Purpose: The BOLD effect is modeled as primarily due to a mismatch of cerebral blood flow (CBF) and cerebral metabolic rate of O2 (CMRO2), but it is still not clear how we should include the effects of changes in cerebral blood volume (CBV) in the model. Having an accurate model is important because it serves as the framework for interpreting combined CBF and BOLD measurements in the calibrated...

AIMS In animals, intracerebroventricular glucose and fructose have opposing effects on appetite and weight regulation. In humans, functional brain magnetic resonance imaging (fMRI) studies during glucose ingestion or infusion have demonstrated suppression of hypothalamic signalling, but no studies have compared the effects of glucose and fructose. We therefore sought to determine if the brain r...

Introduction Imaging sequences based upon blood oxygenation level dependent (BOLD) contrast are currently the predominant method for functional magnetic resonance imaging (fMRI) of the brain. BOLD weighted sequences offer both high contrast-to-noise ratio and good temporal resolution. The BOLD signal reflects the total amount of deoxyhemoglobin (dHBO2), and is thus a complex function of cerebra...

Introduction While the dynamics and mechanism of the positive BOLD response have been well studied, much less is known about the mechanism of the negative BOLD response. Although the negative BOLD response is related to decreases in neural activity [1] and in CBF [2], the temporal dynamics differ from that of the positive BOLD signal [1]. Here, we studied the properties of the negative BOLD res...

BACKGROUND AND PURPOSE Functional MRI is a powerful tool to investigate recovery of brain function in patients with stroke. An inherent assumption in functional MRI data analysis is that the blood oxygenation level-dependent (BOLD) signal is stable over the course of the examination. In this study, we evaluated the validity of such assumption in patients with chronic stroke. METHODS Fifteen p...

Cortical spreading depression (CSD) has been suggested to underlie migraine visual aura. However, it has been challenging to test this hypothesis in human cerebral cortex. Using high-field functional MRI with near-continuous recording during visual aura in three subjects, we observed blood oxygenation level-dependent (BOLD) signal changes that demonstrated at least eight characteristics of CSD,...

24 We investigated the effects of resting state type on the blood oxygen level-dependent (BOLD) signal and 25 functional connectivity in two paradigms: participants either alternated between fixation and eyes closed or 26 maintained fixation or eyes closed throughout each scan. The BOLD signal and functional connectivity of lower 27 and higher tiers of the visual cortical hierarchy were found t...

In contrast to the limited use of functional magnetic resonance imaging (fMRI) in clinical diagnostics, it is currently a mainstay of neuroimaging in clinical and basic brain research. However, its non-invasive use in combination with its high temporal and spatial resolution would make fMRI a perfect diagnostic tool. We are interested in whether a pharmacological challenge imposed on the brain ...

Functional magnetic resonance imaging (fMRI) using the blood oxygenation level-dependent (BOLD) contrast is now increasingly applied for measuring drug effects on brain activity. A possible confound in pharmacologic fMRI (phMRI) is that the BOLD signal may be sensitive to systemic cardiovascular or respiratory parameters, which can themselves be modulated by a drug. To assess whether abrupt cha...

Brain maturation in adolescence is mirrored by the EEG as a pronounced decrease in low frequency activity. This EEG power attenuation parallels reductions of structural and metabolic markers of neuronal maturation (i.e., gray matter loss and decrease of absolute cerebral glucose utilization). However, it is largely unknown what causes these electrophysiological changes, and how this functional ...