Axel Lindner

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 a median forward head pitch of 24.4°, while the vertical VOR was nullified at an average roll angle of 15.9° 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). No conclusions can be drawn regarding torsional eye movements, as those were not recorded. 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.

Depersonalization/derealization (DPDR) involves feeling detached from one’s body, thoughts, or emotions and is often triggered by trauma, stress, mental health issues, or drug use, typically causing high distress. Similar experiences are also reported in meditation contexts, where they are often described as positive, insightful, and meaningful. However, no study has systematically compared DPDR-like experiences across these contexts. This preregistered, cross-sectional study addresses this gap. Participants who had experienced DPDR-like states triggered through meditation (MEDT, n = 60) or through other triggers (NMEDT, n = 61) completed five questionnaires and provided additional information about their DPDR experience and meditation practice. The two groups significantly differed on all questionnaires except the Cambridge Depersonalisation Scale, including its subscales covering different DPDR aspects. The MEDT group rated their experiences as substantially more positive than NMEDT, though most participants in both groups described them as mixed. In MEDT, these experiences were reported across meditation types and experience levels. Overall, meditation can induce states phenomenologically similar to DPDR, but these are often experienced as more welcome, pleasant, and spiritually meaningful than those triggered by trauma, stress, or cannabis, although distress is not uncommon. These findings suggest contemplative approaches may inform clinical support for DPDR, while highlighting the need for recognition and guidance within meditation settings.

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°, while the vertical VOR was nullified at an average roll angle of 15.9° 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.

BACKGROUND: Depersonalization/derealization (DPDR) involves feeling detached from one’s body, thoughts, or emotions. These symptoms are often triggered by trauma, stress, mental health issues, or drug use, and tend to be highly distressing. While similar experiences can also arise from meditation, anecdotal reports refer to them as positive, insightful, and meaningful. However, no study has systematically compared them across contexts. This preregistered study does so by examining DPDR-like experiences from meditation versus other triggers.METHODS: In this cross-sectional survey, participants who had experienced DPDR-like states through meditation (MED, n = 60) or other triggers (NMED, n = 61) completed five questionnaires: the Cambridge Depersonalisation Scale (CDS), Mysticism Scale (MS), Ego Dissolution Inventory (EDI), Challenging Experience Questionnaire (CEQ), and Five Facet Mindfulness Questionnaire (FFMQ). They also rated the emotional valence of their experiences and described their meditation practice.RESULTS: The two groups significantly differed on all questionnaires except the CDS, including its subscales covering different DPDR aspects. The MED group also rated their experiences as much more positive than NMED, though most in both groups described them as mixed. These experiences were reported across any meditation type and experience level.CONCLUSIONS: Meditation can trigger states highly similar to DPDR in phenomenology, but they’re often considered more welcome, pleasant, and spiritually meaningful than those triggered by trauma, stress, or cannabis—though distress is not uncommon in the meditation context. The findings suggest that contemplative approaches could inform clinical support for DPDR, while also underscoring the need for recognition and guidance within meditation settings.

Executing precise actions and perceiving them as one’s own is a fundamental ability underlying the sense of agency (SoA). The SoA thereby heavily relies on the accuracy and reliability of forward models, capturing sensory movement consequences. Impairments thereof thus represent a promising candidate mechanism contributing to cases of SoA pathogenesis. In obsessive-compulsive disorder (OCD), for example, the feeling of control over one’s actions is perturbed: Compulsive actions are often experienced as uncontrollable and performed without conscious awareness. At the same time, compulsions can be coupled with an inflated sense of illusory control for uncontrollable events. Here we studied self-action perception in virtual reality with and without veridical or rotated visual feedback about subjects’ pointing movements to test whether patients’ internal forward models are indeed less reliable compared to controls. Interestingly, OCD patients did not exhibit deficits in their accuracy and reliability of motor performance and self-action perception in the absence of visual feedback, suggesting intact forward models. Nonetheless, OCD patients weighted rotated visual action-feedback significantly stronger perceptually. Furthermore, they adapted their movement to this false feedback on a trial-by-trial basis. Finally, increasing the social relevance of action consequences led to stronger feedback weighting in all participants while this effect increased with the strength of OCD symptomatology under conditions with strongest social relevance. We suggest that internal forward models are equally reliable in OCD but their weight is pathologically decreased leading to patients’ overreliance on explicit visual action-feedback and, more generally, to their over-attribution of unrelated events to themselves.

When lying inside a MRI scanner and even in the absence of any motion, the static magnetic field of MRI scanners induces a magneto-hydrodynamic stimulation of subjects’ vestibular organ (MVS). MVS thereby 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 3 T 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, which were statistically no longer detectable after 7 min. 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.

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.

Delusions of control in schizophrenia are characterized by the striking feeling that one’s actions are controlled by external forces. We here tested qualitative predictions inspired by Bayesian causal inference models, which suggest that such misattributions of agency should lead to decreased intentional binding. Intentional binding refers to the phenomenon that subjects perceive a compression of time between their intentional actions and consequent sensory events. We demonstrate that patients with delusions of control perceived less self-agency in our intentional binding task. This effect was accompanied by significant reductions of intentional binding as compared to healthy controls and patients without delusions. Furthermore, the strength of delusions of control tightly correlated with decreases in intentional binding. Our study validated a critical prediction of Bayesian accounts of intentional binding, namely that a pathological reduction of the prior likelihood of a causal relation between one’s actions and consequent sensory events—here captured by delusions of control—should lead to lesser intentional binding. Moreover, our study highlights the import of an intact perception of temporal contiguity between actions and their effects for the sense of agency.