Behle, L. | bioRxiv Science

bioRxiv2025

Minimizing the influence of magnetic vestibular stimulation inside MRI-scanners by adjusting head position

Magnetic resonance imaging (MRI) offers detailed diagnostic insights but also unintentionally induces vestibular side effects by its static magnetic field. Magnetic vestibular stimulation (MVS) may cause dizziness and confound behavioral and physiological measures in fMRI by introducing an unavoidable mixture of neural activation in vestibular projection areas, driven both by the signal of interest and by vestibular system activation. This study investigated how different head orientations within a 3T MRI scanner influence the MVS-induced vestibulo-ocular reflex (VOR) in complete darkness, with the goal of identifying a head position that minimizes or eliminates MVS effects. Results revealed a linear relationship between head pitch and the horizontal VOR (Experiment 1), as well as between head roll and the vertical VOR (Experiment 2). Across participants, the horizontal VOR was eliminated at an average forward head pitch of 24.4{degrees}, while the vertical VOR was nullified at an average roll angle of 15.9{degrees} towards the right shoulder. A head position combining this forward pitch with this rightward roll effectively minimized both horizontal and vertical VOR components across subjects (Experiment 3). The findings provide a practical solution to reduce the impact of MVS effects in MRI with important implications for improving data quality in neuroscientific fMRI studies and patient comfort during clinical imaging.

neuroscience↗

bioRxiv2024

Sustained bias of spatial attention in a 3T MRI scanner

The static magnetic field of MRI scanners induces magneto-hydrodynamic stimulation of the vestibular organ (MVS) in the inner ear. This not only causes a horizontal vestibular nystagmus but also induces a horizontal bias in spatial attention. In this study, we aimed to determine the time course of MVS-induced biases in both VOR and spatial attention inside a 3T MRI-scanner as well as their respective aftereffects after participants left the scanner. Eye movements and overt spatial attention in a visual search task were assessed in healthy volunteers before, during and after a one-hour MVS period. All participants exhibited a VOR inside the scanner, which declined over time but never vanished completely. Importantly, there was also an MVS-induced horizontal bias in spatial attention and exploration, which persisted throughout the entire hour within the scanner. Upon exiting the scanner, we observed aftereffects in the opposite direction manifested in both the VOR and in spatial attention, lasting for about 6 minutes. Sustained MVS effects on spatial attention have important implications for the design and interpretation of fMRI-studies and for the development of therapeutic interventions counteracting spatial neglect.

neuroscience↗