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Wang ZJ, Lee HC, Chuang CH, Hsiao FC, Lee SH, Hsu AL, Wu CW. Traces of EEG-fMRI coupling reveals neurovascular dynamics on sleep inertia. Sci Rep 2024; 14:1537. [PMID: 38233587 PMCID: PMC10794702 DOI: 10.1038/s41598-024-51694-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 01/08/2024] [Indexed: 01/19/2024] Open
Abstract
Upon emergence from sleep, individuals experience temporary hypo-vigilance and grogginess known as sleep inertia. During the transient period of vigilance recovery from prior nocturnal sleep, the neurovascular coupling (NVC) may not be static and constant as assumed by previous neuroimaging studies. Stemming from this viewpoint of sleep inertia, this study aims to probe the NVC changes as awakening time prolongs using simultaneous EEG-fMRI. The time-lagged coupling between EEG features of vigilance and BOLD-fMRI signals, in selected regions of interest, was calculated with one pre-sleep and three consecutive post-awakening resting-state measures. We found marginal changes in EEG theta/beta ratio and spectral slope across post-awakening sessions, demonstrating alterations of vigilance during sleep inertia. Time-varying EEG-fMRI coupling as awakening prolonged was evidenced by the changing time lags of the peak correlation between EEG alpha-vigilance and fMRI-thalamus, as well as EEG spectral slope and fMRI-anterior cingulate cortex. This study provides the first evidence of potential dynamicity of NVC occurred in sleep inertia and opens new avenues for non-invasive neuroimaging investigations into the neurophysiological mechanisms underlying brain state transitions.
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Affiliation(s)
- Zhitong John Wang
- Graduate Institute of Mind, Brain and Consciousness, Taipei Medical University, 5 Floor, 301, Yuantong Rd., Zhonghe Dist, New Taipei, 235040, Taiwan
| | - Hsin-Chien Lee
- Department of Psychiatry, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
- Research Center of Sleep Medicine, Taipei Medical University Hospital, Taipei, Taiwan
| | - Chun-Hsiang Chuang
- Research Center for Education and Mind Sciences, College of Education, National Tsing Hua University, Hsinchu, Taiwan
| | - Fan-Chi Hsiao
- Department of Counseling, Clinical and Industrial/Organizational Psychology, Ming Chuan University, Taoyuan, Taiwan
| | - Shwu-Hua Lee
- Department of Psychiatry, Chang Gung Memorial Hospital at Linkou, 259, Wenhua 1St Rd., Guishan Dist., Taoyuan, 33302, Taiwan
- School of Medicine, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Ai-Ling Hsu
- Department of Psychiatry, Chang Gung Memorial Hospital at Linkou, 259, Wenhua 1St Rd., Guishan Dist., Taoyuan, 33302, Taiwan.
- Bachelor Program in Artificial Intelligence, Chang Gung University, Taoyuan, Taiwan.
| | - Changwei W Wu
- Graduate Institute of Mind, Brain and Consciousness, Taipei Medical University, 5 Floor, 301, Yuantong Rd., Zhonghe Dist, New Taipei, 235040, Taiwan.
- Research Center of Sleep Medicine, Taipei Medical University Hospital, Taipei, Taiwan.
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Caporale AS, Barclay AM, Xu J, Rao H, Lee H, Langham MC, Detre JA, Wehrli FW. Superior sagittal sinus flow as a proxy for tracking global cerebral blood flow dynamics during wakefulness and sleep. J Cereb Blood Flow Metab 2023; 43:1340-1350. [PMID: 36927172 PMCID: PMC10369151 DOI: 10.1177/0271678x231164423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 01/18/2023] [Accepted: 02/10/2023] [Indexed: 03/18/2023]
Abstract
Sleep, a state of reduced consciousness, affects brain oxygen metabolism and lowers cerebral metabolic rate of oxygen (CMRO2). Previously, we quantified CMRO2 during sleep via Fick's Principle, with a single-band MRI sequence measuring both hemoglobin O2 saturation (SvO2) and superior sagittal sinus (SSS) blood flow, which was upscaled to obtain total cerebral blood flow (tCBF). The procedure involves a brief initial calibration scan to determine the upscaling factor (fc), assumed state-invariant. Here, we used a dual-band sequence to simultaneously provide SvO2 in SSS and tCBF in the neck every 16 seconds, allowing quantification of fc dynamically. Ten healthy subjects were scanned by MRI with simultaneous EEG for 80 minutes, yielding 300 temporal image frames per subject. Four volunteers achieved slow-wave sleep (SWS), as evidenced by increased δ-wave activity (per American Academy of Sleep Medicine criteria). SWS was maintained for 13.5 ± 7.0 minutes, with CMRO2 28.6 ± 5.5% lower than pre-sleep wakefulness. Importantly, there was negligible bias between tCBF obtained by upscaling SSS-blood flow, and tCBF measured directly in the inflowing arteries of the neck (intra-class correlation 0.95 ± 0.04, averaged across all subjects), showing that the single-band approach is a valid substitute for quantifying tCBF, simplifying image data collection and analysis without sacrificing accuracy.
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Affiliation(s)
- Alessandra S Caporale
- Laboratory for Structural, Physiological, and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Neuroscience, Imaging and Clinical Sciences, ‘G. d’Annunzio University’ of Chieti-Pescara, Chieti, Italy
- Institute for Advanced Biomedical Technologies (ITAB), ‘G. d’Annunzio University’ of Chieti-Pescara, Chieti, Italy
| | - Alexander M Barclay
- Laboratory for Structural, Physiological, and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jing Xu
- Laboratory for Structural, Physiological, and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Hengyi Rao
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Division of Sleep and Chronobiology, Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Hyunyeol Lee
- Laboratory for Structural, Physiological, and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- School of Electronics Engineering, Kyungpook National University, Daegu, South Korea
| | - Michael C Langham
- Laboratory for Structural, Physiological, and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - John A Detre
- Laboratory for Structural, Physiological, and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Felix W Wehrli
- Laboratory for Structural, Physiological, and Functional Imaging, Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Lee WJ, Jung KH, Park HM, Sohn CH, Lee ST, Park KI, Chu K, Jung KY, Kim M, Lee SK, Roh JK. Periodicity of cerebral flow velocity during sleep and its association with white-matter hyperintensity volume. Sci Rep 2019; 9:15510. [PMID: 31664128 PMCID: PMC6820785 DOI: 10.1038/s41598-019-52029-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 10/11/2019] [Indexed: 11/12/2022] Open
Abstract
Impaired sleep-related activation of the cerebral waste-clearance system might be related with the brain aging process. We hypothesized that cerebral blood-flow pattern changes during sleep might reflect the activation of the cerebral waste-clearance system and investigated its association with the cerebral white-matter hyperintensity (WMH) volume. Fifty healthy volunteers were prospectively recruited. In addition to the baseline transcranial Doppler parameters, the mean flow velocity (MFV) of the middle cerebral artery was monitored during waking and short-term non-REM sleep. Spectral density analysis was performed to analyze the periodic MFV variation patterns. For the aged subgroup (>50 years, n = 25), the WMH volumes in the total, subcortical, and periventricular regions were measured. The MFV periodic pattern during sleep was substantially augmented over that in the waking status. Spectral density analysis of MFV showed a noticeable peak in the very-low–frequency (VLF) band during sleep status (sleep/waking ratio 2.87 ± 2.71, P < 0.001). In linear regression analysis in the aged subgroup, the sleep/waking ratio of the VLF peak was inversely associated with total (P = 0.013) and subcortical (P = 0.020) WMH volumes. Sleep-related amplification of the cerebral flow-velocity periodicity might reflect the activation of cerebral waste clearance system during sleep, and be related to the pathogenesis of cerebral WMH.
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Affiliation(s)
- Woo-Jin Lee
- Department of Neurology, Seoul National University Hospital, Seoul, South Korea
| | - Keun-Hwa Jung
- Department of Neurology, Seoul National University Hospital, Seoul, South Korea.
| | - Hyun-Min Park
- Department of Neurology, Seoul National University Hospital, Seoul, South Korea
| | - Chul-Ho Sohn
- Department of Radiology, Seoul National University Hospital, Seoul, South Korea
| | - Soon-Tae Lee
- Department of Neurology, Seoul National University Hospital, Seoul, South Korea
| | - Kyung-Il Park
- Department of Neurology, Seoul National University Hospital, Seoul, South Korea.,Department of Neurology, Seoul National University Healthcare System Gangnam Center, Seoul, South Korea
| | - Kon Chu
- Department of Neurology, Seoul National University Hospital, Seoul, South Korea
| | - Ki-Young Jung
- Department of Neurology, Seoul National University Hospital, Seoul, South Korea
| | - Manho Kim
- Department of Neurology, Seoul National University Hospital, Seoul, South Korea.,Protein Metabolism Research Center, Seoul National University College of Medicine, Seoul, South Korea
| | - Sang Kun Lee
- Department of Neurology, Seoul National University Hospital, Seoul, South Korea
| | - Jae-Kyu Roh
- Department of Neurology, The Armed Forces Capital Hospital, Sungnam, South Korea
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Perdomo SJ, Balzer JR, Jakicic JM, Kline CE, Gibbs BB. Acute effects of aerobic exercise duration on blood pressure, pulse wave velocity and cerebral blood flow velocity in middle-aged adults. Sport Sci Health 2019. [DOI: 10.1007/s11332-019-00566-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Meghdadi AH, Popovic D, Rupp G, Smith S, Berka C, Verma A. Transcranial Impedance Changes during Sleep: A Rheoencephalography Study. IEEE J Transl Eng Health Med 2019; 7:2700107. [PMID: 30867999 PMCID: PMC6404797 DOI: 10.1109/jtehm.2019.2898193] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 12/24/2018] [Accepted: 01/23/2019] [Indexed: 02/03/2023]
Abstract
OBJECTIVE To demonstrate the utility of rheoencephalography (REG) for measuring cerebral blood flow and fluid dynamics during different stages of sleep. METHODS Anteroposterior cranial electrical impedance was measured with concurrent polysomnography in a group of healthy subjects during sleep. Transcranial electrical impedance was characterized by measuring the peak-to-trough and envelope of the filtered pulsative REG signal as well as its frequency. The sensitivity of the REG amplitude to changes in cerebral blood flow (CBF) was confirmed by the analysis of the signal during breathing maneuvers with known effects on CBF. The mean amplitude and variability of the REG characteristic parameters were averaged across all participants and were compared between different stages of sleep. RESULTS Average transcranial impedance was significantly lower during non-REM stages N1 and N2, compared to other sleep stages, suggesting a decrease in CBF volume. Stage N3 showed the slowest frequency indicating a slow heart rate during this stage. N3 also had the lowest variability in frequency and peak-to-trough amplitude. CONCLUSION Measurement of transcranial electrical conductivity may be a viable non-invasive method for monitoring any potential changes in intracranial fluid homeostasis. Clinical Impact: In the absence of other convenient non-invasive methods, using REG to track intracranial fluid dynamics during sleep can facilitate an improved understanding of pathogenesis in Alzheimer's disease.
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Affiliation(s)
| | | | - Gregory Rupp
- Advanced Brain Monitoring, Inc.CarlsbadCA92008USA
| | | | - Chris Berka
- Advanced Brain Monitoring, Inc.CarlsbadCA92008USA
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Abstract
The nonrapid eye movement (NREM) parasomnias range from age-related developmental phenomena in children to aggressive and injurious motor behaviors in all age groups. These parasomnias are commonly referred to as disorders of arousal and are an important cause of sleep-related injury. Genetic predisposition plays a role in the disorders of arousal, most evident in sleepwalking. Important concepts guiding our current understanding of the pathophysiology of the NREM parasomnias include sleep state instability (a propensity for arousal during NREM sleep), sleep inertia (incomplete awakening from NREM sleep), state dissociation (an ability to simultaneously straddle both NREM sleep and wakefulness), and activation of central pattern generators (permitting expression of subcortically determined motor behaviors without conscious higher cortical input). Management is multifaceted with an emphasis on education and nonpharmacologic measures. The purpose of this chapter is to review wake and NREM neurobiology and update our current understanding of NREM parasomnia pathophysiology, epidemiology, genetics, clinical features, precipitating factors, neurophysiologic evaluation, diagnosis, and clinical management.
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Affiliation(s)
- Carlos L Rodriguez
- Cleveland Clinic Sleep Disorders Center, Neurological Institute, Cleveland, OH, United States.
| | - Nancy Foldvary-Schaefer
- Cleveland Clinic Sleep Disorders Center, Neurological Institute, Cleveland, OH, United States
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Abstract
Sleep inertia, or the grogginess felt upon awakening, is associated with significant cognitive performance decrements that dissipate as time awake increases. This impairment in cognitive performance has been observed in both tightly controlled in-laboratory studies and in real-world scenarios. Further, these decrements in performance are exaggerated by prior sleep loss and the time of day in which a person awakens. This review will examine current insights into the causes of sleep inertia, factors that may positively or negatively influence the degree of sleep inertia, the consequences of sleep inertia both in the laboratory and in real-world settings, and lastly discuss potential countermeasures to lessen the impact of sleep inertia.
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Affiliation(s)
- Cassie J Hilditch
- Fatigue Countermeasures Laboratory, San Jose State University Research Foundation, Moffett Field, San Jose, CA 94035, USA
| | - Andrew W McHill
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, Portland, OR 97239, USA
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Elvsåshagen T, Mutsaerts HJ, Zak N, Norbom LB, Quraishi SH, Pedersen PØ, Malt UF, Westlye LT, van Someren EJ, Bjørnerud A, Groote IR. Cerebral blood flow changes after a day of wake, sleep, and sleep deprivation. Neuroimage 2018; 186:497-509. [PMID: 30471387 DOI: 10.1016/j.neuroimage.2018.11.032] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Revised: 11/01/2018] [Accepted: 11/20/2018] [Indexed: 10/27/2022] Open
Abstract
Elucidating the neurobiological effects of sleep and wake is an important goal of the neurosciences. Whether and how human cerebral blood flow (CBF) changes during the sleep-wake cycle remain to be clarified. Based on the synaptic homeostasis hypothesis of sleep and wake, we hypothesized that a day of wake and a night of sleep deprivation would be associated with gray matter resting CBF (rCBF) increases and that sleep would be associated with rCBF decreases. Thirty-eight healthy adult males (age 22.1 ± 2.5 years) underwent arterial spin labeling perfusion magnetic resonance imaging at three time points: in the morning after a regular night's sleep, the evening of the same day, and the next morning, either after total sleep deprivation (n = 19) or a night of sleep (n = 19). All analyses were adjusted for hematocrit and head motion. rCBF increased from morning to evening and decreased after a night of sleep. These effects were most prominent in bilateral hippocampus, amygdala, thalamus, and in the occipital and sensorimotor cortices. Group × time interaction analyses for evening versus next morning revealed significant interaction in bilateral lateral and medial occipital cortices and in bilateral insula, driven by rCBF increases in the sleep deprived individuals and decreases in the sleepers, respectively. Furthermore, group × time interaction analyses for first morning versus next morning showed significant effects in medial and lateral occipital cortices, in anterior cingulate gyrus, and in the insula, in both hemispheres. These effects were mainly driven by CBF increases from TP1 to TP3 in the sleep deprived individuals. There were no associations between the rCBF changes and sleep characteristics, vigilant attention, or subjective sleepiness that remained significant after adjustments for multiple analyses. Altogether, these results encourage future studies to clarify mechanisms underlying sleep-related rCBF changes.
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Affiliation(s)
- Torbjørn Elvsåshagen
- Norwegian Centre for Mental Disorders Research (NORMENT), KG Jebsen Centre for Psychosis Research, Oslo University Hospital, Norway; Department of Neurology, Oslo University Hospital, Norway; Institute of Clinical Medicine, University of Oslo, Norway.
| | - Henri Jmm Mutsaerts
- Cognitive Neurology Research Unit, Sunnybrook Health Sciences Centre, Toronto, Canada; Department of Radiology, Amsterdam University Medical Center, the Netherlands
| | - Nathalia Zak
- Norwegian Centre for Mental Disorders Research (NORMENT), KG Jebsen Centre for Psychosis Research, Oslo University Hospital, Norway
| | - Linn B Norbom
- Norwegian Centre for Mental Disorders Research (NORMENT), KG Jebsen Centre for Psychosis Research, Oslo University Hospital, Norway
| | | | - Per Ø Pedersen
- Institute of Clinical Medicine, University of Oslo, Norway
| | - Ulrik F Malt
- Institute of Clinical Medicine, University of Oslo, Norway; Department of Research and Education, Oslo University Hospital, Norway
| | - Lars T Westlye
- Norwegian Centre for Mental Disorders Research (NORMENT), KG Jebsen Centre for Psychosis Research, Oslo University Hospital, Norway; Department of Psychology, University of Oslo, Norway
| | - Eus Jw van Someren
- Department of Sleep and Cognition, Netherlands Institute for Neuroscience, Amsterdam, the Netherlands; Department of Psychiatry, Amsterdam University Medical Center, the Netherlands; Department of Integrative Neurophysiology, Amsterdam University Medical Center, the Netherlands
| | - Atle Bjørnerud
- Department of Psychology, University of Oslo, Norway; Department of Physics, University of Oslo, Norway; The Intervention Center, Oslo University Hospital, Norway
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Trotti LM. Waking up is the hardest thing I do all day: Sleep inertia and sleep drunkenness. Sleep Med Rev 2017; 35:76-84. [PMID: 27692973 DOI: 10.1016/j.smrv.2016.08.005] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 04/28/2016] [Accepted: 08/23/2016] [Indexed: 11/24/2022]
Abstract
The transition from sleep to wake is marked by sleep inertia, a distinct state that is measurably different from wakefulness and manifests as performance impairments and sleepiness. Although the precise substrate of sleep inertia is unknown, electroencephalographic, evoked potential, and neuroimaging studies suggest the persistence of some features of sleep beyond the point of awakening. Forced desynchrony studies have demonstrated that sleep inertia impacts cognition differently than do homeostatic and circadian drives and that sleep inertia is most intense during awakenings from the biological night. Recovery sleep after sleep deprivation also amplifies sleep inertia, although the effects of deep sleep vary based on task and timing. In patients with hypersomnolence disorders, especially but not exclusively idiopathic hypersomnia, a more pronounced period of confusion and sleepiness upon awakening, known as "sleep drunkenness", is common and problematic. Optimal treatment of sleep drunkenness is unknown, although several medications have been used with benefit in small case series. Difficulty with awakening is also commonly endorsed by individuals with mood disorders, disproportionately to the general population. This may represent an important treatment target, but evidence-based treatment guidance is not yet available.
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Gorgoni M, Ferrara M, D'atri A, Lauri G, Scarpelli S, Truglia I, De Gennaro L. EEG topography during sleep inertia upon awakening after a period of increased homeostatic sleep pressure. Sleep Med 2015; 16:883-90. [PMID: 26004680 DOI: 10.1016/j.sleep.2015.03.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 02/11/2015] [Accepted: 03/13/2015] [Indexed: 02/08/2023]
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Tsai PJ, Chen SCJ, Hsu CY, Wu CW, Wu YC, Hung CS, Yang AC, Liu PY, Biswal B, Lin CP. Local awakening: Regional reorganizations of brain oscillations after sleep. Neuroimage 2014; 102 Pt 2:894-903. [DOI: 10.1016/j.neuroimage.2014.07.032] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 06/21/2014] [Accepted: 07/18/2014] [Indexed: 12/11/2022] Open
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Metz AJ, Pugin F, Huber R, Achermann P, Wolf M. Brain Tissue Oxygen Saturation Increases During the Night in Adolescents. Oxygen Transport to Tissue XXXV 2013; 789:113-119. [DOI: 10.1007/978-1-4614-7411-1_16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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Pierro ML, Sassaroli A, Bergethon PR, Ehrenberg BL, Fantini S. Phase-amplitude investigation of spontaneous low-frequency oscillations of cerebral hemodynamics with near-infrared spectroscopy: a sleep study in human subjects. Neuroimage 2012; 63:1571-84. [PMID: 22820416 DOI: 10.1016/j.neuroimage.2012.07.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Revised: 05/24/2012] [Accepted: 07/10/2012] [Indexed: 11/25/2022] Open
Abstract
We have investigated the amplitude and phase of spontaneous low-frequency oscillations (LFOs) of the cerebral deoxy- and oxy-hemoglobin concentrations ([Hb] and [HbO]) in a human sleep study using near-infrared spectroscopy (NIRS). Amplitude and phase analysis was based on the analytic signal method, and phasor algebra was used to decompose measured [Hb] and [HbO] oscillations into cerebral blood volume (CBV) and flow velocity (CBFV) oscillations. We have found a greater phase lead of [Hb] vs. [HbO] LFOs during non-REM sleep with respect to the awake and REM sleep states (maximum increase in [Hb] phase lead: ~π/2). Furthermore, during non-REM sleep, the amplitudes of [Hb] and [HbO] LFOs are suppressed with respect to the awake and REM sleep states (maximum amplitude decrease: 87%). The associated cerebral blood volume and flow velocity oscillations are found to maintain their relative phase difference during sleep, whereas their amplitudes are attenuated during non-REM sleep. These results show the potential of phase-amplitude analysis of [Hb] and [HbO] oscillations measured by NIRS in the investigation of hemodynamics associated with cerebral physiology, activation, and pathological conditions.
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Affiliation(s)
- Michele L Pierro
- Department of Biomedical Engineering, Tufts University, Medford, MA, USA.
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Marzano C, Ferrara M, Moroni F, De Gennaro L. Electroencephalographic sleep inertia of the awakening brain. Neuroscience 2011; 176:308-17. [PMID: 21167917 DOI: 10.1016/j.neuroscience.2010.12.014] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Accepted: 12/10/2010] [Indexed: 02/08/2023]
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Affiliation(s)
- Viktor Hanak
- Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN 55905, USA.
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Abstract
STUDY OBJECTIVE To determine the effect of arousal from sleep on cerebral blood flow velocity (CBFV) in relation to associated ventilatory and systemic hemodynamic changes. PARTICIPANTS Eleven healthy individuals (6 men, 5 women). MEASUREMENTS Pulsed Doppler ultrasonography was used to measure CBFV in the middle cerebral artery with simultaneous measurements of sleep state (EEG, EOG, and EMG), ventilation (inductance plethysmography), heart rate (ECG), and arterial pressure (finger plethysmography). Arousals were induced by auditory tones (range: 40-80 dB; duration: 0.5 sec). Cardiovascular responses were examined beat-by-beat for 30 sec before and 30 sec after auditory tones. RESULTS During NREM sleep, CBFV declined following arousals (-15% +/- 2%; group mean +/- SEM) with a nadir at 9 sec after the auditory tone, followed by a gradual return to baseline. Mean arterial pressure (MAP; +20% +/- 1%) and heart rate (HR; +17% +/- 2%) increased with peaks at 5 and 3 sec after the auditory tone, respectively. Minute ventilation (VE) was increased (+35% +/- 10%) for 2 breaths after the auditory tone. In contrast, during REM sleep, CBFV increased following arousals (+15% +/- 3%) with a peak at 3 sec. MAP (+17% +/- 2%) and HR (+15% +/- 2%) increased during arousals from REM sleep with peaks at 5 and 3 sec post tone. VE increased (+16% +/- 7%) in a smaller, more sustained manner during arousals from REM sleep. CONCLUSIONS Arousals from NREM sleep transiently reduce CBFV, whereas arousals from REM sleep transiently increase CBFV, despite qualitatively and quantitatively similar increases in MAP, HR, and VE in the two sleep states.
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Affiliation(s)
| | | | | | | | | | - Barbara J. Morgan
- Orthopedics and Rehabilitation, University of Wisconsin-Madison and the Middleton Veterans Administration Hospital, Madison, WI
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Abstract
Previous studies of the maturation of periodic breathing cycle duration (PCD) with postnatal age in infants have yielded conflicting results. PCD is reported to fall in term infants over the first 6 mo postnatally, whereas in preterm infants PCD is reported either not to change or to fall. Contrary to measured values, use of a theoretical respiratory control model predicts PCD should increase with postnatal age. We re-examined this issue in a longitudinal study of 17 term and 22 preterm infants. PCD decreased exponentially from birth in both groups, reaching a plateau between 4 and 6 mo of age. In preterm infants, PCD fell from a mean of 18.3 s to 9.8 s [95% confidence interval (CI) is +/- 3.2 s]. In term infants, PCD fell from 15.4 s to 10.1 s (95% CI is +/- 3.1 s). The higher PCD at birth in preterm infants, and the similar PCD value at 6 mo in the two groups, suggest a more rapid maturation of PCD in preterm infants. This study confirms that PCD declines after birth. The disagreement between our data and theoretical predictions of PCD may point to important differences between the respiratory controller of the infant and adult.
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Affiliation(s)
- Malcolm H Wilkinson
- Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University, Clayton, Victoria, 3168, Australia.
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Cummings KJ, Swart M, Ainslie PN. Morning attenuation in cerebrovascular CO2 reactivity in healthy humans is associated with a lowered cerebral oxygenation and an augmented ventilatory response to CO2. J Appl Physiol (1985) 2007; 102:1891-8. [PMID: 17317869 DOI: 10.1152/japplphysiol.01437.2006] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We hypothesized that, in healthy subjects without pharmacological intervention, an overnight reduction in cerebrovascular CO2 reactivity would be associated with an elevated hypercapnic ventilatory [ventilation (V̇e)] responsiveness and a reduction in cerebral oxygenation. In 20 healthy male individuals with no sleep-related disorders, continuous recordings of blood velocity in the middle cerebral artery, arterial blood pressure, V̇e, end-tidal gases, and frontal cortical oxygenation using near infrared spectroscopy were monitored during hypercapnia (inspired CO2, 5%), hypoxia [arterial O2 saturation (SaO2) ∼84%], and during a 20-s breath hold to investigate the related responses to hypercapnia, hypoxia, and apnea, respectively. Measurements were conducted in the evening (6–8 PM) and in the early morning (6–8 AM). From evening to morning, the cerebrovascular reactivity to hypercapnia was reduced (5.3 ± 0.6 vs. 4.6 ± 1.1%/Torr; P < 0.05) and was associated with a reduced increase in cerebral oxygenation ( r = 0.39; P < 0.05) and an elevated morning hypercapnic V̇e response ( r = 0.54; P < 0.05). While there were no overnight changes in cerebrovascular reactivity or V̇e response to hypoxia, there was greater cerebral desaturation for a given SaO2 in the morning (AM, −0.45 ± 0.14 vs. PM, −0.35 ± 0.14%/SaO2; P < 0.05). Following the 20-s breath hold, in the morning, there was a smaller surge middle cerebral artery velocity and cerebral oxygenation ( P < 0.05 vs. PM). These data indicate that normal diurnal changes in the cerebrovascular response to CO2 influence the hypercapnic ventilatory response as well as the level of cerebral oxygenation during changes in arterial Pco2; this may be a contributing factor for diurnal changes in breathing stability and the high incidence of stroke in the morning.
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Ainslie PN, Burgess K, Subedi P, Burgess KR. Alterations in cerebral dynamics at high altitude following partial acclimatization in humans: wakefulness and sleep. J Appl Physiol (1985) 2007; 102:658-64. [PMID: 17053102 DOI: 10.1152/japplphysiol.00911.2006] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We tested the hypothesis that, following exposure to high altitude, cerebrovascular reactivity to CO2 and cerebral autoregulation would be attenuated. Such alterations may predispose to central sleep apnea at high altitude by promoting changes in brain Pco2 and thus breathing stability. We measured middle cerebral artery blood flow velocity (MCAv; transcranial Doppler ultrasound) and arterial blood pressure during wakefulness in conditions of eucapnia (room air), hypocapnia (voluntary hyperventilation), and hypercapnia (isooxic rebeathing), and also during non-rapid eye movement (stage 2) sleep at low altitude (1,400 m) and at high altitude (3,840 m) in five individuals. At each altitude, sleep was studied using full polysomnography, and resting arterial blood gases were obtained. During wakefulness and polysomnographic-monitored sleep, dynamic cerebral autoregulation and steady-state changes in MCAv in relation to changes in blood pressure were evaluated using transfer function analysis. High altitude was associated with an increase in central sleep apnea index (0.2 ± 0.4 to 20.7 ± 23.2 per hour) and an increase in mean blood pressure and cerebrovascular resistance during wakefulness and sleep. MCAv was unchanged during wakefulness, whereas there was a greater decrease during sleep at high altitude compared with low altitude (−9.1 ± 1.7 vs. −4.8 ± 0.7 cm/s; P < 0.05). At high altitude, compared with low altitude, the cerebrovascular reactivity to CO2 in the hypercapnic range was unchanged (5.5 ± 0.7 vs. 5.3 ± 0.7%/mmHg; P = 0.06), while it was lowered in the hypocapnic range (3.1 ± 0.7 vs. 1.9 ± 0.6%/mmHg; P < 0.05). Dynamic cerebral autoregulation was further reduced during sleep ( P < 0.05 vs. low altitude). Lowered cerebrovascular reactivity to CO2 and reduction in both dynamic cerebral autoregulation and MCAv during sleep at high altitude may be factors in the pathogenesis of breathing instability.
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Aittokallio T, Gyllenberg M, Polo O, Toivonen J, Virkki A. Model-Based Analysis of Mechanisms Responsible for Sleep-Induced Carbon Dioxide Differences. Bull Math Biol 2006; 68:315-41. [PMID: 16794933 DOI: 10.1007/s11538-005-9059-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This work describes a comprehensive mathematical model of the human respiratory control system which incorporates the central mechanisms for predicting sleep-induced changes in chemical regulation of ventilation. The model integrates four individual compartments for gas storage and exchange, namely alveolar air, pulmonary blood, tissue capillary blood, body tissues, and gas transport between them. An essential mechanism in the carbon dioxide transport is its dissociation into bicarbonate and acid, where a buffering mechanism through hemoglobin is used to prevent harmfully low pH levels. In the current model, we assume high oxygen levels and consider intracellular hydrogen ion concentration as the principal respiratory control variable. The resulting system of delayed differential equations is solved numerically. With an appropriate choice of key parameters, such as velocity of blood flow and gain of a non-linear controller function, the model provides steady-state results consistent with our experimental observations measured in subjects across sleep onset. Dynamic predictions from the model give new insights into the behaviour of the system in subjects with different buffering capacities and suggest novel hypotheses for future experimental and clinical studies.
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Affiliation(s)
- T Aittokallio
- Department of Mathematics, University of Turku, FIN-20014, Turku, and Department of Pulmonary Medicine, Tampere University Hospital, Finland
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21
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Abstract
During wakefulness, cerebral blood flow (CBF) is closely coupled to regional cerebral metabolism; however CBF is also strongly modulated by breathing, increasing in response to both hypercapnia and hypoxia. During stage III/IV non-rapid eye (NREM) sleep, cerebral metabolism and CBF decrease whilst the partial pressure of arterial CO2 increases due to a reduction in alveolar ventilation. The reduction in CBF during NREM sleep therefore occurs despite a relative state of hypercapnia. We have used transcranial Doppler ultrasound to determine middle cerebral artery velocity, as an index of CBF, and have determined that NREM sleep is associated with a reduction in the cerebrovascular response to hypercapnia. This reduction in reactivity would, at least in part, allow the observed reductions in CBF in this state. Similarly, we have observed that the CBF response to hypoxia is absent during stage III/IV NREM sleep. Nocturnal hypoxia and hypercapnia are major pathogenic factor associated with cardio-respiratory diseases. These marked changes in cerebrovascular control that occur during sleep suggest that the cerebral circulation may be particularly vulnerable to cardio-respiratory insults during this period.
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Affiliation(s)
- Douglas R Corfield
- Institute of Science and Technology in Medicine, School of Life Sciences, Keele University, Keele, UK.
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22
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Abstract
This paper reviews a novel hypothesis about the functions of slow wave sleep-the synaptic homeostasis hypothesis. According to the hypothesis, plastic processes occurring during wakefulness result in a net increase in synaptic strength in many brain circuits. The role of sleep is to downscale synaptic strength to a baseline level that is energetically sustainable, makes efficient use of gray matter space, and is beneficial for learning and memory. Thus, sleep is the price we have to pay for plasticity, and its goal is the homeostatic regulation of the total synaptic weight impinging on neurons. The hypothesis accounts for a large number of experimental facts, makes several specific predictions, and has implications for both sleep and mood disorders.
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Affiliation(s)
- Giulio Tononi
- Department of Psychiatry, University of Wisconsin, 6001 Research Park Blvd., Madison, WI 53719, USA.
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Kotajima F, Meadows GE, Morrell MJ, Corfield DR. Cerebral blood flow changes associated with fluctuations in alpha and theta rhythm during sleep onset in humans. J Physiol 2005; 568:305-13. [PMID: 16002438 PMCID: PMC1474761 DOI: 10.1113/jphysiol.2005.092577] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 06/14/2005] [Accepted: 07/05/2005] [Indexed: 12/30/2022] Open
Abstract
Cerebral blood flow (CBF) is typically reduced during stable non-rapid eye movement (non-REM) sleep compared with the waking level. It is not known when in the sleep cycle these changes occur. However, spontaneous fluctuations in alpha and theta rhythm during sleep onset are associated with marked changes in cardio-respiratory control. The aim of this study was to test the hypothesis that changes in CBF would occur during sleep onset and would be related to changes in cortical activity. Middle cerebral artery velocity (MCAV) was measured using transcranial Doppler ultrasound, as an index of CBF, in 10 healthy subjects. Sleep state, ventilation, end tidal carbon dioxide (PET,CO2), arterial oxygen saturation (SaO2), mean arterial blood pressure (MABP) and cardiac R-R interval (RR) were monitored simultaneously. Immediately following the transition from alpha to theta rhythm (the transition from wake to sleep), ventilation decreased by 13.4% and tidal volume (VT) by 12.2% (P<0.01); PET,CO2 increased by 1.9% (P<0.01); respiratory frequency (fR) and SaO2 did not change significantly. MCAV increased by 9.7% (P<0.01); MABP decreased by 3.2% (P<0.01) but RR did not change significantly. Immediately following the transition from theta to alpha rhythm (spontaneous awakening), increased by 13.3% (P<0.01); VT increased by 11.4% (P<0.01); PET,CO2 decreased by 1.9% (P<0.01); MCAV decreased by 11.1% (P<0.01) and MABP decreased by 7.5%; fR, SaO2 and RR did not change significantly. These changes in MCAV during sleep onset cannot be attributed to changes in ventilation or MABP. We speculate that the changes in cerebral vascular tone during sleep onset are mediated neurally, by regulatory mechanisms linked to the changes in cortical state, and that these mechanisms are different from those regulating the longer-term reduction in CBF associated with stable non-REM sleep.
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24
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Abstract
BACKGROUND: CBFV (cerebral blood flow velocity) is lower in the morning than in the afternoon and evening. Two hypotheses have been proposed to explain the time of day changes in CBFV: 1) CBFV changes are due to sleep-associated processes or 2) time of day changes in CBFV are due to an endogenous circadian rhythm independent of sleep. The aim of this study was to examine CBFV over 30 hours of sustained wakefulness to determine whether CBFV exhibits fluctuations associated with time of day. METHODS: Eleven subjects underwent a modified constant routine protocol. CBFV from the middle cerebral artery was monitored by chronic recording of Transcranial Doppler (TCD) ultrasonography. Other variables included core body temperature (CBT), end-tidal carbon dioxide (EtCO2), blood pressure, and heart rate. Salivary dim light melatonin onset (DLMO) served as a measure of endogenous circadian phase position. RESULTS: A non-linear multiple regression, cosine fit analysis revealed that both the CBT and CBFV rhythm fit a 24 hour rhythm (R2 = 0.62 and R2 = 0.68, respectively). Circadian phase position of CBT occurred at 6:05 am while CBFV occurred at 12:02 pm, revealing a six hour, or 90 degree difference between these two rhythms (t = 4.9, df = 10, p < 0.01). Once aligned, the rhythm of CBFV closely tracked the rhythm of CBT as demonstrated by the substantial correlation between these two measures (r = 0.77, p < 0.01). CONCLUSION: In conclusion, time of day variations in CBFV have an approximately 24 hour rhythm under constant conditions, suggesting regulation by a circadian oscillator. The 90 degree-phase angle difference between the CBT and CBFV rhythms may help explain previous findings of lower CBFV values in the morning. The phase difference occurs at a time period during which cognitive performance decrements have been observed and when both cardiovascular and cerebrovascular events occur more frequently. The mechanisms underlying this phase angle difference require further exploration.
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Affiliation(s)
- Deirdre A Conroy
- Department of Psychology, The Graduate School and University Center of the City University of New York, New York, USA
| | - Arthur J Spielman
- Department of Psychology, The Graduate School and University Center of the City University of New York, New York, USA
- Department of Neurology and Neuroscience, New York Presbyterian Hospital, New York, USA
| | - Rebecca Q Scott
- Department of Health Psychology, Albert Einstein Medical College at Yeshiva University, Bronx, USA
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Abstract
We assume that alertness should be highest at the end of a sleep episode: it is not. There is always sleep inertia upon awakening, which can last minutes to hours, and whose underlying physiological mechanisms are largely unknown. Previously, we had found a functional relationship between the degree of distal vasodilatation (as measured by the distal-proximal skin temperature gradient (DPG) and sleepiness (as measured by subjective ratings), promoting rapid sleep onset. This led us to hypothesize that the dissipation of sleep inertia (sleepiness) would be associated with reverse thermoregulatory mechanisms, i.e. distal vasoconstriction. In two sets of experiments with either a nocturnal sleep episode (study 1) or an afternoon nap (study 2) we could show that vasodilatation of hands and feet increased after lights off and that this was reversed after lights on. The time course of the DPG was significantly and positively correlated with subjective sleepiness (KSS), reflecting similar temporal relationships in both studies 1 and 2. The extremities cooled at a rate very closely parallel to the decay of sleepiness [time constants for the exponential decline calculated for study 2: DPG, 0.286 +/- 0.048 h versus KSS, 0.332 +/- 0.050 h; NS], indicating redistribution of heat from the shell to the core during dissipation of sleepiness. There was no statistical evidence that the time course of sleep inertia and its thermophysiological correlates depend on sleep structure prior to awakening. The symmetry between the thermoregulatory processes initiating sleepiness and those dissipating it is striking. In order to directly test our hypothesis, further studies with thermophysiological interventions (e.g. cooling the extremities) are needed.
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Affiliation(s)
- Kurt Kräuchi
- Centre for Chronobiology, Psychiatric University Clinic, Basel, Switzerland.
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Meadows GE, Dunroy HMA, Morrell MJ, Corfield DR. Hypercapnic cerebral vascular reactivity is decreased, in humans, during sleep compared with wakefulness. J Appl Physiol (1985) 2003; 94:2197-202. [PMID: 12576408 DOI: 10.1152/japplphysiol.00606.2002] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During wakefulness, increases in the partial pressure of arterial CO(2) result in marked rises in cortical blood flow. However, during stage III-IV, non-rapid eye movement (NREM) sleep, and despite a relative state of hypercapnia, cortical blood flow is reduced compared with wakefulness. In the present study, we tested the hypothesis that, in normal subjects, hypercapnic cerebral vascular reactivity is decreased during stage III-IV NREM sleep compared with wakefulness. A 2-MHz pulsed Doppler ultrasound system was used to measure the left middle cerebral artery velocity (MCAV; cm/s) in 12 healthy individuals while awake and during stage III-IV NREM sleep. The end-tidal Pco(2) (Pet(CO(2))) was elevated during the awake and sleep states by regulating the inspired CO(2) load. The cerebral vascular reactivity to CO(2) was calculated from the relationship between Pet(CO(2)) and MCAV by using linear regression. From wakefulness to sleep, the Pet(CO(2)) increased by 3.4 Torr (P < 0.001) and the MCAV fell by 11.7% (P < 0.001). A marked decrease in cerebral vascular reactivity was noted in all subjects, with an average fall of 70.1% (P = 0.001). This decrease in hypercapnic cerebral vascular reactivity may, at least in part, explain the stage III-IV NREM sleep-related reduction in cortical blood flow.
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Affiliation(s)
- Guy E Meadows
- Department of Respiratory Medicine, National Heart and Lung Institute, Imperial College, Charing Cross Campus, London, W6 8RP, United Kingdom.
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27
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Abstract
Cerebral blood flow measurements during sleep are reviewed and discussed in relation to the different techniques utilized (Positron Emission Tomography, functional Magnetic Resonance Imaging, Flowmeters, Radioactive MicroIspheres, Brain Temperature Recordings, Spectrophotometry) since these methodological approaches aim at diverse features of circulation changes in the spatial or temporal domain. The regulation of cerebral circulation during sleep reveals no specific state-dependent features, flow-activity coupling being the prevailing mechanism, with O(2) as the primary candidate for the metabolic side of the link. On a general level, the latest data on brain circulation are compatible with the classical hypothesis of a "restorative" function of sleep processes.
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Affiliation(s)
- Giovanna Zoccoli
- Department of Human and General Physiology, University of Bologna, Piazza di Porta S. Donato, Italy
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Ferrara M, De Gennaro L, Ferlazzo F, Curcio G, Cristiani R, Bertini M. Topographical changes in N1-P2 amplitude upon awakening from recovery sleep after slow-wave sleep deprivation. Clin Neurophysiol 2002; 113:1183-90. [PMID: 12139996 DOI: 10.1016/s1388-2457(02)00146-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVES To assess auditory evoked potentials (AEPs) before sleep and upon 3 awakenings during an undisturbed baseline night and to compare them to AEPs during a night characterized by a recuperative increase in the amount of slow-wave sleep (SWS) as a consequence of two consecutive nights of selective SWS deprivation. METHODS Ten male subjects slept in the laboratory for 6 consecutive nights. The first 2 nights were undisturbed. The 3rd night was considered as baseline. During the 4th and 5th nights, selective SWS deprivation was obtained by means of acoustic stimulation. The 6th night was a recovery. The data reported here were collected during the baseline and the recovery night. Subjects were awakened 3 times: after 2 h, 5 h (nocturnal awakenings) and 7.5 h (final morning awakening) of sleep, respectively. All the awakenings were carried out from stage 2. The AEP recordings were carried out in bed, while subjects were performing a simple auditory reaction time task. RESULTS The amplitude of the N1-P2 complex decreased upon the first awakening of the baseline night as compared to pre-sleep wakefulness levels; during the recovery night, the decrease of N1-P2 amplitude was present also upon the second and final awakening. N1 latency increased upon the two nocturnal awakenings regardless of the night, while P2 latency was not affected. Moreover, the N1-P2 amplitude increased during recovery at the frontal midline derivation as compared to baseline, while it decreased at Pz and Oz. CONCLUSIONS The N1-P2 amplitude and, to a lesser extent, the N1 latency, are sensitive in showing a state of brain deactivation during the sleep-wake transition. The decrease of N1-P2 amplitude at the parieto-occipital locations during recovery is coherent with the hypothesis of a functional link between SWS amount and cortical hypoarousal upon awakening. The unexpected increase of the same variable at Fz can be interpreted as the effect of a compensatory effort of the frontal areas for the increased homeostatic drive for sleep during the recovery night.
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Affiliation(s)
- Michele Ferrara
- Department of Psychology, University of Rome La Sapienza, Via dei Marsi 78, Rome, Italy.
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Diamant M, Harms MPM, Immink RV, Van Lieshout JJ, Van Montfrans GA. Twenty-four-hour non-invasive monitoring of systemic haemodynamics and cerebral blood flow velocity in healthy humans. Acta Physiol Scand 2002; 175:1-9. [PMID: 11982498 DOI: 10.1046/j.1365-201x.2002.00953.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Acute short-term changes in blood pressure (BP) and cardiac output (CO) affect cerebral blood flow (CBF) in healthy subjects. As yet, however, we do not know how spontaneous fluctuations in BP and CO influence cerebral circulation throughout 24 h. We performed simultaneous monitoring of BP, systemic haemodynamic parameters and blood flow velocity in the middle cerebral artery (MCAV) in seven healthy subjects during a 24-h period. Finger BP was recorded continuously during 24 h by Portapres and bilateral MCAV was measured by transcranial Doppler (TCD) during the first 15 min of every hour. The subjects remained supine during TCD recordings and during the night, otherwise they were seated upright in bed. Stroke volume (SV), CO and total peripheral resistance (TPR) were determined by Modelflow analysis. The 15 min mean value of each parameter was assumed to represent the mean of the corresponding hour. There were no significant differences between right vs. left, nor between mean daytime vs. night time MCAV. Intrasubject comparison of the twenty-four 15-min MCAV recordings showed marked variations (P < 0.001). Within each single 15-min recording period, however, MCAV was stable whereas BP showed significant short-term variations (P < 0.01). A day-night difference in BP was only observed when daytime BP was evaluated from recordings in the seated position (P < 0.02), not in supine recordings. Throughout 24 h, MCAV was associated with SV and CO (P < 0.001), to a lesser extent with mean arterial pressure (MAP; P < 0.005), not with heart rate (HR) or TPR. These results indicate that in healthy subjects MCAV remains stable when measured under constant supine conditions but shows significant variations throughout 24 h because of activity. Moreover, changes in SV and CO, and to a lesser extent BP variations, affect MCAV throughout 24 h.
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Affiliation(s)
- M Diamant
- Department of Endocrinology, 'Vrije Universiteit' Medical Centre, Amsterdam, The Netherlands
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Hosking SL, Evans DW, Embleton SJ, Houde B, Amos JF, Bartlett JD. Hypercapnia invokes an acute loss of contrast sensitivity in untreated glaucoma patients. Br J Ophthalmol 2001; 85:1352-6. [PMID: 11673305 PMCID: PMC1723756 DOI: 10.1136/bjo.85.11.1352] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND/AIM It is widely accepted that hypercapnia results in increased retinal, choroidal, and retrobulbar blood flow. Reports of a visual response to hypercapnia appear mixed, with normal subjects exhibiting reduced temporal contrast sensitivity in some studies, while glaucoma patients demonstrate mid-peripheral visual field improvements in others. This suggests that under hypercapnic conditions a balance exists between the beneficial effects of improved ocular blood flow and some other factor such as induced metabolic stress; the outcome may be influenced by the disease process. The aim of this study was to evaluate the contrast sensitivity response of untreated glaucoma patients and normal subjects during mild hypercapnia. METHODS 10 previously untreated glaucoma patients and 10 control subjects were evaluated for contrast sensitivity and intraocular pressure while breathing room air and then again during mild hypercapnia. RESULTS During room air breathing, compared with normal subjects, glaucoma patients had higher IOP (p = 0.0003) and lower contrast sensitivity at 3 cycles/degree (cpd) (p = 0.001). Mild hypercapnia caused a significant fall in contrast sensitivity at 6, 12, and 18 cpd (p < 0.05), only in the glaucoma group. CONCLUSION Glaucoma patients with early disease exhibit central vision deficits as shown by contrast sensitivity testing at 3 cpd. Hypercapnia induces further contrast loss through a range of spatial frequencies (6-18 cpd) which may be predictive of further neuronal damage due to glaucoma.
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Affiliation(s)
- S L Hosking
- Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
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Abstract
A recent, well-publicized case in which murder during sleepwalking was offered as a defense, underscores the fact that sleep medicine specialists are asked to render opinions or judgements regarding culpability in legal cases regarding violence claimed to have arisen from sleepwalking episodes. This review addresses this difficult issue from scientific, clinical and legal aspects, with emphasis upon the need for further research, calling for close collaboration between the legal and medical (both clinical and basic science) professions.
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Affiliation(s)
- Mark W. Mahowald
- Minnesota Regional Sleep Disorders Center, and Departments of Psychiatry (CHS) and Neurology (MWM), Hennepin County Medical Center and the University of Minnesota Medical School, Minneapolis, MN, USA
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Abstract
Impaired vasomotor reactivity of the cerebral vessels on morning awakening has been suggested as one of the mechanisms underlying the predisposition to stroke in the morning. This study investigated cerebrovascular reactivity to hypercapnia on morning awakening and its association with specific sleep-related parameters, including sleep-disordered breathing. Thirty patients undergoing nocturnal diagnostic polysomnography for sleep apnea underwent transcranial Doppler ultrasonography of the middle cerebral artery immediately before going to bed and immediately on morning awakening. Results indicated a morning reduction in cerebral blood flow velocity (CBFV) relative to values from the preceding evening both while breathing room air and 5% CO(2). Hypercapnia was associated with the expected increase in CBFV in both evening and morning. The evening-to-morning difference in CBFV during CO(2) inhalation was independently associated with both overnight CO(2) retention and number of movements with arousal per hour of sleep. Results indicated that more fragmented sleep and greater CO(2) retention during sleep predicted a diminished hypercapnic vasomotor response in the morning. Sleep fragmentation predicted approximately twice the variance in morning hypercapnic vasomotor reactivity relative to overnight CO(2) retention (24 versus 13%). No other polysomnographic measures predicted evening-to-morning differences in vasomotor reactivity. These results are consistent with a body of literature suggesting that sleep loss and sleep fragmentation are associated with blunted hypercapnic ventilatory response.
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Affiliation(s)
- A I Qureshi
- Sleep Disorders Center, Department of Neurology, Emory University Medical School, Atlanta, Georgia, USA
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Abstract
The study of sleep and dreams has enjoyed a major breakthrough with recent findings from brain imaging studies in humans. Several independent groups have shown global deactivation of the brain during non rapid eye movement sleep and a regionally selective reactivation during rapid eye movement sleep. These results are complemented by new brain lesion and electrophysiological recording data to give a detailed picture of the brain dynamics of changes in conscious state.
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Affiliation(s)
- J A Hobson
- Department of Psychiatry, Harvard Medical School, Massachusetts Mental Health Center, Boston 02115, USA.
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