The adult brain exhibits a local increase in cortical blood flow in response to external stimulus. However, broadly varying hemodynamic responses in the brains of newborn and young infants have been reported. Particular controversy exists over whether the "true" neonatal response to stimulation consists of a decrease or an increase in local deoxyhemoglobin, corresponding to a positive (adult-li...

A theoretical framework is presented for converting Blood Oxygenation Level Dependent (BOLD) images to brain temperature maps, based on the idea that disproportional local changes in cerebral blood flow (CBF) as compared with cerebral metabolic rate of oxygen consumption (CMRO₂) during functional brain activity, lead to both brain temperature changes and the BOLD effect. Using an oxygen limitat...

The purpose of this paper is to present a literature review of the theoretical and experimental work that describes the blood-oxygen-level-dependent or BOLD effect using quantitative T2 relaxation mechanism. The BOLD effect is mediated by paramagnetic deoxyhemoglobin which generates magnetic field inhomogeneities around erythrocytes; T2 is modulated by diffusion of spins in and around erythrocy...

Age-related performance declines in visual tasks have been attributed to reductions in processing efficiency. The neural basis of these declines has been explored by comparing the blood-oxygen-level-dependent (BOLD) index of neural activity in older and younger adults during visual task performance. However, neural activity is one of many factors that change with age and lead to BOLD signal dif...

PURPOSE The magnocellular and parvocellular pathways (M and P pathways) are the major pathways of the visual system, with distinct histologic and physiologic properties that may also have different metabolic characteristics. We hypothesize that the differences of the 2 visual pathways would also manifest as differences in the signal time course of blood oxygen level-dependent functional MR imag...

INTRODUCTION Recent studies have demonstrated a link between the use of gadolinium-based contrast agents and the development of nephrogenic systemic fibrosis (NSF) [1]. Given growing concerns of developing NSF, it has become important to investigate non-contrast methods of evaluating renal function. We have developed an MRI perfusion technique employing arterial spin labeling (ASL) [2] that all...

The spatial distribution of signals from magnetic resonance imaging (MRI) using measures of Blood Oxygen Level Dependent (BOLD) activations presents a fundamental limit on the ability of MRI to resolve the neural signals from the brain. Here we show that the multiple samples of low-level BOLD activity comprise a form of neural “imaging dust” with distinct spatial characteristics. We apply the d...

The human default mode network (DMN) shows decreased blood oxygen level dependent (BOLD) signals in response to a wide range of attention-demanding tasks. Our understanding of the specifics regarding the neural activity underlying these "task-negative" BOLD responses remains incomplete. We paired oxygen polarography, an electrode-based oxygen measurement technique, with standard electrophysiolo...

Introduction Quantitative BOLD (Blood Oxygen Level Dependent) has been proposed to map brain oxygenation levels using MRI [1]. This approach yields tissular SO2 (oxygen saturation) estimates, i.e. a mean SO2 across the microvascular network in the MRI voxel. To improve the accuracy and the spatial resolution of SO2MR maps, an approach which combines a steady-state Blood Volume fraction (BVf) me...