Biology subjects

Rasch, B.

Publications and source records attributed to Rasch, B..

7 recordsLinked to original sources

bioRxiv2018

The effect of dream report collection and dream incorporation on memory consolidation during sleep

Waking up during the night to collect dream reports is a commonly used method to study dreams. This method has also been applied in studies on the relationship between dreams and memory consolidation. However, it is unclear if these awakenings influence ongoing memory consolidation processes. Furthermore, only few studies have examined if task incorporation into dreams is related to enhanced performance in the task. Here we compare memory performance in a word-picture association learning task after a night with (up to six awakenings) and without awakenings in 22 young and healthy participants. We then examine if the task is successfully incorporated into the dreams and if this incorporation is related to the task performance the next morning. We show that while the awakenings impair both subjective and objective sleep quality, these awakenings did not impair ongoing memory consolidation during sleep. When dreams were collected during the night by awakenings, memories of the learning task were successfully incorporated into dreams. No incorporation occurred in dreams collected only in the morning. Task incorporation into NREM sleep dreams, but not REM sleep dreams showed a relationship with task performance the next morning.\n\nWe conclude that the method of awakenings to collect dream reports is suitable for dream and memory studies, and is even crucial to uncover task incorporations. Furthermore, our study suggests that dreams in NREM rather than REM sleep might be related to processes of memory consolidation during sleep.

neuroscience↗

bioRxiv2018

Quantification of Phase-Amplitude Coupling in Neuronal Oscillations: Comparison of Phase-Locking Value, Mean Vector Length, and Modulation Index

Phase-amplitude coupling is a promising construct to study cognitive processes in electroencephalography (EEG) and magnetencephalography (MEG). Due to the novelty of the concept, various measures are used in the literature to calculate phase-amplitude coupling. Here, performance of the three most widely used phase-amplitude coupling measures - phase-locking value (PLV), mean vector length (MVL), and modulation index (MI) - is thoroughly compared with the help of simulated data. We combine advantages of previous reviews and use a realistic data simulation, examine moderators and provide inferential statistics for the comparison of all three indices of phase-amplitude coupling. Our analyses show that all three indices successfully differentiate coupling strength and coupling width when monophasic coupling is present. While the mean vector length was most sensitive to modulations in coupling strengths and width, biphasic coupling can solely be detected by the modulation index. Coupling values of all three indices were influenced by moderators including data length, signal-to-noise-ratio, and sampling rate when approaching Nyquist frequencies. The modulation index was most robust against confounding influences of these moderators. Based on our analyses, we recommend the modulation index for noisy and short data epochs with unknown forms of coupling. For high quality and long data epochs with monophasic coupling and a high signal-to-noise ratio, the use of the mean vector length is recommended. Ideally, both indices are reported simultaneously for one data set.\n\nHighlightsO_LImean vector length is most sensitive for differentiating coupling strength\nC_LIO_LImodulation index is most robust to differences in data length, sampling rate and SNR\nC_LIO_LIphase-locking value and mean vector length cannot detect biphasic phase-amplitude coupling\nC_LI

neuroscience↗

bioRxiv2018

Improving night-time sleep with hypnotic suggestions

Slow-wave sleep (SWS) is fundamental for maintaining our health and well-being, and SWS is typically reduced in stress-related sleep disturbances and age-related sleep disorders. We have previously reported that exposure to hypnotic suggestions before sleep effectively increases the duration of SWS during a midday nap in younger and older women suggestible for hypnosis.\n\nHowever, it remains unclear whether this beneficial effect of hypnosis on SWS can be generalized to night-time sleep and men. Therefore, we tested the effect of the hypnotic suggestions on SWS across an 8 hours night-time sleeping interval in 43 healthy young French-speaking subjects (19 males) of high and low suggestibility. In accordance with our previous results, listening to hypnotic suggestions before sleep increased the amount of SWS in highly suggestible subjects significantly by 13 min compared to a control condition in both genders. Particularly in the first hour, slow-wave activity was significantly increased after hypnosis as compared to the control night in high suggestible. The hypnosis-induced benefits on objective sleep parameters were also reflected in increased subjective sleep quality ratings. Our results demonstrate that hypnotic suggestions are an effective tool to deepen sleep and improve sleep quality also across a whole night of sleep in young healthy men and women. Our findings provide an important basis for the examination and potential application of hypnosis to improve deep sleep in populations with sleep disturbances.

neuroscience↗

bioRxiv2018

Youth-like Precision of Slow Oscillation-Spindle Coupling Promotes Memory Consolidation Across the Adult Lifespan

Memory consolidation during sleep relies on the precisely timed interaction of rhythmic neural events. Here, we investigate differences in slow oscillations (SO) and sleep spindles (SP) and their coupling across the adult human lifespan and ask whether observed alterations relate to the ability to retain associative memories across sleep. We demonstrate that the fine-tuned SO-SP coupling that is present in younger adults diffuses with advanced age and shifts both in time and frequency. Crucially, we show that the tight precision of SO-SP coupling promotes memory consolidation in younger and older adults, and that brain integrity in source regions for the generation of SOs and SPs reinforces this beneficial SO-SP coupling in old age. Our results reveal age-related differences in SO-SP coupling in healthy elderly individuals. Furthermore, they broaden our understanding of the conditions and the functional significance of SO-SP coupling across the entire adult lifespan.

neuroscience↗

bioRxiv2017

Reactivating vocabularies in the elderly

Quality of memory and sleep decline with age, but the mechanistic interactions underlying the memory function of sleep in older adults are still unknown. It is widely assumed that the beneficial effect of sleep on memory relies on reactivation during Non-rapid eye movement (NREM) sleep, and targeting these reactivations by cue re-exposure reliably improves memory in younger participants. Here we tested whether the reactivation mechanism during sleep is still functional in old age by applying targeted memory reactivation (TMR) during NREM sleep in healthy adults over 60 years. In contrast to previous studies in young participants, older adults memories do not generally benefit from TMR during NREM sleep. On an individual level, a subgroup of older adults still profited from cueing during sleep. These improvers tended to have a better sleep efficiency than non-improvers. In addition, the oscillatory results resembled those obtained in younger participants, involving increases in theta (~6Hz) and spindle (~13 Hz) power for remembered and gained words in a later time windows. In contrast, non-improvers showed no increases in theta activity and even strongly reduced spindle power for later gained vs. lost words. Our results suggest that reactivations during sleep might lose their functionality for memory in some older adults, while this mechanism is still intact in a subgroup of participants. Further studies need to examine more closely the determinants of preserving the memory function of sleep during healthy aging.\n\nGrant informationThe study was supported by grant of the Swiss National Science Foundation (SNSF) No. 100014_162388. T.S. is supported by a grant of the Swiss National Science Foundation (SNSF) No. P2ZHP1_164994.\n\nAbbreviations

neuroscience↗

bioRxiv2017

Theta phase coordinated memory reactivation reoccurs in a slow-oscillatory rhythm during NREM sleep

It has been proposed that sleeps contribution to memory consolidation is to reactivate prior encoded information. To elucidate the neural mechanisms carrying reactivation-related mnemonic information, we investigated whether content-specific memory signatures associated with memory reactivation during wakefulness reoccur during subsequent sleep. We show that theta oscillations orchestrate the reactivation of memories, irrespective of the physiological state. Reactivation patterns during sleep autonomously re-emerged at a rate of 1 Hz, indicating a coordination by slow oscillatory activity.

neuroscience↗

bioRxiv2017

Cueing memory during sleep is optimal during slow-oscillatory up-states

Slow oscillations play a major role in neural plasticity. It is assumed that slow oscillatory up-states represent crucial time windows for memory reactivation and consolidation during sleep. Here we experimentally tested this assumption by utilizing closed-loop targeted memory reactivation (closed-loop TMR): Healthy participants were re-exposed to prior learned foreign vocabulary during up- and down-states of slow oscillations, respectively, in a within-subject design. We show that presenting memory cues during slow oscillatory up-states robustly improves recall performance, whereas memory cueing during down-states did not result in a clear behavioral benefit. On a neural basis successful memory reactivation during up-states was associated with a characteristic power increase in the theta and sleep spindle band. Such increases were completely absent for down-state memory cues. Our findings provide experimental support for the assumption that slow oscillatory up-states represent privileged time windows for memory reactivation, while the interplay of slow oscillations, theta and sleep spindle activity promote successful memory consolidation during sleep.

neuroscience↗