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Zhang Y, Kim M, Prerau M, Mobley D, Rueschman M, Sparks K, Tully M, Purcell S, Redline S. The National Sleep Research Resource: making data findable, accessible, interoperable, reusable and promoting sleep science. Sleep 2024; 47:zsae088. [PMID: 38688470 DOI: 10.1093/sleep/zsae088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 03/15/2024] [Indexed: 05/02/2024] Open
Abstract
This paper presents a comprehensive overview of the National Sleep Research Resource (NSRR), a National Heart Lung and Blood Institute-supported repository developed to share data from clinical studies focused on the evaluation of sleep disorders. The NSRR addresses challenges presented by the heterogeneity of sleep-related data, leveraging innovative strategies to optimize the quality and accessibility of available datasets. It provides authorized users with secure centralized access to a large quantity of sleep-related data including polysomnography, actigraphy, demographics, patient-reported outcomes, and other data. In developing the NSRR, we have implemented data processing protocols that ensure de-identification and compliance with FAIR (Findable, Accessible, Interoperable, Reusable) principles. Heterogeneity stemming from intrinsic variation in the collection, annotation, definition, and interpretation of data has proven to be one of the primary obstacles to efficient sharing of datasets. Approaches employed by the NSRR to address this heterogeneity include (1) development of standardized sleep terminologies utilizing a compositional coding scheme, (2) specification of comprehensive metadata, (3) harmonization of commonly used variables, and (3) computational tools developed to standardize signal processing. We have also leveraged external resources to engineer a domain-specific approach to data harmonization. We describe the scope of data within the NSRR, its role in promoting sleep and circadian research through data sharing, and harmonization of large datasets and analytical tools. Finally, we identify opportunities for approaches for the field of sleep medicine to further support data standardization and sharing.
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Affiliation(s)
- Ying Zhang
- Division of Sleep Medicine and Circadian Disorders, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Matthew Kim
- Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Michael Prerau
- Division of Sleep Medicine and Circadian Disorders, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Daniel Mobley
- Division of Sleep Medicine and Circadian Disorders, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Michael Rueschman
- Division of Sleep Medicine and Circadian Disorders, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Kathryn Sparks
- Division of Sleep Medicine and Circadian Disorders, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Meg Tully
- Division of Sleep Medicine and Circadian Disorders, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Shaun Purcell
- Department of Psychiatry, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Susan Redline
- Division of Sleep Medicine and Circadian Disorders, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
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Alnes SL, Bächlin LZM, Schindler K, Tzovara A. Neural complexity and the spectral slope characterise auditory processing in wakefulness and sleep. Eur J Neurosci 2024; 59:822-841. [PMID: 38100263 DOI: 10.1111/ejn.16203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 10/11/2023] [Accepted: 11/10/2023] [Indexed: 12/17/2023]
Abstract
Auditory processing and the complexity of neural activity can both indicate residual consciousness levels and differentiate states of arousal. However, how measures of neural signal complexity manifest in neural activity following environmental stimulation and, more generally, how the electrophysiological characteristics of auditory responses change in states of reduced consciousness remain under-explored. Here, we tested the hypothesis that measures of neural complexity and the spectral slope would discriminate stages of sleep and wakefulness not only in baseline electroencephalography (EEG) activity but also in EEG signals following auditory stimulation. High-density EEG was recorded in 21 participants to determine the spatial relationship between these measures and between EEG recorded pre- and post-auditory stimulation. Results showed that the complexity and the spectral slope in the 2-20 Hz range discriminated between sleep stages and had a high correlation in sleep. In wakefulness, complexity was strongly correlated to the 20-40 Hz spectral slope. Auditory stimulation resulted in reduced complexity in sleep compared to the pre-stimulation EEG activity and modulated the spectral slope in wakefulness. These findings confirm our hypothesis that electrophysiological markers of arousal are sensitive to sleep/wake states in EEG activity during baseline and following auditory stimulation. Our results have direct applications to studies using auditory stimulation to probe neural functions in states of reduced consciousness.
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Affiliation(s)
- Sigurd L Alnes
- Institute of Computer Science, University of Bern, Bern, Switzerland
- Zentrum für Experimentelle Neurologie, Department of Neurology, Inselspital University Hospital Bern, Bern, Switzerland
| | - Lea Z M Bächlin
- Institute of Computer Science, University of Bern, Bern, Switzerland
| | - Kaspar Schindler
- Sleep-Wake-Epilepsy Center, NeuroTec, Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Athina Tzovara
- Institute of Computer Science, University of Bern, Bern, Switzerland
- Zentrum für Experimentelle Neurologie, Department of Neurology, Inselspital University Hospital Bern, Bern, Switzerland
- Sleep-Wake-Epilepsy Center, NeuroTec, Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Bódizs R, Schneider B, Ujma PP, Horváth CG, Dresler M, Rosenblum Y. Fundamentals of sleep regulation: Model and benchmark values for fractal and oscillatory neurodynamics. Prog Neurobiol 2024; 234:102589. [PMID: 38458483 DOI: 10.1016/j.pneurobio.2024.102589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 01/26/2024] [Accepted: 03/05/2024] [Indexed: 03/10/2024]
Abstract
Homeostatic, circadian and ultradian mechanisms play crucial roles in the regulation of sleep. Evidence suggests that ratios of low-to-high frequency power in the electroencephalogram (EEG) spectrum indicate the instantaneous level of sleep pressure, influenced by factors such as individual sleep-wake history, current sleep stage, age-related differences and brain topography characteristics. These effects are well captured and reflected in the spectral exponent, a composite measure of the constant low-to-high frequency ratio in the periodogram, which is scale-free and exhibits lower interindividual variability compared to slow wave activity, potentially serving as a suitable standardization and reference measure. Here we propose an index of sleep homeostasis based on the spectral exponent, reflecting the level of membrane hyperpolarization and/or network bistability in the central nervous system in humans. In addition, we advance the idea that the U-shaped overnight deceleration of oscillatory slow and fast sleep spindle frequencies marks the biological night, providing somnologists with an EEG-index of circadian sleep regulation. Evidence supporting this assertion comes from studies based on sleep replacement, forced desynchrony protocols and high-resolution analyses of sleep spindles. Finally, ultradian sleep regulatory mechanisms are indicated by the recurrent, abrupt shifts in dominant oscillatory frequencies, with spindle ranges signifying non-rapid eye movement and non-spindle oscillations - rapid eye movement phases of the sleep cycles. Reconsidering the indicators of fundamental sleep regulatory processes in the framework of the new Fractal and Oscillatory Adjustment Model (FOAM) offers an appealing opportunity to bridge the gap between the two-process model of sleep regulation and clinical somnology.
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Affiliation(s)
- Róbert Bódizs
- Institute of Behavioural Sciences, Semmelweis University, Budapest, Hungary.
| | - Bence Schneider
- Institute of Behavioural Sciences, Semmelweis University, Budapest, Hungary
| | - Péter P Ujma
- Institute of Behavioural Sciences, Semmelweis University, Budapest, Hungary
| | - Csenge G Horváth
- Institute of Behavioural Sciences, Semmelweis University, Budapest, Hungary
| | - Martin Dresler
- Radboud University Medical Centre, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
| | - Yevgenia Rosenblum
- Radboud University Medical Centre, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands
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Höhn C, Hahn MA, Lendner JD, Hoedlmoser K. Spectral Slope and Lempel-Ziv Complexity as Robust Markers of Brain States during Sleep and Wakefulness. eNeuro 2024; 11:ENEURO.0259-23.2024. [PMID: 38471778 PMCID: PMC10978822 DOI: 10.1523/eneuro.0259-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 01/22/2024] [Accepted: 02/09/2024] [Indexed: 03/14/2024] Open
Abstract
Nonoscillatory measures of brain activity such as the spectral slope and Lempel-Ziv complexity are affected by many neurological disorders and modulated by sleep. A multitude of frequency ranges, particularly a broadband (encompassing the full spectrum) and a narrowband approach, have been used especially for estimating the spectral slope. However, the effects of choosing different frequency ranges have not yet been explored in detail. Here, we evaluated the impact of sleep stage and task engagement (resting, attention, and memory) on slope and complexity in a narrowband (30-45 Hz) and broadband (1-45 Hz) frequency range in 28 healthy male human subjects (21.54 ± 1.90 years) using a within-subject design over 2 weeks with three recording nights and days per subject. We strived to determine how different brain states and frequency ranges affect slope and complexity and how the two measures perform in comparison. In the broadband range, the slope steepened, and complexity decreased continuously from wakefulness to N3 sleep. REM sleep, however, was best discriminated by the narrowband slope. Importantly, slope and complexity also differed between tasks during wakefulness. While narrowband complexity decreased with task engagement, the slope flattened in both frequency ranges. Interestingly, only the narrowband slope was positively correlated with task performance. Our results show that slope and complexity are sensitive indices of brain state variations during wakefulness and sleep. However, the spectral slope yields more information and could be used for a greater variety of research questions than Lempel-Ziv complexity, especially when a narrowband frequency range is used.
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Affiliation(s)
- Christopher Höhn
- Laboratory for Sleep, Cognition and Consciousness Research, Department of Psychology, University of Salzburg, 5020 Salzburg, Austria
- Centre for Cognitive Neuroscience Salzburg (CCNS), University of Salzburg, 5020 Salzburg, Austria
| | - Michael A Hahn
- Hertie-Institute for Clinical Brain Research, University Medical Center Tübingen, 72076 Tübingen, Germany
| | - Janna D Lendner
- Hertie-Institute for Clinical Brain Research, University Medical Center Tübingen, 72076 Tübingen, Germany
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Tübingen, 72076 Tübingen, Germany
| | - Kerstin Hoedlmoser
- Laboratory for Sleep, Cognition and Consciousness Research, Department of Psychology, University of Salzburg, 5020 Salzburg, Austria
- Centre for Cognitive Neuroscience Salzburg (CCNS), University of Salzburg, 5020 Salzburg, Austria
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Akbarian F, Rossi C, Costers L, D'hooghe MB, D'haeseleer M, Nagels G, Van Schependom J. The spectral slope as a marker of excitation/inhibition ratio and cognitive functioning in multiple sclerosis. Hum Brain Mapp 2023; 44:5784-5794. [PMID: 37672569 PMCID: PMC10619404 DOI: 10.1002/hbm.26476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 06/09/2023] [Accepted: 08/20/2023] [Indexed: 09/08/2023] Open
Abstract
Multiple sclerosis (MS) is a neurodegenerative disease characterized by neuronal and synaptic loss, resulting in an imbalance of excitatory and inhibitory synaptic transmission and potentially cognitive impairment. Current methods for measuring the excitation/inhibition (E/I) ratio are mostly invasive, but recent research combining neurocomputational modeling with measurements of local field potentials has indicated that the slope with which the power spectrum of neuronal activity captured by electro- and/or magnetoencephalography rolls off, is a non-invasive biomarker of the E/I ratio. A steeper roll-off is associated with a stronger inhibition. This novel method can be applied to assess the E/I ratio in people with multiple sclerosis (pwMS), detect the effect of medication such as benzodiazepines, and explore its utility as a biomarker for cognition. We recruited 44 healthy control subjects and 95 pwMS who underwent resting-state magnetoencephalographic recordings. The 1/f spectral slope of the neural power spectra was calculated for each subject and for each brain region. As expected, the spectral slope was significantly steeper in pwMS treated with benzodiazepines (BZDs) compared to pwMS not receiving BZDs (p = .01). In the sub-cohort of pwMS not treated with BZDs, we observed a steeper slope in cognitively impaired pwMS compared to cognitively preserved pwMS (p = .01) and healthy subjects (p = .02). Furthermore, we observed a significant correlation between 1/f spectral slope and verbal and spatial working memory functioning in the brain regions located in the prefrontal and parietal cortex. In this study, we highlighted the value of the spectral slope in MS by quantifying the effect of benzodiazepines and by putting it forward as a potential biomarker of cognitive deficits in pwMS.
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Affiliation(s)
- Fahimeh Akbarian
- Department of Electronics and Informatics (ETRO)Vrije Universiteit BrusselBrusselsBelgium
- AIMS LabCenter for Neurosciences, Vrije Universiteit BrusselBrusselsBelgium
| | - Chiara Rossi
- Department of Electronics and Informatics (ETRO)Vrije Universiteit BrusselBrusselsBelgium
- AIMS LabCenter for Neurosciences, Vrije Universiteit BrusselBrusselsBelgium
| | - Lars Costers
- AIMS LabCenter for Neurosciences, Vrije Universiteit BrusselBrusselsBelgium
- icometrixLeuvenBelgium
| | | | - Miguel D'haeseleer
- National MS Center MelsbroekMelsbroekBelgium
- Department of NeurologyUZ BrusselBrusselsBelgium
| | - Guy Nagels
- AIMS LabCenter for Neurosciences, Vrije Universiteit BrusselBrusselsBelgium
- Department of NeurologyUZ BrusselBrusselsBelgium
- St Edmund HallUniversity of OxfordOxfordUK
| | - Jeroen Van Schependom
- Department of Electronics and Informatics (ETRO)Vrije Universiteit BrusselBrusselsBelgium
- AIMS LabCenter for Neurosciences, Vrije Universiteit BrusselBrusselsBelgium
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Lendner JD, Niethard N, Mander BA, van Schalkwijk FJ, Schuh-Hofer S, Schmidt H, Knight RT, Born J, Walker MP, Lin JJ, Helfrich RF. Human REM sleep recalibrates neural activity in support of memory formation. SCIENCE ADVANCES 2023; 9:eadj1895. [PMID: 37624898 PMCID: PMC10456851 DOI: 10.1126/sciadv.adj1895] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 07/25/2023] [Indexed: 08/27/2023]
Abstract
The proposed mechanisms of sleep-dependent memory consolidation involve the overnight regulation of neural activity at both synaptic and whole-network levels. Now, there is a lack of in vivo data in humans elucidating if, and how, sleep and its varied stages balance neural activity, and if such recalibration benefits memory. We combined electrophysiology with in vivo two-photon calcium imaging in rodents as well as intracranial and scalp electroencephalography (EEG) in humans to reveal a key role for non-oscillatory brain activity during rapid eye movement (REM) sleep to mediate sleep-dependent recalibration of neural population dynamics. The extent of this REM sleep recalibration predicted the success of overnight memory consolidation, expressly the modulation of hippocampal-neocortical activity, favoring remembering rather than forgetting. The findings describe a non-oscillatory mechanism how human REM sleep modulates neural population activity to enhance long-term memory.
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Affiliation(s)
- Janna D. Lendner
- Hertie Institute for Clinical Brain Research, Center for Neurology, University Medical Center Tübingen, Hoppe-Seyler-Str 3, 72076 Tübingen, Germany
- Department of Anesthesiology and Intensive Care Medicine, University Medical Center Tübingen, Hoppe-Seyler-Str 3, 72076 Tübingen, Germany
| | - Niels Niethard
- Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen 72076, Germany
| | - Bryce A. Mander
- Department of Psychiatry and Human Behavior, UC Irvine, 101 The City Dr, Orange, CA 92868, USA
| | - Frank J. van Schalkwijk
- Hertie Institute for Clinical Brain Research, Center for Neurology, University Medical Center Tübingen, Hoppe-Seyler-Str 3, 72076 Tübingen, Germany
| | - Sigrid Schuh-Hofer
- Department of Neurophysiology, University Medical Center Mannheim, Ludolf-Krehl-Str. 13-17, 68167 Mannheim, Germany
- Department of Neurology and Epileptology, University Medical Center Tübingen, Hoppe-Seyler-Str 3, 72076 Tübingen, Germany
| | - Hannah Schmidt
- Department of Neurophysiology, University Medical Center Mannheim, Ludolf-Krehl-Str. 13-17, 68167 Mannheim, Germany
| | - Robert T. Knight
- Helen Wills Neuroscience Institute, UC Berkeley, 130 Barker Hall, CA 94720, USA
- Department of Psychology, UC Berkeley, 2121 Berkeley Way, CA 94720, USA
| | - Jan Born
- Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Tübingen 72076, Germany
- Center for Integrative Neuroscience, University of Tübingen, Tübingen 72076, Germany
- German Center for Diabetes Research (DZD), Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen (IDM), Tübingen 72076, Germany
| | - Matthew P. Walker
- Helen Wills Neuroscience Institute, UC Berkeley, 130 Barker Hall, CA 94720, USA
- Department of Psychology, UC Berkeley, 2121 Berkeley Way, CA 94720, USA
| | - Jack J. Lin
- Department of Neurology, UC Davis, 3160 Folsom Blvd., Sacramento, CA 95816, USA
- Center for Mind and Brain, UC Davis, 267 Cousteau Pl, Davis, CA 95618, USA
| | - Randolph F. Helfrich
- Hertie Institute for Clinical Brain Research, Center for Neurology, University Medical Center Tübingen, Hoppe-Seyler-Str 3, 72076 Tübingen, Germany
- Department of Neurology and Epileptology, University Medical Center Tübingen, Hoppe-Seyler-Str 3, 72076 Tübingen, Germany
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