The Effects of Changes in Pa
            <scp>CO</scp>
            <sub>2</sub>
            Cerebral Blood Volume, Blood Flow, and Vascular Mean Transit Time

Grubb, Robert L.; Raichle, Marcus E.; Eichling, John O.; Ter‐Pogossian, Michel M.

doi:10.1161/01.str.5.5.630

Cited by 988 publications

(706 citation statements)

References 51 publications

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“…This is in close accordance with the range 0.18-0.36 determined by several groups using recent techniques such as laser Doppler flowmetry and optical imaging in brain activation studies (Mandeville et al, 1999;Jones et al, 2001; Sheth et al, 2004a and references therein, Leung et al, 2009;Boas and Payne, 2009). Note that the original value ϕ = 0.38 was experimentally determined by Grubb et al (1974) in PET studies using a prolonged hypercapnia challenge in primates.In addition, it is interesting to note that the mean transit time variation is non-monotonic ( Fig. 2D): an initial decrease in the mean transit time is observed because the blood volume initially increases more slowly than the regional blood flow (consistent with the values of ϕ obtained above).…”

supporting

confidence: 87%

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network. Part II: Flow variations induced by global or localized modifications of arteriolar diameters

Lorthois¹,

Cassot²,

Lauwers³

2011

NeuroImage

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. In a companion paper (Lorthois et al., Neuroimage, in press), we perform the first simulations of blood flow in an anatomically accurate large human intra-cortical vascular network (~10000 segments), using a 1D non-linear model taking into account the complex rheological properties of blood flow in microcirculation. This model predicts blood pressure, blood flow and hematocrit distributions, volumes of functional vascular territories, regional flow at voxel and network scales, etc. Using the same approach, we study flow reorganizations induced by global arteriolar vasodilations (an isometabolic global increase in cerebral blood flow). For small to moderate global vasodilations, the relationship between changes in volume and changes in flow is in close agreement with Grubb's law, providing a quantitative tool for studying the variations of its exponent with underlying vascular architecture. A significant correlation between blood flow and vascular structure at the voxel scale, practically unchanged with respect to baseline, is demonstrated. Furthermore, the effects of localized arteriolar vasodilations, representative of a local increase in metabolic demand, are analyzed. In particular, localized vasodilations induce flow changes, including vascular steal, in the neighboring arteriolar trunks at small distances (b 300 μm), while their influence in the neighboring veins is much larger (about 1 mm), which provides an estimate of the vascular point spread function. More generally, for the first time, the hemodynamic component of various functional neuroimaging techniques has been isolated from metabolic and neuronal components, and a direct relationship with several known characteristics of the BOLD signal has been demonstrated. IntroductionThere is increasing recognition that, by its structural implication in neuro-vascular coupling, underlying vascular architecture is a key player in hemodynamically based functional imaging techniques (including fMRI and PET) (Harrison et al., 2002;d'Esposito et al., 2003;Logothetis and Wandell, 2004;Lauwers et al., 2008;Weber et al., 2008). In particular, the spatial resolution and specificity of such techniques are bound to the density of blood capillary vasculature and blood flow regulating structures (Harel et al., 2006). This is especially important in the context of high field fMRI Harel et al., 2006), because, despite a dramatic increase in the theoretical spatial resolution obtained by using higher magnetic fields, associated with other hardware advancements, "the spatial extent of the hemodynamic response ultimately will impose a fundamental limitation on the spatial resolution of fMRI modalities" ).However, little is known about the fundamentals of the relationship between vascular structure and hemodynamic changes induced by brain activation. A growing body of evidence indicates that neurons, glia, and cerebral blood vessels, actin...

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supporting

confidence: 87%

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network. Part II: Flow variations induced by global or localized modifications of arteriolar diameters

Lorthois¹,

Cassot²,

Lauwers³

2011

NeuroImage

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“…However, it is not clear why the changes in PETCO2 were significantly different between the three tasks (no change in PETCO2 for MA) but led to very similar changes in [O2Hb] and StO2. This is unexpected since PaCO2 and CBF are almost linearly correlated in the normal physiological range [11]. Thus, the hemodynamic and oxygenation changes cannot solely be explained by PaCO2.…”

Section: Discussionmentioning

confidence: 92%

The Effect of Inner Speech on Arterial CO2 and Cerebral Hemodynamics and Oxygenation: A Functional NIRS Study

Scholkmann

Wolf²,

Wolf

2013

Oxygen Transport to Tissue XXXV

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The aim of the present study was (i) to investigate the effect of inner speech on cerebral hemodynamics and oxygenation, and (ii) to analyze if these changes could be the result of alternations of the arterial carbon dioxide pressure (PaCO2). To this end, in seven adult volunteers, we measured changes of cerebral absolute [O2Hb], [HHb], [tHb] concentrations and tissue oxygen saturation (StO2) (over the left and right anterior prefrontal cortex (PFC)), as well as changes in end-tidal CO2 (PETCO2), a reliable and accurate estimate of PaCO2. Each subject performed three different tasks (inner recitation of hexameter (IRH) or prose (IRP) verses) and a control task (mental arithmetic (MA)) on different days according to a randomized crossover design. Statistical analysis was applied to the differences between pre-baseline, two tasks, and four post-baseline periods. The two brain hemispheres and three tasks were tested separately. During the tasks, we found (i) PETCO2 decreased significantly (p < 0.05) during the IRH ( 3 mmHg) and MA ( 0.5 mmHg) task. (ii) [O2Hb] and StO2 decreased significantly during IRH ( 1.5 M; 2 %), IRP ( 1 M; 1.5 %), and MA ( 1 M; 1.5 %) tasks. During the post-baseline period, [O2Hb] and [tHb] of the left PFC decreased significantly after the IRP and MA task ( 1 M and 2 M, respectively). In conclusion, the study showed that inner speech affects PaCO2, probably due to changes in respiration. Although a decrease in PaCO2 is causing cerebral vasoconstriction and could potentially explain the decreases of [O2Hb] and StO2 during inner speech, the changes in PaCO2 were significantly different between the three tasks (no change in PaCO2 for MA) but led to very similar changes in [O2Hb] and StO2. Thus, the cerebral changes cannot solely be explained by PaCO2. Abstract: The aim of the present study was (i) to investigate the effect of inner speech on cerebral hemodynamics and oxygenation, and (ii) to analyze if these changes could be the result of alternations of the arterial carbon dioxide pressure (Pa-CO2). To this end, in seven adult volunteers, we measured changes of cerebral absolute [O2Hb], [HHb], [tHb] concentrations and tissue oxygen saturation (StO2) (over the left and right anterior prefrontal cortex (PFC)), as well as changes in end-tidal CO2 (PETCO2), a reliable and accurate estimate of PaCO2. Each subject performed three different tasks (inner recitation of hexameter (IRH) or prose (IRP) verses) and a control task (mental arithmetic (MA)) on different days according to a randomized crossover design. Statistical analysis was applied to the differences between pre-baseline, two tasks, and four postbaseline periods. The two brain hemispheres and three tasks were tested separately. During the tasks, we found (i) PETCO2 decreased significantly (p < 0.05) during the IRH (~3 mmHg) and MA (~0.5 mmHg) task. (ii) [O2Hb] and StO2 decreased significantly during IRH (~1.5 μM; ~2 %), IRP (~1 μM; ~1.5 %), and MA (~1 μM; ~1.5 %) tasks. During the post-baseline period, [O2Hb] and [tHb] of t...

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“…These vessels may also expand due to the increased pressure, further increasing the CBV. Experimental studies (Grubb et al, 1974) have indicated that the steady-state relationship between CBF and CBV can be described with a power law:…”

Section: Physiological Relationshipsmentioning

confidence: 99%

“…In the original formulation of the balloon model (Buxton et al, 1998c), the outflow was modeled as a pure function of blood volume v. Steady-state experiments (Grubb et al, 1974), altering CBF with inhaled CO 2 , found that the steady-state relationship between CBF and total blood volume was well described by an empirical power law (Eq. (1)).…”

Section: The Balloon Modelmentioning

confidence: 99%

Modeling the hemodynamic response to brain activation

et al. 2004

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Neural activity in the brain is accompanied by changes in cerebral blood flow (CBF) and blood oxygenation that are detectable with functional magnetic resonance imaging (fMRI) techniques. In this paper, recent mathematical models of this hemodynamic response are reviewed and integrated. Models are described for: (1) the blood oxygenation level dependent (BOLD) signal as a function of changes in cerebral oxygen extraction fraction (E) and cerebral blood volume (CBV); (2) the balloon model, proposed to describe the transient dynamics of CBV and deoxyhemoglobin (Hb) and how they affect the BOLD signal; (3) neurovascular coupling, relating the responses in CBF and cerebral metabolic rate of oxygen (CMRO 2 ) to the neural activity response; and (4) a simple model for the temporal nonlinearity of the neural response itself. These models are integrated into a mathematical framework describing the steps linking a stimulus to the measured BOLD and CBF responses. Experimental results examining transient features of the BOLD response (post-stimulus undershoot and initial dip), nonlinearities of the hemodynamic response, and the role of the physiologic baseline state in altering the BOLD signal are discussed in the context of the proposed models. Quantitative modeling of the hemodynamic response, when combined with experimental data measuring both the BOLD and CBF responses, makes possible a more specific and quantitative assessment of brain physiology than is possible with standard BOLD imaging alone. This approach has the potential to enhance numerous studies of brain function in development, health, and disease. D

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The Effects of Changes in Pa CO ₂ Cerebral Blood Volume, Blood Flow, and Vascular Mean Transit Time

Cited by 988 publications

References 51 publications

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network. Part II: Flow variations induced by global or localized modifications of arteriolar diameters

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network. Part II: Flow variations induced by global or localized modifications of arteriolar diameters

The Effect of Inner Speech on Arterial CO2 and Cerebral Hemodynamics and Oxygenation: A Functional NIRS Study

Modeling the hemodynamic response to brain activation

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The Effects of Changes in Pa CO 2 Cerebral Blood Volume, Blood Flow, and Vascular Mean Transit Time

Cited by 988 publications

References 51 publications

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network. Part II: Flow variations induced by global or localized modifications of arteriolar diameters

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network. Part II: Flow variations induced by global or localized modifications of arteriolar diameters

The Effect of Inner Speech on Arterial CO2 and Cerebral Hemodynamics and Oxygenation: A Functional NIRS Study

Modeling the hemodynamic response to brain activation

Contact Info

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The Effects of Changes in Pa CO ₂ Cerebral Blood Volume, Blood Flow, and Vascular Mean Transit Time