Psychiatry Research Neuroimaging
November 1, 2001
Dietrich Lehmann, P.L Faber, Peter Achermann et al.
212 citations
EEG recordings from an advanced meditator showed that different meditation states—visualization, verbalization, and dissolution of self—activate distinct brain regions. Gamma-band (35–44 Hz) activity patterns differed significantly across four meditations. Visualization engaged the right posterior brain, verbalization the left central area, and self-dissolution involved right fronto-temporal regions. These findings align with known functional neuroanatomy and are discussed in relation to self-representation, reality testing, depersonalization disorders, and brain lesions.
Brain Topography
March 1, 2024
Sarah Diezig, Simone Denzer, Peter Achermann et al.
19 citations
During the transition to sleep, reflective awareness—the ability to recognize experiences as internally generated—breaks down before phenomenal awareness, the basic experience itself, fades. Dream-like experiences, characterized by uncontrolled thinking and perceptual images mistaken as real, are associated with an inverse relationship between cognitive effects and physiological activation in the brain. In 45 healthy young subjects, EEG microstate analysis showed that dream-like experiences correlated with increased presence of a microstate sourced in the superior and middle frontal gyrus and precuneus, and decreased presence of a microstate linked to higher-order visual areas. This suggests disengagement of cognitive control systems mediated by specific inhibitory microstates.
Mindfulness
July 1, 2023
Kanishka Sharma, Peter Achermann, Bhawna Panwar et al.
12 citations
During Brahma Kumaris Rajyoga meditation—a practice done with open eyes—long-term meditators show reduced delta and increased low alpha brain activity compared to resting. Source localization of EEG from 52 experienced meditators reveals that the meditation alters activation in the central executive, mirroring, task-positive, and task-negative networks. These changes correspond to attention modulation, self-related processing, visual imagery, and an extra-corporeal sense of being a soul in communion with a Supreme Soul. The findings suggest that seed-stage meditation involves distinct cognitive and affective processes, and future work should differentiate its stages.
European Journal of Neuroscience
September 11, 2024
Simone Denzer, Sarah Diezig, Peter Achermann et al.
6 citations
Monitoring whether an experience is real or not is crucial for everyday functioning, but this reality monitoring can go awry during dreams or hallucinations. To investigate brain processes underlying perceptual reality monitoring—the online assessment of reality during an experience—healthy young participants were immersed in a highly naturalistic virtual reality environment containing either realistic or dream-like bizarre elements. Dream-like bizarreness altered subjective experiences of reality and bizarreness and increased the contribution of a specific EEG microstate, labeled C'. This microstate is linked to suspending disbelief, or suppressing mismatches that seem bizarre. The findings suggest that prefrontal meta-conscious control processes are important for perceptual reality monitoring.
International journal of psychophysiology : official journal of the International Organization of Psychophysiology
June 1, 2023
Sarah Diezig, Melissa Spaar, Simone Denzer et al.
The ability to organize self-generated thought into coherent, meaningful semantic representations is a central aspect of human cognition and undergoes regular alterations throughout the day. To investigate whether changes in semantic processing might explain the loss of coherence, logic, and voluntary control over thinking typically accompanying the transition to sleep, N400 evoked potentials were recorded from 44 healthy subjects. Auditory word pairs with varying semantic distance were presented while subjects were allowed to fall asleep. Semantic distance reliably elicited an N400, and lower wakefulness levels were associated with increased frontal negativity. Contrary to the initial hypothesis, the results showed an increased N400 effect with decreasing wakefulness, suggesting that semantic processes alone may not explain diminished thought control during sleep onset.