Pharmacological magnetic resonance imaging (phMRI) is increasingly being used in drug discovery and development to speed the translation from the laboratory to the clinic. The two primary methods in phMRI include blood-oxygen-level-dependent (BOLD) contrast and arterial spin-labeled (ASL) perfusion MRI. BOLD contrast has been widely applied in existing phMRI studies. However, because of the lac...

The objective of the study was to introduce the availability of bold imaging facility at Aga Khan University Hospital Karachi for the first time in Pakistan and also to review the practical application and advantages of functional magnetic resonance imaging (fMRI) and blood oxygen level dependant (BOLD) Imaging Procedures. The study was conducted at Aga Khan University Hospital, Karachi from Au...

Mapping cortical columnar structures is important to understand cortical information processing. To map submillimeter columnar structures noninvasively, we have evaluated various functional magnetic resonance imaging (fMRI) techniques using a well-established feline orientation column model. The conventional positive blood oxygenation level-dependent (BOLD) signal is widespread and diffuse due ...

OBJECTIVE Changes in blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) signal are closely related to changes in fetal oxygenation. In this study, we aimed to investigate the changes in human fetal oxygenation during maternal hyperoxia by using the non-invasive BOLD MRI technique. METHOD Eight healthy pregnant women in gestational week 28 to 34 were included. With the use of...

Most functional magnetic resonance imaging (fMRI) studies are based on measuring the changes in the blood oxygenation level-dependent (BOLD) contrast that arise from a complex interplay between cerebral hemodynamics and oxidative metabolism. To separate these effects, we consecutively applied two different stimuli: visual stimulation (black/white checkerboard alternating with a frequency of 8 H...

Our goal is to model the coupling between neuronal activity, cerebral metabolic rates of glucose and oxygen consumption, cerebral blood flow (CBF), electroencephalography (EEG) and blood oxygenation level-dependent (BOLD) responses. In order to accomplish this, two previous models are coupled: a metabolic/hemodynamic model (MHM) for a voxel, linking BOLD signals and neuronal activity, and a neu...

Although functional MRI (fMRI) based on blood oxygenation level-dependent (BOLD) signal changes is a sensitive tool for mapping brain activation, quantitative studies of the physiological effects of pharmacological agents using fMRI alone are difficult to interpret due to the complexities inherent in the BOLD response. Hypercapnia-calibrated BOLD methodology is potentially a more powerful physi...

This study explored the possible use of caffeine as an agent to improve the BOLD (blood oxygen level-dependent) signal response in fMRI. Previous research has demonstrated that caffeine has the ability to reset the level of coupling between blood flow and neuronal activity. In the present study, it has been shown that caffeine causes a decrease in cerebral perfusion by as much as 13.2% without ...

Popular hemodynamic brain imaging methods, such as blood oxygen-level dependent functional magnetic resonance imaging (BOLD fMRI), would benefit from a detailed understanding of the mechanisms by which oxygen is delivered to the cortex in response to brief periods of neural activity. Tissue oxygen responses in visual cortex following brief visual stimulation exhibit rich dynamics, including an ...

BOLD Effect (Blood Oxygen Level Dependent Effect) The change in T ∗ 2 that is caused by changes in the amount of oxygenated hemoglobin in the venous circulation of the brain. Because oxygenated hemoglobin has a much smaller magnetic susceptibility than deoxygenated hemoglobin, and because neural activity causes a change in the amount of oxygenated hemoglobin in the venous blood, the magnetic su...