New TP Dieterich/Brandt, Glasauer
Hemispheric lateralization and dominance in vestibular and visual cortex during circularvection
Background and Goals
The vestibular sense is characterized by a hemispheric dominance that is located in the right hemisphere in right-handers and in the left hemisphere in left-handers. This has been determined with caloric irrigation in PET  as well as galvanic stimulation  and auditory evoked vestibular otolith stimulation , in fMRI ,. The dominance of the right hemispheric posterior insular/opercular area (OP2) in right-handers has been confirmed in studies on the meta-analytical definition and functional connectivity of the human vestibular cortex ,. Based on these findings of a hemispheric dominance within the vestibular cortical areas we hypothezised that ontogenetically the vestibular system determines the lateralization of brain functions, i.e, the individual handedness .
Circularvection (CV) with large-field visual motion stimulation was generally believed to activate the vestibular system. However, this has not been demonstrated by earlier PET and fMRI studies ,,. Instead, the critical cortical area that appeared to be involved in visually induced apparent self-motion was in the medial and superior part of the parieto-occipital cortex bilaterally, e.g., PO. Re-evaluation of our data on optokinetic stimulation suggests that there may also be a right hemispheric dominance in the region of PO.
The major questions are the following: Is this dominance also dependent on, first, handedness and, second, the percept of either object-motion or self-motion? Is PO part of the cortical vestibular, the cortical visual, or both networks in accordance with the structural and functional concept? To the best of our knowledge these questions have not been addressed before.
In the proposed project we will combine fMRI/PET imaging and psychophysical methods in humans with mathematical modelling on the basis of our data.
Methodology and Work Program
In the psychophysical approach the PhD candidate will measure the CV latencies under different visual stimulation conditions (right and left half-field stimulation in opposite movement directions horizontally, vertically, rotatory). These psychophysical data will be correlated to fMRI/PET data from a similar set-up under imaging conditions. Furthermore, the data will be fed into our model using an attractor network based on a neural network model consisting on four layers of neurons (retina, multisensory orientation center, visual cortex V1, and superior colliculus). The goal of this approach is to differentiate the mechanism for self-motion perception induced by visual flow in comparison to vestibular stimulation.
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