نتایج جستجو برای: blood oxygen level dependent bold
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One of the current topics of research in neuroimaging techniques is related to explaining and modelling the Blood Oxygen Level Dependent (BOLD) responses. BOLD responses are estimated by processing functional Magnetic Resonance Imaging (fMRI) data. BOLD responses are caused by hemodynamic responses to neural activity which alter the levels of blood oxygenation at local brain regions. The main a...
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...
Simultaneously acquired functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) data hold great promise for localizing the spatial source of epileptiform events detected in the EEG trace. Despite a number of studies applying this method, there has been no independent and systematic validation of the approach. The present study uses a nonparametric method to show that inter...
Blood oxygenation level-dependent (BOLD) fMRI signals often exhibit pronounced over- or undershoot upon changes in stimulation state. Current models postulate that this is due to the delayed onset or decay of perfusion-dependent attenuating responses such as increased cerebral blood volume or oxygen consumption, which are presumed to lag behind the rapid adjustment of blood flow rate to a new s...
The precise mechanisms that give rise to the blood-oxygen-level-dependent (BOLD) activation differences that accompany age-related cognitive slowing remain fundamentally unknown. We sought to isolate the origin of age-related BOLD changes by comparing blood-flow and oxygen-metabolic constituents of the BOLD response using dual-echo arterial spin labeling during visual stimulation and CO2 ingest...
The blood oxygenation level-dependent (BOLD) contrast is widely used in functional magnetic resonance imaging (fMRI) studies aimed at investigating neuronal activity. However, the BOLD signal reflects changes in blood volume and oxygenation rather than neuronal activity per se. Therefore, understanding the transformation of microscopic vascular behavior into macroscopic BOLD signals is at the f...
Introduction: Functional MRI has been extensively used to indirectly measure changes in neuronal activation via the BOLD (blood oxygenation level dependent) effect. While BOLD fMRI provides a relative signal that fluctuates based on changes in venous oxygenation, the absolute value of venous oxygen saturation at baseline and during activation is unknown. Additionally, the BOLD response is highl...
Background The mechanisms underlying hibernating myocardium are controversial. Whether de-oxygenation occurs at rest and/or stress in severely dysfunctional viable (i.e. hibernating) myocardium is currently unknown. By utlising the paramagnetic properties of deoxy-haemoglobin, blood oxygen level dependent magnetic resonance imaging (BOLD-MRI) can detect oxygenation and myocardial ischemia. We a...
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