Introduction Studies comparing visual evoked potentials (VEPs) and BOLD signals have found a positive correlation between the VEP amplitude and the magnitude and extent of the BOLD signal [1, 2], but some VEP components are better related to the BOLD signal than others. The strongest spatial correlation have been found between the source location of the N1 peak* and the location of the BOLD sig...

The relation between the blood-oxygen-level-dependent (BOLD) signal, which forms the basis of functional magnetic resonance imaging (fMRI), and underlying neural activity is not well understood. We performed high-resolution fMRI in patients scheduled for implantation with depth electrodes for seizure monitoring while they navigated a virtual environment. We then recorded local field potentials ...

INTRODUCTION Spontaneous fluctuations in BOLD signal are used for functional connectivity [1]. It has been suggested that these spontaneous fluctuations may influence trial-to-trial variability of the evoked BOLD response [2]. Taken together, these studies suggest that the amplitude of the spontaneous fluctuation has significance for the strength of the functional connectivity (between symmetri...

In functional magnetic resonance imaging studies changes in blood oxygenation level-dependent (BOLD) signal intensities during task activation are related to multiple physiological parameters such as cerebral blood flow, volume, and oxidative metabolism, as well as to the regional microvascular anatomy. Consequently, the magnitude of activation-induced BOLD signal changes may vary regionally an...

The blood oxygen level-dependent (BOLD) signal time course in the auditory cortex is characterized by two components, an initial transient peak and a subsequent sustained plateau with smaller amplitude. Because the T(2)(*) signal detected by functional magnetic resonance imaging (fMRI) depends on at least two counteracting factors, blood oxygenation and volume, we examined whether the reduction...

Introduction The vast majority of functional magnetic resonance imaging (fMRI) studies use measures of the blood oxygenation level dependent (BOLD) signal as a reflection of neural activity. However, the BOLD signal is a complex function of a number of physiological variables, and there is growing evidence indicating that changes in the baseline vascular and metabolic state can significantly mo...

Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) is widely used as a tool for functional brain mapping. During brain activation, increases in the regional blood flow lead to an increase in blood oxygenation and a decrease in paramagnetic deoxygenated hemoglobin (deoxy-Hb), causing an increase in the MR signal intensity at the site of brain activation. However,...

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...

Introduction The baseline fMRI signal and the blood oxygenation level-dependent (BOLD) signal amplitude are not a quantitative reflection of neuronal activity as physiological and physical parameters (e.g. baseline CBF, echo time, coil sensitivity ...) contribute to the the signal. One goal of quantitative fMRI is to determine oxygen metabolism (CMRO2) from fMRI data. To this end, a calibrated ...