Sleep advances : a journal of the Sleep Research Society最新文献

A central tenet of Freudian dream theory holds that there is thematic coherence within all dreams, even those containing scene and plot discontinuities. While other models support varying degrees of dream coherence, none address the question of how, or even whether, coherence can be identified in dreams with such discontinuities. Here, we objectively test the ability of judges to evaluate the coherence of individual dream narratives. Twenty reports with complete scene and plot discontinuities were collected, and half were cut apart at their discontinuities and their two halves spliced together with segments from dreams of other subjects. The remaining 10 reports were left intact. Judges correctly identified reports as intact or spliced only 57% of the time, a rate only slightly better than chance. Only 3 of the 20 reports, one intact and two spliced, were reliably scored correctly, while one intact report was mis-scored by 80% of the judges. Judges had no greater confidence in correct decisions than incorrect ones. Dream report features identified by the judges that were effectively used in scoring dreams included characters, locations and objects, while psychoanalytic content and writing style were least effectively used. In sum, we find no evidence that dream construction consistently results in identifiable thematic coherence. Rather, scene and plot discontinuities in many cases represent such complete breaks as to be unrecognizable. We conclude that the finding of continuity by those reading these reports reflects ineluctable synthetic activity in the mind of the dream researcher or analyst rather than in the mind of the dreamer. This paper is part of the Festschrift in honor of Dr. Robert Stickgold.

Model organisms such as Drosophila are powerful tools to study the genetic basis of sleep. Previously, we identified the genes pointed and Arginine kinase 1 using selective breeding for long and short sleep duration in an outbred population of Drosophila. pointed is a transcription factor that is part of the epidermal growth factor receptor signaling pathway, while Arginine kinase 1 is involved in proline and arginine metabolism. Conserved orthologs of these genes exist in mice, leading us to hypothesize that they would also impact sleep in a murine model. We generated mutations in the murine orthologs Ets1 and Ckm using CRISPR in a C57BL/6N background and used video analysis to measure sleep in the mice. Both mutations affected sleep parameters, and the effects were observed predominantly in female mice, with males showing fewer differences from littermate controls. The study of natural populations in flies therefore leads to candidate genes with functional conservation on sleep in mammals.

Study objectives: Sleep spindles, defining electroencephalographic oscillations of nonrapid eye movement (NREM) stage 2 sleep (N2), mediate sleep-dependent memory consolidation (SDMC). Spindles are also thought to protect sleep continuity by suppressing thalamocortical sensory relay. Schizophrenia is characterized by spindle deficits and a correlated reduction of SDMC. We investigated whether this relationship is mediated by sleep fragmentation.

Methods: We detected spindles (12-15 Hz) during N2 at central electrodes in overnight polysomnography records from 56 participants with chronic schizophrenia and 59 healthy controls. Our primary measures of sleep continuity were the sleep fragmentation index and, in a subset of the data, visually scored arousals. SDMC was measured as overnight improvement on the finger-tapping motor sequence task.

Results: Participants with schizophrenia showed reductions of both spindle density (#/min) and SDMC in the context of normal sleep continuity and architecture. Spindle density predicted SDMC in both groups. In contrast, neither increased sleep fragmentation nor arousals predicted lower spindle density or worse SDMC in either group.

Conclusions: Our findings fail to support the hypothesis that sleep fragmentation accounts for spindle deficits, impaired SDMC, or their relationship in individuals with chronic schizophrenia. Instead, our findings are consistent with the hypothesis that spindle deficits directly impair memory consolidation in schizophrenia. Since sleep continuity and architecture are intact in this population, research aimed at developing interventions should instead focus on understanding dysfunction within the thalamocortical-hippocampal circuitry that both generates spindles and synchronizes them with other NREM oscillations to mediate SDMC.

Study objectives: The complete blood count (CBC) is one of the most commonly ordered blood tests with a large range of reference values that does not consider time of day for interpretation. Our objective was to systematically review this topic to report on peak and trough timing of CBC values.

Methods: A systematic search was performed for studies evaluating any component of the CBC with at least three collections over 24 hours. The studies were screened based on the predetermined eligibility criteria. Meta-analysis of aggregated data was analyzed with polynomial functions and forest plots.

Results: In total, 164 full-text articles were screened and 32 included in the final analysis with 548 total patients considering either leukocytes (n = 13), erythrocytes (n = 7), hemoglobin (n = 5), hematocrit (n = 5), platelets (n = 12), neutrophils (n = 11), lymphocytes (n = 13), monocytes (n = 8), eosinophils (n = 15), or basophils (n = 9). CBC components were analyzed by polynomial and forest plot analysis. Lymphocytes fitted best to a third-degree polynomial function (p = .010) with peak at 2264.87 cells/µL at 23:54 (CI: 1783.44 to 2746.31) with a trough of 1598.91 cells/µL at 10:47 (CI: 1230.12 to 1967.71). Lymphocytes and eosinophils peaked overnight, while erythrocytes, hemoglobin, and hematocrit peaked in the morning, and platelets, neutrophils, monocytes, and basophils peaked in late afternoon. Limitations include small sample size and significant study heterogeneity.

Conclusion: We identified a limited scope of studies characterizing CBC component rhythms. However, we still noted significant differences, particularly with lymphocytes. Future work should evaluate larger datasets to inform time-dependent interpretation of the CBC as we move toward precision medicine.

Study objectives: Polysomnography (PSG) currently serves as the benchmark for evaluating sleep disorders. Its discomfort makes long-term monitoring unfeasible, leading to bias in sleep quality assessment. Hence, less invasive, cost-effective, and portable alternatives need to be explored. One promising contender is the in-ear-electroencephalography (EEG) sensor. This study aims to establish a methodology to assess the similarity between the single-channel in-ear-EEG and standard PSG derivations.

Methods: The study involves 4-hour signals recorded from 10 healthy subjects aged 18-60 years. Recordings are analyzed following two complementary approaches: (1) a hypnogram-based analysis aimed at assessing the agreement between PSG and in-ear-EEG-derived hypnograms; and (2) a feature- and analysis-based on time- and frequency-domain feature extraction, unsupervised feature selection, and definition of Feature-based Similarity Index via Jensen-Shannon Divergence (JSD-FSI).

Results: We find large variability between PSG and in-ear-EEG hypnograms scored by the same sleep expert according to Cohen's kappa metric, with significantly greater agreements for PSG scorers than for in-ear-EEG scorers (p < .001) based on Fleiss' kappa metric. On average, we demonstrate a high similarity between PSG and in-ear-EEG signals in terms of JSD-FSI-0.79 ± 0.06-awake, 0.77 ± 0.07-nonrapid eye movement, and 0.67 ± 0.10-rapid eye movement-and in line with the similarity values computed independently on standard PSG channel combinations.

Conclusions: In-ear-EEG is a valuable solution for home-based sleep monitoring; however, further studies with a larger and more heterogeneous dataset are needed.

Study objectives: The "Zeigarnik effect" refers to the phenomenon where future intentions are remembered effectively only as long as they are not executed. This study investigates whether these intentions, which remain active during sleep, influence dream content.

Methods: After an adaptation night, each of the 19 participants (10 women and 9 men) received three different task plans in the evening before the experimental night, each describing how to perform specific tasks. One of the task plans (completed) was then to be executed before the sleep period, another task (uncompleted) was told to be executed in the next morning, and on the third task (interrupted) participants were interrupted during the enactment before sleep and told to resume it the next morning. Polysomnography and multiple awakenings were conducted, resulting in 86 dream reports, 36 in NREM stage 2, and 50 in rapid eye movement sleep. After a traditional rating-based analysis of dream reports yielded inconsistent results, we analyzed the reports using a transformer-based assessment of dream incorporation, which quantified the semantic similarity between the dreams and pre-sleep tasks.

Results: The number of dreams showing above-criterion similarity to the respective task was significantly lower for the completed than the uncompleted or interrupted tasks (p < .05, χ² test). This pattern was confirmed through a forced choice approach, where-based on the similarity of single sentences of the dream reports-each dream report was allocated to one of the three task plans (p < 0.01, one-tailed χ² test).

Conclusions: Active intentions increase the likelihood of dream content being semantically similar to these intentions.

Over time, memories lose episodic detail and become distorted, a process with serious ramifications for eyewitness identification. What are the processes contributing to such transformations over time? We investigated the roles of post-learning sleep and retrieval practice in memory accuracy and distortion, using a naturalistic story recollection task. Undergraduate students listened to a recording of the "War of the Ghosts," a Native American folktale, and were assigned to either a sleep or wake delay group, and either a retrieval practice or listen-only study condition. We found higher accuracy after sleep compared to wake in the listen-only condition, but not in the retrieval practice condition. This effect was driven by participants in the wake, retrieval practice condition showing superior memory compared to the wake, listen-only condition. A similar pattern was found for memory distortion, with both sleep and retrieval practice being associated with more inferences of nonpresented, but story-related information, compared to the wake, listen-only condition. These findings suggest both sleep and retrieval practice contribute to narrative memory stabilization and distortion.

Sleep has been demonstrated to support memory formation from early life on. The precise temporal coupling of slow oscillations (SOs) with spindles has been suggested as a mechanism facilitating this consolidation process in thalamocortical networks. Here, we investigated the development of sleep spindles and SOs and their coordinate interplay by comparing frontal, central, and parietal electroencephalogram recordings during a nap between infants aged 2-3 months (n = 31) and toddlers aged 14-17 months (n = 49). Spindles and SOs showed quite different maturational patterns between age groups, as to topography, amplitude, and density. Notably, spindle-SO co-occurrence in the infants did not exceed chance levels and was increased to significant levels only in the toddlers. In the infants, the slow SO upstate over frontocortical regions was even associated with a significant decrease in spindles, contrasting with the adult-like increase in spindles seen in toddlers. These results point to an immature processing in thalamocortical networks during sleep in early infancy, possibly diminishing the efficacy of sleep-dependent memory formation at this age.

This is a personal review of a research life focused on sleep in everyday life. It finds that irregular work hours shorten sleep duration and increase sleepiness, both subjectively and objectively (polysomnography). Also, experimental lab studies demonstrate reduced sleep duration (and sleep stages N2 and REM) when sleep is moved into the daylight hours (and the circadian upswing). Stage N3% seems not affected, and homeostatic experiments suggest that awakenings should not occur until the need for N3% or total spectral power has been satisfied. Furthermore, sleepiness is associated with increased alpha activity and slow eye movements, although the best indicator of dangerous sleepiness is subjective ratings (linked to perceptions of heavy eye lids). Everyday stress has very modest negative effects on objective sleep quality. Sleep loss as well as excessive sleep durations are linked to mortality, but with modest risk, and mainly in older individuals. Finally, objective sleep poorly reflects subjective sleep quality, and women appear to report poorer sleep than men, while objective data show better sleep quality in women. The discrepancy is considerably greater in older age groups.

After describing my serendipitous discovery of sleep research as a potential career, I note how my openness and inquisitiveness led to a broad contribution to sleep science. After a PhD in biological psychology, I completed a postdoctoral fellowship in alcoholism and drug abuse. This led to my first studies on rebound insomnia. I then describe early studies on the relation of sleep continuity/sleep time to daytime sleepiness and function. This led to studies of how basal sleep time/sleepiness interacts with the effects of sedating and alerting drugs. Several collaborations led to studies on sleep and hot flashes in perimenopausal women and on sleep and acute and chronic pain.