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Mekbib DB, Cai M, Wu D, Dai W, Liu X, Zhao L. Reproducibility and Sensitivity of Resting-State fMRI in Patients With Parkinson's Disease Using Cross Validation-Based Data Censoring. J Magn Reson Imaging 2024; 59:1630-1642. [PMID: 37584329 DOI: 10.1002/jmri.28958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 08/02/2023] [Accepted: 08/02/2023] [Indexed: 08/17/2023] Open
Abstract
BACKGROUND Uncontrollable body movements are typical symptoms of Parkinson's disease (PD), which results in inconsistent findings regarding resting-state functional connectivity (rsFC) networks, especially for group difference clusters. Systematically identifying the motion-associated data was highly demanded. PURPOSE To determine data censoring criteria using a quantitative cross validation-based data censoring (CVDC) method and to improve the detection of rsFC deficits in PD. STUDY TYPE Prospective. SUBJECTS Forty-one PD patients (68.63 ± 9.17 years, 44% female) and 20 healthy controls (66.83 ± 12.94 years, 55% female). FIELD STRENGTH/SEQUENCE 3-T, T1-weighted gradient echo and EPI sequences. ASSESSMENT Clusters with significant differences between groups were found in three visual networks, default network, and right sensorimotor network. Five-fold cross-validation tests were performed using multiple motion exclusion criteria, and the selected criteria were determined based on cluster sizes, significance values, and Dice coefficients among the cross-validation tests. As a reference method, whole brain rsFC comparisons between groups were analyzed using a FMRIB Software Library (FSL) pipeline with default settings. STATISTICAL TESTS Group difference clusters were calculated using nonparametric permutation statistics of FSL-randomize. The family-wise error was corrected. Demographic information was evaluated using independent sample t-tests and Pearson's Chi-squared tests. The level of statistical significance was set at P < 0.05. RESULTS With the FSL processing pipeline, the mean Dice coefficient of the network clusters was 0.411, indicating a low reproducibility. With the proposed CVDC method, motion exclusion criteria were determined as frame-wise displacement >0.55 mm. Group-difference clusters showed a mean P-value of 0.01 and a 72% higher mean Dice coefficient compared to the FSL pipeline. Furthermore, the CVDC method was capable of detecting subtle rsFC deficits in the medial sensorimotor network and auditory network that were unobservable using the conventional pipeline. DATA CONCLUSION The CVDC method may provide superior sensitivity and improved reproducibility for detecting rsFC deficits in PD. LEVEL OF EVIDENCE 1 TECHNICAL EFFICACY: Stage 2.
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Affiliation(s)
- Destaw Bayabil Mekbib
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
- Department of Physics and Statistics, Addis Ababa Science and Technology University, Addis Ababa, Ethiopia
| | - Miao Cai
- Department of Neurology, Affiliated Zhejiang Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Dan Wu
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
| | - Weiying Dai
- Department of Computer Science, State University of New York at Binghamton, Binghamton, New York, USA
| | - Xiaoli Liu
- Department of Neurology, Affiliated Zhejiang Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Li Zhao
- Key Laboratory for Biomedical Engineering of Ministry of Education, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
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Buxton RB. Thermodynamic limitations on brain oxygen metabolism: physiological implications. J Physiol 2024; 602:683-712. [PMID: 38349000 DOI: 10.1113/jp284358] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 01/03/2024] [Indexed: 02/20/2024] Open
Abstract
Recent thermodynamic modelling indicates that maintaining the brain tissue ratio of O2 to CO2 (abbreviated tissue O2 /CO2 ) is critical for preserving the entropy increase available from oxidative metabolism of glucose, with a fall of that available entropy leading to a reduction of the phosphorylation potential and impairment of brain energy metabolism. This provides a novel perspective for understanding physiological responses under different conditions in terms of preserving tissue O2 /CO2 . To enable estimation of tissue O2 /CO2 in the human brain, a detailed mathematical model of O2 and CO2 transport was developed, and applied to reported physiological responses to different challenges, asking: how well is tissue O2 /CO2 preserved? Reported experimental results for increased neural activity, hypercapnia and hypoxia due to high altitude are consistent with preserving tissue O2 /CO2 . The results highlight two physiological mechanisms that control tissue O2 /CO2 : cerebral blood flow, which modulates tissue O2 ; and ventilation rate, which modulates tissue CO2 . The hypoxia modelling focused on humans at high altitude, including acclimatized lowlanders and Tibetan and Andean adapted populations, with a primary finding that decreasing CO2 by increasing ventilation rate is more effective for preserving tissue O2 /CO2 than increasing blood haemoglobin content to maintain O2 delivery to tissue. This work focused on the function served by particular physiological responses, and the underlying mechanisms require further investigation. The modelling provides a new framework and perspective for understanding how blood flow and other physiological factors support energy metabolism in the brain under a wide range of conditions. KEY POINTS: Thermodynamic modelling indicates that preserving the O2 /CO2 ratio in brain tissue is critical for preserving the entropy change available from oxidative metabolism of glucose and the phosphorylation potential underlying energy metabolism. A detailed model of O2 and CO2 transport was developed to allow estimation of the tissue O2 /CO2 ratio in the human brain in different physiological states. Reported experimental results during hypoxia, hypercapnia and increased oxygen metabolic rate in response to increased neural activity are consistent with maintaining brain tissue O2 /CO2 ratio. The hypoxia modelling of high-altitude acclimatization and adaptation in humans demonstrates the critical role of reducing CO2 with increased ventilation for preserving tissue O2 /CO2 . Preservation of tissue O2 /CO2 provides a novel perspective for understanding the function of observed physiological responses under different conditions in terms of preserving brain energy metabolism, although the mechanisms underlying these functions are not well understood.
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Affiliation(s)
- Richard B Buxton
- Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California, San Diego, California, USA
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Buxton RB. The thermodynamics of thinking: connections between neural activity, energy metabolism and blood flow. Philos Trans R Soc Lond B Biol Sci 2020; 376:20190624. [PMID: 33190604 DOI: 10.1098/rstb.2019.0624] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Several current functional neuroimaging methods are sensitive to cerebral metabolism and cerebral blood flow (CBF) rather than the underlying neural activity itself. Empirically, the connections between metabolism, flow and neural activity are complex and somewhat counterintuitive: CBF and glycolysis increase more than seems to be needed to provide oxygen and pyruvate for oxidative metabolism, and the oxygen extraction fraction is relatively low in the brain and decreases when oxygen metabolism increases. This work lays a foundation for the idea that this unexpected pattern of physiological changes is consistent with basic thermodynamic considerations related to metabolism. In the context of this thermodynamic framework, the apparent mismatches in metabolic rates and CBF are related to preserving the entropy change of oxidative metabolism, specifically the O2/CO2 ratio in the mitochondria. However, the mechanism supporting this CBF response is likely not owing to feedback from a hypothetical O2 sensor in tissue, but rather is consistent with feed-forward control by signals from both excitatory and inhibitory neural activity. Quantitative predictions of the thermodynamic framework, based on models of O2 and CO2 transport and possible neural drivers of CBF control, are in good agreement with a wide range of experimental data, including responses to neural activation, hypercapnia, hypoxia and high-altitude acclimatization. This article is part of the theme issue 'Key relationships between non-invasive functional neuroimaging and the underlying neuronal activity'.
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Affiliation(s)
- Richard B Buxton
- Department of Radiology, University of California San Diego, 9500 Gilman Drive, MC 0677, La Jolla, CA 92093-0677, USA
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BOLD signal physiology: Models and applications. Neuroimage 2019; 187:116-127. [DOI: 10.1016/j.neuroimage.2018.03.018] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 02/14/2018] [Accepted: 03/08/2018] [Indexed: 12/14/2022] Open
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Bednařík P, Tkáč I, Giove F, Eberly LE, Deelchand DK, Barreto FR, Mangia S. Neurochemical responses to chromatic and achromatic stimuli in the human visual cortex. J Cereb Blood Flow Metab 2018; 38:347-359. [PMID: 28273721 PMCID: PMC5951013 DOI: 10.1177/0271678x17695291] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In the present study, we aimed at determining the metabolic responses of the human visual cortex during the presentation of chromatic and achromatic stimuli, known to preferentially activate two separate clusters of neuronal populations (called "blobs" and "interblobs") with distinct sensitivity to color or luminance features. Since blobs and interblobs have different cytochrome-oxidase (COX) content and micro-vascularization level (i.e., different capacities for glucose oxidation), different functional metabolic responses during chromatic vs. achromatic stimuli may be expected. The stimuli were optimized to evoke a similar load of neuronal activation as measured by the bold oxygenation level dependent (BOLD) contrast. Metabolic responses were assessed using functional 1H MRS at 7 T in 12 subjects. During both chromatic and achromatic stimuli, we observed the typical increases in glutamate and lactate concentration, and decreases in aspartate and glucose concentration, that are indicative of increased glucose oxidation. However, within the detection sensitivity limits, we did not observe any difference between metabolic responses elicited by chromatic and achromatic stimuli. We conclude that the higher energy demands of activated blobs and interblobs are supported by similar increases in oxidative metabolism despite the different capacities of these neuronal populations.
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Affiliation(s)
- Petr Bednařík
- 1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA.,2 Division of Endocrinology and Diabetes, Department of Medicine, University of Minnesota, Minneapolis, MN, USA.,3 CEITEC - Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Ivan Tkáč
- 1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA
| | - Federico Giove
- 4 MARBILab, Museo storico della fisica e Centro di studi e ricerche Enrico Fermi, Rome, Italy.,5 Fondazione Santa Lucia IRCCS, Rome, Italy
| | - Lynn E Eberly
- 6 Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, MN, USA
| | - Dinesh K Deelchand
- 1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA
| | - Felipe R Barreto
- 7 Physics Department, University of Sao Paulo, Ribeirao Preto, SP, Brazil
| | - Silvia Mangia
- 1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA
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Jang H, Huang S, Hammer DX, Wang L, Rafi H, Ye M, Welle CG, Fisher JAN. Alterations in neurovascular coupling following acute traumatic brain injury. NEUROPHOTONICS 2017; 4:045007. [PMID: 29296629 PMCID: PMC5741992 DOI: 10.1117/1.nph.4.4.045007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 11/28/2017] [Indexed: 06/07/2023]
Abstract
Following acute traumatic brain injury (TBI), timely transport to a hospital can significantly improve the prognosis for recovery. There is, however, a dearth of quantitative biomarkers for brain injury that can be rapidly acquired and interpreted in active, field environments in which TBIs are frequently incurred. We explored potential functional indicators for TBI that can be noninvasively obtained through portable detection modalities, namely optical and electrophysiological approaches. By combining diffuse correlation spectroscopy with colocalized electrophysiological measurements in a mouse model of TBI, we observed concomitant alterations in sensory-evoked cerebral blood flow (CBF) and electrical potentials following controlled cortical impact. Injury acutely reduced the peak amplitude of both electrophysiological and CBF responses, which mostly recovered to baseline values within 30 min, and intertrial variability for these parameters was also acutely altered. Notably, the postinjury dynamics of the CBF overshoot and undershoot amplitudes differed significantly; whereas the amplitude of the initial peak of stimulus-evoked CBF recovered relatively rapidly, the ensuing undershoot did not appear to recover within 30 min of injury. Additionally, acute injury induced apparent low-frequency oscillatory behavior in CBF ([Formula: see text]). Histological assessment indicated that these physiological alterations were not associated with any major, persisting anatomical changes. Several time-domain features of the blood flow and electrophysiological responses showed strong correlations in recovery kinetics. Overall, our results reveal an array of stereotyped, injury-induced alterations in electrophysiological and hemodynamic responses that can be rapidly obtained using a combination of portable detection techniques.
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Affiliation(s)
- Hyounguk Jang
- New York Medical College, Department of Physiology, Valhalla, New York, United States
- U.S. Food and Drug Administration, Division of Biomedical Physics, Silver Spring, Maryland, United States
| | - Stanley Huang
- U.S. Food and Drug Administration, Division of Biomedical Physics, Silver Spring, Maryland, United States
| | - Daniel X. Hammer
- U.S. Food and Drug Administration, Division of Biomedical Physics, Silver Spring, Maryland, United States
| | - Lin Wang
- New York Medical College, Department of Physiology, Valhalla, New York, United States
| | - Harmain Rafi
- New York Medical College, Department of Physiology, Valhalla, New York, United States
| | - Meijun Ye
- U.S. Food and Drug Administration, Division of Biomedical Physics, Silver Spring, Maryland, United States
| | - Cristin G. Welle
- U.S. Food and Drug Administration, Division of Biomedical Physics, Silver Spring, Maryland, United States
- University of Colorado Denver, Departments of Neurosurgery and Bioengineering, Aurora, Colorado, United States
| | - Jonathan A. N. Fisher
- New York Medical College, Department of Physiology, Valhalla, New York, United States
- U.S. Food and Drug Administration, Division of Biomedical Physics, Silver Spring, Maryland, United States
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Buxton RB, Griffeth VEM, Simon AB, Moradi F, Shmuel A. Variability of the coupling of blood flow and oxygen metabolism responses in the brain: a problem for interpreting BOLD studies but potentially a new window on the underlying neural activity. Front Neurosci 2014; 8:139. [PMID: 24966808 PMCID: PMC4052822 DOI: 10.3389/fnins.2014.00139] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 05/19/2014] [Indexed: 12/31/2022] Open
Abstract
Recent studies from our group and others using quantitative fMRI methods have found that variations of the coupling ratio of blood flow (CBF) and oxygen metabolism (CMRO2) responses to a stimulus have a strong effect on the BOLD response. Across a number of studies an empirical pattern is emerging in the way CBF and CMRO2 changes are coupled to neural activation: if the stimulus is modulated to create a stronger response (e.g., increasing stimulus contrast), CBF is modulated more than CMRO2; on the other hand, if the brain state is altered such that the response to the same stimulus is increased (e.g., modulating attention, adaptation, or excitability), CMRO2 is modulated more than CBF. Because CBF and CMRO2 changes conflict in producing BOLD signal changes, this finding has an important implication for conventional BOLD-fMRI studies: the BOLD response exaggerates the effects of stimulus variation but is only weakly sensitive to modulations of the brain state that alter the response to a standard stimulus. A speculative hypothesis is that variability of the coupling ratio of the CBF and CMRO2 responses reflects different proportions of inhibitory and excitatory evoked activity, potentially providing a new window on neural activity in the human brain.
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Affiliation(s)
- Richard B Buxton
- Department of Radiology, Center for Functional MRI, University of California San Diego, La Jolla, CA, USA
| | - Valerie E M Griffeth
- Department of Radiology, Center for Functional MRI, University of California San Diego, La Jolla, CA, USA
| | - Aaron B Simon
- Department of Radiology, Center for Functional MRI, University of California San Diego, La Jolla, CA, USA
| | - Farshad Moradi
- Department of Radiology, Center for Functional MRI, University of California San Diego, La Jolla, CA, USA
| | - Amir Shmuel
- Departments of Neurology and Neurosurgery, Physiology and Biomedical Engineering, Montreal Neurological Institute Brain Imaging Centre, McGill University, Montreal QC, Canada
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The oxygen paradox of neurovascular coupling. J Cereb Blood Flow Metab 2014; 34:19-29. [PMID: 24149931 PMCID: PMC3887356 DOI: 10.1038/jcbfm.2013.181] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 09/12/2013] [Accepted: 09/22/2013] [Indexed: 01/09/2023]
Abstract
The coupling of cerebral blood flow (CBF) to neuronal activity is well preserved during evolution. Upon changes in the neuronal activity, an incompletely understood coupling mechanism regulates diameter changes of supplying blood vessels, which adjust CBF within seconds. The physiologic brain tissue oxygen content would sustain unimpeded brain function for only 1 second if continuous oxygen supply would suddenly stop. This suggests that the CBF response has evolved to balance oxygen supply and demand. Surprisingly, CBF increases surpass the accompanying increases of cerebral metabolic rate of oxygen (CMRO2). However, a disproportionate CBF increase may be required to increase the concentration gradient from capillary to tissue that drives oxygen delivery. However, the brain tissue oxygen content is not zero, and tissue pO2 decreases could serve to increase oxygen delivery without a CBF increase. Experimental evidence suggests that CMRO2 can increase with constant CBF within limits and decreases of baseline CBF were observed with constant CMRO2. This conflicting evidence may be viewed as an oxygen paradox of neurovascular coupling. As a possible solution for this paradox, we hypothesize that the CBF response has evolved to safeguard brain function in situations of moderate pathophysiological interference with oxygen supply.
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Buxton RB. The physics of functional magnetic resonance imaging (fMRI). REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2013; 76:096601. [PMID: 24006360 PMCID: PMC4376284 DOI: 10.1088/0034-4885/76/9/096601] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Functional magnetic resonance imaging (fMRI) is a methodology for detecting dynamic patterns of activity in the working human brain. Although the initial discoveries that led to fMRI are only about 20 years old, this new field has revolutionized the study of brain function. The ability to detect changes in brain activity has a biophysical basis in the magnetic properties of deoxyhemoglobin, and a physiological basis in the way blood flow increases more than oxygen metabolism when local neural activity increases. These effects translate to a subtle increase in the local magnetic resonance signal, the blood oxygenation level dependent (BOLD) effect, when neural activity increases. With current techniques, this pattern of activation can be measured with resolution approaching 1 mm(3) spatially and 1 s temporally. This review focuses on the physical basis of the BOLD effect, the imaging methods used to measure it, the possible origins of the physiological effects that produce a mismatch of blood flow and oxygen metabolism during neural activation, and the mathematical models that have been developed to understand the measured signals. An overarching theme is the growing field of quantitative fMRI, in which other MRI methods are combined with BOLD methods and analyzed within a theoretical modeling framework to derive quantitative estimates of oxygen metabolism and other physiological variables. That goal is the current challenge for fMRI: to move fMRI from a mapping tool to a quantitative probe of brain physiology.
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Affiliation(s)
- Richard B Buxton
- Department of Radiology, University of California, San Diego, USA
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