title: Functional MRI of galvanic vestibular stimulation with alternating currents at different frequencies.
abstract: 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.
authors.affiliation: Department of Neurology, Center for Sensorimotor Research, Klinikum Grosshadern, Ludwig-Maximilians University, Marchioninistr. 23, 81377 Munich, Germany. tstephan@brain.nefo.med.uni-muenchen.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Stephan
authors.forename: Angela
authors.initials: A
authors.lastname: Deutschländer
authors.forename: Annina
authors.initials: A
authors.lastname: Nolte
authors.forename: Erich
authors.initials: E
authors.lastname: Schneider
authors.forename: Martin
authors.initials: M
authors.lastname: Wiesmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Brandt
authors.forename: Marianne
authors.initials: M
authors.lastname: Dieterich
mesh_terms: D000328:Adult; D000465:Algorithms; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009039:Motion Perception / Q000502:physiology; D009415:Nerve Net / Q000502:physiology; D010100:Oxygen / Q000097:blood; D014722:Vestibule, Labyrinth / Q000502:physiology*
chemical_list: D010100:Oxygen