201
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Peng SL, Ravi H, Sheng M, Thomas BP, Lu H. Searching for a truly "iso-metabolic" gas challenge in physiological MRI. J Cereb Blood Flow Metab 2017; 37:715-725. [PMID: 26980756 PMCID: PMC5381460 DOI: 10.1177/0271678x16638103] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Revised: 01/14/2016] [Accepted: 01/25/2016] [Indexed: 11/16/2022]
Abstract
Hypercapnia challenge (e.g. inhalation of CO2) has been used in calibrated fMRI as well as in the mapping of vascular reactivity in cerebrovascular diseases. An important assumption underlying these measurements is that CO2 is a pure vascular challenge but does not alter neural activity. However, recent reports have suggested that CO2 inhalation may suppress neural activity and brain metabolic rate. Therefore, the goal of this study is to propose and test a gas challenge that is truly "iso-metabolic," by adding a hypoxic component to the hypercapnic challenge, since hypoxia has been shown to enhance cerebral metabolic rate of oxygen (CMRO2). Measurement of global CMRO2 under various gas challenge conditions revealed that, while hypercapnia (P = 0.002) and hypoxia (P = 0.002) individually altered CMRO2 (by -7.6 ± 1.7% and 16.7 ± 4.1%, respectively), inhalation of hypercapnic-hypoxia gas (5% CO2/13% O2) did not change brain metabolism (CMRO2 change: 1.5 ± 3.9%, P = 0.92). Moreover, cerebral blood flow response to the hypercapnic-hypoxia challenge (in terms of % change per mmHg CO2 change) was even greater than that to hypercapnia alone (P = 0.007). Findings in this study suggest that hypercapnic-hypoxia gas challenge may be a useful maneuver in physiological MRI as it preserves vasodilatory response yet does not alter brain metabolism.
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Affiliation(s)
- Shin-Lei Peng
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, USA
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, USA
- Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung, Taiwan
| | - Harshan Ravi
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, USA
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, USA
- Department of Bioengineering, UT Arlington, Arlington, USA
| | - Min Sheng
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, USA
| | - Binu P Thomas
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, USA
| | - Hanzhang Lu
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, USA
- Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, USA
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202
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A three-dimensional single-scan approach for the measurement of changes in cerebral blood volume, blood flow, and blood oxygenation-weighted signals during functional stimulation. Neuroimage 2017; 147:976-984. [DOI: 10.1016/j.neuroimage.2016.12.082] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2016] [Revised: 11/10/2016] [Accepted: 12/28/2016] [Indexed: 11/23/2022] Open
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203
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Bulte D, Wartolowska K. Monitoring cardiac and respiratory physiology during FMRI. Neuroimage 2016; 154:81-91. [PMID: 27916663 DOI: 10.1016/j.neuroimage.2016.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 11/28/2016] [Accepted: 12/01/2016] [Indexed: 10/20/2022] Open
Abstract
This article will consider how physiological monitoring can be used both as an intrinsic part of an experiment, or for removing unwanted physiological signals from the FMRI time series. As functional MRI is used for a wide variety of applications beyond the identification of regions involved in a task, different sources of noise in the time series become important. The use of arterial spin labelling sequences, either in isolation or combined with BOLD imaging, means that temporal noise must be dealt with differently. Moreover, when these are combined with global cerebrovascular stimuli, such as respiratory challenges, the standard analysis tools must be employed with great care so as not to detrimentally distort the data. Acquiring and analysing physiological data is sometimes more art than science, and this article attempts to provide some insight into common techniques as well as advice on identifying and correcting some of the problems that may be encountered.
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Affiliation(s)
- Daniel Bulte
- Functional Magnetic Resonance Imaging of the Brain Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK; Institute of Biomedical Engineering, Department of Engineering Science, Old Road Campus Research Building, University of Oxford, Oxford OX3 7DQ, UK.
| | - Karolina Wartolowska
- Botnar Research Centre, Nuffiled Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Old Road, Oxford OX3 7LD, UK
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204
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Shah YS, Hernandez-Garcia L, Jahanian H, Peltier SJ. Support vector machine classification of arterial volume-weighted arterial spin tagging images. Brain Behav 2016; 6:e00549. [PMID: 28031993 PMCID: PMC5167003 DOI: 10.1002/brb3.549] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Revised: 06/01/2016] [Accepted: 06/23/2016] [Indexed: 11/15/2022] Open
Abstract
INTRODUCTION In recent years, machine-learning techniques have gained growing popularity in medical image analysis. Temporal brain-state classification is one of the major applications of machine-learning techniques in functional magnetic resonance imaging (fMRI) brain data. This article explores the use of support vector machine (SVM) classification technique with motor-visual activation paradigm to perform brain-state classification into activation and rest with an emphasis on different acquisition techniques. METHODS Images were acquired using a recently developed variant of traditional pseudocontinuous arterial spin labeling technique called arterial volume-weighted arterial spin tagging (AVAST). The classification scheme is also performed on images acquired using blood oxygenation-level dependent (BOLD) and traditional perfusion-weighted arterial spin labeling (ASL) techniques for comparison. RESULTS The AVAST technique outperforms traditional pseudocontinuous ASL, achieving classification accuracy comparable to that of BOLD contrast images. CONCLUSION This study demonstrates that AVAST has superior signal-to-noise ratio and improved temporal resolution as compared with traditional perfusion-weighted ASL and reduced sensitivity to scanner drift as compared with BOLD. Owing to these characteristics, AVAST lends itself as an ideal choice for dynamic fMRI and real-time neurofeedback experiments with sustained activation periods.
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Affiliation(s)
- Yash S Shah
- Functional MRI Laboratory Biomedical Engineering University of Michigan Ann Arbor MI USA
| | - Luis Hernandez-Garcia
- Functional MRI Laboratory Biomedical Engineering University of Michigan Ann Arbor MI USA
| | | | - Scott J Peltier
- Functional MRI Laboratory Biomedical Engineering University of Michigan Ann Arbor MI USA
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205
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Gutiérrez-Jiménez E, Cai C, Mikkelsen IK, Rasmussen PM, Angleys H, Merrild M, Mouridsen K, Jespersen SN, Lee J, Iversen NK, Sakadzic S, Østergaard L. Effect of electrical forepaw stimulation on capillary transit-time heterogeneity (CTH). J Cereb Blood Flow Metab 2016; 36:2072-2086. [PMID: 26858243 PMCID: PMC5363666 DOI: 10.1177/0271678x16631560] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 11/26/2015] [Accepted: 12/23/2015] [Indexed: 11/16/2022]
Abstract
Functional hyperemia reduces oxygen extraction efficacy unless counteracted by a reduction of capillary transit-time heterogeneity of blood. We adapted a bolus tracking approach to capillary transit-time heterogeneity estimation for two-photon microscopy and then quantified changes in plasma mean transit time and capillary transit-time heterogeneity during forepaw stimulation in anesthetized mice (C57BL/6NTac). In addition, we analyzed transit time coefficient of variance = capillary transit-time heterogeneity/mean transit time, which we expect to remain constant in passive, compliant microvascular networks. Electrical forepaw stimulation reduced, both mean transit time (11.3% ± 1.3%) and capillary transit-time heterogeneity (24.1% ± 3.3%), consistent with earlier literature and model predictions. We observed a coefficient of variance reduction (14.3% ± 3.5%) during functional activation, especially for the arteriolar-to-venular passage. Such coefficient of variance reduction during functional activation suggests homogenization of capillary flows beyond that expected as a passive response to increased blood flow by other stimuli. This finding is consistent with an active neurocapillary coupling mechanism, for example via pericyte dilation. Mean transit time and capillary transit-time heterogeneity reductions were consistent with the relative change inferred from capillary hemodynamics (cell velocity and flux). Our findings support the important role of capillary transit-time heterogeneity in flow-metabolism coupling during functional activation.
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Affiliation(s)
| | - Changsi Cai
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | | | | | - Hugo Angleys
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Mads Merrild
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Kim Mouridsen
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Sune Nørhøj Jespersen
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
| | - Jonghwan Lee
- Department of Radiology, Harvard Medical School, Boston, USA
| | | | - Sava Sakadzic
- Department of Radiology, Harvard Medical School, Boston, USA
| | - Leif Østergaard
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Neuroradiology, Aarhus University Hospital, Aarhus, Denmark
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206
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Soares JM, Magalhães R, Moreira PS, Sousa A, Ganz E, Sampaio A, Alves V, Marques P, Sousa N. A Hitchhiker's Guide to Functional Magnetic Resonance Imaging. Front Neurosci 2016; 10:515. [PMID: 27891073 PMCID: PMC5102908 DOI: 10.3389/fnins.2016.00515] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 10/25/2016] [Indexed: 12/12/2022] Open
Abstract
Functional Magnetic Resonance Imaging (fMRI) studies have become increasingly popular both with clinicians and researchers as they are capable of providing unique insights into brain functions. However, multiple technical considerations (ranging from specifics of paradigm design to imaging artifacts, complex protocol definition, and multitude of processing and methods of analysis, as well as intrinsic methodological limitations) must be considered and addressed in order to optimize fMRI analysis and to arrive at the most accurate and grounded interpretation of the data. In practice, the researcher/clinician must choose, from many available options, the most suitable software tool for each stage of the fMRI analysis pipeline. Herein we provide a straightforward guide designed to address, for each of the major stages, the techniques, and tools involved in the process. We have developed this guide both to help those new to the technique to overcome the most critical difficulties in its use, as well as to serve as a resource for the neuroimaging community.
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Affiliation(s)
- José M. Soares
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga, Portugal
| | - Ricardo Magalhães
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga, Portugal
| | - Pedro S. Moreira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga, Portugal
| | - Alexandre Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga, Portugal
- Department of Informatics, University of MinhoBraga, Portugal
| | - Edward Ganz
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga, Portugal
| | - Adriana Sampaio
- Neuropsychophysiology Lab, CIPsi, School of Psychology, University of MinhoBraga, Portugal
| | - Victor Alves
- Department of Informatics, University of MinhoBraga, Portugal
| | - Paulo Marques
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga, Portugal
| | - Nuno Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of MinhoBraga, Portugal
- ICVS/3B's - PT Government Associate LaboratoryBraga, Portugal
- Clinical Academic Center – BragaBraga, Portugal
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207
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Kazan SM, Huber L, Flandin G, Ivanov D, Bandettini P, Weiskopf N. Physiological basis of vascular autocalibration (VasA): Comparison to hypercapnia calibration methods. Magn Reson Med 2016; 78:1168-1173. [PMID: 27851867 PMCID: PMC5573956 DOI: 10.1002/mrm.26494] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 08/26/2016] [Accepted: 09/14/2016] [Indexed: 11/21/2022]
Abstract
Purpose The statistical power of functional MRI (fMRI) group studies is significantly hampered by high intersubject spatial and magnitude variance. We recently presented a vascular autocalibration method (VasA) to account for vascularization differences between subjects and hence improve the sensitivity in group studies. Here, we validate the novel calibration method by means of direct comparisons of VasA with more established measures of baseline venous blood volume (and indirectly vascular reactivity), the M‐value. Methods Seven healthy volunteers participated in two 7 T (T) fMRI experiments to compare M‐values with VasA estimates: (i) a hypercapnia experiment to estimate voxelwise M‐value maps, and (ii) an fMRI experiment using visual stimulation to estimate voxelwise VasA maps. Results We show that VasA and M‐value calibration maps show the same spatial profile, providing strong evidence that VasA is driven by local variations in vascular reactivity as reflected in the M‐value. Conclusion The agreement of vascular reactivity maps obtained with VasA when compared with M‐value maps confirms empirically the hypothesis that the VasA method is an adequate tool to account for variations in fMRI response amplitudes caused by vascular reactivity differences in healthy volunteers. VasA can therefore directly account for them and increase the statistical power of group studies. The VasA toolbox is available as a statistical parametric mapping (SPM) toolbox, facilitating its general application. Magn Reson Med 78:1168–1173, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Samira M Kazan
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, London, U.K
| | - Laurentius Huber
- Section on Functional Imaging Methods, National Institute of Mental Health, Bethesda, MD, USA
| | - Guillaume Flandin
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, London, U.K
| | - Dimo Ivanov
- Maastricht Brain Imaging Centre, Maastricht University, Maastricht, The Netherlands
| | - Peter Bandettini
- Section on Functional Imaging Methods, National Institute of Mental Health, Bethesda, MD, USA
| | - Nikolaus Weiskopf
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, London, U.K.,Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
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208
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Hubbard NA, Turner M, Hutchison JL, Ouyang A, Strain J, Oasay L, Sundaram S, Davis S, Remington G, Brigante R, Huang H, Hart J, Frohman T, Frohman E, Biswal BB, Rypma B. Multiple sclerosis-related white matter microstructural change alters the BOLD hemodynamic response. J Cereb Blood Flow Metab 2016; 36:1872-1884. [PMID: 26661225 PMCID: PMC5094308 DOI: 10.1177/0271678x15615133] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 09/15/2015] [Indexed: 01/21/2023]
Abstract
Multiple sclerosis (MS) results in inflammatory damage to white matter microstructure. Prior research using blood-oxygen-level dependent (BOLD) imaging indicates MS-related alterations to brain function. What is currently unknown is the extent to which white matter microstructural damage influences BOLD signal in MS. Here we assessed changes in parameters of the BOLD hemodynamic response function (HRF) in patients with relapsing-remitting MS compared to healthy controls. We also used diffusion tensor imaging to assess whether MS-related changes to the BOLD-HRF were affected by changes in white matter microstructural integrity. Our results showed MS-related reductions in BOLD-HRF peak amplitude. These MS-related amplitude decreases were influenced by individual differences in white matter microstructural integrity. Other MS-related factors including altered reaction time, limited spatial extent of BOLD activity, elevated lesion burden, or lesion proximity to regions of interest were not mediators of group differences in BOLD-HRF amplitude. Results are discussed in terms of functional hyperemic mechanisms and implications for analysis of BOLD signal differences.
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Affiliation(s)
- Nicholas A Hubbard
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA
| | - Monroe Turner
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA
| | - Joanna L Hutchison
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA.,Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Austin Ouyang
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jeremy Strain
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA
| | - Larry Oasay
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA
| | - Saranya Sundaram
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA
| | - Scott Davis
- Department of Applied Physiology and Wellness, Southern Methodist University, Dallas, TX, USA
| | - Gina Remington
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ryan Brigante
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA
| | - Hao Huang
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - John Hart
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA.,Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Teresa Frohman
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Elliot Frohman
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Bharat B Biswal
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, NJ, USA
| | - Bart Rypma
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA .,Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA
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209
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Guidi M, Huber L, Lampe L, Gauthier CJ, Möller HE. Lamina-dependent calibrated BOLD response in human primary motor cortex. Neuroimage 2016; 141:250-261. [DOI: 10.1016/j.neuroimage.2016.06.030] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 06/07/2016] [Accepted: 06/17/2016] [Indexed: 02/06/2023] Open
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210
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Field strength dependence of grey matter R 2* on venous oxygenation. Neuroimage 2016; 146:327-332. [PMID: 27720821 PMCID: PMC5312785 DOI: 10.1016/j.neuroimage.2016.10.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 09/19/2016] [Accepted: 10/01/2016] [Indexed: 11/25/2022] Open
Abstract
The relationship between venous blood oxygenation and change in transverse relaxation rate (ΔR2*) plays a key role in calibrated BOLD fMRI. This relationship, defined by the parameter β, has previously been determined using theoretical simulations and experimental measures. However, these earlier studies have been confounded by the change in venous cerebral blood volume (CBV) in response to functional tasks. This study used a double-echo gradient echo EPI scheme in conjunction with a graded isocapnic hyperoxic sequence to assess quantitatively the relationship between the fractional venous blood oxygenation (1−Yv) and transverse relaxation rate of grey matter (ΔR2GM*), without inducing a change in vCBV. The results demonstrate that the relationship between ΔR2* and fractional venous oxygenation at all magnet field strengths studied was adequately described by a linear relationship. The gradient of this relationship did not increase monotonically with field strength, which may be attributed to the relative contributions of intravascular and extravascular signals which will vary with both field strength and blood oxygenation. We assess the relationship between grey matter R2* and venous oxygenation. Isocapnic hyperoxia prevented confounding changes in cerebral blood volume. A linear dependency is an appropriate assumption at 1.5, 3 and 7 T. Intravascular/extravascular signal ratios will vary with both B0 and oxygenation.
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211
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Turner R. Uses, misuses, new uses and fundamental limitations of magnetic resonance imaging in cognitive science. Philos Trans R Soc Lond B Biol Sci 2016; 371:20150349. [PMID: 27574303 PMCID: PMC5003851 DOI: 10.1098/rstb.2015.0349] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/24/2016] [Indexed: 11/29/2022] Open
Abstract
When blood oxygenation level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI) was discovered in the early 1990s, it provoked an explosion of interest in exploring human cognition, using brain mapping techniques based on MRI. Standards for data acquisition and analysis were rapidly put in place, in order to assist comparison of results across laboratories. Recently, MRI data acquisition capabilities have improved dramatically, inviting a rethink of strategies for relating functional brain activity at the systems level with its neuronal substrates and functional connections. This paper reviews the established capabilities of BOLD contrast fMRI, the perceived weaknesses of major methods of analysis, and current results that may provide insights into improved brain modelling. These results have inspired the use of in vivo myeloarchitecture for localizing brain activity, individual subject analysis without spatial smoothing and mapping of changes in cerebral blood volume instead of BOLD activation changes. The apparent fundamental limitations of all methods based on nuclear magnetic resonance are also discussed.This article is part of the themed issue 'Interpreting BOLD: a dialogue between cognitive and cellular neuroscience'.
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Affiliation(s)
- Robert Turner
- Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1A, 04103 Leipzig, Germany
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212
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Puckett AM, Aquino KM, Robinson P, Breakspear M, Schira MM. The spatiotemporal hemodynamic response function for depth-dependent functional imaging of human cortex. Neuroimage 2016; 139:240-248. [DOI: 10.1016/j.neuroimage.2016.06.019] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 05/27/2016] [Accepted: 06/10/2016] [Indexed: 11/15/2022] Open
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213
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Zhang X, Li CX. Arterial spin labeling perfusion magnetic resonance imaging of non-human primates. Quant Imaging Med Surg 2016; 6:573-581. [PMID: 27942478 DOI: 10.21037/qims.2016.10.05] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Non-human primates (NHPs) resemble most aspects of humans in brain physiology and anatomy and are excellent animal models for translational research in neuroscience, biomedical research and pharmaceutical development. Cerebral blood flow (CBF) offers essential physiological information of the brain to examine the abnormal functionality in NHP models with cerebral vascular diseases and neurological disorders or dementia. Arterial spin labeling (ASL) perfusion MRI techniques allow for high temporal and spatial CBF measurement and are intensively used in studies of animals and humans. In this article, current high-resolution ASL perfusion MRI techniques for quantitative evaluation of brain physiology and function in NHPs are described and their applications and limitation are discussed as well.
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Affiliation(s)
- Xiaodong Zhang
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA;; Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Emory University, Atlanta, GA, 30329, USA
| | - Chun-Xia Li
- Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
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214
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Donahue MJ, Strother MK, Lindsey KP, Hocke LM, Tong Y, Frederick BD. Time delay processing of hypercapnic fMRI allows quantitative parameterization of cerebrovascular reactivity and blood flow delays. J Cereb Blood Flow Metab 2016; 36:1767-1779. [PMID: 26661192 PMCID: PMC5076782 DOI: 10.1177/0271678x15608643] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 07/29/2015] [Indexed: 11/17/2022]
Abstract
Blood oxygenation level-dependent fMRI contrast depends on the volume and oxygenation of blood flowing through the circulatory system. The effects on image intensity depend temporally on the arrival of blood within a voxel, and signal can be monitored during the time course of such blood flow. It has been previously shown that the passage of global endogenous variations in blood volume and oxygenation can be tracked as blood passes through the brain by determining the strength and peak time lag of their cross-correlation with blood oxygenation level-dependent data. By manipulating blood composition using transient hypercarbia and hyperoxia, we can induce much larger oxygenation and volume changes in the blood oxygenation level-dependent signal than result from natural endogenous fluctuations. This technique was used to examine cerebrovascular parameters in healthy subjects (n = 8) and subjects with intracranial stenosis (n = 22), with a subgroup of intracranial stenosis subjects scanned before and after surgical revascularization (n = 6). The halfwidth of cross-correlation lag times in the brain was larger in IC stenosis subjects (21.21 ± 14.22 s) than in healthy control subjects (8.03 ± 3.67), p < 0.001, and was subsequently reduced in regions that co-localized with surgical revascularization. These data show that blood circulatory timing can be measured robustly and longitudinally throughout the brain using simple respiratory challenges.
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Affiliation(s)
- Manus J Donahue
- Department of Radiology, Vanderbilt Medical Center, Nashville, TN, USA Department of Neurology, Vanderbilt Medical Center, Nashville, TN, USA Department of Psychiatry, Vanderbilt Medical Center, Nashville, TN, USA Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
| | - Megan K Strother
- Department of Radiology, Vanderbilt Medical Center, Nashville, TN, USA
| | - Kimberly P Lindsey
- Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Lia M Hocke
- Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Bioengineering, Tufts University, Medford, MA, USA
| | - Yunjie Tong
- Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Blaise deB Frederick
- Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Psychiatry, Harvard Medical School, Boston, MA, USA
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215
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A forward modelling approach for the estimation of oxygen extraction fraction by calibrated fMRI. Neuroimage 2016; 139:313-323. [DOI: 10.1016/j.neuroimage.2016.06.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 05/20/2016] [Accepted: 06/03/2016] [Indexed: 11/22/2022] Open
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216
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217
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Donahue MJ, Juttukonda MR, Watchmaker JM. Noise concerns and post-processing procedures in cerebral blood flow (CBF) and cerebral blood volume (CBV) functional magnetic resonance imaging. Neuroimage 2016; 154:43-58. [PMID: 27622397 DOI: 10.1016/j.neuroimage.2016.09.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 08/22/2016] [Accepted: 09/03/2016] [Indexed: 01/19/2023] Open
Abstract
Functional neuroimaging with blood oxygenation level-dependent (BOLD) contrast has emerged as the most popular method for evaluating qualitative changes in brain function in humans. At typical human field strengths (1.5-3.0T), BOLD contrast provides a measure of changes in transverse water relaxation rates in and around capillary and venous blood, and as such provides only a surrogate marker of brain function that depends on dynamic changes in hemodynamics (e.g., cerebral blood flow and volume) and metabolism (e.g., oxygen extraction fraction and the cerebral metabolic rate of oxygen consumption). Alternative functional neuroimaging methods that are specifically sensitive to these constituents of the BOLD signal are being developed and applied in a growing number of clinical and neuroscience applications of quantitative cerebral physiology. These methods require additional considerations for interpreting and quantifying their contrast responsibly. Here, an overview of two popular methods, arterial spin labeling and vascular space occupancy, is presented specifically in the context of functional neuroimaging. Appropriate post-processing and experimental acquisition strategies are summarized with the motivation of reducing sensitivity to noise and unintended signal sources and improving quantitative accuracy of cerebral hemodynamics.
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Affiliation(s)
- Manus J Donahue
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA; Neurology, Vanderbilt University School of Medicine, Nashville, TN, USA; Psychiatry, Vanderbilt University School of Medicine, Nashville, TN, USA.
| | - Meher R Juttukonda
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Jennifer M Watchmaker
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA
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218
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Fernández-Seara MA, Rodgers ZB, Englund EK, Wehrli FW. Calibrated bold fMRI with an optimized ASL-BOLD dual-acquisition sequence. Neuroimage 2016; 142:474-482. [PMID: 27502047 DOI: 10.1016/j.neuroimage.2016.08.007] [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: 04/15/2016] [Revised: 07/11/2016] [Accepted: 08/04/2016] [Indexed: 11/25/2022] Open
Abstract
Calibrated fMRI techniques estimate task-induced changes in the cerebral metabolic rate of oxygen (CMRO2) based on simultaneous measurements of cerebral blood flow (CBF) and blood-oxygen-level-dependent (BOLD) signal changes evoked by stimulation. To determine the calibration factor M (corresponding to the maximum possible BOLD signal increase), BOLD signal and CBF are measured in response to a gas breathing challenge (usually CO2 or O2). Here we describe an ASL dual-acquisition sequence that combines a background-suppressed 3D-GRASE readout with 2D multi-slice EPI. The concatenation of these two imaging sequences allowed separate optimization of the acquisition for CBF and BOLD data. The dual-acquisition sequence was validated by comparison to an ASL sequence with a dual-echo EPI readout, using a visual fMRI paradigm. Results showed a 3-fold increase in temporal signal-to-noise ratio (tSNR) of the ASL time-series data while BOLD tSNR was similar to that obtained with the dual-echo sequence. The longer TR of the proposed dual-acquisition sequence, however, resulted in slightly lower T-scores (by 30%) in the BOLD activation maps. Further, the potential of the dual-acquisition sequence for M-mapping on the basis of a hypercapnia gas breathing challenge and for quantification of CMRO2 changes in response to a motor activation task was assessed. In five subjects, an average gray matter M-value of 8.71±1.03 and fractional changes of CMRO2 of 12.5±5% were found. The new sequence remedies the deficiencies of prior combined BOLD-ASL acquisition strategies by substantially enhancing perfusion tSNR, which is essential for accurate BOLD calibration.
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Affiliation(s)
| | - Zachary B Rodgers
- Laboratory for Structural, Physiologic and Functional Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA, USA
| | - Erin K Englund
- Laboratory for Structural, Physiologic and Functional Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA, USA
| | - Felix W Wehrli
- Laboratory for Structural, Physiologic and Functional Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA, USA
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219
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Bennett MR, Hatton S, Hermens DF, Lagopoulos J. Behavior, neuropsychology and fMRI. Prog Neurobiol 2016; 145-146:1-25. [PMID: 27393370 DOI: 10.1016/j.pneurobio.2016.07.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Revised: 06/14/2016] [Accepted: 07/03/2016] [Indexed: 11/19/2022]
Abstract
Cognitive neuroscientists in the late 20th century began the task of identifying the part(s) of the brain concerned with normal behavior as manifest in the psychological capacities as affective powers, reasoning, behaving purposively and the pursuit of goals, following introduction of the 'functional magnetic resonance imaging' (fMRI) method for identifying brain activity. For this research program to be successful two questions require satisfactory answers. First, as the fMRI method can currently only be used on stationary subjects, to what extent can neuropsychological tests applicable to such stationary subjects be correlated with normal behavior. Second, to what extent can correlations between the various neuropsychological tests on the one hand, and sites of brain activity determined with fMRI on the other, be regarded as established. The extent to which these questions have yet received satisfactory answers is reviewed, and suggestions made both for improving correlations of neuropsychological tests with behavior as well as with the results of fMRI-based observations.
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Affiliation(s)
- Maxwell R Bennett
- Brain & Mind Centre, University of Sydney, Camperdown, NSW 2050, Australia.
| | - Sean Hatton
- Brain & Mind Centre, University of Sydney, Camperdown, NSW 2050, Australia.
| | - Daniel F Hermens
- Brain & Mind Centre, University of Sydney, Camperdown, NSW 2050, Australia.
| | - Jim Lagopoulos
- Brain & Mind Centre, University of Sydney, Camperdown, NSW 2050, Australia; Sunshine Coast Mind and Neuroscience - Thompson Institute, Birtinya, QLD, Australia.
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220
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Rodgers ZB, Detre JA, Wehrli FW. MRI-based methods for quantification of the cerebral metabolic rate of oxygen. J Cereb Blood Flow Metab 2016; 36:1165-85. [PMID: 27089912 PMCID: PMC4929705 DOI: 10.1177/0271678x16643090] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 02/22/2016] [Indexed: 11/16/2022]
Abstract
The brain depends almost entirely on oxidative metabolism to meet its significant energy requirements. As such, the cerebral metabolic rate of oxygen (CMRO2) represents a key measure of brain function. Quantification of CMRO2 has helped elucidate brain functional physiology and holds potential as a clinical tool for evaluating neurological disorders including stroke, brain tumors, Alzheimer's disease, and obstructive sleep apnea. In recent years, a variety of magnetic resonance imaging (MRI)-based CMRO2 quantification methods have emerged. Unlike positron emission tomography - the current "gold standard" for measurement and mapping of CMRO2 - MRI is non-invasive, relatively inexpensive, and ubiquitously available in modern medical centers. All MRI-based CMRO2 methods are based on modeling the effect of paramagnetic deoxyhemoglobin on the magnetic resonance signal. The various methods can be classified in terms of the MRI contrast mechanism used to quantify CMRO2: T2*, T2', T2, or magnetic susceptibility. This review article provides an overview of MRI-based CMRO2 quantification techniques. After a brief historical discussion motivating the need for improved CMRO2 methodology, current state-of-the-art MRI-based methods are critically appraised in terms of their respective tradeoffs between spatial resolution, temporal resolution, and robustness, all of critical importance given the spatially heterogeneous and temporally dynamic nature of brain energy requirements.
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Affiliation(s)
- Zachary B Rodgers
- University of Pennsylvania Medical Center, Philadelphia, PA, USA Laboratory for Structural, Physiologic, and Functional Imaging, Department of Radiology, Philadelphia, PA, USA
| | - John A Detre
- University of Pennsylvania Medical Center, Philadelphia, PA, USA Center for Functional Neuroimaging, Department of Neurology, Philadelphia, PA, USA
| | - Felix W Wehrli
- University of Pennsylvania Medical Center, Philadelphia, PA, USA
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222
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Lundengård K, Cedersund G, Sten S, Leong F, Smedberg A, Elinder F, Engström M. Mechanistic Mathematical Modeling Tests Hypotheses of the Neurovascular Coupling in fMRI. PLoS Comput Biol 2016; 12:e1004971. [PMID: 27310017 PMCID: PMC4911100 DOI: 10.1371/journal.pcbi.1004971] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 05/04/2016] [Indexed: 11/22/2022] Open
Abstract
Functional magnetic resonance imaging (fMRI) measures brain activity by detecting the blood-oxygen-level dependent (BOLD) response to neural activity. The BOLD response depends on the neurovascular coupling, which connects cerebral blood flow, cerebral blood volume, and deoxyhemoglobin level to neuronal activity. The exact mechanisms behind this neurovascular coupling are not yet fully investigated. There are at least three different ways in which these mechanisms are being discussed. Firstly, mathematical models involving the so-called Balloon model describes the relation between oxygen metabolism, cerebral blood volume, and cerebral blood flow. However, the Balloon model does not describe cellular and biochemical mechanisms. Secondly, the metabolic feedback hypothesis, which is based on experimental findings on metabolism associated with brain activation, and thirdly, the neurotransmitter feed-forward hypothesis which describes intracellular pathways leading to vasoactive substance release. Both the metabolic feedback and the neurotransmitter feed-forward hypotheses have been extensively studied, but only experimentally. These two hypotheses have never been implemented as mathematical models. Here we investigate these two hypotheses by mechanistic mathematical modeling using a systems biology approach; these methods have been used in biological research for many years but never been applied to the BOLD response in fMRI. In the current work, model structures describing the metabolic feedback and the neurotransmitter feed-forward hypotheses were applied to measured BOLD responses in the visual cortex of 12 healthy volunteers. Evaluating each hypothesis separately shows that neither hypothesis alone can describe the data in a biologically plausible way. However, by adding metabolism to the neurotransmitter feed-forward model structure, we obtained a new model structure which is able to fit the estimation data and successfully predict new, independent validation data. These results open the door to a new type of fMRI analysis that more accurately reflects the true neuronal activity. Functional magnetic resonance imaging (fMRI) is a widely used technique for measuring brain activity. However, the signal registered by fMRI is not a direct measurement of the neuronal activity in the brain, but it is influenced by the interplay between the metabolism, blood flow and blood volume in the active area. This signal is called the blood-oxygen-level dependent (BOLD) response and occurs when the blood supply to the active area increases in response to neuronal activity. The mechanisms that the cells use to influence the blood supply are not fully known, and therefore it is difficult to know the true neuronal signalling only from inspection of the fMRI signal. In this article, we present a new mathematical model built on the physiological mechanisms thought to underlie the BOLD response. We could successfully fit the model to data and predict the activity caused by new stimuli. By using the validated model we investigated physiological mechanisms that cause different parts of the BOLD response.
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Affiliation(s)
- Karin Lundengård
- Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - Gunnar Cedersund
- Department of Biomedical Engineering, Linköping University, Linköping, Sweden
- Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - Sebastian Sten
- Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
| | - Felix Leong
- Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
| | - Alexander Smedberg
- Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
| | - Fredrik Elinder
- Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - Maria Engström
- Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
- * E-mail:
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223
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Olaru AM, Roy SS, Lloyd LS, Coombes S, Green GGR, Duckett SB. Creating a hyperpolarised pseudo singlet state through polarisation transfer from parahydrogen under SABRE. Chem Commun (Camb) 2016; 52:7842-5. [PMID: 27242264 PMCID: PMC5159739 DOI: 10.1039/c6cc02020h] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 05/18/2016] [Indexed: 12/11/2022]
Abstract
The creation of magnetic states that have long lifetimes has been the subject of intense investigation, in part because of their potential to survive the time taken to travel from the point of injection in a patient to the point where a clinically diagnostic MRI trace is collected. We show here that it is possible to harness the signal amplification by reversible exchange (SABRE) process to create such states in a hyperpolarised form that improves their detectability in seconds without the need for any chemical change by reference to the model substrate 2-aminothiazole. We achieve this by transferring Zeeman derived polarisation that is 1500 times larger than that normally available at 400 MHz with greater than 90% efficiency into the new state, which in this case has a 27 second lifetime.
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Affiliation(s)
- Alexandra M Olaru
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | - Soumya S Roy
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | - Lyrelle S Lloyd
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | - Steven Coombes
- AstraZeneca R&D Pharmaceutical Development, Silk Road Business Park, Charter Way, Macclesfield, Cheshire SK10 2NA, UK
| | - Gary G R Green
- York Neuroimaging Centre, The Biocentre, York Science Park, Innovation Way, Heslington, York YO10 5DD, UK
| | - Simon B Duckett
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
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224
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Bhogal AA, De Vis JB, Siero JCW, Petersen ET, Luijten PR, Hendrikse J, Philippens MEP, Hoogduin H. The BOLD cerebrovascular reactivity response to progressive hypercapnia in young and elderly. Neuroimage 2016; 139:94-102. [PMID: 27291492 DOI: 10.1016/j.neuroimage.2016.06.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 05/30/2016] [Accepted: 06/08/2016] [Indexed: 12/01/2022] Open
Abstract
Blood Oxygenation Level Dependent (BOLD) imaging in combination with vasoactive stimuli can be used to probe cerebrovascular reactivity (CVR). Characterizing the healthy, age-related changes in the BOLD-CVR response can provide a reference point from which to distinguish abnormal CVR from the otherwise normal effects of ageing. Using a computer controlled gas delivery system, we examine differences in BOLD-CVR response to progressive hypercapnia between 16 young (28±3years, 9 female) and 30 elderly subjects (66±4years, 13 female). Furthermore, we incorporate baseline T2* information to broaden our interpretation of the BOLD-CVR response. Significant age-related differences were observed. Grey matter CVR at 7mmHg above resting PetCO2 was lower amongst elderly (0.19±0.06%ΔBOLD/mmHg) as compared to young subjects (0.26±0.07%ΔBOLD/mmHg). White matter CVR at 7mmHg above baseline PetCO2 showed no significant difference between young (0.04±0.02%ΔBOLD/mmHg) and elderly subjects (0.05±0.03%ΔBOLD/mmHg). We saw no significant differences in the BOLD signal response to progressive hypercapnia between male and female subjects in either grey or white matter. The observed differences in the healthy BOLD-CVR response could be explained by age-related changes in vascular mechanical properties.
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Affiliation(s)
- Alex A Bhogal
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
| | - Jill B De Vis
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jeroen C W Siero
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Esben T Petersen
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital, Hvidovre, Denmark
| | - Peter R Luijten
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jeroen Hendrikse
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Hans Hoogduin
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
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225
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Chandra SB, Mohan S, Ford BM, Huang L, Janardhanan P, Deo KS, Cong L, Muir ER, Duong TQ. Targeted overexpression of endothelial nitric oxide synthase in endothelial cells improves cerebrovascular reactivity in Ins2Akita-type-1 diabetic mice. J Cereb Blood Flow Metab 2016; 36:1135-42. [PMID: 26661212 PMCID: PMC4908624 DOI: 10.1177/0271678x15612098] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 09/23/2015] [Indexed: 11/16/2022]
Abstract
Reduced bioavailability of nitric oxide due to impaired endothelial nitric oxide synthase (eNOS) activity is a leading cause of endothelial dysfunction in diabetes. Enhancing eNOS activity in diabetes is a potential therapeutic target. This study investigated basal cerebral blood flow and cerebrovascular reactivity in wild-type mice, diabetic mice (Ins2(Akita+/-)), nondiabetic eNOS-overexpressing mice (TgeNOS), and the cross of two transgenic mice (TgeNOS-Ins2(Akita+/-)) at six months of age. The cross was aimed at improving eNOS expression in diabetic mice. The major findings were: (i) Body weights of Ins2(Akita+/-) and TgeNOS-Ins2(Akita+/-) were significantly different from wild-type and TgeNOS mice. Blood pressure of TgeNOS mice was lower than wild-type. (ii) Basal cerebral blood flow of the TgeNOS group was significantly higher than cerebral blood flow of the other three groups. (iii) The cerebrovascular reactivity in the Ins2(Akita+/-) mice was significantly lower compared with wild-type, whereas that in the TgeNOS-Ins2(Akita+/-) was significantly higher compared with the Ins2(Akita+/-) and TgeNOS groups. Overexpression of eNOS rescued cerebrovascular dysfunction in diabetic animals, resulting in improved cerebrovascular reactivity. These results underscore the possible role of eNOS in vascular dysfunction in the brain of diabetic mice and support the notion that enhancing eNOS activity in diabetes is a potential therapeutic target.
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Affiliation(s)
- Saurav B Chandra
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, USA
| | - Sumathy Mohan
- Department of Pathology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Bridget M Ford
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, USA
| | - Lei Huang
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, USA
| | - Preethi Janardhanan
- Department of Pathology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Kaiwalya S Deo
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, USA
| | - Linlin Cong
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, USA
| | - Eric R Muir
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, USA Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Timothy Q Duong
- Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, USA Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX, USA
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226
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Uhlirova H, Kılıç K, Tian P, Thunemann M, Desjardins M, Saisan PA, Sakadžić S, Ness TV, Mateo C, Cheng Q, Weldy KL, Razoux F, Vandenberghe M, Cremonesi JA, Ferri CG, Nizar K, Sridhar VB, Steed TC, Abashin M, Fainman Y, Masliah E, Djurovic S, Andreassen OA, Silva GA, Boas DA, Kleinfeld D, Buxton RB, Einevoll GT, Dale AM, Devor A. Cell type specificity of neurovascular coupling in cerebral cortex. eLife 2016; 5. [PMID: 27244241 PMCID: PMC4933561 DOI: 10.7554/elife.14315] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Accepted: 05/30/2016] [Indexed: 12/16/2022] Open
Abstract
Identification of the cellular players and molecular messengers that communicate neuronal activity to the vasculature driving cerebral hemodynamics is important for (1) the basic understanding of cerebrovascular regulation and (2) interpretation of functional Magnetic Resonance Imaging (fMRI) signals. Using a combination of optogenetic stimulation and 2-photon imaging in mice, we demonstrate that selective activation of cortical excitation and inhibition elicits distinct vascular responses and identify the vasoconstrictive mechanism as Neuropeptide Y (NPY) acting on Y1 receptors. The latter implies that task-related negative Blood Oxygenation Level Dependent (BOLD) fMRI signals in the cerebral cortex under normal physiological conditions may be mainly driven by the NPY-positive inhibitory neurons. Further, the NPY-Y1 pathway may offer a potential therapeutic target in cerebrovascular disease.
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Affiliation(s)
- Hana Uhlirova
- Department of Radiology, University of California, San Diego, La Jolla, United States
| | - Kıvılcım Kılıç
- Department of Neurosciences, University of California, San Diego, La Jolla, United States
| | - Peifang Tian
- Department of Neurosciences, University of California, San Diego, La Jolla, United States.,Department of Physics, John Carroll University, University Heights, United States
| | - Martin Thunemann
- Department of Radiology, University of California, San Diego, La Jolla, United States
| | - Michèle Desjardins
- Department of Radiology, University of California, San Diego, La Jolla, United States
| | - Payam A Saisan
- Department of Neurosciences, University of California, San Diego, La Jolla, United States
| | - Sava Sakadžić
- Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, United States
| | - Torbjørn V Ness
- Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Celine Mateo
- Department of Physics, University of California, San Diego, La Jolla, United States
| | - Qun Cheng
- Department of Neurosciences, University of California, San Diego, La Jolla, United States
| | - Kimberly L Weldy
- Department of Neurosciences, University of California, San Diego, La Jolla, United States
| | - Florence Razoux
- Department of Neurosciences, University of California, San Diego, La Jolla, United States
| | - Matthieu Vandenberghe
- Department of Radiology, University of California, San Diego, La Jolla, United States.,NORMENT, KG Jebsen Centre for Psychosis Research, Division of Mental Health and Addiction, University of Oslo, Oslo, Norway
| | - Jonathan A Cremonesi
- Biology Undergraduate Program, University of California, San Diego, La Jolla, United States
| | - Christopher Gl Ferri
- Department of Neurosciences, University of California, San Diego, La Jolla, United States
| | - Krystal Nizar
- Neurosciences Graduate Program, University of California, San Diego, La Jolla, United States
| | - Vishnu B Sridhar
- Department of Bioengineering, University of California, San Diego, La Jolla, United States
| | - Tyler C Steed
- Neurosciences Graduate Program, University of California, San Diego, La Jolla, United States
| | - Maxim Abashin
- Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, United States
| | - Yeshaiahu Fainman
- Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, United States
| | - Eliezer Masliah
- Department of Neurosciences, University of California, San Diego, La Jolla, United States
| | - Srdjan Djurovic
- Department of Medical Genetics, Oslo University Hospital, Oslo, Norway.,NORMENT, KG Jebsen Centre for Psychosis Research, Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Ole A Andreassen
- NORMENT, KG Jebsen Centre for Psychosis Research, Division of Mental Health and Addiction, University of Oslo, Oslo, Norway
| | - Gabriel A Silva
- Department of Bioengineering, University of California, San Diego, La Jolla, United States.,Department of Ophthalmology, University of California, San Diego, La Jolla, United States
| | - David A Boas
- Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, United States
| | - David Kleinfeld
- Department of Physics, University of California, San Diego, La Jolla, United States.,Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, United States.,Section of Neurobiology, University of California, San Diego, La Jolla, United States
| | - Richard B Buxton
- Department of Radiology, University of California, San Diego, La Jolla, United States
| | - Gaute T Einevoll
- Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway.,Department of Physics, University of Oslo, Oslo, Norway
| | - Anders M Dale
- Department of Radiology, University of California, San Diego, La Jolla, United States.,Department of Neurosciences, University of California, San Diego, La Jolla, United States
| | - Anna Devor
- Department of Radiology, University of California, San Diego, La Jolla, United States.,Department of Neurosciences, University of California, San Diego, La Jolla, United States.,Martinos Center for Biomedical Imaging, Harvard Medical School, Charlestown, United States
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227
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Tardif CL, Gauthier CJ, Steele CJ, Bazin PL, Schäfer A, Schaefer A, Turner R, Villringer A. Advanced MRI techniques to improve our understanding of experience-induced neuroplasticity. Neuroimage 2016; 131:55-72. [DOI: 10.1016/j.neuroimage.2015.08.047] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 08/18/2015] [Accepted: 08/20/2015] [Indexed: 12/13/2022] Open
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228
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Ellis MJ, Ryner LN, Sobczyk O, Fierstra J, Mikulis DJ, Fisher JA, Duffin J, Mutch WAC. Neuroimaging Assessment of Cerebrovascular Reactivity in Concussion: Current Concepts, Methodological Considerations, and Review of the Literature. Front Neurol 2016; 7:61. [PMID: 27199885 PMCID: PMC4850165 DOI: 10.3389/fneur.2016.00061] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 04/11/2016] [Indexed: 01/07/2023] Open
Abstract
Concussion is a form of traumatic brain injury (TBI) that presents with a wide spectrum of subjective symptoms and few objective clinical findings. Emerging research suggests that one of the processes that may contribute to concussion pathophysiology is dysregulation of cerebral blood flow (CBF) leading to a mismatch between CBF delivery and the metabolic needs of the injured brain. Cerebrovascular reactivity (CVR) is defined as the change in CBF in response to a measured vasoactive stimulus. Several magnetic resonance imaging (MRI) techniques can be used as a surrogate measure of CBF in clinical and laboratory studies. In order to provide an accurate assessment of CVR, these sequences must be combined with a reliable, reproducible vasoactive stimulus that can manipulate CBF. Although CVR imaging currently plays a crucial role in the diagnosis and management of many cerebrovascular diseases, only recently have studies begun to apply this assessment tool in patients with concussion. In order to evaluate the quality, reliability, and relevance of CVR studies in concussion, it is important that clinicians and researchers have a strong foundational understanding of the role of CBF regulation in health, concussion, and more severe forms of TBI, and an awareness of the advantages and limitations of currently available CVR measurement techniques. Accordingly, in this review, we (1) discuss the role of CVR in TBI and concussion, (2) examine methodological considerations for MRI-based measurement of CVR, and (3) provide an overview of published CVR studies in concussion patients.
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Affiliation(s)
- Michael J Ellis
- Department of Surgery, University of Manitoba, Winnipeg, MB, Canada; Department of Pediatrics and Child Health, University of Manitoba, Winnipeg, MB, Canada; Section of Neurosurgery, University of Manitoba, Winnipeg, MB, Canada; Pan Am Concussion Program, University of Manitoba, Winnipeg, MB, Canada; Childrens Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, MB, Canada; Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; University of Manitoba, Winnipeg, MB, Canada
| | - Lawrence N Ryner
- Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; Department of Radiology, University of Manitoba, Winnipeg, MB, Canada; Health Sciences Centre, University of Manitoba, Winnipeg, MB, Canada
| | - Olivia Sobczyk
- Institute of Medical Sciences, University of Toronto , Toronto, ON , Canada
| | - Jorn Fierstra
- Department of Neurosurgery, University Hospital Zurich , Zurich , Switzerland
| | - David J Mikulis
- Department of Medical Imaging, University of Toronto, Toronto, ON, Canada; University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada
| | - Joseph A Fisher
- University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada; Department of Anesthesia, University of Toronto, Toronto, ON, Canada
| | - James Duffin
- University of Toronto, Toronto, ON, Canada; University Health Network Cerebrovascular Reactivity Research Group, Toronto, ON, Canada; Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - W Alan C Mutch
- Canada North Concussion Network, University of Manitoba, Winnipeg, MB, Canada; University of Manitoba, Winnipeg, MB, Canada; Health Sciences Centre, University of Manitoba, Winnipeg, MB, Canada; Department of Anesthesia and Perioperative Medicine, University of Manitoba, Winnipeg, MB, Canada
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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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230
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Jog MA, Yan L, Kilroy E, Krasileva K, Jann K, LeClair H, Elashoff D, Wang DJJ. Developmental trajectories of cerebral blood flow and oxidative metabolism at baseline and during working memory tasks. Neuroimage 2016; 134:587-596. [PMID: 27103136 DOI: 10.1016/j.neuroimage.2016.04.035] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2015] [Revised: 04/11/2016] [Accepted: 04/14/2016] [Indexed: 01/12/2023] Open
Abstract
The neurobiological interpretation of developmental BOLD fMRI findings remains difficult due to the confounding issues of potentially varied baseline of brain function and varied strength of neurovascular coupling across age groups. The central theme of the present research is to study the development of brain function and neuronal activity through in vivo assessments of cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2) both at baseline and during the performance of a working memory task in a cohort of typically developing children aged 7 to 18years. Using a suite of 4 emerging MRI technologies including MR blood oximetry, phase-contrast MRI, pseudo-continuous arterial spin labeling (pCASL) perfusion MRI and concurrent CBF/BOLD fMRI, we found: 1) At baseline, both global CBF and CMRO2 showed an age related decline while global OEF was stable across the age group; 2) During the working memory task, neither BOLD nor CBF responses showed significant variations with age in the activated fronto-parietal brain regions. Nevertheless, detailed voxel-wise analyses revealed sub-regions within the activated fronto-parietal regions that show significant decline of fractional CMRO2 responses with age. These findings suggest that the brain may become more "energy efficient" with age during development.
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Affiliation(s)
- Mayank A Jog
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, CA, USA
| | - Lirong Yan
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, CA, USA
| | - Emily Kilroy
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, CA, USA
| | - Kate Krasileva
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, CA, USA
| | - Kay Jann
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, CA, USA
| | - Holly LeClair
- Department of Medicine Statistics Core, UCLA, Los Angeles, CA, USA
| | - David Elashoff
- Department of Medicine Statistics Core, UCLA, Los Angeles, CA, USA
| | - Danny J J Wang
- Laboratory of FMRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, CA, USA.
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231
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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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232
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Leung J, Kosinski PD, Croal PL, Kassner A. Developmental trajectories of cerebrovascular reactivity in healthy children and young adults assessed with magnetic resonance imaging. J Physiol 2016; 594:2681-9. [PMID: 26847953 DOI: 10.1113/jp271056] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 01/28/2016] [Indexed: 01/13/2023] Open
Abstract
KEY POINTS Cerebrovascular reactivity (CVR) reflects the vasodilatory reserve of cerebral resistance vessels. Normal development in children is associated with significant changes in blood pressure, cerebral blood flow (CBF) and cerebral oxygen metabolism. Therefore, it stands to reason that CVR will also undergo changes during this period. The study acquired magnetic resonance imaging measures of CVR and CBF in healthy children and young adults to trace their changes with age. We found that CVR changes in two phases, increasing with age until the mid-teens, followed by a decrease. Baseline CBF declined steadily with age. We conclude that CVR varies with age during childhood, which prompts future CVR studies involving children to take into account the effect of development. ABSTRACT Cerebrovascular reactivity (CVR) reflects the vasculature's ability to accommodate changes in blood flow demand thereby serving as a critical imaging tool for mapping vascular reserve. Normal development is associated with extensive physiological changes in blood pressure, cerebral blood flow and cerebral metabolic rate of oxygen, all of which can affect CVR. Moreover, the evolution of these physiological parameters is most prominent during childhood. Therefore, the aim of this study was to use non-invasive magnetic resonance imaging (MRI) to characterize the developmental trajectories of CVR in healthy children and young adults, and relate them to changes in cerebral blood flow (CBF). Thirty-four healthy subjects (17 males, 17 females; age 9-30 years) underwent CVR assessment using blood oxygen level-dependent MRI in combination with a computer controlled CO2 stimulus. In addition, baseline CBF was measured with a pulsed arterial spin labelling sequence. CVR exhibited a gradual increase with age in both grey and white matter up to 14.7 years. After this break point, a negative correlation with age was detected. Baseline CBF maintained a consistent negative linear correlation across the entire age range. The significant age-dependent changes in CVR and CBF demonstrate the evolution of cerebral haemodynamics in children and should be taken into consideration. The shift in developmental trajectory of CVR from increasing to decreasing suggests that physiological factors beyond baseline CBF also influence CVR.
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Affiliation(s)
- Jackie Leung
- Department of Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada, M5G 1X8
| | - Przemyslaw D Kosinski
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada, M5S 3E2
| | - Paula L Croal
- Department of Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada, M5G 1X8
| | - Andrea Kassner
- Department of Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada, M5G 1X8.,Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada, M5S 3E2
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233
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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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234
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Golestani AM, Kwinta JB, Strother SC, Khatamian YB, Chen JJ. The association between cerebrovascular reactivity and resting-state fMRI functional connectivity in healthy adults: The influence of basal carbon dioxide. Neuroimage 2016; 132:301-313. [PMID: 26908321 DOI: 10.1016/j.neuroimage.2016.02.051] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 12/23/2015] [Accepted: 02/15/2016] [Indexed: 12/28/2022] Open
Abstract
Although widely used in resting-state fMRI (fMRI) functional connectivity measurement (fcMRI), the BOLD signal is only an indirect measure of neuronal activity, and is inherently modulated by both neuronal activity and vascular physiology. For instance, cerebrovascular reactivity (CVR) varies widely across individuals irrespective of neuronal function, but the implications for fcMRI are currently unknown. This knowledge gap compromises our ability to correctly interpret fcMRI measurements. In this work, we investigate the relationship between CVR and resting fcMRI measurements in healthy young adults, in both the motor and the executive-control networks. We modulate CVR within each individual by subtly increasing and decreasing resting vascular tension through baseline end-tidal CO2 (PETCO2), and measure fcMRI during these hypercapnic, hypocapnic and normocapnic states. Furthermore, we assess the association between CVR and fcMRI within and across individuals. Within individuals, resting PETCO2 is found to significantly influence both CVR and resting fcMRI values. In addition, we find resting fcMRI to be significantly and positively associated with CVR across the group in both networks. This relationship is potentially mediated by concomitant alterations in BOLD signal fluctuation amplitude. This work clearly demonstrates and quantifies a major vascular modulator of resting fcMRI, one that is also subject and regional dependent. We suggest that individualized correction for CVR effects in fcMRI measurements is essential for fcMRI studies of healthy brains, and can be even more important in studying diseased brains.
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Affiliation(s)
| | - Jonathan B Kwinta
- Rotman Research Institute at Baycrest Centre, Canada; Department of Medical Biophysics, University of Toronto, Canada
| | - Stephen C Strother
- Rotman Research Institute at Baycrest Centre, Canada; Department of Medical Biophysics, University of Toronto, Canada
| | | | - J Jean Chen
- Rotman Research Institute at Baycrest Centre, Canada; Department of Medical Biophysics, University of Toronto, Canada.
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235
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Hays CC, Zlatar ZZ, Wierenga CE. The Utility of Cerebral Blood Flow as a Biomarker of Preclinical Alzheimer's Disease. Cell Mol Neurobiol 2016; 36:167-79. [PMID: 26898552 DOI: 10.1007/s10571-015-0261-z] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 08/25/2015] [Indexed: 12/20/2022]
Abstract
There is accumulating evidence suggesting that changes in brain perfusion are present long before the clinical symptoms of Alzheimer's disease (AD), perhaps even before amyloid-β accumulation or brain atrophy. This evidence, consistent with the vascular hypothesis of AD, implicates cerebral blood flow (CBF) in the pathogenesis of AD and suggests its utility as a biomarker of preclinical AD. The extended preclinical phase of AD holds particular significance for disease modification, as treatment would likely be most effective in this early asymptomatic stage of disease. This highlights the importance of identifying reliable and accurate biomarkers of AD that can differentiate normal aging from preclinical AD prior to clinical symptom manifestation. Cerebral perfusion, as measured by arterial spin labeling magnetic resonance imaging (ASL-MRI), has been shown to distinguish between normal controls and adults with AD. In addition to demonstrating diagnostic utility, CBF has shown usefulness as a tool for identifying those who are at risk for AD and for predicting subtle cognitive decline and conversion to mild cognitive impairment and AD. Taken together, this evidence not only implicates CBF as a useful biomarker for tracking disease severity and progression, but also suggests that ASL-measured CBF may be useful for identifying candidates for future AD treatment trials, especially in the preclinical, asymptomatic phases of the disease.
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Affiliation(s)
- Chelsea C Hays
- VA San Diego Healthcare System, 3350 La Jolla Village Dr., MC 151B, San Diego, CA, 92161, USA.,SDSU/UC San Diego Joint Doctoral Program in Clinical Psychology, 6363 Alvarado Court, Suite 103, San Diego, CA, 92120, USA
| | - Zvinka Z Zlatar
- VA San Diego Healthcare System, 3350 La Jolla Village Dr., MC 151B, San Diego, CA, 92161, USA.,Department of Psychiatry, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA, 92093, USA
| | - Christina E Wierenga
- VA San Diego Healthcare System, 3350 La Jolla Village Dr., MC 151B, San Diego, CA, 92161, USA. .,Department of Psychiatry, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA, 92093, USA.
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236
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Sobczyk O, Crawley AP, Poublanc J, Sam K, Mandell DM, Mikulis DJ, Duffin J, Fisher JA. Identifying Significant Changes in Cerebrovascular Reactivity to Carbon Dioxide. AJNR Am J Neuroradiol 2016; 37:818-24. [PMID: 26846924 DOI: 10.3174/ajnr.a4679] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 10/23/2015] [Indexed: 01/04/2023]
Abstract
BACKGROUND AND PURPOSE Changes in cerebrovascular reactivity can be used to assess disease progression and response to therapy but require discrimination of pathology from normal test-to-test variability. Such variability is due to variations in methodology, technology, and physiology with time. With uniform test conditions, our aim was to determine the test-to-test variability of cerebrovascular reactivity in healthy subjects and in patients with known cerebrovascular disease. MATERIALS AND METHODS Cerebrovascular reactivity was the ratio of the blood oxygen level-dependent MR imaging response divided by the change in carbon dioxide stimulus. Two standardized cerebrovascular reactivity tests were conducted at 3T in 15 healthy men (36.7 ± 16.1 years of age) within a 4-month period and were coregistered into standard space to yield voxelwise mean cerebrovascular reactivity interval difference measures, composing a reference interval difference atlas. Cerebrovascular reactivity interval difference maps were prepared for 11 male patients. For each patient, the test-retest difference of each voxel was scored statistically as z-values of the corresponding voxel mean difference in the reference atlas and then color-coded and superimposed on the anatomic images to create cerebrovascular reactivity interval difference z-maps. RESULTS There were no significant test-to-test differences in cerebrovascular reactivity in either gray or white matter (mean gray matter, P = .431; mean white matter, P = .857; paired t test) in the healthy cohort. The patient cerebrovascular reactivity interval difference z-maps indicated regions where cerebrovascular reactivity increased or decreased and the probability that the changes were significant. CONCLUSIONS Accounting for normal test-to-test differences in cerebrovascular reactivity enables the assessment of significant changes in disease status (stability, progression, or regression) in patients with time.
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Affiliation(s)
- O Sobczyk
- From the Institute of Medical Science (O.S., D.J.M., J.A.F.)
| | - A P Crawley
- Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory (A.P.C., J.P., K.S., D.M.M., D.J.M.)
| | - J Poublanc
- Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory (A.P.C., J.P., K.S., D.M.M., D.J.M.)
| | - K Sam
- Department of Physiology (K.S., J.D., J.A.F.), University of Toronto, Toronto, Canada Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory (A.P.C., J.P., K.S., D.M.M., D.J.M.)
| | - D M Mandell
- Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory (A.P.C., J.P., K.S., D.M.M., D.J.M.)
| | - D J Mikulis
- From the Institute of Medical Science (O.S., D.J.M., J.A.F.) Joint Department of Medical Imaging and the Functional Neuroimaging Laboratory (A.P.C., J.P., K.S., D.M.M., D.J.M.)
| | - J Duffin
- Department of Physiology (K.S., J.D., J.A.F.), University of Toronto, Toronto, Canada Department of Anaesthesia and Pain Management (J.D., J.A.F.), University Health Network, Toronto, Canada
| | - J A Fisher
- From the Institute of Medical Science (O.S., D.J.M., J.A.F.) Department of Physiology (K.S., J.D., J.A.F.), University of Toronto, Toronto, Canada Department of Anaesthesia and Pain Management (J.D., J.A.F.), University Health Network, Toronto, Canada
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237
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Merola A, Murphy K, Stone AJ, Germuska MA, Griffeth VEM, Blockley NP, Buxton RB, Wise RG. Measurement of oxygen extraction fraction (OEF): An optimized BOLD signal model for use with hypercapnic and hyperoxic calibration. Neuroimage 2016; 129:159-174. [PMID: 26801605 DOI: 10.1016/j.neuroimage.2016.01.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 01/06/2016] [Accepted: 01/09/2016] [Indexed: 11/24/2022] Open
Abstract
Several techniques have been proposed to estimate relative changes in cerebral metabolic rate of oxygen consumption (CMRO2) by exploiting combined BOLD fMRI and cerebral blood flow data in conjunction with hypercapnic or hyperoxic respiratory challenges. More recently, methods based on respiratory challenges that include both hypercapnia and hyperoxia have been developed to assess absolute CMRO2, an important parameter for understanding brain energetics. In this paper, we empirically optimize a previously presented "original calibration model" relating BOLD and blood flow signals specifically for the estimation of oxygen extraction fraction (OEF) and absolute CMRO2. To do so, we have created a set of synthetic BOLD signals using a detailed BOLD signal model to reproduce experiments incorporating hypercapnic and hyperoxic respiratory challenges at 3T. A wide range of physiological conditions was simulated by varying input parameter values (baseline cerebral blood volume (CBV0), baseline cerebral blood flow (CBF0), baseline oxygen extraction fraction (OEF0) and hematocrit (Hct)). From the optimization of the calibration model for estimation of OEF and practical considerations of hypercapnic and hyperoxic respiratory challenges, a new "simplified calibration model" is established which reduces the complexity of the original calibration model by substituting the standard parameters α and β with a single parameter θ. The optimal value of θ is determined (θ=0.06) across a range of experimental respiratory challenges. The simplified calibration model gives estimates of OEF0 and absolute CMRO2 closer to the true values used to simulate the experimental data compared to those estimated using the original model incorporating literature values of α and β. Finally, an error propagation analysis demonstrates the susceptibility of the original and simplified calibration models to measurement errors and potential violations in the underlying assumptions of isometabolism. We conclude that using the simplified calibration model results in a reduced bias in OEF0 estimates across a wide range of potential respiratory challenge experimental designs.
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Affiliation(s)
- Alberto Merola
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK
| | - Kevin Murphy
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK
| | - Alan J Stone
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK
| | - Michael A Germuska
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK
| | - Valerie E M Griffeth
- Department of Bioengineering and Medical Scientist Training Program, University of California San Diego, La Jolla, CA, United States
| | - Nicholas P Blockley
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK; Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California San Diego, La Jolla, CA, United States
| | - Richard B Buxton
- Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California San Diego, La Jolla, CA, United States; Kavli Institute for Brain and Mind, University of California San Diego, La Jolla, CA, United States
| | - Richard G Wise
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK.
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238
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Whittaker JR, Driver ID, Bright MG, Murphy K. The absolute CBF response to activation is preserved during elevated perfusion: Implications for neurovascular coupling measures. Neuroimage 2016; 125:198-207. [PMID: 26477657 PMCID: PMC4692513 DOI: 10.1016/j.neuroimage.2015.10.023] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 10/06/2015] [Accepted: 10/08/2015] [Indexed: 12/31/2022] Open
Abstract
Functional magnetic resonance imaging (fMRI) techniques in which the blood oxygenation level dependent (BOLD) and cerebral blood flow (CBF) response to a neural stimulus are measured, can be used to estimate the fractional increase in the cerebral metabolic rate of oxygen consumption (CMRO2) that accompanies evoked neural activity. A measure of neurovascular coupling is obtained from the ratio of fractional CBF and CMRO2 responses, defined as n, with the implicit assumption that relative rather than absolute changes in CBF and CMRO2 adequately characterise the flow-metabolism response to neural activity. The coupling parameter n is important in terms of its effect on the BOLD response, and as potential insight into the flow-metabolism relationship in both normal and pathological brain function. In 10 healthy human subjects, BOLD and CBF responses were measured to test the effect of baseline perfusion (modulated by a hypercapnia challenge) on the coupling parameter n during graded visual stimulation. A dual-echo pulsed arterial spin labelling (PASL) sequence provided absolute quantification of CBF in baseline and active states as well as relative BOLD signal changes, which were used to estimate CMRO2 responses to the graded visual stimulus. The absolute CBF response to the visual stimuli were constant across different baseline CBF levels, meaning the fractional CBF responses were reduced at the hyperperfused baseline state. For the graded visual stimuli, values of n were significantly reduced during hypercapnia induced hyperperfusion. Assuming the evoked neural responses to the visual stimuli are the same for both baseline CBF states, this result has implications for fMRI studies that aim to measure neurovascular coupling using relative changes in CBF. The coupling parameter n is sensitive to baseline CBF, which would confound its interpretation in fMRI studies where there may be significant differences in baseline perfusion between groups. The absolute change in CBF, as opposed to the change relative to baseline, may more closely match the underlying increase in neural activity in response to a stimulus.
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Affiliation(s)
- Joseph R Whittaker
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, CF10 3AT Cardiff, UK
| | - Ian D Driver
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, CF10 3AT Cardiff, UK
| | - Molly G Bright
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, CF10 3AT Cardiff, UK; Sir Peter Mansfield Imaging Centre, Clinical Neurology, School of Medicine, University of Nottingham, Nottingham, UK
| | - Kevin Murphy
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, CF10 3AT Cardiff, UK.
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239
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Stüber C, Pitt D, Wang Y. Iron in Multiple Sclerosis and Its Noninvasive Imaging with Quantitative Susceptibility Mapping. Int J Mol Sci 2016; 17:ijms17010100. [PMID: 26784172 PMCID: PMC4730342 DOI: 10.3390/ijms17010100] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 01/05/2016] [Accepted: 01/07/2016] [Indexed: 01/06/2023] Open
Abstract
Iron is considered to play a key role in the development and progression of Multiple Sclerosis (MS). In particular, iron that accumulates in myeloid cells after the blood-brain barrier (BBB) seals may contribute to chronic inflammation, oxidative stress and eventually neurodegeneration. Magnetic resonance imaging (MRI) is a well-established tool for the non-invasive study of MS. In recent years, an advanced MRI method, quantitative susceptibility mapping (QSM), has made it possible to study brain iron through in vivo imaging. Moreover, immunohistochemical investigations have helped defining the lesional and cellular distribution of iron in MS brain tissue. Imaging studies in MS patients and of brain tissue combined with histological studies have provided important insights into the role of iron in inflammation and neurodegeneration in MS.
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Affiliation(s)
- Carsten Stüber
- Department of Radiology, Weill Cornell Medical College, New York, NY 10044, USA.
- Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT 06511, USA.
| | - David Pitt
- Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT 06511, USA.
| | - Yi Wang
- Department of Radiology, Weill Cornell Medical College, New York, NY 10044, USA.
- Department of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA.
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240
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Stüber C, Pitt D, Wang Y. Iron in Multiple Sclerosis and Its Noninvasive Imaging with Quantitative Susceptibility Mapping. Int J Mol Sci 2016. [PMID: 26784172 DOI: 10.3390/ijmsl17010100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023] Open
Abstract
Iron is considered to play a key role in the development and progression of Multiple Sclerosis (MS). In particular, iron that accumulates in myeloid cells after the blood-brain barrier (BBB) seals may contribute to chronic inflammation, oxidative stress and eventually neurodegeneration. Magnetic resonance imaging (MRI) is a well-established tool for the non-invasive study of MS. In recent years, an advanced MRI method, quantitative susceptibility mapping (QSM), has made it possible to study brain iron through in vivo imaging. Moreover, immunohistochemical investigations have helped defining the lesional and cellular distribution of iron in MS brain tissue. Imaging studies in MS patients and of brain tissue combined with histological studies have provided important insights into the role of iron in inflammation and neurodegeneration in MS.
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Affiliation(s)
- Carsten Stüber
- Department of Radiology, Weill Cornell Medical College, New York, NY 10044, USA.
- Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT 06511, USA.
| | - David Pitt
- Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT 06511, USA.
| | - Yi Wang
- Department of Radiology, Weill Cornell Medical College, New York, NY 10044, USA.
- Department of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA.
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241
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Simon AB, Dubowitz DJ, Blockley NP, Buxton RB. A novel Bayesian approach to accounting for uncertainty in fMRI-derived estimates of cerebral oxygen metabolism fluctuations. Neuroimage 2016; 129:198-213. [PMID: 26790354 DOI: 10.1016/j.neuroimage.2016.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 11/30/2015] [Accepted: 01/01/2016] [Indexed: 10/22/2022] Open
Abstract
Calibrated blood oxygenation level dependent (BOLD) imaging is a multimodal functional MRI technique designed to estimate changes in cerebral oxygen metabolism from measured changes in cerebral blood flow and the BOLD signal. This technique addresses fundamental ambiguities associated with quantitative BOLD signal analysis; however, its dependence on biophysical modeling creates uncertainty in the resulting oxygen metabolism estimates. In this work, we developed a Bayesian approach to estimating the oxygen metabolism response to a neural stimulus and used it to examine the uncertainty that arises in calibrated BOLD estimation due to the presence of unmeasured model parameters. We applied our approach to estimate the CMRO2 response to a visual task using the traditional hypercapnia calibration experiment as well as to estimate the metabolic response to both a visual task and hypercapnia using the measurement of baseline apparent R2' as a calibration technique. Further, in order to examine the effects of cerebral spinal fluid (CSF) signal contamination on the measurement of apparent R2', we examined the effects of measuring this parameter with and without CSF-nulling. We found that the two calibration techniques provided consistent estimates of the metabolic response on average, with a median R2'-based estimate of the metabolic response to CO2 of 1.4%, and R2'- and hypercapnia-calibrated estimates of the visual response of 27% and 24%, respectively. However, these estimates were sensitive to different sources of estimation uncertainty. The R2'-calibrated estimate was highly sensitive to CSF contamination and to uncertainty in unmeasured model parameters describing flow-volume coupling, capillary bed characteristics, and the iso-susceptibility saturation of blood. The hypercapnia-calibrated estimate was relatively insensitive to these parameters but highly sensitive to the assumed metabolic response to CO2.
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Affiliation(s)
- Aaron B Simon
- Department of Bioengineering, University of California San Diego, La Jolla, CA, USA; Medical Scientist Training Program, University of California San Diego, La Jolla, CA, USA
| | - David J Dubowitz
- Keck Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California San Diego, La Jolla, CA, USA
| | - Nicholas P Blockley
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Richard B Buxton
- Keck Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California San Diego, La Jolla, CA, USA; Kavli Institute for Brain and Mind, University of California San Diego, La Jolla, CA, USA.
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242
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Ciris PA, Qiu M, Constable RT. Non-invasive quantification of absolute cerebral blood volume during functional activation applicable to the whole human brain. Magn Reson Med 2016; 71:580-90. [PMID: 23475774 DOI: 10.1002/mrm.24694] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
PURPOSE Cerebral blood volume (CBV) changes in many diverse pathologic conditions, and in response to functional challenges along with changes in blood flow, blood oxygenation, and the cerebral metabolic rate of oxygen. The feasibility of a new method for non-invasive quantification of absolute cerebral blood volume that can be applicable to the whole human brain was investigated. METHODS Multi-slice data were acquired at 3 T using a novel inversion recovery echo planar imaging (IR-EPI) pulse sequence with varying contrast weightings and an efficient rotating slice acquisition order, at rest and during visual activation. A biophysical model was used to estimate absolute cerebral blood volume at rest and during activation, and oxygenation during activation, on data from 13 normal human subjects. RESULTS Cerebral blood volume increased by 21.7% from 6.6 ± 0.8 mL/100 mL of brain parenchyma at rest to 8.0 ± 1.3 mL/100 mL of brain parenchyma in the occipital cortex during visual activation, with average blood oxygenation of 84 ± 2.1% during activation, comparing well with literature. CONCLUSION The method is feasible, and could foster improved understanding of the fundamental physiological relationship between neuronal activity, hemodynamic changes, and metabolism underlying brain activation; complement existing methods for estimating compartmental changes; and potentially find utility in evaluating vascular health.
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Affiliation(s)
- Pelin Aksit Ciris
- Department of Biomedical Engineering, Yale University, School of Medicine, Magnetic Resonance Research Center, New Haven, Connecticut, USA
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243
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Abstract
Functional magnetic resonance imaging (fMRI) maps the spatiotemporal distribution of neural activity in the brain under varying cognitive conditions. Since its inception in 1991, blood oxygen level-dependent (BOLD) fMRI has rapidly become a vital methodology in basic and applied neuroscience research. In the clinical realm, it has become an established tool for presurgical functional brain mapping. This chapter has three principal aims. First, we review key physiologic, biophysical, and methodologic principles that underlie BOLD fMRI, regardless of its particular area of application. These principles inform a nuanced interpretation of the BOLD fMRI signal, along with its neurophysiologic significance and pitfalls. Second, we illustrate the clinical application of task-based fMRI to presurgical motor, language, and memory mapping in patients with lesions near eloquent brain areas. Integration of BOLD fMRI and diffusion tensor white-matter tractography provides a road map for presurgical planning and intraoperative navigation that helps to maximize the extent of lesion resection while minimizing the risk of postoperative neurologic deficits. Finally, we highlight several basic principles of resting-state fMRI and its emerging translational clinical applications. Resting-state fMRI represents an important paradigm shift, focusing attention on functional connectivity within intrinsic cognitive networks.
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Affiliation(s)
- Bradley R Buchbinder
- Department of Radiology, Division of Neuroradiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
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244
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Chodkowski BA, Cowan RL, Niswender KD. Imbalance in Resting State Functional Connectivity is Associated with Eating Behaviors and Adiposity in Children. Heliyon 2016; 2:e00058. [PMID: 26878067 PMCID: PMC4750053 DOI: 10.1016/j.heliyon.2015.e00058] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 12/17/2015] [Accepted: 12/22/2015] [Indexed: 12/05/2022] Open
Abstract
Background and Hypothesis Over the past 30 years, childhood obesity in the US has nearly doubled, while obesity has tripled among adolescents. Non-homeostatic eating, influenced by impulsivity and inhibition, may undermine successful long-term weight loss. We hypothesized that unhealthy eating habits and adiposity among children are associated with functional connectivity between brain regions associated with impulsivity, response inhibition, and reward. Methods We analyzed resting state functional magnetic resonance images from 38 children, ages 8–13. Using seed-based resting state functional connectivity, we quantified connectivity between brain regions associated with response inhibition (inferior parietal lobe [IPL]), impulsivity (frontal pole), and reward (nucleus accumbens [NAc]). We assessed the relationship of resting state functional connectivity with adiposity, quantified by BMI z-score, and eating behaviors, as measured by the Child Eating Behaviour Questionnaire (CEBQ). We computed an imbalance measure—the difference between [frontal pole:NAC] and [ipl:nac] functional connectivity—and investigated the relationship of this imbalance with eating behaviors and adiposity. Results As functional connectivity imbalance is increasingly biased toward impulsivity, adiposity increases. Similarly, as impulsivity-biased imbalance increases, food approach behaviors increase and food avoidance behaviors decrease. Increased adiposity is associated with increased food approach behaviors and decreased food avoidance behaviors. Conclusions In the absence of any explicit eating-related stimuli, the developing brain is primed toward food approach and away from food avoidance behavior with increasing adiposity. Imbalance in resting state functional connectivity that is associated with non-homeostatic eating develops during childhood, as early as 8–13 years of age. Our results indicate the importance of identifying children at risk for obesity for earlier intervention. In addition to changing eating habits and physical activity, strategies that normalize neural functional connectivity imbalance are needed to maintain healthy weight. Mindfulness may be one such approach as it is associated with increased response inhibition and decreased impulsivity.
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Affiliation(s)
- BettyAnn A. Chodkowski
- Chemical and Physical Biology Program, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Ronald L. Cowan
- Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Psychology, Vanderbilt University, Nashville, TN, USA
| | - Kevin D. Niswender
- Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, TN, USA
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, USA
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA
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245
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Baseline oxygenation in the brain: Correlation between respiratory-calibration and susceptibility methods. Neuroimage 2016; 125:920-931. [DOI: 10.1016/j.neuroimage.2015.11.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 11/03/2015] [Accepted: 11/03/2015] [Indexed: 01/21/2023] Open
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246
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Kazan SM, Mohammadi S, Callaghan MF, Flandin G, Huber L, Leech R, Kennerley A, Windischberger C, Weiskopf N. Vascular autorescaling of fMRI (VasA fMRI) improves sensitivity of population studies: A pilot study. Neuroimage 2016; 124:794-805. [PMID: 26416648 PMCID: PMC4655941 DOI: 10.1016/j.neuroimage.2015.09.033] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 09/11/2015] [Accepted: 09/17/2015] [Indexed: 11/04/2022] Open
Abstract
The blood oxygenation level-dependent (BOLD) signal is widely used for functional magnetic resonance imaging (fMRI) of brain function in health and disease. The statistical power of fMRI group studies is significantly hampered by high inter-subject variance due to differences in baseline vascular physiology. Several methods have been proposed to account for physiological vascularization differences between subjects and hence improve the sensitivity in group studies. However, these methods require the acquisition of additional reference scans (such as a full resting-state fMRI session or ASL-based calibrated BOLD). We present a vascular autorescaling (VasA) method, which does not require any additional reference scans. VasA is based on the observation that slow oscillations (<0.1Hz) in arterial blood CO2 levels occur naturally due to changes in respiration patterns. These oscillations yield fMRI signal changes whose amplitudes reflect the blood oxygenation levels and underlying local vascularization and vascular responsivity. VasA estimates proxies of the amplitude of these CO2-driven oscillations directly from the residuals of task-related fMRI data without the need for reference scans. The estimates are used to scale the amplitude of task-related fMRI responses, to account for vascular differences. The VasA maps compared well to cerebrovascular reactivity (CVR) maps and cerebral blood volume maps based on vascular space occupancy (VASO) measurements in four volunteers, speaking to the physiological vascular basis of VasA. VasA was validated in a wide variety of tasks in 138 volunteers. VasA increased t-scores by up to 30% in specific brain areas such as the visual cortex. The number of activated voxels was increased by up to 200% in brain areas such as the orbital frontal cortex while still controlling the nominal false-positive rate. VasA fMRI outperformed previously proposed rescaling approaches based on resting-state fMRI data and can be readily applied to any task-related fMRI data set, even retrospectively.
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Affiliation(s)
- Samira M Kazan
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, London WC1N 3BG, United Kingdom.
| | - Siawoosh Mohammadi
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, London WC1N 3BG, United Kingdom
| | - Martina F Callaghan
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, London WC1N 3BG, United Kingdom
| | - Guillaume Flandin
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, London WC1N 3BG, United Kingdom
| | - Laurentius Huber
- NMR-Unit, Max Planck Institute for Human Cognition and Brain Sciences, Leipzig, Germany
| | - Robert Leech
- Cognitive, Clinical and Computational Neuroimaging Lab, Imperial College, Hammersmith Hospital, University of London, London W12 0NN, United Kingdom
| | - Aneurin Kennerley
- Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom
| | - Christian Windischberger
- MR Centre of Excellence, Centre for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, Vienna A-1090, Austria
| | - Nikolaus Weiskopf
- Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, University College London, London WC1N 3BG, United Kingdom; Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
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247
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fMRI in Neurodegenerative Diseases: From Scientific Insights to Clinical Applications. NEUROMETHODS 2016. [DOI: 10.1007/978-1-4939-5611-1_23] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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248
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Ma Y, Berman AJ, Pike GB. The effect of dissolved oxygen on the relaxation rates of blood plasma: Implications for hyperoxia calibrated BOLD. Magn Reson Med 2015; 76:1905-1911. [DOI: 10.1002/mrm.26069] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 10/05/2015] [Accepted: 11/02/2015] [Indexed: 12/18/2022]
Affiliation(s)
- Yuhan Ma
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University; Montreal Quebec Canada
| | - Avery J.L. Berman
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University; Montreal Quebec Canada
- Department of Radiology and Hotchkiss Brain Institute; University of Calgary; Calgary Alberta Canada
| | - G. Bruce Pike
- Department of Radiology and Hotchkiss Brain Institute; University of Calgary; Calgary Alberta Canada
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249
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Bao P, Purington CJ, Tjan BS. Using an achiasmic human visual system to quantify the relationship between the fMRI BOLD signal and neural response. eLife 2015; 4. [PMID: 26613411 PMCID: PMC4764551 DOI: 10.7554/elife.09600] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 11/26/2015] [Indexed: 12/15/2022] Open
Abstract
Achiasma in humans causes gross mis-wiring of the retinal-fugal projection, resulting in overlapped cortical representations of left and right visual hemifields. We show that in areas V1-V3 this overlap is due to two co-located but non-interacting populations of neurons, each with a receptive field serving only one hemifield. Importantly, the two populations share the same local vascular control, resulting in a unique organization useful for quantifying the relationship between neural and fMRI BOLD responses without direct measurement of neural activity. Specifically, we can non-invasively double local neural responses by stimulating both neuronal populations with identical stimuli presented symmetrically across the vertical meridian to both visual hemifields, versus one population by stimulating in one hemifield. Measurements from a series of such doubling experiments show that the amplitude of BOLD response is proportional to approximately 0.5 power of the underlying neural response. Reanalyzing published data shows that this inferred relationship is general.
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Affiliation(s)
- Pinglei Bao
- Neuroscience Graduate Program, University of Southern California, Los Angeles, United States
| | - Christopher J Purington
- School of Optometry, University of California, Berkeley, Berkeley, CA, United States.,Vision Science Graduate Program, University of California, Berkeley, Berkeley, United States.,Department of Psychology, University of Southern California, Los Angeles, CA, United States
| | - Bosco S Tjan
- Neuroscience Graduate Program, University of Southern California, Los Angeles, United States.,Department of Psychology, University of Southern California, Los Angeles, CA, United States
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250
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Shu CY, Sanganahalli BG, Coman D, Herman P, Rothman DL, Hyder F. Quantitative β mapping for calibrated fMRI. Neuroimage 2015; 126:219-28. [PMID: 26619788 DOI: 10.1016/j.neuroimage.2015.11.042] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 11/12/2015] [Accepted: 11/16/2015] [Indexed: 11/27/2022] Open
Abstract
The metabolic and hemodynamic dependencies of the blood oxygenation level-dependent (BOLD) signal form the basis for calibrated fMRI, where the focus is on oxidative energy demanded by neural activity. An important part of calibrated fMRI is the power-law relationship between the BOLD signal and the deoxyhemoglobin concentration, which in turn is related to the ratio between oxidative demand (CMRO2) and blood flow (CBF). The power-law dependence between BOLD signal and deoxyhemoglobin concentration is signified by a scaling exponent β. Until recently most studies assumed a β value of 1.5, which is based on numerical simulations of the extravascular BOLD component. Since the basal value of CMRO2 and CBF can vary from subject-to-subject and/or region-to-region, a method to independently measure β in vivo should improve the accuracy of calibrated fMRI results. We describe a new method for β mapping through characterizing R2' - the most sensitive relaxation component of BOLD signal (i.e., the reversible magnetic susceptibility component that is predominantly of extravascular origin at high magnetic field) - as a function of intravascular magnetic susceptibility induced by an FDA-approved superparamagnetic contrast agent. In α-chloralose anesthetized rat brain, at 9.4 T, we measured β values of ~0.8 uniformly across large neocortical swathes, with lower magnitude and more heterogeneity in subcortical areas. Comparison of β maps in rats anesthetized with medetomidine and α-chloralose revealed that β is independent of neural activity levels at these resting states. We anticipate that this method for β mapping can help facilitate calibrated fMRI for clinical studies.
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Affiliation(s)
- Christina Y Shu
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA.
| | - Basavaraju G Sanganahalli
- Department of Radiology and Biomedical Imaging and Magnetic Resonance Research Center, Yale University, New Haven, CT, USA
| | - Daniel Coman
- Department of Radiology and Biomedical Imaging and Magnetic Resonance Research Center, Yale University, New Haven, CT, USA
| | - Peter Herman
- Department of Radiology and Biomedical Imaging and Magnetic Resonance Research Center, Yale University, New Haven, CT, USA
| | - Douglas L Rothman
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA; Department of Radiology and Biomedical Imaging and Magnetic Resonance Research Center, Yale University, New Haven, CT, USA
| | - Fahmeed Hyder
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA; Department of Radiology and Biomedical Imaging and Magnetic Resonance Research Center, Yale University, New Haven, CT, USA.
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