Labyrinthectomy abolishes the behavioral and neural response of rats to a high-strength static magnetic field

Kwon

American Journal of Physiology-Regulatory, Integrative and Comp

et al. 2013

Self Cite

High-strength static magnetic fields (>7 tesla) perturb the vestibular system causing dizziness, nystagmus, and nausea in humans; and head motion, locomotor circling, conditioned taste aversion, and c-Fos induction in brain stem vestibular nuclei in rodents. To determine the role of head orientation, mice were exposed for 15 min within a 14.1-tesla magnet at six different angles (mice oriented parallel to the field with the head toward B+ at 0°; or pitched rostrally down at 45°, 90°, 90° sideways, 135°, and 180°), followed by a 2-min swimming test. Additional mice were exposed at 0°, 90°, and 180° and processed for c-Fos immunohistochemistry. Magnetic field exposure induced circular swimming that was maximal at 0° and 180° but attenuated at 45° and 135°. Mice exposed at 0° and 45° swam counterclockwise, whereas mice exposed at 135° and 180° swam clockwise. Mice exposed at 90° (with their rostral-caudal axis perpendicular to the magnetic field) did not swim differently than controls. In parallel, exposure at 0° and 180° induced c-Fos in vestibular nuclei with left-right asymmetries that were reversed at 0° vs. 180°. No significant c-Fos was induced after 90° exposure. Thus, the optimal orientation for magnetic field effects is the rostral-caudal axis parallel to the field, such that the horizontal canal and utricle are also parallel to the field. These results have mechanistic implications for modeling magnetic field interactions with the vestibular apparatus of the inner ear (e.g., the model of Roberts et al. of an induced Lorenz force causing horizontal canal cupula deflection).

supporting

confidence: 59%

mentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

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Orientation within a high magnetic field determines swimming direction and laterality of c-Fos induction in mice

Kwon

American Journal of Physiology-Regulatory, Integrative and Comp

et al. 2013

Self Cite

“…Effects on the vestibular system are believed to underlie these phenomena. Definitive experiments that implicate the vestibular system in animal behavior showed no effects if the vestibular system is ablated [122]. …”

Section: Physiological Effects and Safety At 14 T And Abovementioning

confidence: 99%

Toward 20 T magnetic resonance for human brain studies: opportunities for discovery and neuroscience rationale

Budinger

Bird

Frydman

et al. 2016

Magn Reson Mater Phy

An initiative to design and build magnetic resonance imaging (MRI) and spectroscopy (MRS) instruments at 14 T and beyond to 20 T has been underway since 2012. This initiative has been supported by 22 interested participants from the USA and Europe, of which 15 are authors of this review. Advances in high temperature superconductor materials, advances in cryocooling engineering, prospects for non-persistent mode stable magnets, and experiences gained from large-bore, high-field magnet engineering for the nuclear fusion endeavors support the feasibility of a human brain MRI and MRS system with 1 ppm homogeneity over at least a 16-cm diameter volume and a bore size of 68 cm. Twelve neuroscience opportunities are presented as well as an analysis of the biophysical and physiological effects to be investigated before exposing human subjects to the high fields of 14 T and beyond.

“…After removal of the labyrinth, rats are oblivious to the field exposure. The vertigo effect has thus been confirmed as an action of the magnetic field on the primary transducer -rather than directly on the Central Nervous System (CNS) [7].…”

Section: Magnetic Field Induced Vertigomentioning

confidence: 99%

Magnetic Field-Induced Vertigo in the MRI Environment

Glover

2015

Curr Radiol Rep

This review discusses the theory behind, and the experimental evidence for, the perception of vertigo in a high magnetic field found in an MRI environment. Recent experiments have shown that there is an eye nystagmus response that is proportional to magnetic field exposure and not purely one of rate of change of magnetic field. The mechanism of transduction can be attributed to the Lorentz forces on the endolymph in the ear canals, producing a static pressure due to the vector product of the magnetic field and current density. The adaption and response of the measureable effect reveals time constants which support such a mechanism and explain why the balance system responds in the way we observe and feel. The position and movement of the head relative to the direction of field is of fundamental importance to the sensation of vertigo, as are ambient conditions such as lighting levels. Recent surveys of subjects undergoing seven tesla or higher MRI scans report that, although there is a high perception of vertigo-like effects, these are not intolerable and are not generally the cause of subject withdrawal. This review argues that the ICNIRP guidelines on low frequency fields still need to acknowledge the role of a high magnetic field in producing vertigo sensations rather than rate of change of field alone.