1
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Le TT, Im GH, Lee CH, Choi SH, Kim SG. Mapping cerebral perfusion in mice under various anesthesia levels using highly sensitive BOLD MRI with transient hypoxia. SCIENCE ADVANCES 2024; 10:eadm7605. [PMID: 38416820 PMCID: PMC10901365 DOI: 10.1126/sciadv.adm7605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Accepted: 01/24/2024] [Indexed: 03/01/2024]
Abstract
Cerebral perfusion is critical for the early detection of neurological diseases and for effectively monitoring disease progression and treatment responses. Mouse models are widely used in brain research, often under anesthesia, which can affect vascular physiology. However, the impact of anesthesia on regional cerebral blood volume and flow in mice has not been thoroughly investigated. In this study, we have developed a whole-brain perfusion MRI approach by using a 5-second nitrogen gas stimulus under inhalational anesthetics to induce transient BOLD dynamic susceptibility contrast (DSC). This method proved to be highly sensitive, repeatable within each imaging session, and across four weekly sessions. Relative cerebral blood volumes measured by BOLD DSC agree well with those by contrast agents. Quantitative cerebral blood volume and flow metrics were successfully measured in mice under dexmedetomidine and various isoflurane doses using both total vasculature-sensitive gradient-echo and microvasculature-sensitive spin-echo BOLD MRI. Dexmedetomidine reduces cerebral perfusion, while isoflurane increases cerebral perfusion in a dose-dependent manner.
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Affiliation(s)
- Thuy Thi Le
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
- Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Republic of Korea
| | - Geun Ho Im
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, Republic of Korea
| | - Chan Hee Lee
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, Republic of Korea
| | - Sang Han Choi
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, Republic of Korea
| | - Seong-Gi Kim
- Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, Republic of Korea
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
- Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Republic of Korea
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2
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Buxton RB. Thermodynamic limitations on brain oxygen metabolism: physiological implications. J Physiol 2024; 602:683-712. [PMID: 38349000 DOI: 10.1113/jp284358] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 01/03/2024] [Indexed: 02/20/2024] Open
Abstract
Recent thermodynamic modelling indicates that maintaining the brain tissue ratio of O2 to CO2 (abbreviated tissue O2 /CO2 ) is critical for preserving the entropy increase available from oxidative metabolism of glucose, with a fall of that available entropy leading to a reduction of the phosphorylation potential and impairment of brain energy metabolism. This provides a novel perspective for understanding physiological responses under different conditions in terms of preserving tissue O2 /CO2 . To enable estimation of tissue O2 /CO2 in the human brain, a detailed mathematical model of O2 and CO2 transport was developed, and applied to reported physiological responses to different challenges, asking: how well is tissue O2 /CO2 preserved? Reported experimental results for increased neural activity, hypercapnia and hypoxia due to high altitude are consistent with preserving tissue O2 /CO2 . The results highlight two physiological mechanisms that control tissue O2 /CO2 : cerebral blood flow, which modulates tissue O2 ; and ventilation rate, which modulates tissue CO2 . The hypoxia modelling focused on humans at high altitude, including acclimatized lowlanders and Tibetan and Andean adapted populations, with a primary finding that decreasing CO2 by increasing ventilation rate is more effective for preserving tissue O2 /CO2 than increasing blood haemoglobin content to maintain O2 delivery to tissue. This work focused on the function served by particular physiological responses, and the underlying mechanisms require further investigation. The modelling provides a new framework and perspective for understanding how blood flow and other physiological factors support energy metabolism in the brain under a wide range of conditions. KEY POINTS: Thermodynamic modelling indicates that preserving the O2 /CO2 ratio in brain tissue is critical for preserving the entropy change available from oxidative metabolism of glucose and the phosphorylation potential underlying energy metabolism. A detailed model of O2 and CO2 transport was developed to allow estimation of the tissue O2 /CO2 ratio in the human brain in different physiological states. Reported experimental results during hypoxia, hypercapnia and increased oxygen metabolic rate in response to increased neural activity are consistent with maintaining brain tissue O2 /CO2 ratio. The hypoxia modelling of high-altitude acclimatization and adaptation in humans demonstrates the critical role of reducing CO2 with increased ventilation for preserving tissue O2 /CO2 . Preservation of tissue O2 /CO2 provides a novel perspective for understanding the function of observed physiological responses under different conditions in terms of preserving brain energy metabolism, although the mechanisms underlying these functions are not well understood.
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Affiliation(s)
- Richard B Buxton
- Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California, San Diego, California, USA
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3
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Bohraus Y, Merkle H, Logothetis NK, Goense J. Laminar differences in functional oxygen metabolism in monkey visual cortex measured with calibrated fMRI. Cell Rep 2023; 42:113341. [PMID: 37897728 DOI: 10.1016/j.celrep.2023.113341] [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: 04/26/2023] [Revised: 08/23/2023] [Accepted: 10/10/2023] [Indexed: 10/30/2023] Open
Abstract
Blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) of cortical layers relies on the hemodynamic response and is biased toward large veins on the cortical surface. Functional changes in the cerebral metabolic rate of oxygen (ΔCMRO2) may reflect neural cortical function better than BOLD fMRI, but it is unknown whether the calibrated BOLD model for functional CMRO2 measurement remains valid at high resolution. Here, we measure laminar ΔCMRO2 elicited by visual stimulation in macaque primary visual cortex (V1) and find that ΔCMRO2 peaks in the middle of the cortex, in agreement with autoradiographic measures of metabolism. ΔCMRO2 values in gray matter are similar as found previously. Reductions in CMRO2 are associated with veins at the cortical surface, suggesting that techniques for vein removal may improve the accuracy of the model at very high resolution. However, our results show feasibility of laminar ΔCMRO2 measurement, providing a physiologically meaningful metric of laminar functional metabolism.
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Affiliation(s)
- Yvette Bohraus
- Department of Physiology of Cognitive Processes, Max-Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany
| | | | - Nikos K Logothetis
- Department of Physiology of Cognitive Processes, Max-Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany; Department of Physiology of Cognitive Processes, International Center for Primate Brain Research, Songjiang District, Shanghai 201602, China; Centre for Imaging Sciences, University of Manchester, Manchester M13 9PT, UK
| | - Jozien Goense
- Department of Physiology of Cognitive Processes, Max-Planck Institute for Biological Cybernetics, 72076 Tübingen, Germany; Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA; Department of Psychology, University of Illinois, Urbana-Champaign, Champaign, IL 61820, USA; Department of Bioengineering, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA; Neuroscience Program, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA.
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4
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Theriault JE, Shaffer C, Dienel GA, Sander CY, Hooker JM, Dickerson BC, Barrett LF, Quigley KS. A functional account of stimulation-based aerobic glycolysis and its role in interpreting BOLD signal intensity increases in neuroimaging experiments. Neurosci Biobehav Rev 2023; 153:105373. [PMID: 37634556 PMCID: PMC10591873 DOI: 10.1016/j.neubiorev.2023.105373] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 07/28/2023] [Accepted: 08/23/2023] [Indexed: 08/29/2023]
Abstract
In aerobic glycolysis, oxygen is abundant, and yet cells metabolize glucose without using it, decreasing their ATP per glucose yield by 15-fold. During task-based stimulation, aerobic glycolysis occurs in localized brain regions, presenting a puzzle: why produce ATP inefficiently when, all else being equal, evolution should favor the efficient use of metabolic resources? The answer is that all else is not equal. We propose that a tradeoff exists between efficient ATP production and the efficiency with which ATP is spent to transmit information. Aerobic glycolysis, despite yielding little ATP per glucose, may support neuronal signaling in thin (< 0.5 µm), information-efficient axons. We call this the efficiency tradeoff hypothesis. This tradeoff has potential implications for interpretations of task-related BOLD "activation" observed in fMRI. We hypothesize that BOLD "activation" may index local increases in aerobic glycolysis, which support signaling in thin axons carrying "bottom-up" information, or "prediction error"-i.e., the BIAPEM (BOLD increases approximate prediction error metabolism) hypothesis. Finally, we explore implications of our hypotheses for human brain evolution, social behavior, and mental disorders.
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Affiliation(s)
- Jordan E Theriault
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA.
| | - Clare Shaffer
- Northeastern University, Department of Psychology, Boston, MA, USA
| | - Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Little Rock, AR, USA; Department of Cell Biology and Physiology, University of New Mexico, Albuquerque, NM, USA
| | - Christin Y Sander
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Jacob M Hooker
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Bradford C Dickerson
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA; Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Lisa Feldman Barrett
- Northeastern University, Department of Psychology, Boston, MA, USA; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA; Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Karen S Quigley
- Northeastern University, Department of Psychology, Boston, MA, USA; VA Bedford Healthcare System, Bedford, MA, USA
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5
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Turner MP, Zhao Y, Abdelkarim D, Liu P, Spence JS, Hutchison JL, Sivakolundu DK, Thomas BP, Hubbard NA, Xu C, Taneja K, Lu H, Rypma B. Altered linear coupling between stimulus-evoked blood flow and oxygen metabolism in the aging human brain. Cereb Cortex 2022; 33:135-151. [PMID: 35388407 PMCID: PMC9758587 DOI: 10.1093/cercor/bhac057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 01/13/2022] [Accepted: 01/14/2022] [Indexed: 11/14/2022] Open
Abstract
Neural-vascular coupling (NVC) is the process by which oxygen and nutrients are delivered to metabolically active neurons by blood vessels. Murine models of NVC disruption have revealed its critical role in healthy neural function. We hypothesized that, in humans, aging exerts detrimental effects upon the integrity of the neural-glial-vascular system that underlies NVC. To test this hypothesis, calibrated functional magnetic resonance imaging (cfMRI) was used to characterize age-related changes in cerebral blood flow (CBF) and oxygen metabolism during visual cortex stimulation. Thirty-three younger and 27 older participants underwent cfMRI scanning during both an attention-controlled visual stimulation task and a hypercapnia paradigm used to calibrate the blood-oxygen-level-dependent signal. Measurement of stimulus-evoked blood flow and oxygen metabolism permitted calculation of the NVC ratio to assess the integrity of neural-vascular communication. Consistent with our hypothesis, we observed monotonic NVC ratio increases with increasing visual stimulation frequency in younger adults but not in older adults. Age-related changes in stimulus-evoked cerebrovascular and neurometabolic signal could not fully explain this disruption; increases in stimulus-evoked neurometabolic activity elicited corresponding increases in stimulus-evoked CBF in younger but not in older adults. These results implicate age-related, demand-dependent failures of the neural-glial-vascular structures that comprise the NVC system.
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Affiliation(s)
- Monroe P Turner
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA,Center for BrainHealth, University of Texas at Dallas, Dallas, TX, 75235, USA
| | - Yuguang Zhao
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA,Center for BrainHealth, University of Texas at Dallas, Dallas, TX, 75235, USA
| | - Dema Abdelkarim
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA,Center for BrainHealth, University of Texas at Dallas, Dallas, TX, 75235, USA
| | - Peiying Liu
- Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD 21287, USA
| | - Jeffrey S Spence
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA,Center for BrainHealth, University of Texas at Dallas, Dallas, TX, 75235, USA
| | - Joanna L Hutchison
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA,Center for BrainHealth, University of Texas at Dallas, Dallas, TX, 75235, USA
| | - Dinesh K Sivakolundu
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA,Department of Biological Sciences, University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Binu P Thomas
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
| | - Nicholas A Hubbard
- Department of Psychology, Center for Brain, Biology, and Behavior, University of Nebraska, Lincoln, NE 68588, USA
| | - Cuimei Xu
- Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD 21287, USA
| | - Kamil Taneja
- Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD 21287, USA
| | - Hanzhang Lu
- Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD 21287, USA
| | - Bart Rypma
- Corresponding author: School of Behavioral and Brain Sciences, Center for Brain Health, University of Texas at Dallas, 800 West Campbell Road, Richardson, TX 75080, USA.
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6
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Herculano-Houzel S, Rothman DL. From a Demand-Based to a Supply-Limited Framework of Brain Metabolism. Front Integr Neurosci 2022; 16:818685. [PMID: 35431822 PMCID: PMC9012138 DOI: 10.3389/fnint.2022.818685] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 01/10/2022] [Indexed: 12/20/2022] Open
Abstract
What defines the rate of energy use by the brain, as well as per neurons of different sizes in different structures and animals, is one fundamental aspect of neuroscience for which much has been theorized, but very little data are available. The prevalent theories and models consider that energy supply from the vascular system to different brain regions is adjusted both dynamically and in the course of development and evolution to meet the demands of neuronal activity. In this perspective, we offer an alternative view: that regional rates of energy use might be mostly constrained by supply, given the properties of the brain capillary network, the highly stable rate of oxygen delivery to the whole brain under physiological conditions, and homeostatic constraints. We present evidence that these constraints, based on capillary density and tissue oxygen homeostasis, are similar between brain regions and mammalian species, suggesting they derive from fundamental biophysical limitations. The same constraints also determine the relationship between regional rates of brain oxygen supply and usage over the full physiological range of brain activity, from deep sleep to intense sensory stimulation, during which the apparent uncoupling of blood flow and oxygen use is still a predicted consequence of supply limitation. By carefully separating "energy cost" into energy supply and energy use, and doing away with the problematic concept of energetic "demands," our new framework should help shine a new light on the neurovascular bases of metabolic support of brain function and brain functional imaging. We speculate that the trade-offs between functional systems and even the limitation to a single attentional spot at a time might be consequences of a strongly supply-limited brain economy. We propose that a deeper understanding of brain energy supply constraints will provide a new evolutionary understanding of constraints on brain function due to energetics; offer new diagnostic insight to disturbances of brain metabolism; lead to clear, testable predictions on the scaling of brain metabolic cost and the evolution of brains of different sizes; and open new lines of investigation into the microvascular bases of progressive cognitive loss in normal aging as well as metabolic diseases.
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Affiliation(s)
- Suzana Herculano-Houzel
- Department of Psychology, Vanderbilt University, Nashville, TN, United States,Department of Biological Sciences, Vanderbilt University, Nashville, TN, United States,Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, United States,*Correspondence: Suzana Herculano-Houzel,
| | - Douglas L. Rothman
- Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States,Department of Biomedical Engineering, Yale University, New Haven, CT, United States,Magnetic Resonance Research Center, Yale University, New Haven, CT, United States
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7
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Buxton RB. The thermodynamics of thinking: connections between neural activity, energy metabolism and blood flow. Philos Trans R Soc Lond B Biol Sci 2020; 376:20190624. [PMID: 33190604 DOI: 10.1098/rstb.2019.0624] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Several current functional neuroimaging methods are sensitive to cerebral metabolism and cerebral blood flow (CBF) rather than the underlying neural activity itself. Empirically, the connections between metabolism, flow and neural activity are complex and somewhat counterintuitive: CBF and glycolysis increase more than seems to be needed to provide oxygen and pyruvate for oxidative metabolism, and the oxygen extraction fraction is relatively low in the brain and decreases when oxygen metabolism increases. This work lays a foundation for the idea that this unexpected pattern of physiological changes is consistent with basic thermodynamic considerations related to metabolism. In the context of this thermodynamic framework, the apparent mismatches in metabolic rates and CBF are related to preserving the entropy change of oxidative metabolism, specifically the O2/CO2 ratio in the mitochondria. However, the mechanism supporting this CBF response is likely not owing to feedback from a hypothetical O2 sensor in tissue, but rather is consistent with feed-forward control by signals from both excitatory and inhibitory neural activity. Quantitative predictions of the thermodynamic framework, based on models of O2 and CO2 transport and possible neural drivers of CBF control, are in good agreement with a wide range of experimental data, including responses to neural activation, hypercapnia, hypoxia and high-altitude acclimatization. This article is part of the theme issue 'Key relationships between non-invasive functional neuroimaging and the underlying neuronal activity'.
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Affiliation(s)
- Richard B Buxton
- Department of Radiology, University of California San Diego, 9500 Gilman Drive, MC 0677, La Jolla, CA 92093-0677, USA
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8
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Englund EK, Fernández-Seara MA, Rodríguez-Soto AE, Lee H, Rodgers ZB, Vidorreta M, Detre JA, Wehrli FW. Calibrated fMRI for dynamic mapping of CMRO 2 responses using MR-based measurements of whole-brain venous oxygen saturation. J Cereb Blood Flow Metab 2020; 40:1501-1516. [PMID: 31394960 PMCID: PMC7308517 DOI: 10.1177/0271678x19867276] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Functional MRI (fMRI) can identify active foci in response to stimuli through BOLD signal fluctuations, which represent a complex interplay between blood flow and cerebral metabolic rate of oxygen (CMRO2) changes. Calibrated fMRI can disentangle the underlying contributions, allowing quantification of the CMRO2 response. Here, whole-brain venous oxygen saturation (Yv) was computed alongside ASL-measured CBF and BOLD-weighted data to derive the calibration constant, M, using the proposed Yv-based calibration. Data were collected from 10 subjects at 3T with a three-part interleaved sequence comprising background-suppressed 3D-pCASL, 2D BOLD-weighted, and single-slice dual-echo GRE (to measure Yv via susceptometry-based oximetry) acquisitions while subjects breathed normocapnic/normoxic, hyperoxic, and hypercapnic gases, and during a motor task. M was computed via Yv-based calibration from both hypercapnia and hyperoxia stimulus data, and results were compared to conventional hypercapnia or hyperoxia calibration methods. Mean M in gray matter did not significantly differ between calibration methods, ranging from 8.5 ± 2.8% (conventional hyperoxia calibration) to 11.7 ± 4.5% (Yv-based calibration in response to hyperoxia), with hypercapnia-based M values between (p = 0.56). Relative CMRO2 changes from finger tapping were computed from each M map. CMRO2 increased by ∼20% in the motor cortex, and good agreement was observed between the conventional and proposed calibration methods.
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Affiliation(s)
- Erin K Englund
- Laboratory for Structural, Physiologic and Functional Imaging (LSPFI), Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Ana E Rodríguez-Soto
- Laboratory for Structural, Physiologic and Functional Imaging (LSPFI), Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Hyunyeol Lee
- Laboratory for Structural, Physiologic and Functional Imaging (LSPFI), Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Zachary B Rodgers
- Laboratory for Structural, Physiologic and Functional Imaging (LSPFI), Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA.,Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Marta Vidorreta
- Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA.,Siemens Healthineers, Madrid, Spain
| | - John A Detre
- Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA
| | - Felix W Wehrli
- Laboratory for Structural, Physiologic and Functional Imaging (LSPFI), Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA
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9
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Vazquez AL, Fukuda M, Kim SG. Inhibitory Neuron Activity Contributions to Hemodynamic Responses and Metabolic Load Examined Using an Inhibitory Optogenetic Mouse Model. Cereb Cortex 2019; 28:4105-4119. [PMID: 30215693 PMCID: PMC6188559 DOI: 10.1093/cercor/bhy225] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 08/18/2018] [Indexed: 12/19/2022] Open
Abstract
Hemodynamic signals are routinely used to noninvasively assess brain function in humans and animals. This work examined the contribution of inhibitory neuron activity on hemodynamic responses captured by changes in blood flow, volume and oxygenation in the cortex of lightly anesthetized mice. Because cortical activity is not commonly initiated by inhibitory neurons, experiments were conducted to examine the neuronal activity properties elicited by photo-stimulation. We observed comparable increases in neuronal activity evoked by forelimb and photo-stimulation; however, significantly larger increases in blood flow and volume were produced by photo-stimulation of inhibitory neurons compared with forelimb stimulation. Following blockade of glutamate and GABA-A receptors to reduce postsynaptic activity contributions, neuronal activity was reliably modulated and hemodynamic changes persisted, though slightly reduced. More importantly, photo-stimulation-evoked changes in blood flow and volume were suppressed by 75–80% with the administration of a nitric oxide synthase inhibitor, suggesting that inhibitory neurons regulate blood flow mostly via nitric oxide. Lastly, forelimb and photo-stimulation of excitatory neurons produced local decreases in blood oxygenation, while large increases were generated by photo-stimulation of inhibitory neurons. Estimates of oxygen metabolism suggest that inhibitory neuron activity has a small impact on tissue metabolic load, indicating a mismatch between the metabolic demand and blood flow regulation properties of inhibitory and excitatory neurons.
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Affiliation(s)
- Alberto L Vazquez
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Mitsuhiro Fukuda
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Seong-Gi Kim
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Korea.,Center for Neuroscience Imaging Research, Institute for Basic Science, Sungkyunkwan University, Suwon, Korea
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10
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Non-BOLD contrast for laminar fMRI in humans: CBF, CBV, and CMRO2. Neuroimage 2019; 197:742-760. [DOI: 10.1016/j.neuroimage.2017.07.041] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 07/10/2017] [Accepted: 07/19/2017] [Indexed: 12/22/2022] Open
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11
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Abstract
Advanced neuroimaging techniques are increasingly being implemented in clinical practice as complementary tools to conventional imaging because they can provide crucial functional information about the pathophysiology of a variety of disorders. Therefore, it is important to understand the basic principles underlying them and their role in diagnosis and management. In this review, we will primarily focus on the basic principles and clinical applications of perfusion imaging, diffusion imaging, magnetic resonance spectroscopy, functional MRI, and dual-energy computerized tomography. Our goal is to provide the reader with a basic understanding of these imaging techniques and when they should be used in clinical practice.
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12
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Calvetti D, Prezioso J, Somersalo E. Estimating hemodynamic stimulus and blood vessel compliance from cerebral blood flow data. J Theor Biol 2019; 460:243-261. [PMID: 30312691 PMCID: PMC8201967 DOI: 10.1016/j.jtbi.2018.10.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Revised: 09/14/2018] [Accepted: 10/04/2018] [Indexed: 11/23/2022]
Abstract
Several key brain imaging modalities that are intended for retrieving information about neuronal activity in brain, the BOLD fMRI as a foremost example, rely on the assumption that elevated neuronal activity elicits spatiotemporally well localized increase of the oxygenated blood volume, which in turn can be monitored non-invasively. The details of the signaling in the neurovascular unit during hyperemia are still not completely understood, and remain a topic of active research, requiring good mathematical models that are able to couple the different aspects of the signaling event. In this work, the question of estimating the hemodynamic stimulus function from cerebral blood flow data is addressed. In the present model, the hemodynamic stimulus is a non-specific signal from the electrophysiological and metabolic complex that controls the compliance of the blood vessels, leading to a vasodilation and thereby to an increase of blood flow. The underlying model is based on earlier literature, and it is further developed in this article for the needs of the inverse problem, which is solved using hierarchical Bayesian methodology, addressing also the poorly known model parameters.
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Affiliation(s)
- D Calvetti
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, OH, USA.
| | - J Prezioso
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, OH, USA.
| | - E Somersalo
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, OH, USA.
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13
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Kim SG. Biophysics of BOLD fMRI investigated with animal models. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 292:82-89. [PMID: 29705033 DOI: 10.1016/j.jmr.2018.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 02/14/2018] [Accepted: 04/09/2018] [Indexed: 06/08/2023]
Abstract
The widely-used BOLD fMRI signal depends on various anatomical, physiological, and imaging parameters. Thus, it is important to examine its biophysical and physiological source in order to optimize, model and accurately interpret fMRI. Animal models have been used to investigate these issues to take systematic measurements and combine with conventional invasive approaches. Here, we reviewed and discussed multiple issues, including the echo time-dependent intravascular contribution and extravascular contributions, gradient-echo vs. spin-echo fMRI, the physiological source of BOLD fMRI, arterial vs. venous cerebral blood volume change, cerebral oxygen consumption change, and arterial oxygen saturation change. We then discuss future directions of animal fMRI and translation to human fMRI. Systematic biophysical BOLD fMRI studies provide insight into the modeling and interpretation of BOLD fMRI in animals and humans.
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Affiliation(s)
- Seong-Gi Kim
- Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.
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14
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Zhu XH, Lu M, Chen W. Quantitative imaging of brain energy metabolisms and neuroenergetics using in vivo X-nuclear 2H, 17O and 31P MRS at ultra-high field. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 292:155-170. [PMID: 29866434 PMCID: PMC5996770 DOI: 10.1016/j.jmr.2018.05.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 04/27/2018] [Accepted: 05/08/2018] [Indexed: 05/13/2023]
Abstract
Brain energy metabolism relies predominantly on glucose and oxygen utilization to generate biochemical energy in the form of adenosine triphosphate (ATP). ATP is essential for maintaining basal electrophysiological activities in a resting brain and supporting evoked neuronal activity under an activated state. Studying complex neuroenergetic processes in the brain requires sophisticated neuroimaging techniques enabling noninvasive and quantitative assessment of cerebral energy metabolisms and quantification of metabolic rates. Recent state-of-the-art in vivo X-nuclear MRS techniques, including 2H, 17O and 31P MRS have shown promise, especially at ultra-high fields, in the quest for understanding neuroenergetics and brain function using preclinical models and in human subjects under healthy and diseased conditions.
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Affiliation(s)
- Xiao-Hong Zhu
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, School of Medicine, Minneapolis, MN 55455, USA
| | - Ming Lu
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, School of Medicine, Minneapolis, MN 55455, USA
| | - Wei Chen
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, School of Medicine, Minneapolis, MN 55455, USA.
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15
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Hua J, Liu P, Kim T, Donahue M, Rane S, Chen JJ, Qin Q, Kim SG. MRI techniques to measure arterial and venous cerebral blood volume. Neuroimage 2018; 187:17-31. [PMID: 29458187 DOI: 10.1016/j.neuroimage.2018.02.027] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 02/12/2018] [Accepted: 02/14/2018] [Indexed: 12/14/2022] Open
Abstract
The measurement of cerebral blood volume (CBV) has been the topic of numerous neuroimaging studies. To date, however, most in vivo imaging approaches can only measure CBV summed over all types of blood vessels, including arterial, capillary and venous vessels in the microvasculature (i.e. total CBV or CBVtot). As different types of blood vessels have intrinsically different anatomy, function and physiology, the ability to quantify CBV in different segments of the microvascular tree may furnish information that is not obtainable from CBVtot, and may provide a more sensitive and specific measure for the underlying physiology. This review attempts to summarize major efforts in the development of MRI techniques to measure arterial (CBVa) and venous CBV (CBVv) separately. Advantages and disadvantages of each type of method are discussed. Applications of some of the methods in the investigation of flow-volume coupling in healthy brains, and in the detection of pathophysiological abnormalities in brain diseases such as arterial steno-occlusive disease, brain tumors, schizophrenia, Huntington's disease, Alzheimer's disease, and hypertension are demonstrated. We believe that the continual development of MRI approaches for the measurement of compartment-specific CBV will likely provide essential imaging tools for the advancement and refinement of our knowledge on the exquisite details of the microvasculature in healthy and diseased brains.
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Affiliation(s)
- Jun Hua
- Neurosection, Div. of MRI Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.
| | - Peiying Liu
- Neurosection, Div. of MRI Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Tae Kim
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Manus Donahue
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Swati Rane
- Radiology, University of Washington Medical Center, Seattle, WA, USA
| | - J Jean Chen
- Rotman Research Institute, Baycrest Centre, Canada; Department of Medical Biophysics, University of Toronto, Canada
| | - Qin Qin
- Neurosection, Div. of MRI Research, Dept. of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Seong-Gi Kim
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, South Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea
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16
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Freeman RD, Li B. Neural-metabolic coupling in the central visual pathway. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0357. [PMID: 27574310 DOI: 10.1098/rstb.2015.0357] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/18/2016] [Indexed: 01/19/2023] Open
Abstract
Studies are described which are intended to improve our understanding of the primary measurements made in non-invasive neural imaging. The blood oxygenation level-dependent signal used in functional magnetic resonance imaging (fMRI) reflects changes in deoxygenated haemoglobin. Tissue oxygen concentration, along with blood flow, changes during neural activation. Therefore, measurements of tissue oxygen together with the use of a neural sensor can provide direct estimates of neural-metabolic interactions. We have used this relationship in a series of studies in which a neural microelectrode is combined with an oxygen micro-sensor to make simultaneous co-localized measurements in the central visual pathway. Oxygen responses are typically biphasic with small initial dips followed by large secondary peaks during neural activation. By the use of established visual response characteristics, we have determined that the oxygen initial dip provides a better estimate of local neural function than the positive peak. This contrasts sharply with fMRI for which the initial dip is unreliable. To extend these studies, we have examined the relationship between the primary metabolic agents, glucose and lactate, and associated neural activity. For this work, we also use a Doppler technique to measure cerebral blood flow (CBF) together with neural activity. Results show consistent synchronously timed changes such that increases in neural activity are accompanied by decreases in glucose and simultaneous increases in lactate. Measurements of CBF show clear delays with respect to neural response. This is consistent with a slight delay in blood flow with respect to oxygen delivery during neural activation.This article is part of the themed issue 'Interpreting BOLD: a dialogue between cognitive and cellular neuroscience'.
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Affiliation(s)
- Ralph D Freeman
- Group in Vision Science, School of Optometry, Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720-2020, USA
| | - Baowang Li
- Group in Vision Science, School of Optometry, Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720-2020, USA
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17
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Cheng H, Newman SD, Kent JS, Bolbecker A, Klaunig MJ, O'Donnell BF, Puce A, Hetrick WP. White matter abnormalities of microstructure and physiological noise in schizophrenia. Brain Imaging Behav 2016; 9:868-77. [PMID: 25560665 DOI: 10.1007/s11682-014-9349-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
White matter abnormalities in schizophrenia have been revealed by many imaging techniques and analysis methods. One of the findings by diffusion tensor imaging is a decrease in fractional anisotropy (FA), which is an indicator of white matter integrity. On the other hand, elevation of metabolic rate in white matter was observed from positron emission tomography (PET) studies. In this report, we aim to compare the two structural and functional effects on the same subjects. Our comparison is based on the hypothesis that signal fluctuation in white matter is associated with white matter functional activity. We examined the variance of the signal in resting state fMRI and found significant differences between individuals with schizophrenia and non-psychiatric controls specifically in white matter tissue. Controls showed higher temporal signal-to-noise ratios clustered in regions including temporal, frontal, and parietal lobes, cerebellum, corpus callosum, superior longitudinal fasciculus, and other major white matter tracts. These regions with higher temporal signal-to-noise ratio agree well with those showing higher metabolic activity reported by studies using PET. The results suggest that individuals with schizophrenia tend to have higher functional activity in white matter in certain brain regions relative to healthy controls. Despite some overlaps, the distinct regions for physiological noise are different from those for FA derived from diffusion tensor imaging, and therefore provide a unique angle to explore potential mechanisms to white matter abnormality.
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Affiliation(s)
- Hu Cheng
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA.
| | - Sharlene D Newman
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
| | - Jerillyn S Kent
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
| | - Amanda Bolbecker
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
| | - Mallory J Klaunig
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
| | - Brian F O'Donnell
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
| | - Aina Puce
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
| | - William P Hetrick
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
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18
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Markuerkiaga I, Barth M, Norris DG. A cortical vascular model for examining the specificity of the laminar BOLD signal. Neuroimage 2016; 132:491-498. [DOI: 10.1016/j.neuroimage.2016.02.073] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 02/23/2016] [Accepted: 02/26/2016] [Indexed: 12/31/2022] Open
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19
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Age-related deficits in voluntary control over saccadic eye movements: consideration of electrical brain stimulation as a therapeutic strategy. Neurobiol Aging 2016; 41:53-63. [PMID: 27103518 DOI: 10.1016/j.neurobiolaging.2016.02.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 01/30/2016] [Accepted: 02/09/2016] [Indexed: 11/21/2022]
Abstract
Sudden changes in our visual environment trigger reflexive eye movements, so automatically they often go unnoticed. Consequently, voluntary control over reflexive eye movements entails considerable effort. In relation to frontal-lobe deterioration, adult aging adversely impacts voluntary saccadic eye movement control in particular, which compromises effective performance of daily activities. Here, we review the nature of age-related changes in saccadic control, focusing primarily on the antisaccade task because of its assessment of 2 key age-sensitive control functions: reflexive saccade inhibition and voluntary saccade generation. With an ultimate view toward facilitating development of therapeutic strategies, we systematically review the neuroanatomy underpinning voluntary control over saccadic eye movements and natural mechanisms that kick in to compensate for age-related declines. We then explore the potential of noninvasive electrical brain stimulation to counteract aging deficits. Based on evidence that anodal transcranial direct current stimulation can confer a range of benefits specifically relevant to aging brains, we put forward this neuromodulation technique as a therapeutic strategy for improving voluntary saccadic eye movement control in older adults.
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20
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Viski S, Orgovan D, Szabo K, Rosengarten B, Csiba L, Olah L. Effect of reading on blood flow changes in the posterior cerebral artery in early blind and sighted people--A transcranial Doppler study. J Neurol Sci 2016; 363:132-9. [PMID: 27000238 DOI: 10.1016/j.jns.2016.02.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 02/17/2016] [Accepted: 02/19/2016] [Indexed: 10/22/2022]
Abstract
BACKGROUND Neuroimaging studies proved that Braille reading resulted in visual cortex activation in blind people, however, very few data are available about the measure of flow increase in these subjects. Therefore, we investigated the flow response in the posterior cerebral artery (PCA) of eleven early blind and ten sighted subjects induced by reading Braille and print, respectively. METHODS Two experimental protocols were used in both groups: PCA flow velocity during reading was compared to the resting phase and "NLC" phase (volunteers "read" non-lexical characters; e.g. .,-.:,-.:...,). The use of these experimental protocols allowed to investigate separately the effect of "light stimulus+print reading" versus "print reading alone" in sighted, and "hand/finger movement+Braille reading" versus "Braille reading alone" in blind subjects. RESULTS The flow response in the PCA evoked by "Braille reading alone" in blind (10.5±4.5%) and "print reading alone" in sighted subjects (8.1±3.5%) was similar. The flow increase induced by "hand/finger movement+Braille reading" and by "Braille reading alone" did not differ in blind people, however, "light stimulus+print reading" in sighted subjects caused higher PCA flow increase (25.9±6.9%) than "print reading alone" (8.1±3.5%). CONCLUSION The similar PCA flow response induced by Braille and print reading alone suggested a similar degree of occipital cortex activation in blind and sighted subjects. In sighted people, the 3-times higher flow velocity increase induced by "light stimulus+print reading" compared with "print reading alone" indicated that 2/3 of PCA flow increase during reading was due to the light stimulus and only 1/3 of flow response was caused by reading alone.
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Affiliation(s)
- Sandor Viski
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary
| | - David Orgovan
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary
| | - Katalin Szabo
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary
| | - Bernhard Rosengarten
- Department of Neurology, University of Giessen, Giessen, Amsteg 14, Giessen D-35385, Germany
| | - Laszlo Csiba
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary
| | - Laszlo Olah
- Department of Neurology, University of Debrecen, Moricz Zs. str. 22, H-4032 Debrecen, Hungary.
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21
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Shu CY, Sanganahalli BG, Coman D, Herman P, Hyder F. New horizons in neurometabolic and neurovascular coupling from calibrated fMRI. PROGRESS IN BRAIN RESEARCH 2016; 225:99-122. [PMID: 27130413 DOI: 10.1016/bs.pbr.2016.02.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Neurovascular coupling relates changes in neuronal activity to constriction/dilation of microvessels. However neurometabolic coupling, which is less well known, relates alterations in neuronal activity with metabolic demands. The link between the blood oxygenation level dependent (BOLD) signal and neural activity opened doors for functional MRI (fMRI) to be a powerful neuroimaging tool in the neurosciences. But due to the complex makeup of BOLD contrast, researchers began to investigate the relationship between BOLD signal and blood flow and/or volume changes during functional brain activation, which together provided the tools to measure oxygen consumption on the basis of the biophysical model of BOLD. This field is called calibrated fMRI, thereby allowed probing of both neurometabolic and neurovascular couplings for a variety of health conditions in animals and humans. Calibrated fMRI may provide brain disorder biomarkers that could be used for monitoring effective therapies.
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Affiliation(s)
- C Y Shu
- Yale University, New Haven, CT, United States
| | - B G Sanganahalli
- Yale University, New Haven, CT, United States; Magnetic Resonance Research Center (MRRC), Yale University, New Haven, CT, United States
| | - D Coman
- Yale University, New Haven, CT, United States; Magnetic Resonance Research Center (MRRC), Yale University, New Haven, CT, United States
| | - P Herman
- Yale University, New Haven, CT, United States; Magnetic Resonance Research Center (MRRC), Yale University, New Haven, CT, United States
| | - F Hyder
- Yale University, New Haven, CT, United States; Magnetic Resonance Research Center (MRRC), Yale University, New Haven, CT, United States.
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22
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Reproducing the Hemoglobin Saturation Profile, a Marker of the Blood Oxygenation Level Dependent (BOLD) fMRI Effect, at the Microscopic Level. PLoS One 2016; 11:e0149935. [PMID: 26939128 PMCID: PMC4777512 DOI: 10.1371/journal.pone.0149935] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 02/06/2016] [Indexed: 11/29/2022] Open
Abstract
The advent of functional MRI in the mid-1990s has catalyzed progress pertaining to scientific discoveries in neuroscience. With the prospect of elucidating the physiological aspect of the Blood Oxygenation Level Dependent (BOLD) effect we present a computational capillary-tissue system capable of mapping venous hemoglobin saturation— a marker of the BOLD hemodynamic response. Free and facilitated diffusion and convection for hemoglobin and oxygen are considered in the radial and axial directions. Hemoglobin reaction kinetics are governed by the oxyhemoglobin dissociation curve. Brain activation, mimicked by dynamic transitions in cerebral blood velocity (CBv) and oxidative metabolism (CMRO2), is simulated by normalized changes in m = (ΔCBv/CBv)/(ΔCMRO2/CMRO2) of values 2, 3 and 4. Venous hemoglobin saturation profiles and peak oxygenation results, for m = 2, based upon a 50% and a 25% increase in CBv and CMRO2, respectively, lie within physiological limits exhibiting excellent correlation with the BOLD signal, for short-duration stimuli. Our analysis suggests basal CBv and CMRO2 values of 0.6 mm/s and 200 μmol/100g/min. Coupled CBv and CMRO2 responses, for m = 3 and m = 4, overestimate peak hemoglobin saturation, confirming the system’s responsiveness to changes in hematocrit, CBv and CMRO2. Finally, factoring in neurovascular effects, we show that no initial dip will be observed unless there is a time delay in the onset of increased CBv relative to CMRO2.
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23
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Macey PM, Ogren JA, Kumar R, Harper RM. Functional Imaging of Autonomic Regulation: Methods and Key Findings. Front Neurosci 2016; 9:513. [PMID: 26858595 PMCID: PMC4726771 DOI: 10.3389/fnins.2015.00513] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 12/22/2015] [Indexed: 01/06/2023] Open
Abstract
Central nervous system processing of autonomic function involves a network of regions throughout the brain which can be visualized and measured with neuroimaging techniques, notably functional magnetic resonance imaging (fMRI). The development of fMRI procedures has both confirmed and extended earlier findings from animal models, and human stroke and lesion studies. Assessments with fMRI can elucidate interactions between different central sites in regulating normal autonomic patterning, and demonstrate how disturbed systems can interact to produce aberrant regulation during autonomic challenges. Understanding autonomic dysfunction in various illnesses reveals mechanisms that potentially lead to interventions in the impairments. The objectives here are to: (1) describe the fMRI neuroimaging methodology for assessment of autonomic neural control, (2) outline the widespread, lateralized distribution of function in autonomic sites in the normal brain which includes structures from the neocortex through the medulla and cerebellum, (3) illustrate the importance of the time course of neural changes when coordinating responses, and how those patterns are impacted in conditions of sleep-disordered breathing, and (4) highlight opportunities for future research studies with emerging methodologies. Methodological considerations specific to autonomic testing include timing of challenges relative to the underlying fMRI signal, spatial resolution sufficient to identify autonomic brainstem nuclei, blood pressure, and blood oxygenation influences on the fMRI signal, and the sustained timing, often measured in minutes of challenge periods and recovery. Key findings include the lateralized nature of autonomic organization, which is reminiscent of asymmetric motor, sensory, and language pathways. Testing brain function during autonomic challenges demonstrate closely-integrated timing of responses in connected brain areas during autonomic challenges, and the involvement with brain regions mediating postural and motoric actions, including respiration, and cardiac output. The study of pathological processes associated with autonomic disruption shows susceptibilities of different brain structures to altered timing of neural function, notably in sleep disordered breathing, such as obstructive sleep apnea and congenital central hypoventilation syndrome. The cerebellum, in particular, serves coordination roles for vestibular stimuli and blood pressure changes, and shows both injury and substantially altered timing of responses to pressor challenges in sleep-disordered breathing conditions. The insights into central autonomic processing provided by neuroimaging have assisted understanding of such regulation, and may lead to new treatment options for conditions with disrupted autonomic function.
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Affiliation(s)
- Paul M Macey
- UCLA School of Nursing, University of California at Los AngelesLos Angeles, CA, USA; Brain Research Institute, University of California at Los AngelesLos Angeles, CA, USA
| | - Jennifer A Ogren
- Department of Neurobiology, University of California at Los Angeles Los Angeles, CA, USA
| | - Rajesh Kumar
- Brain Research Institute, University of California at Los AngelesLos Angeles, CA, USA; Department of Anesthesiology, University of California at Los AngelesLos Angeles, CA, USA; Department of Radiological Sciences, David Geffen School of Medicine at University of California at Los AngelesLos Angeles, CA, USA; Department of Bioengineering, University of California at Los AngelesLos Angeles, CA, USA
| | - Ronald M Harper
- Brain Research Institute, University of California at Los AngelesLos Angeles, CA, USA; Department of Neurobiology, University of California at Los AngelesLos Angeles, CA, USA
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24
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Park CS, Payne SJ. Modelling the effects of cerebral microvasculature morphology on oxygen transport. Med Eng Phys 2016; 38:41-7. [PMID: 26499366 PMCID: PMC4751405 DOI: 10.1016/j.medengphy.2015.09.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 07/29/2015] [Accepted: 09/10/2015] [Indexed: 12/28/2022]
Abstract
The cerebral microvasculature plays a vital role in adequately supplying blood to the brain. Determining the health of the cerebral microvasculature is important during pathological conditions, such as stroke and dementia. Recent studies have shown the complex relationship between cerebral metabolic rate and transit time distribution, the transit times of all the possible pathways available dependent on network topology. In this paper, we extend a recently developed technique to solve for residue function, the amount of tracer left in the vasculature at any time, and transit time distribution in an existing model of the cerebral microvasculature to calculate cerebral metabolism. We present the mathematical theory needed to solve for oxygen concentration followed by results of the simulations. It is found that oxygen extraction fraction, the fraction of oxygen removed from the blood in the capillary network by the tissue, and cerebral metabolic rate are dependent on both mean and heterogeneity of the transit time distribution. For changes in cerebral blood flow, a positive correlation can be observed between mean transit time and oxygen extraction fraction, and a negative correlation between mean transit time and metabolic rate of oxygen. A negative correlation can also be observed between transit time heterogeneity and the metabolic rate of oxygen for a constant cerebral blood flow. A sensitivity analysis on the mean and heterogeneity of the transit time distribution was able to quantify their respective contributions to oxygen extraction fraction and metabolic rate of oxygen. Mean transit time has a greater contribution than the heterogeneity for oxygen extraction fraction. This is found to be opposite for metabolic rate of oxygen. These results provide information on the role of the cerebral microvasculature and its effects on flow and metabolism. They thus open up the possibility of obtaining additional valuable clinical information for diagnosing and treating cerebrovascular diseases.
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Affiliation(s)
- Chang Sub Park
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, United Kingdom.
| | - Stephen J Payne
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, United Kingdom
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25
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Chen JE, Glover GH. Functional Magnetic Resonance Imaging Methods. Neuropsychol Rev 2015; 25:289-313. [PMID: 26248581 PMCID: PMC4565730 DOI: 10.1007/s11065-015-9294-9] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Accepted: 07/28/2015] [Indexed: 12/11/2022]
Abstract
Since its inception in 1992, Functional Magnetic Resonance Imaging (fMRI) has become an indispensible tool for studying cognition in both the healthy and dysfunctional brain. FMRI monitors changes in the oxygenation of brain tissue resulting from altered metabolism consequent to a task-based evoked neural response or from spontaneous fluctuations in neural activity in the absence of conscious mentation (the "resting state"). Task-based studies have revealed neural correlates of a large number of important cognitive processes, while fMRI studies performed in the resting state have demonstrated brain-wide networks that result from brain regions with synchronized, apparently spontaneous activity. In this article, we review the methods used to acquire and analyze fMRI signals.
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Affiliation(s)
- Jingyuan E Chen
- Department of Radiology, Department of Electrical Engineering, Stanford University, Stanford, CA, 94305, USA,
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26
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Vazquez AL, Murphy MC, Kim SG. Neuronal and physiological correlation to hemodynamic resting-state fluctuations in health and disease. Brain Connect 2015; 4:727-40. [PMID: 25300278 DOI: 10.1089/brain.2014.0276] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Low-frequency, spatially coherent fluctuations present in functional magnetic resonance imaging time series have had a tremendous impact on brain connectomics. This work aims to explore the degree with which hemodynamic connectivity is associated with neuronal, metabolic, and vascular connectivity measures. For this purpose, GCaMP and nontransgenic mice were used to image neuronal activity and oxidative metabolism activity, respectively, along with blood-oxygenation- and cerebral blood volume (CBV)-sensitive hemodynamic changes from the same animals. Although network clusters calculated using either GCaMP (neuronal activity) or optical imaging of intrinsic signal (OIS)-BOLD (blood oxygenation) data did not exhibit strong spatial similarity, the strengths of node-to-node connectivity measured with these modalities were strongly correlated with one another. This finding suggests that hemodynamic connectivity as measured by blood oxygenation measurements, such as functional connectivity magnetic resonance imaging, is a valuable surrogate for the underlying neuronal connectivity. In nontransgenic animals, greater connectivity correlation was observed between tissue oxidative metabolism (flavoprotein autofluorescence imaging [FAI]) and blood oxygenation measurements, suggesting that metabolic contributions to hemodynamic signals are likely responsible for its significant correlation with neuronal connectivity. Lastly, a mouse model of Alzheimer's disease was used to explore the source of decreases in connectivity reported in these mice, a finding that is thought to be associated with amyloid load-driven metabolic decline. The intercluster connectivity measured by metabolic-sensitive measurements (FAI and OIS-BOLD) was maintained while vascular-only signals (OIS-CBV) provided negligible correlation. Therefore, metabolism-sensitive measurements as used in this work are better positioned to capture changes in neuronal connectivity, such that decreases in hemodynamic connectivity likely reflect decreases in oxidative metabolic function.
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Affiliation(s)
- Alberto L Vazquez
- 1 Department of Bioengineering, University of Pittsburgh , Pittsburgh, Pennsylvania
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27
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Marshall O, Uh J, Lurie D, Lu H, Milham MP, Ge Y. The influence of mild carbon dioxide on brain functional homotopy using resting-state fMRI. Hum Brain Mapp 2015; 36:3912-21. [PMID: 26138728 DOI: 10.1002/hbm.22886] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 06/09/2015] [Accepted: 06/16/2015] [Indexed: 11/10/2022] Open
Abstract
Homotopy reflects the intrinsic functional architecture of the brain through synchronized spontaneous activity between corresponding bilateral regions, measured as voxel mirrored homotopic connectivity (VMHC). Hypercapnia is known to have clear impact on brain hemodynamics through vasodilation, but have unclear effect on neuronal activity. This study investigates the effect of hypercapnia on brain homotopy, achieved by breathing 5% carbon dioxide (CO2 ) gas mixture. A total of 14 healthy volunteers completed three resting state functional MRI (RS-fMRI) scans, the first and third under normocapnia and the second under hypercapnia. VMHC measures were calculated as the correlation between the BOLD signal of each voxel and its counterpart in the opposite hemisphere. Group analysis was performed between the hypercapnic and normocapnic VMHC maps. VMHC showed a diffused decrease in response to hypercapnia. Significant regional decreases in VMHC were observed in all anatomical lobes, except for the occipital lobe, in the following functional hierarchical subdivisions: the primary sensory-motor, unimodal, heteromodal, paralimbic, as well as in the following functional networks: ventral attention, somatomotor, default frontoparietal, and dorsal attention. Our observation that brain homotopy in RS-fMRI is affected by arterial CO2 levels suggests that caution should be used when comparing RS-fMRI data between healthy controls and patients with pulmonary diseases and unusual respiratory patterns such as sleep apnea or chronic obstructive pulmonary disease.
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Affiliation(s)
- Olga Marshall
- Radiology/Center for Biomedical Imaging, New York University School of Medicine, New York, New York
| | - Jinsoo Uh
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Daniel Lurie
- Center for the Developing Brain, Child Mind Institute, New York, New York
| | - Hanzhang Lu
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Michael P Milham
- Center for the Developing Brain, Child Mind Institute, New York, New York.,Nathan S Kline Institute for Psychiatric Research, New York
| | - Yulin Ge
- Radiology/Center for Biomedical Imaging, New York University School of Medicine, New York, New York
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Krieger SN, Gauthier CJ, Ivanov D, Huber L, Roggenhofer E, Sehm B, Turner R, Egan GF. Regional reproducibility of calibrated BOLD functional MRI: Implications for the study of cognition and plasticity. Neuroimage 2014; 101:8-20. [DOI: 10.1016/j.neuroimage.2014.06.072] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 06/24/2014] [Accepted: 06/28/2014] [Indexed: 02/02/2023] Open
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Global brain blood-oxygen level responses to autonomic challenges in obstructive sleep apnea. PLoS One 2014; 9:e105261. [PMID: 25166862 PMCID: PMC4148259 DOI: 10.1371/journal.pone.0105261] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 07/22/2014] [Indexed: 01/18/2023] Open
Abstract
Obstructive sleep apnea (OSA) is accompanied by brain injury, perhaps resulting from apnea-related hypoxia or periods of impaired cerebral perfusion. Perfusion changes can be determined indirectly by evaluation of cerebral blood volume and oxygenation alterations, which can be measured rapidly and non-invasively with the global blood oxygen level dependent (BOLD) signal, a magnetic resonance imaging procedure. We assessed acute BOLD responses in OSA subjects to pressor challenges that elicit cerebral blood flow changes, using a two-group comparative design with healthy subjects as a reference. We separately assessed female and male patterns, since OSA characteristics and brain injury differ between sexes. We studied 94 subjects, 37 with newly-diagnosed, untreated OSA (6 female (age mean ± std: 52.1±8.1 yrs; apnea/hypopnea index [AHI]: 27.7±15.6 events/hr and 31 male 54.3±8.4 yrs; AHI: 37.4±19.6 events/hr), and 20 female (age 50.5±8.1 yrs) and 37 male (age 45.6±9.2 yrs) healthy control subjects. We measured brain BOLD responses every 2 s while subjects underwent cold pressor, hand grip, and Valsalva maneuver challenges. The global BOLD signal rapidly changed after the first 2 s of each challenge, and differed in magnitude between groups to two challenges (cold pressor, hand grip), but not to the Valsalva maneuver (repeated measures ANOVA, p<0.05). OSA females showed greater differences from males in response magnitude and pattern, relative to healthy counterparts. Cold pressor BOLD signal increases (mean ± adjusted standard error) at the 8 s peak were: OSA 0.14±0.08% vs. Control 0.31±0.06%, and hand grip at 6 s were: OSA 0.08±0.03% vs. Control at 0.30±0.02%. These findings, indicative of reduced cerebral blood flow changes to autonomic challenges in OSA, complement earlier reports of altered resting blood flow and reduced cerebral artery responsiveness. Females are more affected than males, an outcome which may contribute to the sex-specific brain injury in the syndrome.
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Schmithorst VJ, Vannest J, Lee G, Hernandez-Garcia L, Plante E, Rajagopal A, Holland SK. Evidence that neurovascular coupling underlying the BOLD effect increases with age during childhood. Hum Brain Mapp 2014; 36:1-15. [PMID: 25137219 DOI: 10.1002/hbm.22608] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/30/2014] [Accepted: 08/03/2014] [Indexed: 12/15/2022] Open
Abstract
Functional MRI using blood-oxygen-level-dependent (BOLD) imaging has provided unprecedented insights into the maturation of the human brain. Task-based fMRI studies have shown BOLD signal increases with age during development (ages 5-18) for many cognitive domains such as language and executive function, while functional connectivity (resting-state) fMRI studies investigating regionally synchronous BOLD fluctuations have revealed a developing functional organization of the brain from a local into a more distributed architecture. However, interpretation of these results is confounded by the fact that the BOLD signal is directly related to blood oxygenation driven by changes in blood flow and only indirectly related to neuronal activity, and may thus be affected by changing neuronal-vascular coupling. BOLD signal and cerebral blood flow (CBF) were measured simultaneously in a cohort of 113 typically developing awake participants ages 3-18 performing a narrative comprehension task. Using a novel voxelwise wild bootstrap analysis technique, an increased ratio of BOLD signal to relative CBF signal change with age (indicative of increased neuronal-vascular coupling) was seen in the middle temporal gyri and the left inferior frontal gyrus. Additionally, evidence of decreased relative oxygen metabolism (indicative of decreased neuronal activity) with age was found in the same regions. These findings raise concern that results of developmental BOLD studies cannot be unambiguously attributed to neuronal activity. Astrocytes and astrocytic processes may significantly affect the maturing functional architecture of the brain, consistent with recent research demonstrating a key role for astrocytes in mediating increased CBF following neuronal activity and for astrocyte processes in modulating synaptic connectivity.
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Affiliation(s)
- Vincent J Schmithorst
- Pediatric Neuroimaging Research Consortium, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
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31
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Gong L, Li B, Wu R, Li A, Xu F. Brain-state dependent uncoupling of BOLD and local field potentials in laminar olfactory bulb. Neurosci Lett 2014; 580:1-6. [PMID: 25079901 DOI: 10.1016/j.neulet.2014.07.034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 06/23/2014] [Accepted: 07/21/2014] [Indexed: 10/25/2022]
Abstract
The neural activities of the olfactory bulb (OB) can be modulated significantly by internal brain states. While blood oxygenation level dependent functional MRI (BOLD-fMRI) has been extensively applied to study OB in small animals, the relationship between BOLD signals and electrophysiological signals remains to be elucidated. Our recent study has revealed a complex relationship between BOLD and local field potentials (LFP) signals in different OB layers during odor stimulation. However, no study has been performed to compare these two types of signals under global brain states. Here, the changes of BOLD and LFP signals in the glomerular, mitral cell, and granular cell layers of the OB under different brain states, which were induced by different concentrations of isoflurane, were sequentially acquired using electrode array and high-resolution MRI. It was found that under deeper anesthesia, the LFP powers in all layers were decreased but the BOLD signals were unexpectedly increased. Furthermore, the decreases of LFP powers were layer-independent, but the increases of BOLD signal were layer-specific, with the order of glomerular>mitral cell>granular cell layer. The results provide new evidence that the direct neural activity levels might not be correlated well with BOLD signals in some cases, and remind us that cautions should be taken to use BOLD signals as the index of neural activities.
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Affiliation(s)
- Ling Gong
- Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bo Li
- Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ruiqi Wu
- Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Anan Li
- Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China.
| | - Fuqiang Xu
- Key Laboratory of Magnetic Resonance in Biological Systems and State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China; Wuhan National Laboratory for Optoelectronics, Wuhan 430074, China.
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32
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Cauda F, Costa T, Diano M, Duca S, Torta DME. Beyond the "Pain Matrix," inter-run synchronization during mechanical nociceptive stimulation. Front Hum Neurosci 2014; 8:265. [PMID: 24955085 PMCID: PMC4017139 DOI: 10.3389/fnhum.2014.00265] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 04/10/2014] [Indexed: 12/26/2022] Open
Abstract
Pain is a complex experience that is thought to emerge from the activity of multiple brain areas, some of which are inconsistently detected using traditional fMRI analysis. One hypothesis is that the traditional analysis of pain-related cerebral responses, by relying on the correlation of a predictor and the canonical hemodynamic response function (HRF)- the general linear model (GLM)- may under-detect the activity of those areas involved in stimulus processing that do not present a canonical HRF. In this study, we employed an innovative data-driven processing approach- an inter-run synchronization (IRS) analysis- that has the advantage of not establishing any pre-determined predictor definition. With this method we were able to evidence the involvement of several brain regions that are not usually found when using predictor-based analysis. These areas are synchronized during the administration of mechanical punctate stimuli and are characterized by a BOLD response different from the canonical HRF. This finding opens to new approaches in the study of pain imaging.
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Affiliation(s)
- Franco Cauda
- GCS fMRI, Koelliker Hospital and Department of Psychology, University of Turin Turin, Italy ; Department of Psychology, University of Turin Turin, Italy
| | - Tommaso Costa
- Department of Psychology, University of Turin Turin, Italy
| | - Matteo Diano
- GCS fMRI, Koelliker Hospital and Department of Psychology, University of Turin Turin, Italy ; Department of Psychology, University of Turin Turin, Italy
| | - Sergio Duca
- GCS fMRI, Koelliker Hospital and Department of Psychology, University of Turin Turin, Italy
| | - Diana M E Torta
- GCS fMRI, Koelliker Hospital and Department of Psychology, University of Turin Turin, Italy ; Department of Psychology, University of Turin Turin, Italy
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33
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Schaller B, Xin L, O'Brien K, Magill AW, Gruetter R. Are glutamate and lactate increases ubiquitous to physiological activation? A (1)H functional MR spectroscopy study during motor activation in human brain at 7Tesla. Neuroimage 2014; 93 Pt 1:138-45. [PMID: 24555953 DOI: 10.1016/j.neuroimage.2014.02.016] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 01/28/2014] [Accepted: 02/10/2014] [Indexed: 11/19/2022] Open
Abstract
Recent studies at high field (7Tesla) have reported small metabolite changes, in particular lactate and glutamate (below 0.3μmol/g) during visual stimulation. These studies have been limited to the visual cortex because of its high energy metabolism and good magnetic resonance spectroscopy (MRS) sensitivity using surface coil. The aim of this study was to extend functional MRS (fMRS) to investigate for the first time the metabolite changes during motor activation at 7T. Small but sustained increases in lactate (0.17μmol/g±0.05μmol/g, p<0.001) and glutamate (0.17μmol/g±0.09μmol/g, p<0.005) were detected during motor activation followed by a return to the baseline after the end of activation. The present study demonstrates that increases in lactate and glutamate during motor stimulation are small, but similar to those observed during visual stimulation. From the observed glutamate and lactate increase, we inferred that these metabolite changes may be a general manifestation of the increased neuronal activity. In addition, we propose that the measured metabolite concentration increases imply an increase in ΔCMRO2 that is transiently below that of ΔCMRGlc during the first 1 to 2min of the stimulation.
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Affiliation(s)
- Benoît Schaller
- Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Federale de Lausanne, Station 6, 1015 Lausanne, Switzerland.
| | - Lijing Xin
- Department of Radiology, University Hospitals of Lausanne Rue du Bugnon 21, 1011 Lausanne, Switzerland.
| | - Kieran O'Brien
- Centre d'Imagerie BioMédicale, University of Geneva, Geneva 14, Geneva, Switzerland.
| | - Arthur W Magill
- Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Federale de Lausanne, Station 6, 1015 Lausanne, Switzerland; Department of Radiology, University Hospitals of Lausanne Rue du Bugnon 21, 1011 Lausanne, Switzerland.
| | - Rolf Gruetter
- Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Federale de Lausanne, Station 6, 1015 Lausanne, Switzerland; Department of Radiology, University Hospitals of Lausanne Rue du Bugnon 21, 1011 Lausanne, Switzerland; Department of Radiology, University Hospitals of Geneva, Rue Gabrielle-Perret-Gentil 4, 1211 Geneva 14, Switzerland.
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34
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Tak S, Wang DJJ, Polimeni JR, Yan L, Chen JJ. Dynamic and static contributions of the cerebrovasculature to the resting-state BOLD signal. Neuroimage 2013; 84:672-80. [PMID: 24099842 DOI: 10.1016/j.neuroimage.2013.09.057] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 09/23/2013] [Accepted: 09/26/2013] [Indexed: 11/19/2022] Open
Abstract
Functional magnetic resonance imaging (fMRI) in the resting state, particularly fMRI based on the blood-oxygenation level-dependent (BOLD) signal, has been extensively used to measure functional connectivity in the brain. However, the mechanisms of vascular regulation that underlie the BOLD fluctuations during rest are still poorly understood. In this work, using dual-echo pseudo-continuous arterial spin labeling and MR angiography (MRA), we assess the spatio-temporal contribution of cerebral blood flow (CBF) to the resting-state BOLD signals and explore how the coupling of these signals is associated with regional vasculature. Using a general linear model analysis, we found that statistically significant coupling between resting-state BOLD and CBF fluctuations is highly variable across the brain, but the coupling is strongest within the major nodes of established resting-state networks, including the default-mode, visual, and task-positive networks. Moreover, by exploiting MRA-derived large vessel (macrovascular) volume fraction, we found that the degree of BOLD-CBF coupling significantly decreased as the ratio of large vessels to tissue volume increased. These findings suggest that the portion of resting-state BOLD fluctuations at the sites of medium-to-small vessels (more proximal to local neuronal activity) is more closely regulated by dynamic regulations in CBF, and that this CBF regulation decreases closer to large veins, which are more distal to neuronal activity.
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Affiliation(s)
- Sungho Tak
- Rotman Research Institute at Baycrest Centre, University of Toronto, Toronto, Ontario M6A 2E1, Canada.
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35
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Krainik A, Villien M, Troprès I, Attyé A, Lamalle L, Bouvier J, Pietras J, Grand S, Le Bas JF, Warnking J. Functional imaging of cerebral perfusion. Diagn Interv Imaging 2013; 94:1259-78. [PMID: 24011870 DOI: 10.1016/j.diii.2013.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The functional imaging of perfusion enables the study of its properties such as the vasoreactivity to circulating gases, the autoregulation and the neurovascular coupling. Downstream from arterial stenosis, this imaging can estimate the vascular reserve and the risk of ischemia in order to adapt the therapeutic strategy. This method reveals the hemodynamic disorders in patients suffering from Alzheimer's disease or with arteriovenous malformations revealed by epilepsy. Functional MRI of the vasoreactivity also helps to better interpret the functional MRI activation in practice and in clinical research.
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Affiliation(s)
- A Krainik
- Clinique universitaire de neuroradiologie et IRM, CHU de Grenoble, CS 10217, 38043 Grenoble cedex, France; Inserm U836, université Joseph-Fourier, site santé, chemin Fortuné-Ferrini, 38706 La Tronche cedex, France; UMS IRMaGe, unité IRM 3T recherche, CHU de Grenoble, CS 10217, 38043 Grenoble cedex 9, France.
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36
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Anderson A, Cohen MS. Decreased small-world functional network connectivity and clustering across resting state networks in schizophrenia: an fMRI classification tutorial. Front Hum Neurosci 2013; 7:520. [PMID: 24032010 PMCID: PMC3759000 DOI: 10.3389/fnhum.2013.00520] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 08/13/2013] [Indexed: 11/26/2022] Open
Abstract
Functional network connectivity (FNC) is a method of analyzing the temporal relationship of anatomical brain components, comparing the synchronicity between patient groups or conditions. We use functional-connectivity measures between independent components to classify between Schizophrenia patients and healthy controls during resting-state. Connectivity is measured using a variety of graph-theoretic connectivity measures such as graph density, average path length, and small-worldness. The Schizophrenia patients showed significantly less clustering (transitivity) among components than healthy controls (p < 0.05, corrected) with networks less likely to be connected, and also showed lower small-world connectivity than healthy controls. Using only these connectivity measures, an SVM classifier (without parameter tuning) could discriminate between Schizophrenia patients and healthy controls with 65% accuracy, compared to 51% chance. This implies that the global functional connectivity between resting-state networks is altered in Schizophrenia, with networks more likely to be disconnected and behave dissimilarly for diseased patients. We present this research finding as a tutorial using the publicly available COBRE dataset of 146 Schizophrenia patients and healthy controls, provided as part of the 1000 Functional Connectomes Project. We demonstrate preprocessing, using independent component analysis (ICA) to nominate networks, computing graph-theoretic connectivity measures, and finally using these connectivity measures to either classify between patient groups or assess between-group differences using formal hypothesis testing. All necessary code is provided for both running command-line FSL preprocessing, and for computing all statistical measures and SVM classification within R. Collectively, this work presents not just findings of diminished FNC among resting-state networks in Schizophrenia, but also a practical connectivity tutorial.
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Affiliation(s)
- Ariana Anderson
- Department of Psychiatry and Biobehavioral Sciences, Center for Cognitive Neuroscience, University of California Los AngelesLos Angeles, CA, USA
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37
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Yablonskiy DA, Sukstanskii AL, He X. Blood oxygenation level-dependent (BOLD)-based techniques for the quantification of brain hemodynamic and metabolic properties - theoretical models and experimental approaches. NMR IN BIOMEDICINE 2013; 26:963-86. [PMID: 22927123 PMCID: PMC3510357 DOI: 10.1002/nbm.2839] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 06/19/2012] [Accepted: 06/22/2012] [Indexed: 05/06/2023]
Abstract
The quantitative evaluation of brain hemodynamics and metabolism, particularly the relationship between brain function and oxygen utilization, is important for the understanding of normal human brain operation, as well as the pathophysiology of neurological disorders. It can also be of great importance for the evaluation of hypoxia within tumors of the brain and other organs. A fundamental discovery by Ogawa and coworkers of the blood oxygenation level-dependent (BOLD) contrast opened up the possibility to use this effect to study brain hemodynamic and metabolic properties by means of MRI measurements. Such measurements require the development of theoretical models connecting the MRI signal to brain structure and function, and the design of experimental techniques allowing MR measurements to be made of the salient features of theoretical models. In this review, we discuss several such theoretical models and experimental methods for the quantification of brain hemodynamic and metabolic properties. The review's main focus is on methods for the evaluation of the oxygen extraction fraction (OEF) based on the measurement of the blood oxygenation level. A combination of the measurement of OEF and the cerebral blood flow (CBF) allows an evaluation to be made of the cerebral metabolic rate of oxygen consumption (CMRO2 ). We first consider in detail the magnetic properties of blood - magnetic susceptibility, MR relaxation and theoretical models of the intravascular contribution to the MR signal under different experimental conditions. We then describe a 'through-space' effect - the influence of inhomogeneous magnetic fields, created in the extravascular space by intravascular deoxygenated blood, on the formation of the MR signal. Further, we describe several experimental techniques taking advantage of these theoretical models. Some of these techniques - MR susceptometry and T2 -based quantification of OEF - utilize the intravascular MR signal. Another technique - quantitative BOLD - evaluates OEF by making use of through-space effects. In this review, we target both scientists just entering the MR field and more experienced MR researchers interested in the application of advanced BOLD-based techniques to the study of the brain in health and disease.
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38
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A New Functional MRI Approach for Investigating Modulations of Brain Oxygen Metabolism. PLoS One 2013; 8:e68122. [PMID: 23826367 PMCID: PMC3694916 DOI: 10.1371/journal.pone.0068122] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 05/29/2013] [Indexed: 11/29/2022] Open
Abstract
Functional MRI (fMRI) using the blood oxygenation level dependent (BOLD) signal is a common technique in the study of brain function. The BOLD signal is sensitive to the complex interaction of physiological changes including cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral oxygen metabolism (CMRO2). A primary goal of quantitative fMRI methods is to combine BOLD imaging with other measurements (such as CBF measured with arterial spin labeling) to derive information about CMRO2. This requires an accurate mathematical model to relate the BOLD signal to the physiological and hemodynamic changes; the most commonly used of these is the Davis model. Here, we propose a new nonlinear model that is straightforward and shows heuristic value in clearly relating the BOLD signal to blood flow, blood volume and the blood flow-oxygen metabolism coupling ratio. The model was tested for accuracy against a more detailed model adapted for magnetic fields of 1.5, 3 and 7T. The mathematical form of the heuristic model suggests a new ratio method for comparing combined BOLD and CBF data from two different stimulus responses to determine whether CBF and CMRO2 coupling differs. The method does not require a calibration experiment or knowledge of parameter values as long as the exponential parameter describing the CBF-CBV relationship remains constant between stimuli. The method was found to work well for 1.5 and 3T but is prone to systematic error at 7T. If more specific information regarding changes in CMRO2 is required, then with accuracy similar to that of the Davis model, the heuristic model can be applied to calibrated BOLD data at 1.5T, 3T and 7T. Both models work well over a reasonable range of blood flow and oxygen metabolism changes but are less accurate when applied to a simulated caffeine experiment in which CBF decreases and CMRO2 increases.
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39
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Cauda F, Costa T, Diano M, Sacco K, Duca S, Geminiani G, Torta DME. Massive modulation of brain areas after mechanical pain stimulation: a time-resolved FMRI study. ACTA ACUST UNITED AC 2013; 24:2991-3005. [PMID: 23796948 DOI: 10.1093/cercor/bht153] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
To date, relatively little is known about the spatiotemporal aspects of whole-brain blood oxygenation level-dependent (BOLD) responses to brief nociceptive stimuli. It is known that the majority of brain areas show a stimulus-locked response, whereas only some are characterized by a canonical hemodynamic response function. Here, we investigated the time course of brain activations in response to mechanical pain stimulation applied to participants' hands while they were undergoing functional magnetic resonance imaging (fMRI) scanning. To avoid any assumption about the shape of BOLD response, we used an unsupervised data-driven method to group voxels sharing a time course similar to the BOLD response to the stimulus and found that whole-brain BOLD responses to painful mechanical stimuli elicit massive activation of stimulus-locked brain areas. This pattern of activations can be segregated into 5 clusters, each with a typical temporal profile. In conclusion, we show that an extensive activity of multiple networks is engaged at different time latencies after presentation of a noxious stimulus. These findings aim to motivate research on a controversial topic, such as the temporal profile of BOLD responses, the variability of these response profiles, and the interaction between the stimulus-related BOLD response and ongoing fluctuations in large-scale brain networks.
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Affiliation(s)
- Franco Cauda
- CCS fMRI, Koelliker Hospital, Turin, Italy and Department of Psychology, University of Turin, Turin, Italy
| | - Tommaso Costa
- Department of Psychology, University of Turin, Turin, Italy
| | - Matteo Diano
- CCS fMRI, Koelliker Hospital, Turin, Italy and Department of Psychology, University of Turin, Turin, Italy
| | - Katiuscia Sacco
- CCS fMRI, Koelliker Hospital, Turin, Italy and Department of Psychology, University of Turin, Turin, Italy
| | - Sergio Duca
- CCS fMRI, Koelliker Hospital, Turin, Italy and
| | - Giuliano Geminiani
- CCS fMRI, Koelliker Hospital, Turin, Italy and Department of Psychology, University of Turin, Turin, Italy
| | - Diana M E Torta
- CCS fMRI, Koelliker Hospital, Turin, Italy and Department of Psychology, University of Turin, Turin, Italy
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40
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Vazquez AL, Fukuda M, Crowley JC, Kim SG. Neural and hemodynamic responses elicited by forelimb- and photo-stimulation in channelrhodopsin-2 mice: insights into the hemodynamic point spread function. Cereb Cortex 2013; 24:2908-19. [PMID: 23761666 DOI: 10.1093/cercor/bht147] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Hemodynamic responses are commonly used to map brain activity; however, their spatial limits have remained unclear because of the lack of a well-defined and malleable spatial stimulus. To examine the properties of neural activity and hemodynamic responses, multiunit activity, local field potential, cerebral blood volume (CBV)-sensitive optical imaging, and laser Doppler flowmetry were measured from the somatosensory cortex of transgenic mice expressing Channelrhodopsin-2 in cortex Layer 5 pyramidal neurons. The magnitude and extent of neural and hemodynamic responses were modulated using different photo-stimulation parameters and compared with those induced by somatosensory stimulation. Photo-stimulation-evoked spiking activity across cortical layers was similar to forelimb stimulation, although their activity originated in different layers. Hemodynamic responses induced by forelimb- and photo-stimulation were similar in magnitude and shape, although the former were slightly larger in amplitude and wider in extent. Altogether, the neurovascular relationship differed between these 2 stimulation pathways, but photo-stimulation-evoked changes in neural and hemodynamic activities were linearly correlated. Hemodynamic point spread functions were estimated from the photo-stimulation data and its full-width at half-maximum ranged between 103 and 175 µm. Therefore, submillimeter functional structures separated by a few hundred micrometers may be resolved using hemodynamic methods, such as optical imaging and functional magnetic resonance imaging.
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Affiliation(s)
- Alberto L Vazquez
- Neuroimaging Laboratory, Department of Radiology, Department of Bioengineering
| | | | - Justin C Crowley
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Seong-Gi Kim
- Neuroimaging Laboratory, Department of Radiology, Department of Bioengineering, Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA, USA and
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41
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Asplund CL, Chee MWL. Time-on-task and sleep deprivation effects are evidenced in overlapping brain areas. Neuroimage 2013; 82:326-35. [PMID: 23747456 DOI: 10.1016/j.neuroimage.2013.05.119] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 05/08/2013] [Accepted: 05/26/2013] [Indexed: 01/13/2023] Open
Abstract
Both sleep deprivation and extended task engagement (time-on-task) have been shown to degrade performance in tasks evaluating sustained attention. Here we used pulsed arterial spin labeling (pASL) to study participants engaged in a demanding selective attention task. The participants were imaged twice, once after a normal night of sleep and once after approximately 24h of total sleep deprivation. We compared task-related changes in BOLD signal alongside ASL-based cerebral blood flow (CBF) changes. We also collected resting baseline CBF data prior to and following task performance. Both BOLD fMRI and ASL identified spatially congruent task activation in ventral visual cortex and fronto-parietal regions. Sleep deprivation and time-on-task caused a decline of both measures in ventral visual cortex. BOLD fMRI also revealed such declines in fronto-parietal cortex. Only early visual cortex showed a significant upward shift in resting baseline CBF following sleep deprivation, suggesting that the neural consequences of both SD and ToT are primarily evident in task-evoked signals. We conclude that BOLD fMRI is preferable to pASL in studies evaluating sleep deprivation given its better signal to noise characteristics and the relative paucity of state differences in baseline CBF.
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Affiliation(s)
- Christopher L Asplund
- Centre for Cognitive Neuroscience, Neuroscience and Behavioral Disorders Program, Duke-NUS Graduate Medical School, Singapore, Singapore
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42
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Crespi F. In vivo oxymetric analysis of mild hypercapnia upon cerebral oxygen, temperature and blood flow: markers of mood as proposed by concomitant bupropion challenge and electrochemical analysis? Exp Brain Res 2013; 230:597-604. [PMID: 23503770 DOI: 10.1007/s00221-013-3443-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Accepted: 02/06/2013] [Indexed: 10/27/2022]
Abstract
Scientific interest has increased the influence of temperature in neurodegenerative and psychiatric disorders, and according to the monoamine hypothesis, depression is a neurochemical disorder arising from hypofunctioning of brain monoamine systems. Here, in vivo flow-oxymetry is applied to verify relationships between cerebral oxygen tension (pO2), blood flow (CBF), that are markers of brain metabolism, and temperature (T), while in vivo voltammetry is concomitantly applied in the medial prefrontal cortex of anaesthetized rats to monitor monoamine levels such as dopamine (DA) and serotonin. An induced mild hypercapnia via increasing exogenous carbon dioxide (CO2) concentration resulted in increased pO2, CBF and T in discrete brain areas. Concomitant in situ voltammetric analysis of extracellular levels of serotonin and DA has revealed significant changes in the latter, only. Parallel treatment with antidepressant bupropion has confirmed its described central thermogenic properties and its positive influence on dopaminergic activity. CBF was also enhanced by such antidepressant. Altogether these data support direct relationships between markers of brain metabolism such as pO2, CBF, T and brain monoamine[s], indicating the coupled in vivo methodology: oxymetry-voltammetry as a rapid in vivo tool for analyses of such indicators in psychiatric disorders.
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Affiliation(s)
- Francesco Crespi
- Biology Department, Neurosciences CEDD GlaxoSmithKline, Medicines Research Centre, Via Fleming 4, 37135, Verona, Italy,
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Gregori J, Schuff N, Kern R, Günther M. T2-based arterial spin labeling measurements of blood to tissue water transfer in human brain. J Magn Reson Imaging 2013; 37:332-42. [PMID: 23019041 PMCID: PMC3554863 DOI: 10.1002/jmri.23822] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 08/14/2012] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To investigate blood to tissue water transfer in human brain, in vivo and spatially resolved using a T2-based arterial spin labeling (ASL) method with 3D readout. MATERIALS AND METHODS A T2-ASL method is introduced to measure the water transfer processes between arterial blood and brain tissue based on a 3D-GRASE (gradient and spin echo) pulsed ASL sequence with multiecho readout. An analytical mathematical model is derived based on the General Kinetic Model, including blood and tissue compartment, T1 and T2 relaxation, and a blood-to-tissue transfer term. Data were collected from healthy volunteers on a 3 T system. The mean transfer time parameter T(bl → ex) (blood to extravascular compartment transfer time) was derived voxelwise by nonlinear least-squares fitting. RESULTS Whole-brain maps of T(bl → ex) show stable results in cortical regions, yielding different values depending on the brain region. The mean value across subjects and regions of interest (ROIs) in gray matter was 440 ± 30 msec. CONCLUSION A novel method to derive whole-brain maps of blood to tissue water transfer dynamics is demonstrated. It is promising for the investigation of underlying physiological mechanisms and development of diagnostic applications in cerebrovascular diseases.
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Affiliation(s)
- Johannes Gregori
- Institute for Medical Image Computing MEVIS, Fraunhofer MEVIS, Bremen, Germany.
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Liu YJ, Huang TY, Lee YH, Juan CJ. The cerebral vasomotor response in varying CO(2) concentrations, as evaluated using cine phase contrast MRI: Flow, volume, and cerebrovascular resistance indices. Med Phys 2013; 39:6534-41. [PMID: 23127048 DOI: 10.1118/1.4754806] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
PURPOSE Previous studies have identified that impaired cerebral vasomotor reactivity (VMR) is associated with a higher risk of stroke and transient ischemic attack. This study aims to evaluate VMR by measuring the blood flow waveforms of the supplying arteries and dural sinuses using cine phase contrast MRI (PC MRI) and hypercapnic challenge. METHODS PC MRI flow quantification was performed on an oblique slice approximately perpendicular to the target vessels to include the left (LICA) and right internal carotid artery (RICA), basilar artery (BA), sinus rectus (SR), and superior sagittal sinus (SSS). A total of four PC MRI scans were performed at different CO(2) concentrations (room air and 3%, 5%, and 7% CO(2)). RESULTS The analyses obtained the flow parameters and cerebrovascular resistance parameters for all five vessels. Results indicated that the vascular resistance indices decreased with increasing CO(2) concentration in four vessels (LICA, RICA, BA, and SR). The obtained VMR parameters demonstrated exponential increases with increasing CO(2) concentration. CONCLUSIONS Using entire blood flow waveforms, this study applied separate flow dynamics during systolic and diastolic periods to obtain cerebrovascular resistance parameters and extensive flow-related information. It is the first to investigate the cerebrovascular resistance parameters under hypercapnic challenge using cine MRI. This technique could provide a useful tool for clinical application in cerebrovascular disease.
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Affiliation(s)
- Yi-Jui Liu
- Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan, Republic of China
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Khalili-Mahani N, van Osch MJ, de Rooij M, Beckmann CF, van Buchem MA, Dahan A, van Gerven JM, Rombouts SARB. Spatial heterogeneity of the relation between resting-state connectivity and blood flow: an important consideration for pharmacological studies. Hum Brain Mapp 2012; 35:929-42. [PMID: 23281174 DOI: 10.1002/hbm.22224] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 10/08/2012] [Accepted: 10/22/2012] [Indexed: 01/28/2023] Open
Abstract
Resting state fMRI (RSfMRI) and arterial spin labeling (ASL) provide the field of pharmacological Neuroimaging tool for investigating states of brain activity in terms of functional connectivity or cerebral blood flow (CBF). Functional connectivity reflects the degree of synchrony or correlation of spontaneous fluctuations--mostly in the blood oxygen level dependent (BOLD) signal--across brain networks; but CBF reflects mean delivery of arterial blood to the brain tissue over time. The BOLD and CBF signals are linked to common neurovascular and hemodynamic mechanisms that necessitate increased oxygen transportation to the site of neuronal activation; however, the scale and the sources of variation in static CBF and spatiotemporal BOLD correlations are likely different. We tested this hypothesis by examining the relation between CBF and resting-state-network consistency (RSNC)--representing average intranetwork connectivity, determined from dual regression analysis with eight standard networks of interest (NOIs)--in a crossover placebo-controlled study of morphine and alcohol. Overall, we observed spatially heterogeneous relations between RSNC and CBF, and between the experimental factors (drug-by-time, time, drug and physiological rates) and each of these metrics. The drug-by-time effects on CBF were significant in all networks, but significant RSNC changes were limited to the sensorimotor, the executive/salience and the working memory networks. The post-hoc voxel-wise statistics revealed similar dissociations, perhaps suggesting differential sensitivity of RSNC and CBF to neuronal and vascular endpoints of drug actions. The spatial heterogeneity of RSNC/CBF relations encourages further investigation into the role of neuroreceptor distribution and cerebrovascular anatomy in predicting spontaneous fluctuations under drugs.
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Affiliation(s)
- Najmeh Khalili-Mahani
- Institute of Psychology, Leiden University, Leiden, The Netherlands; Department of Radiology, Leiden University Medical Center (LUMC), Leiden, The Netherlands; Leiden Institute for Brain and Cognition (LIBC), Leiden University, Leiden, The Netherlands
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Leontiev O, Buracas GT, Liang C, Ances BM, Perthen JE, Shmuel A, Buxton RB. Coupling of cerebral blood flow and oxygen metabolism is conserved for chromatic and luminance stimuli in human visual cortex. Neuroimage 2012; 68:221-8. [PMID: 23238435 DOI: 10.1016/j.neuroimage.2012.11.050] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 11/13/2012] [Accepted: 11/15/2012] [Indexed: 11/19/2022] Open
Abstract
The ratio of the changes in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO(2)) during brain activation is a critical determinant of the magnitude of the blood oxygenation level dependent (BOLD) response measured with functional magnetic resonance imaging (fMRI). Cytochrome oxidase (CO), a key component of oxidative metabolism in the mitochondria, is non-uniformly distributed in visual area V1 in distinct blob and interblob regions, suggesting significant spatial variation in the capacity for oxygen metabolism. The goal of this study was to test whether CBF/CMRO(2) coupling differed when these subpopulations of neurons were preferentially stimulated, using chromatic and luminance stimuli to preferentially stimulate either the blob or interblob regions. A dual-echo spiral arterial spin labeling (ASL) technique was used to measure CBF and BOLD responses simultaneously in 7 healthy human subjects. When the stimulus contrast levels were adjusted to evoke similar CBF responses (mean 65.4% ± 19.0% and 64.6% ± 19.9%, respectively for chromatic and luminance contrast), the BOLD responses were remarkably similar (1.57% ± 0.39% and 1.59% ± 0.35%) for both types of stimuli. We conclude that CBF-CMRO(2) coupling is conserved for the chromatic and luminance stimuli used, suggesting a consistent coupling for blob and inter-blob neuronal populations despite the difference in CO concentration.
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Affiliation(s)
- Oleg Leontiev
- Department of Radiology and Center for Functional MRI, University of California, San Diego, CA 92093-0677, USA
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Nasrallah FA, Lee ELQ, Chuang KH. Optimization of flow-sensitive alternating inversion recovery (FAIR) for perfusion functional MRI of rodent brain. NMR IN BIOMEDICINE 2012; 25:1209-1216. [PMID: 22451418 DOI: 10.1002/nbm.2790] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 12/02/2011] [Accepted: 01/17/2012] [Indexed: 05/31/2023]
Abstract
Arterial spin labeling (ASL) MRI provides a noninvasive method to image perfusion, and has been applied to map neural activation in the brain. Although pulsed labeling methods have been widely used in humans, continuous ASL with a dedicated neck labeling coil is still the preferred method in rodent brain functional MRI (fMRI) to maximize the sensitivity and allow multislice acquisition. However, the additional hardware is not readily available and hence its application is limited. In this study, flow-sensitive alternating inversion recovery (FAIR) pulsed ASL was optimized for fMRI of rat brain. A practical challenge of FAIR is the suboptimal global inversion by the transmit coil of limited dimensions, which results in low effective labeling. By using a large volume transmit coil and proper positioning to optimize the body coverage, the perfusion signal was increased by 38.3% compared with positioning the brain at the isocenter. An additional 53.3% gain in signal was achieved using optimized repetition and inversion times compared with a long TR. Under electrical stimulation to the forepaws, a perfusion activation signal change of 63.7 ± 6.3% can be reliably detected in the primary somatosensory cortices using single slice or multislice echo planar imaging at 9.4 T. This demonstrates the potential of using pulsed ASL for multislice perfusion fMRI in functional and pharmacological applications in rat brain.
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Affiliation(s)
- Fatima A Nasrallah
- Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research, Singapore
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Hayen A, Herigstad M, Kelly M, Okell TW, Murphy K, Wise RG, Pattinson KTS. The effects of altered intrathoracic pressure on resting cerebral blood flow and its response to visual stimulation. Neuroimage 2012; 66:479-88. [PMID: 23108273 PMCID: PMC3547172 DOI: 10.1016/j.neuroimage.2012.10.049] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 10/04/2012] [Accepted: 10/06/2012] [Indexed: 11/19/2022] Open
Abstract
Investigating how intrathoracic pressure changes affect cerebral blood flow (CBF) is important for a clear interpretation of neuroimaging data in patients with abnormal respiratory physiology, intensive care patients receiving mechanical ventilation and in research paradigms that manipulate intrathoracic pressure. Here, we investigated the effect of experimentally increased and decreased intrathoracic pressures upon CBF and the stimulus-evoked CBF response to visual stimulation. Twenty healthy volunteers received intermittent inspiratory and expiratory loads (plus or minus 9cmH2O for 270s) and viewed an intermittent 2Hz flashing checkerboard, while maintaining stable end-tidal CO2. CBF was recorded with transcranial Doppler sonography (TCD) and whole-brain pseudo-continuous arterial spin labeling magnetic resonance imaging (PCASL MRI). Application of inspiratory loading (negative intrathoracic pressure) showed an increase in TCD-measured CBF of 4% and a PCASL-measured increase in grey matter CBF of 5%, but did not alter mean arterial pressure (MAP). Expiratory loading (positive intrathoracic pressure) did not alter CBF, while MAP increased by 3%. Neither loading condition altered the perfusion response to visual stimulation in the primary visual cortex. In both loading conditions localized CBF increases were observed in the somatosensory and motor cortices, and in the cerebellum. Altered intrathoracic pressures, whether induced experimentally, therapeutically or through a disease process, have possible significant effects on CBF and should be considered as a potential systematic confound in the interpretation of perfusion-based neuroimaging data.
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Affiliation(s)
- Anja Hayen
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
| | - Mari Herigstad
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
| | - Michael Kelly
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
| | - Thomas W Okell
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
| | - Kevin Murphy
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Park Place, CF10 3AT, Cardiff, UK.
| | - Richard G Wise
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Park Place, CF10 3AT, Cardiff, UK.
| | - Kyle T S Pattinson
- Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
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Li Z, Zhu Y, Childress AR, Detre JA, Wang Z. Relations between BOLD fMRI-derived resting brain activity and cerebral blood flow. PLoS One 2012; 7:e44556. [PMID: 23028560 PMCID: PMC3448607 DOI: 10.1371/journal.pone.0044556] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 08/06/2012] [Indexed: 11/18/2022] Open
Abstract
Consistent resting brain activity patterns have been repeatedly demonstrated using measures derived from resting BOLD fMRI data. While those metrics are presumed to reflect underlying spontaneous brain activity (SBA), it is challenging to prove that association because resting BOLD fMRI metrics are purely model-free and scale-free variables. Cerebral blood flow (CBF) is typically closely coupled to brain metabolism and is used as a surrogate marker for quantifying regional brain function, including resting function. Assessing the correlations between resting BOLD fMRI measures and CBF correlation should provide a means of linking of those measures to the underlying SBA, and a means to quantify those scale-free measures. The purpose of this paper was to examine the CBF correlations of 3 widely used neuroimaging-based SBA measures, including seed-region based functional connectivity (FC), regional homogeneity (ReHo), and amplitude of low frequency fluctuation (ALFF). Test-retest data were acquired to check the stability of potential correlations across time. Reproducible posterior cingulate cortex (PCC) FC vs regional CBF correlations were found in much of the default mode network and visual cortex. Dorsal anterior cingulate cortex (ACC) FC vs CBF correlations were consistently found in bilateral prefrontal cortex. Both ReHo and ALFF were found to be reliably correlated with CBF in most of brain cortex. None of the assessed SBA measures was correlated with whole brain mean CBF. These findings suggest that resting BOLD fMRI-derived measures are coupled with regional CBF and are therefore linked to regional SBA.
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Affiliation(s)
- Zhengjun Li
- Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Yisheng Zhu
- Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Anna Rose Childress
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - John A. Detre
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Ze Wang
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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Liang CL, Ances BM, Perthen JE, Moradi F, Liau J, Buracas GT, Hopkins SR, Buxton RB. Luminance contrast of a visual stimulus modulates the BOLD response more than the cerebral blood flow response in the human brain. Neuroimage 2012; 64:104-11. [PMID: 22963855 DOI: 10.1016/j.neuroimage.2012.08.077] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 07/23/2012] [Accepted: 08/28/2012] [Indexed: 11/15/2022] Open
Abstract
The blood oxygenation level dependent (BOLD) response measured with functional magnetic resonance imaging (fMRI) depends on the evoked changes in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO(2)) in response to changes in neural activity. This response is strongly modulated by the CBF/CMRO(2) coupling relationship with activation, defined as n, the ratio of the fractional changes. The reliability of the BOLD signal as a quantitative reflection of underlying physiological changes depends on the stability of n in response to different stimuli. The effect of visual stimulus contrast on this coupling ratio was tested in 9 healthy human subjects, measuring CBF and BOLD responses to a flickering checkerboard at four visual contrast levels. The theory of the BOLD effect makes a robust prediction-independent of details of the model-that if the CBF/CMRO(2) coupling ratio n remains constant, then the response ratio between the lowest and highest contrast levels should be higher for the BOLD response than the CBF response because of the ceiling effect on the BOLD response. Instead, this response ratio was significantly lower for the BOLD response (BOLD response: 0.23 ± 0.13, mean ± SD; CBF response: 0.42 ± 0.18; p=0.0054). This data is consistent with a reduced dynamic range (strongest/weakest response ratio) of the CMRO(2) response (~1.7-fold) compared to that of the CBF response (~2.4-fold) as luminance contrast increases, corresponding to an increase of n from 1.7 at the lowest contrast level to 2.3 at the highest contrast level. The implication of these results for fMRI studies is that the magnitude of the BOLD response does not accurately reflect the magnitude of underlying physiological processes.
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Affiliation(s)
- Christine L Liang
- Department of Radiology, University of California, San Diego, CA 92093‐0677, USA
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