scholarly journals Evaluation of BOLD effects in the rat cortex

2021 ◽  
Author(s):  
Nathalie Just
Keyword(s):  
Blood Oxygen Level Dependent ◽  
Metabolite Concentration ◽  
Blood Oxygen Level ◽  
Difference Spectra ◽  
Optogenetic Stimulation ◽  
Line Narrowing ◽  
Concentration Changes ◽  
Definition Of ◽  
Stimulation Paradigm

Purpose: This study aimed to characterize Blood oxygen level-dependent (BOLD) effects in 1H- MR spectra obtained during optogenetic activation of the rat forelimb cortex for the correction and estimation of accurate metabolite concentration changes. Methods : T2*-induced effects were characterized by linewidth changes and amplitude changes of water, NAA and tCr spectral peaks during the stimulation paradigm. Spectral linewidth-matching procedures were used to correct for the line-narrowing effect induced by BOLD. For an increased understanding of spectroscopic BOLD effects and the optimized way to correct them, a 1 Hz line-narrowing effect was also simulated on mouseproton MR spectrum1H-fMRS data acquired using STEAM acquisitions at 9.4T in rats (n=8) upon optogenetic stimulation of the primary somatosensory cortex were used. Data were analyzed with MATLAB routines and LCModel. Uncorrected and corrected 1H-MR spectra of simulated and in-vivo data were quantified and compared. BOLD-corrected difference spectra were also calculated and analyzed. Results: Significant mean increases in water and NAA peak heights (+ 1.1% and +4.5%, respectively) were found accompanied by decreased linewidths (-0.5 Hz and -2.8%) upon optogenetic stimulation. These estimates were used for further definition of an accurate line-broadening factor (lb). Usage of an erroneous lb introduced false-positive errors in metabolite concentration change estimates thereby altering the specificity of findings. Using different water scalings within LCModel, the water and metabolite BOLD contributions were separated. Conclusion : The linewidth-matching procedure using a precise lb factor remains the most performant approach for the accurate quantification of small (0.3 micromol/g) metabolic changes in 1H-fMRS studies. A simple and preliminary compartmentation of BOLD effects was proposed, which will require validation.

scholarly journals Functional White-Laser Imaging to Study Brain Oxygen Uncoupling/Recoupling in Songbirds

2010 ◽  
Vol 31 (2) ◽  
pp. 393-400 ◽  
Author(s):  
Stéphane Mottin ◽  
Bruno Montcel ◽  
Hugues Guillet de Chatellus ◽  
Stéphane Ramstein
Keyword(s):  
Time Course ◽  
Brain Aging ◽  
Optical Tomography ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen ◽  
Blood Oxygen Level ◽  
Subsequent Increase ◽  
Brain Oxygen ◽  
Concentration Changes

Contrary to the intense debate about brain oxygen dynamics and its uncoupling in mammals, very little is known in birds. In zebra finches, picosecond optical tomography with a white laser and a streak camera can measure in vivo oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) concentration changes following physiologic stimulation (familiar calls and songs). Picosecond optical tomography showed sufficient submicromolar sensitivity to resolve the fast changes in the hippocampus and auditory forebrain areas with 250 μm resolution. The time course is composed of (1) an early 2-second-long event with a significant decrease in Hb and HbO2 levels of −0.7 and −0.9 μmol/L, respectively, (2) a subsequent increase in blood oxygen availability with a plateau of HbO2 (+ 0.3 μmol/L), and (3) pronounced vasodilatation events immediately after the end of the stimulus. One of the findings of our study is the direct link between blood oxygen level-dependent signals previously published in birds and our results. Furthermore, the early vasoconstriction event and poststimulus ringing seem to be more pronounced in birds than in mammals. These results in birds, tachymetabolic vertebrates with a long lifespan, can potentially yield new insights, e.g., into brain aging.

Hemoglobin microbubbles for in vivo blood oxygen level dependent imaging: Boldly moving beyond MRI

2021 ◽  
Vol 150 (4) ◽  
pp. A27-A27
Author(s):  
Sugandha Chaudhary ◽  
Nasrin Akter ◽  
Akshay Rajeev ◽  
Misun Hwang ◽  
Shashank Sirsi
Keyword(s):  
Blood Oxygen Level Dependent ◽  
Blood Oxygen ◽  
Oxygen Level ◽  
Blood Oxygen Level

scholarly journals Assessing placental function across gestation: a multi-institutional study of BOLD-MRI for the prediction of adverse pregnancy outcomes

2021 ◽  
Author(s):  
Matthias Schabel ◽  
Victoria Roberts ◽  
Karen Gibbins ◽  
Monica Rincon ◽  
Jessica Gaffney ◽  
...  
Keyword(s):  
T2 Mapping ◽  
Blood Oxygen Level Dependent ◽  
Obstetric Outcomes ◽  
Blood Oxygen Level ◽  
Placental Function ◽  
Bold Mri ◽  
Placental Dysfunction ◽  
High Discriminatory Power ◽  
Adverse Pregnancy

Abstract The placenta is a remarkable organ that coordinates and regulates maternal-fetal interactions during pregnancy to optimize fetal development. A host of obstetric complications are associated with placental dysfunction, and existing methods for evaluating in vivo placental function fail to reliably detect at-risk pregnancies prior to maternal or fetal morbidity. Although routinely used as a monitoring tool, the predictive power of ultrasound for identifying compromised pregnancies is poor. Recent preclinical studies performed in our laboratory, using blood oxygen-level dependent magnetic resonance imaging (BOLD-MRI) in the pregnant nonhuman primate (NHP), established a strong correlation between placental T2* values and maternal-fetal oxygen transport. Here we extend this work to a large, longitudinal, two-site study of quantitative in vivo T2* mapping in human pregnancies across 11 to 38 weeks of gestation to characterize the evolution of placental oxygenation in uncomplicated pregnancies and to elucidate the relationship between aberrant placental T2* and adverse obstetric outcomes attributable to placental dysfunction. This methodology has high discriminatory power and strong potential diagnostic utility.

scholarly journals Electrochemical carbon fiber-based technique for simultaneous recordings of brain tissue PO2, pH, and extracellular field potentials

2020 ◽  
Author(s):  
Patrick S. Hosford ◽  
Jack A. Wells ◽  
Isabel N. Christie ◽  
Mark Lythgoe ◽  
Julian Millar ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Brain Tissue ◽  
Electrochemical Detection ◽  
Neuronal Activity ◽  
Blood Oxygen Level Dependent ◽  
Blood Oxygen Level ◽  
Carbon Fiber Electrodes ◽  
Tissue Po2 ◽  
Fast Cyclic Voltammetry

AbstractA method for simultaneous electrochemical detection of brain tissue PO2 (PtO2) and pH changes together with neuronal activity using a modified form of fast cyclic voltammetry with carbon fiber electrodes is described. This technique has been developed for in vivo applications and recordings from discrete brain nuclei in experimental animals. The small size of the carbon fiber electrode (⍰7μm, length <100μm) ensures minimal disruption of the brain tissue and allows recordings from small brain areas. Sample rate (up to 4 Hz) is sufficient to resolve rapid changes in PtO2 and pH that follow changes in neuronal activity and metabolism. Rapid switching between current and voltage recordings allows combined electrochemical detection and monitoring of extracellular action potentials. For simultaneous electrochemical detection of PtO2 and pH, two consecutive trapezoidal voltage ramps are applied with double differential-subtraction of the background current. This enables changes in current caused by protons and oxygen to be detected separately with minimal interference between the two. The profile of PtO2 changes evoked by increases in local neuronal activity recorded using the described technique was similar to that of blood oxygen level dependent responses recorded using fMRI. This voltammetric technique can be combined with fMRI and brain vessel imaging to study the metabolic mechanisms underlying neurovascular coupling response with much greater spatial and temporal resolution than is currently possible.

scholarly journals Mapping optogenetically-driven single-vessel fMRI with concurrent neuronal calcium recordings in the rat hippocampus

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Xuming Chen ◽  
Filip Sobczak ◽  
Yi Chen ◽  
Yuanyuan Jiang ◽  
Chunqi Qian ◽  
...  
Keyword(s):  
Spreading Depression ◽  
Cerebral Blood Volume ◽  
Blood Oxygen Level Dependent ◽  
Electrophysiological Recording ◽  
Blood Oxygen Level ◽  
Hemodynamic Responses ◽  
Network Function ◽  
Single Vessel ◽  
Ca1 Region

AbstractExtensive in vivo imaging studies investigate the hippocampal neural network function, mainly focusing on the dorsal CA1 region given its optical accessibility. Multi-modality fMRI with simultaneous hippocampal electrophysiological recording reveal broad cortical correlation patterns, but the detailed spatial hippocampal functional map remains lacking given the limited fMRI resolution. In particular, hemodynamic responses linked to specific neural activity are unclear at the single-vessel level across hippocampal vasculature, which hinders the deciphering of the hippocampal malfunction in animal models and the translation to critical neurovascular coupling (NVC) patterns for human fMRI. We simultaneously acquired optogenetically-driven neuronal Ca2+ signals with single-vessel blood-oxygen-level-dependent (BOLD) and cerebral-blood-volume (CBV)-fMRI from individual venules and arterioles. Distinct spatiotemporal patterns of hippocampal hemodynamic responses were correlated to optogenetically evoked and spreading depression-like calcium events. The calcium event-related single-vessel hemodynamic modeling revealed significantly reduced NVC efficiency upon spreading depression-like (SDL) events, providing a direct measure of the NVC function at various hippocampal states.

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