A cortical vascular model for examining the specificity of the laminar BOLD signal

Markuerkiaga, Irati; Barth, Markus; Norris, David G.

doi:10.1016/j.neuroimage.2016.02.073

Cited by 166 publications

(249 citation statements)

References 51 publications

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“…1 and 2, the BOLD signal ratio, which can be defined as the ratio of the contributions from the laminar vasculature and from intracortical veins (Markuerkiaga, I. et al, 2016), is significantly different for GE, SE and bSSFP. Assuming a laminar network that consists of vessels of up to 10 µm and that occupy 2.3% BV (Weber et al, 2008; Boas et al, 2008), and intracortical veins between 10 µm to 70 µm and an averaged BV across layers of 0.6% (from 0.2% at layer 6 linearly increasing to 1.2% at the top layer 1, Cassot et al, 2006; Duvernoy et al, 1981), the BOLD signal ratio (laminar vasculature: intracortical veins) of GE (TE=20ms) amounts to 10:1 (layer 6) to 1.7:1 (top layer 1), that of SE (TE=30ms) to 34:1 to 6:1, and 22:1 to 4:1 for bSSFP (TR/α=10ms/20°).…”

Section: Discussionmentioning

confidence: 99%

The impact of vessel size, orientation and intravascular contribution on the neurovascular fingerprint of BOLD bSSFP fMRI

et al. 2017

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Monte Carlo simulations have been used to analyze oxygenation-related signal changes in pass-band balanced steady state free precession (bSSFP) as well as in gradient echo (GE) and spin echo (SE) sequences. Signal changes were calculated for artificial cylinders and neurovascular networks acquired from the mouse parietal cortex by two-photon laser scanning microscopy at 1 µm isotropic resolution. Signal changes as a function of vessel size, blood volume, vessel orientation to the main magnetic field B0 as well as relations of intra- and extravascular and of micro- and macrovascular contributions have been analyzed. The results show that bSSFP is highly sensitive to extravascular and microvascular components. Furthermore, GE and bSSFP, and to a lesser extent SE, exhibit a strong dependence of their signal change on the orientation of the vessel network to B0.

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Section: Discussionmentioning

confidence: 99%

The impact of vessel size, orientation and intravascular contribution on the neurovascular fingerprint of BOLD bSSFP fMRI

et al. 2017

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“…For Figures and , the sum and the ratio of the contributions from micro‐ and macrovessels were calculated, respectively. Micro‐ and macrovessels have been defined similar to the model used by Markuerkiaga et al and Khajehim et al Microvessels or the laminar network were composed of arterioles having a radius between 5–15 μm, capillaries with a radius of 4 μm, and venules or postcapillary vessels between 6–18 μm, according to the vascular anatomical network (VAN) proposed by Boas et al and Blinder et al The fractional BV of microvessels was 1% for venules, 0.8% for capillaries, and 0.5% for arterioles . Oxygenation levels for the resting and activated state were set to 60% and 70% for venules, 77.5% and 85% for capillaries, and 95% and 100% for arterioles, respectively .…”

Section: Methodsmentioning

confidence: 99%

The BOLD sensitivity of rapid steady‐state sequences

Scheffler

Heule

Báez-Yáñez

et al. 2018

Magnetic Resonance in Med

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Purpose Relaxation and dephasing of water protons embedded in a vascular network is driven by local magnetic field inhomogeneities around deoxygenated blood vessels. These effects strongly depend on the relation between mean diffusion length and diameter of blood vessels, as well as on the chosen imaging sequence. In this work, the BOLD sensitivity of steady‐state sequences as a function of vessel size, field strength, and sequence parameters are analyzed. Methods Steady‐state magnetization within a network of artificial cylinders is simulated with Monte Carlo methods for different coherence pathways. In addition, measurements on microspheres were performed to confirm theoretical results. Results Simulations and phantom results demonstrate a vessel size‐dependent signal attenuation effect of all coherence pathways. Both the FID and ECHO pathways show a signal profile similar to spin echo sequences where in the static dephasing regime the effect of larger vessels is suppressed. Conclusion The BOLD effect measured in steady‐state sequences is most sensitive to microvessels and might therefore be closer to the underlying neuronal event compared to gradient echo sequences.

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“…This is specifically observed as the site of the greatest BOLD activations shift from the brain surface to the parenchyma with GE and SE fMRI, respectively (Fig. 1A–B) (Goense and Logothetis, 2006; Markuerkiaga et al, 2016; Zhao et al, 2004). However, SE fMRI has a poorer sensitivity and temporal resolution compared to GE, so exploration of additional contrasts for preclinical application was necessary.…”

Section: Different Fmri Contrasts and Their Specificity To The Sitmentioning

confidence: 88%

Foundations of layer-specific fMRI and investigations of neurophysiological activity in the laminarized neocortex and olfactory bulb of animal models

2019

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Laminar organization of neuronal circuits is a recurring feature of how the brain processes information. For instance, different layers compartmentalize different cell types, synaptic activities, and have unique intrinsic and extrinsic connections that serve as units for specialized signal processing. Functional MRI is an invaluable tool to investigate laminar processing in the in vivo human brain, but it measures neuronal activity indirectly by way of the hemodynamic response. Therefore, the accuracy of high-resolution laminar fMRI depends on how precisely it can measure localized microvascular changes nearest to the site of evoked activity. To determine the specificity of fMRI responses to the true neurophysiological responses across layers, the flexibility to invasive procedures in animal models has been necessary. In this review, we will examine different fMRI contrasts and their appropriate uses for layer-specific fMRI, and how localized laminar processing was examined in the neocortex and olfactory bulb. Through collective efforts, it was determined that microvessels, including capillaries, are regulated within single layers and that several endogenous and contrast-enhanced fMRI contrast mechanisms can separate these neural-specific vascular changes from the nonspecific, especially cerebral blood volume-weighted fMRI with intravenous contrast agent injection. We will also propose some open questions that are relevant for the successful implementation of layer-specific fMRI and its potential future directions to study laminar processing when combined with optogenetics.

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A cortical vascular model for examining the specificity of the laminar BOLD signal

Cited by 166 publications

References 51 publications

The impact of vessel size, orientation and intravascular contribution on the neurovascular fingerprint of BOLD bSSFP fMRI

The impact of vessel size, orientation and intravascular contribution on the neurovascular fingerprint of BOLD bSSFP fMRI

The BOLD sensitivity of rapid steady‐state sequences

Foundations of layer-specific fMRI and investigations of neurophysiological activity in the laminarized neocortex and olfactory bulb of animal models

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