title: Neural correlates of hemispheric dominance and ipsilaterality within the vestibular system.
abstract: Earlier functional imaging studies on the processing of vestibular information mainly focused on cortical activations due to stimulation of the horizontal semicircular canals in right-handers. Two factors were found to determine its processing in the temporo-parietal cortex: a dominance of the non-dominant hemisphere and an ipsilaterality of the neural pathways. In an investigation of the role of these factors in the vestibular otoliths, we used vestibular evoked myogenic potentials (VEMPs) in a fMRI study of monaural saccular-otolith stimulation. Our aim was to (1) analyze the hemispheric dominance for saccular-otolith information in healthy left-handers, (2) determine if there is a predominance of the ipsilateral saccular-otolith projection, and (3) evaluate the impact of both factors on the temporo-parieto-insular activation pattern. A block design with three stimulation and rest conditions was applied: (1) 102 dB-VEMP stimulation; (2) 65 dB-control-acoustic stimulation, (3) 102 dB-white-noise-control stimulation. After subtraction of acoustic side effects, bilateral activations were found in the posterior insula, the superior/middle/transverse temporal gyri, and the inferior parietal lobule. The distribution of the saccular-otolith activations was influenced by the two factors but with topographic disparity: whereas the inferior parts of the temporo-parietal cortex were mainly influenced by the ipsilaterality of the pathways, the upper parts reflected the dominance of the non-dominant hemisphere. This is in contrast to the processing of acoustic stimulation, which showed a predominance of the contralateral pathways. Our study proves the importance of the hemispheric preponderance also in left-handers, which is of relevance in the superior parts of the insula gyrus V, the inferior parietal lobule, and the superior temporal gyri.
authors.affiliation: Department of Neurology, Johannes Gutenberg-University Mainz, Langenbeckstrasse 1, D-55101 Mainz, Germany. janzen@neurologie.klinik.uni-mainz.de
authors.forename: J
authors.initials: J
authors.lastname: Janzen
authors.forename: P
authors.initials: P
authors.lastname: Schlindwein
authors.forename: S
authors.initials: S
authors.lastname: Bense
authors.forename: T
authors.initials: T
authors.lastname: Bauermann
authors.forename: G
authors.initials: G
authors.lastname: Vucurevic
authors.forename: P
authors.initials: P
authors.lastname: Stoeter
authors.forename: M
authors.initials: M
authors.lastname: Dieterich
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000502:physiology*; D004292:Dominance, Cerebral / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D014722:Vestibule, Labyrinth / Q000502:physiology*; D055815:Young Adult