scholarly journals Negative BOLD-fMRI Signals in Large Cerebral Veins

2010 ◽  
Vol 31 (2) ◽  
pp. 401-412 ◽  
Author(s):  
Marta Bianciardi ◽  
Masaki Fukunaga ◽  
Peter van Gelderen ◽  
Jacco A de Zwart ◽  
Jeff H Duyn
Keyword(s):  
High Resolution ◽  
Blood Volume ◽  
Neural Activity ◽  
Blood Oxygenation ◽  
Cerebral Veins ◽  
Hemodynamic Changes ◽  
Theoretical Predictions ◽  
Oxygenation Level ◽  
Negative Bold ◽  
Task Activation

Reductions in blood oxygenation level dependent (BOLD)-functional magnetic resonance imaging (fMRI) signals below baseline levels have been observed under several conditions as negative activation in task-activation studies or anticorrelation in resting-state experiments. Converging evidence suggests that negative BOLD signals (NBSs) can generally be explained by local reductions in neural activity. Here, we report on NBSs that accompany hemodynamic changes in regions devoid of neural tissue. The NBSs were investigated with high-resolution studies of the visual cortex (VC) at 7T. Task-activation studies were performed to localize a task-positive area in the VC. During rest, robust negative correlation with the task-positive region was observed in focal regions near the ventricles and dispersed throughout the VC. Both positive and NBSs were dependent on behavioral condition. Comparison with high-resolution structural images showed that negatively correlated regions overlapped with larger pial and ependymal veins near sulcal and ventricular cerebrospinal fluid (CSF). Results from multiecho fMRI showed that NBSs were consistent with increases in local blood volume. These findings confirm theoretical predictions that tie neural activity to blood volume increases, which tend to counteract positive fMRI signal changes associated with increased blood oxygenation. This effect may be more salient in high-resolution studies, in which positive and NBS may be more often spatially distinct.

scholarly journals Origin of Negative Blood Oxygenation Level—Dependent fMRI Signals

2002 ◽  
Vol 22 (8) ◽  
pp. 908-917 ◽  
Author(s):  
Noam Harel ◽  
Sang-Pil Lee ◽  
Tsukasa Nagaoka ◽  
Dae-Shik Kim ◽  
Seong-Gi Kim
Keyword(s):  
Neural Activity ◽  
Spike Activity ◽  
Visual Stimulation ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Bold Signal ◽  
Area 18 ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Negative Bold

Functional magnetic resonance imaging (fMRI) techniques are based on the assumption that changes in spike activity are accompanied by modulation in the blood oxygenation level—dependent (BOLD) signal. In addition to conventional increases in BOLD signals, sustained negative BOLD signal changes are occasionally observed and are thought to reflect a decrease in neural activity. In this study, the source of the negative BOLD signal was investigated using T2*-weighted BOLD and cerebral blood volume (CBV) techniques in isoflurane-anesthetized cats. A positive BOLD signal change was observed in the primary visual cortex (area 18) during visual stimulation, while a prolonged negative BOLD change was detected in the adjacent suprasylvian gyrus containing higher-order visual areas. However, in both regions neurons are known to increase spike activity during visual stimulation. The positive and negative BOLD amplitudes obtained at six spatial-frequency stimuli were highly correlated, and negative BOLD percent changes were approximately one third of the postitive changes. Area 18 with positive BOLD signals experienced an increase in CBV, while regions exhibiting the prolonged negative BOLD signal underwent a decrease in CBV. The CBV changes in area 18 were faster than the BOLD signals from the same corresponding region and the CBV changes in the suprasylvian gyrus. The results support the notion that reallocation of cortical blood resources could overcome a local demand for increased cerebral blood flow induced by increased neural activity. The findings of this study imply that caution should be taken when interpreting the negative BOLD signals as a decrease in neuronal activity.

scholarly journals Key Aspects of Neurovascular Control Mediated by Specific Populations of Inhibitory Cortical Interneurons

2019 ◽  
Vol 30 (4) ◽  
pp. 2452-2464 ◽  
Author(s):  
L Lee ◽  
L Boorman ◽  
E Glendenning ◽  
C Christmas ◽  
P Sharp ◽  
...  
Keyword(s):  
Blood Volume ◽  
Neural Activity ◽  
Blood Oxygen Level Dependent ◽  
Brain Regions ◽  
Cortical Inhibition ◽  
Blood Oxygen Level ◽  
Hemodynamic Changes ◽  
Cortical Interneurons ◽  
Negative Bold ◽  
Key Aspects

Abstract Inhibitory interneurons can evoke vasodilation and vasoconstriction, making them potential cellular drivers of neurovascular coupling. However, the specific regulatory roles played by particular interneuron subpopulations remain unclear. Our purpose was therefore to adopt a cell-specific optogenetic approach to investigate how somatostatin (SST) and neuronal nitric oxide synthase (nNOS)-expressing interneurons might influence the neurovascular relationship. In mice, specific activation of SST- or nNOS-interneurons was sufficient to evoke hemodynamic changes. In the case of nNOS-interneurons, robust hemodynamic changes occurred with minimal changes in neural activity, suggesting that the ability of blood oxygen level dependent functional magnetic resonance imaging (BOLD fMRI) to reliably reflect changes in neuronal activity may be dependent on type of neuron recruited. Conversely, activation of SST-interneurons produced robust changes in evoked neural activity with shallow cortical excitation and pronounced deep layer cortical inhibition. Prolonged activation of SST-interneurons often resulted in an increase in blood volume in the centrally activated area with an accompanying decrease in blood volume in the surrounding brain regions, analogous to the negative BOLD signal. These results demonstrate the role of specific populations of cortical interneurons in the active control of neurovascular function.

scholarly journals The Vascular Steal Phenomenon is an Incomplete Contributor to Negative Cerebrovascular Reactivity in Patients with Symptomatic Intracranial Stenosis

2014 ◽  
Vol 34 (9) ◽  
pp. 1453-1462 ◽  
Author(s):  
Daniel F Arteaga ◽  
Megan K Strother ◽  
Carlos C Faraco ◽  
Lori C Jordan ◽  
Travis R Ladner ◽  
...  
Keyword(s):  
Clinical Symptoms ◽  
Blood Oxygenation ◽  
Cerebrovascular Reactivity ◽  
Intracranial Stenosis ◽  
Compensatory Mechanism ◽  
Ischemic Cerebrovascular Disease ◽  
Oxygenation Level ◽  
Fluid Attenuated Inversion Recovery ◽  
Vascular Steal ◽  
Negative Bold

‘Vascular steal’ has been proposed as a compensatory mechanism in hemodynamically compromised ischemic parenchyma. Here, independent measures of cerebral blood flow (CBF) and blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) responses to a vascular stimulus in patients with ischemic cerebrovascular disease are recorded. Symptomatic intracranial stenosis patients ( n = 40) underwent a multimodal 3.0T MRI protocol including structural (T1-weighted and T2-weighted fluid-attenuated inversion recovery) and hemodynamic (BOLD and CBF-weighted arterial spin labeling) functional MRI during room air and hypercarbic gas administration. CBF changes in regions demonstrating negative BOLD reactivity were recorded, as well as clinical correlates including symptomatic hemisphere by infarct and lateralizing symptoms. Fifteen out of forty participants exhibited negative BOLD reactivity. Of these, a positive relationship was found between BOLD and CBF reactivity in unaffected (stenosis degree <50%) cortex. In negative BOLD cerebrovascular reactivity regions, three patients exhibited significant ( P < 0.01) reductions in CBF consistent with vascular steal; six exhibited increases in CBF; and the remaining exhibited no statistical change in CBF. Secondary findings were that negative BOLD reactivity correlated with symptomatic hemisphere by lateralizing clinical symptoms and prior infarcts(s). These data support the conclusion that negative hypercarbia-induced BOLD responses, frequently assigned to vascular steal, are heterogeneous in origin with possible contributions from autoregulation and/or metabolism.

scholarly journals A multi-data based quantitative model for neurovascular coupling in the brain.

2021 ◽  
Author(s):  
Sebastian Sten ◽  
Henrik Podéus ◽  
Nicolas Sundqvist ◽  
Fredrik Elinder ◽  
Maria Engström ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Neurovascular Coupling ◽  
Quantitative Model ◽  
Blood Oxygenation ◽  
Data Types ◽  
Hemodynamic Changes ◽  
Validation Data ◽  
The Core ◽  
Oxygenation Level ◽  
The Brain

The neurovascular coupling (NVC) forms the foundation for functional imaging techniques of the brain, since NVC connects neural activity with observable hemodynamic changes. Many aspects of the NVC have been studied both experimentally and with mathematical models: various combinations of blood volume and flow, electrical activity, oxygen saturation measures, blood oxygenation level-dependent (BOLD) response, and optogenetics have been measured and modeled in rodents, primates, or humans. We now present a first inter-connected mathematical model that describes all such data types simultaneously. The model can predict independent validation data not used for training. Using simulations, we show for example how complex bimodal behaviors appear upon stimulation. These simulations thus demonstrate how our new quantitative model, incorporating most of the core aspects of the NVC, can be used to mechanistically explain each of its constituent datasets.

scholarly journals Modelling the depth-dependent VASO and BOLD responses in human primary visual cortex

2021 ◽  
Author(s):  
Atena Akbari ◽  
Saskia Bollmann ◽  
Tonima Ali ◽  
Markus Barth
Keyword(s):  
Visual Cortex ◽  
Blood Volume ◽  
Primary Visual Cortex ◽  
Cerebral Blood Volume ◽  
Blood Oxygenation ◽  
Physiological Variables ◽  
Oxygenation Level ◽  
Signal Specificity ◽  
Experimental Findings ◽  
Spatial Specificity

Functional magnetic resonance imaging (fMRI) using blood-oxygenation-level-dependent (BOLD) contrast is a common method for studying human brain function non-invasively. Gradient-echo (GRE) BOLD is highly sensitive to the blood oxygenation change in blood vessels; however, the signal specificity can be degraded due to signal leakage from the activated lower layers to the superficial layers in depth-dependent (also called laminar or layer-specific) fMRI. Alternatively, physiological variables such as cerebral blood volume using VAscular-Space-Occupancy (VASO) measurements have shown higher spatial specificity compared to BOLD. To better understand the physiological mechanisms (e.g., blood volume and oxygenation change) and to interpret the measured depth-dependent responses we need models that reflect vascular properties at this scale. For this purpose, we adapted a cortical vascular model previously developed to predict the layer-specific BOLD signal change in human primary visual cortex to also predict layer-specific VASO response. To evaluate the model, we compared the predictions with experimental results of simultaneous VASO and BOLD measurements in a group of healthy participants. Fitting the model to our experimental findings provided an estimate of CBV change in different vascular compartments upon neural activity. We found that stimulus-evoked CBV changes mainly occur in intracortical arteries as well as small arterioles and capillaries and that the contribution from venules is small for a long stimulus (~30 sec). Our results confirm the notion that VASO contrast is less susceptible to large vessel effects compared to BOLD.

scholarly journals Basal Cerebral Blood Volume during the Poststimulation Undershoot in BOLD MRI of the Human Brain

2010 ◽  
Vol 31 (1) ◽  
pp. 82-89 ◽  
Author(s):  
Peter Dechent ◽  
Gunther Schütze ◽  
Gunther Helms ◽  
Klaus Dietmar Merboldt ◽  
Jens Frahm
Keyword(s):  
Contrast Agent ◽  
Blood Volume ◽  
Animal Studies ◽  
Cerebral Blood Volume ◽  
Visual Stimulation ◽  
Three Dimensional ◽  
Blood Pool ◽  
Blood Oxygenation ◽  
Bold Mri ◽  
Oxygenation Level

One of the characteristics of the blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) response to functional challenges of the brain is the poststimulation undershoot, which has been suggested to originate from a delayed recovery of either cerebral blood volume (CBV) or cerebral metabolic rate of oxygen to baseline. Using bolus-tracking MRI in humans, we recently showed that relative CBV rapidly normalizes after the end of stimulation. As this observation contradicts at least part of the blood-pool contrast agent studies performed in animals, we reinvestigated the CBV contribution by dynamic T1-weighted three-dimensional MRI (8 seconds temporal resolution) and Vasovist at 3 T (12 subjects). Initially, we determined the time constants of individual BOLD responses. After injection of Vasovist, CBV-related T1-weighted signal changes revealed a signal increase during visual stimulation (1.7%±0.4%), but no change relative to baseline in the poststimulation phase (0.2%±0.3%). This finding renders the specific nature of the contrast agent unlikely to be responsible for the discrepancy between human and animal studies. With the assumption of normalized cerebral blood flow after stimulus cessation, a normalized CBV lends support to the idea that the BOLD MRI undershoot reflects a prolonged elevation of oxidative metabolism.

scholarly journals Assessment of single-vessel cerebral blood velocity by phase contrast fMRI

PLoS Biology ◽  
2021 ◽  
Vol 19 (9) ◽  
pp. e3000923
Author(s):  
Xuming Chen ◽  
Yuanyuan Jiang ◽  
Sangcheon Choi ◽  
Rolf Pohmann ◽  
Klaus Scheffler ◽  
...  
Keyword(s):  
High Resolution ◽  
High Field ◽  
Phase Contrast ◽  
Cerebral Blood Volume ◽  
Blood Velocity ◽  
Blood Oxygenation ◽  
Single Vessel ◽  
Oxygenation Level ◽  
Cerebral Blood Velocity ◽  
Human Brains

Current approaches to high-field functional MRI (fMRI) provide 2 means to map hemodynamics at the level of single vessels in the brain. One is through changes in deoxyhemoglobin in venules, i.e., blood oxygenation level–dependent (BOLD) fMRI, while the second is through changes in arteriole diameter, i.e., cerebral blood volume (CBV) fMRI. Here, we introduce cerebral blood flow–related velocity-based fMRI, denoted CBFv-fMRI, which uses high-resolution phase contrast (PC) MRI to form velocity measurements of flow. We use CBFv-fMRI in measure changes in blood velocity in single penetrating microvessels across rat parietal cortex. In contrast to the venule-dominated BOLD and arteriole-dominated CBV fMRI signals, CBFv-fMRI is comparable from both arterioles and venules. A single fMRI platform is used to map changes in blood pO2 (BOLD), volume (CBV), and velocity (CBFv). This combined high-resolution single-vessel fMRI mapping scheme enables vessel-specific hemodynamic mapping in animal models of normal and diseased states and further has translational potential to map vascular dementia in diseased or injured human brains with ultra–high-field fMRI.

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