The blood oxygenation level-dependent (BOLD) phenomenon has profoundly revolutionized neuroscience, with applications ranging from normal brain development and aging, to brain disorders and diseases. While the BOLD effect represents an invaluable tool to map brain function, it does not measure neural activity directly; rather, it reflects changes in blood oxygenation resulting from the relative...

BACKGROUND Functional near-infrared spectroscopy (fNIRS) and functional MRI (fMRI) are non-invasive techniques used to relate activity in different brain regions to certain tasks. Respiratory calibration of the blood oxygen level dependent (BOLD) signal, and combined fNIRS-fMRI approaches have been used to quantify physiological subcomponents giving rise to the BOLD signal. A comparison of abso...

PURPOSE Blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is a technique used to infer neuronal activity from the observed changes in blood flow. Cerebrovascular reactivity (CVR) is the ability of arterioles to increase blood flow in response to vasodilatory stimulus. We hypothesize that in areas of disease where there is exhausted vascular reserve and impaired CV...

PURPOSE To demonstrate blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) of vascular oxygenation changes in normal, unanesthetized human retinas associated with oxygen and carbogen challenge. METHODS MRI was performed with a 3-T human scanner and a custom-made surface-coil detector on normal volunteers. BOLD MRI with inversion recovery was used to suppress the vitreous...

introduction as functional magnetic resonance imaging (fmri) is too expensive and time consuming, its frequent implementation is difficult. the aim of this study is to evaluate repeatability of detecting visual cortex activity in fmri. materials and methods in this study, 15 normal volunteers (10 female, 5 male; mean age±sd: 24.7±3.8 years) attended. functional magnetic resonance images were ob...

Functional MRI (fMRI) using the blood oxygenation level dependent (BOLD) signal is a common technique in the study of brain function. The BOLD signal is sensitive to the complex interaction of physiological changes including cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral oxygen metabolism (CMRO2). A primary goal of quantitative fMRI methods is to combine BOLD imaging with ...

Recently a new class of calibrated blood oxygen level dependent (BOLD) functional magnetic resonance imaging (MRI) methods were introduced to quantitatively measure the baseline oxygen extraction fraction (OEF). These methods rely on two respiratory challenges and a mathematical model of the resultant changes in the BOLD functional MRI signal to estimate the OEF. However, this mathematical mode...

Functional connectivity MRI (fcMRI) studies have provided enormous insight into the functional organization of the human brain. fcMRI measures temporal correlations in at-rest blood oxygen level dependent signals (BOLD), which, at best, provide an indirect measure of neural activity. Though much effort has been put towards understanding the relationship between neural activity and BOLD response...

Introduction Low-frequency fluctuations in the blood oxygen level-dependent (BOLD) signal are an important component of ‘physiological noise’ in functional MRI signals. Identification and characterization of these sources is extremely important in order to develop noise reduction strategies and hence obtain more accurate activation maps. Spontaneous low frequency fluctuations in arterial carbon...

Simultaneous implementation of magnetic resonance imaging methods for Arterial Spin Labeling (ASL) and Blood Oxygenation Level Dependent (BOLD) imaging makes it possible to quantitatively measure the changes in cerebral blood flow (CBF) and cerebral oxygen metabolism (CMRO(2)) that occur in response to neural stimuli. To date, however, the range of neural stimuli amenable to quantitative analys...