search strategies) as well as dissociations (e.g. non-lateralized exploration behavior) compared to neglect patients. The present doctoral thesis addressed the aspect of multimodality for the visual, auditory and tactile domain concerning exploration as well as localization and identification. In both studies, visual neglect screening tests were used to assign right brain damaged patients to any of the two patient subgroups (right brain damaged controls vs. neglect patients). In study 1, visual and tactile exploration behavior was analyzed using the same task for both modalities, allowing a direct comparison of search patterns concerning omissions and perseverations (repetitive search) as well as their modulation by galvanic vestibular stimulation. Subjects were instructed to name 96 stimuli on a large exploration board either with (visual condition: each of the 96 stimuli had to be named by terms of shape and attached) or without (tactile condition: blindfolded subjects were asked to name each stimulus’ shape by only using the ipsilesional, i.e. right hand) the help of vision. The typical neglect associated lateralization bias (left-right-gradient) in exploration was found in both modalities in neglect patients, with higher omission rates in the left compared to the right hemispace of the search board in both tasks (visual and tactile), even if that difference of leftward vs. rightward attention bias did not reach a significant statistical level. No such gradient was found in right brain damaged controls. A similar pattern was found for perseveration rates in neglect patients, showing a rightward bias in repeated search, whereas right brain damaged controls showed similar repetition rates in their search in both hemifields. Interestingly, right brain damaged patients without neglect also showed deficits in exploration behavior compared to healthy controls. They showed omission rates in the left and right hemispace in the visual task as well as in the left hemispace of the tactile task, which scored between those of neglect patients and healthy controls. In the right hemispace of the tactile task, they even performed on the same level as neglect patients. Perseveration rates were even higher in the left hemispace compared to neglect patients, while both patient groups showed similar perseveration rates in the left hemispace. Notably, all three subject groups, including the healthy controls, showed a similar, high level of perseverations in the tactile task across the whole exploration board. In the present study 1, galvanic vestibular stimulation did not have any clear ameliorating effect on the exploration performance. The results are discussed with respect to recent literature on the basis of the assumption of a multimodal representation of space, which seems to be impaired in right brain damaged patients with and without neglect in various degrees. Study 2 investigated the characteristics of auditory neglect concerning auditory localization and identification performance and its modulation by passive head-on-trunk-rotation (passive head rotation 20° left vs. straight vs. 20° right, the trunk remained in straight position in all conditions) as a form of neck-proprioceptive sensory stimulation. Similarly to the visual system, the auditory system is assumed to be organized in two main processing paths, namely a dorsal (“where” and “how”) and a ventral (“what”) stream providing different auditory functions. While localization seems to be realized by the dorsal auditory processing stream, identification tasks are assumed to be processed preferentially in the ventral stream. In the first task (experiment 2a), subjects’ auditory subjective median plane (ASMP) was measured for sound locations in the horizontal plane presented via headphones using binaural sound parameters derived by head related transfer functions (HRTF), simulating a sum of 37 sound locations with 90° to le left and right from the subjective midline of the subject in azimuth (=the horizontal plane). While there was a right sided shift of the ASMP observable in head straight and head right conditions in those patients with left neglect, passive leftward head rotation led to a significant shift of the ASMP to the left, resulting in a relocation of the ASMP and transient amelioration of auditory neglect. Furthermore, that ameliorating effect of passive head rotation was also observable in the second task which was an auditory identification task. Subjects were asked to perform a same-different task using pairs of monosyllabic words presented in a left (-90°, -30°), a central (-30°, +30°), or a right space sector (+30°, +90°) in the horizontal plane. As in experiment 2a sounds were monosyllabic words. Their spatial position in the horizontal plane was manipulated by using the directional dependent head-related transfer functions (HRTF) for these different spatial positions. The final sounds were monosyllabic words with a definite spatial position in azimuth, and were delivered via headphones. Although sound localization did not have to be explicitly computed by the subjects, it did affect the performance in the identification task: the proportion of correctly identified word pairs followed a left-to-right gradient with highest proportions of correct identifications in the right (ipsilesional) sector in the neglect group. Interestingly, passive head rotation to the left – with unchanged auditory input via headphones - significantly increased the proportions of correct word pair identifications in the left and mid spatial position of the tasks, selectively in the group of neglect patients. These results are also discussed with respect to current literature and on the basis of the assumption of the two auditory processing streams mentioned above. The results of both studies indicate four aspects, which are discussed in more detail with respect to current literature: a) visual neglect screening tests seem to be suitable to identify neglect patients with multimodal neglect associated deficits; b) space coding may be realized with a higher order, multimodal representation of space, which seems to be impaired in right brain damaged patients with and without neglect; c) exploration deficits in right brain damaged patients, namely omissions and repetitive search behavior, seem to deflect two distinct phenomena affecting right brain damaged patients; and d) sensory, bottom-up stimulation techniques are suitable to ameliorate multimodal neglect even in a crossmodal way. In sum, the present doctoral thesis brings new insights towards the exploration and localization performance of right brain damaged patients with and without neglect and their modulation using sensory, bottom-up treatments, which need to be replicated and extended by future studies.
Räumlicher Neglect bezeichnet eine neurologische Störung, die zumeist nach vaskulär bedingtem, rechtshemisphärischem Hirnschaden entsteht. Sie bezeichnet die verminderte Fähigkeit Aufmerksamkeit auf kontraläsional dargebotene Stimuli zu richten, sich zu ihnen hin zu orientieren oder auf diese zu reagieren. Per definitionem gilt Neglect als eine räumliche Störung höherer Ordnung, die nicht rein durch sensorische oder motorische Beeinträchtigungen verursacht wird. Sensorische, sog. "bottom-up"-Stimulationsverfahren gelten als vielversprechende Verfahren zur temporären Kompensation Neglect-assoziierter Beeinträchtigungen. Ihre Wirksamkeit wird in zahlreichen Studien nahegelegt. Allerdings zeigen nicht nur rechtshemisphärisch geschädigte Patienten mit, sondern auch solche ohne Neglect Beeinträchtigungen in den dort präsentierten Aufgaben. Die vorliegende Arbeit befasst sich mit mutimodalem Neglect in der visuellen, taktilen sowie auditorischen Modalität in Explorations-, Lokalisations- sowie Identifikationsaufgaben und dessen Modulierbarkeit mithilfe galvanisch vestibulärer Stimulation sowie propriozeptiver Stimulation der Nackenmuskulatur durch Kopf-auf-Rumpf-Rotation. In Studie 1 wurde das visuelle und taktile Explorationsverhalten rechtshemisphärischer Patienten mit und ohne Neglect mithilfe desselben Paradigmas untersucht. Ein Links-Rechts-Gradient (statistisch nicht signifikant) wird hinsichtlich der Auslassungstendenz nur bei den Neglectpatienten beobachtet, nicht jedoch bei den rechtshemisphärisch geschädigten Kontrollprobanden. Allerdings zeigen sich bei den rechtshemisphärischen Kontrollprobanden Explorationsdefizite im Vergleich zu den gesunden Kontrollprobanden, die eingehend untersucht und erläutert werden. Studie 2 befasst sich mit der Modulierbarkeit der akustischen Lokalisations- und Identifikationsleistung mithilfe propriozeptiver Stimulation der Nackenmuskulatur durch passive Kopfdrehung (0° geradeaus, 20° links, 20° rechts). Es zeigt sich ein deutlicher temporär kompensatorischer Effekt der Kopf-auf-Rumpfdrehung nach links auf die auditive Lokalisations- sowie Identifikationsleistung. Die Ergebnisse der vorliegenden Studien werden im Kontext der aktuellen Studienlage kritisch diskutiert.
Link to this record: urn:nbn:de:bsz:291-scidok-63105
Advisor: Kerkhoff, Georg
Date of oral examination: 11-Nov-2015
Date of registration: 7-Dec-2015
Faculty: HW - Fakultät für Empirische Humanwissenschaften und Wirtschaftswissenschaft
Department: HW - Psychologie
Collections:SciDok - Der Wissenschaftsserver der Universität des Saarlandes

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