Functional Magnetic Resonance Imaging

Functional Magnetic Resonance Imaging (fMRI) is a variation of conventional Magnetic Resonance Imaging (MRI) and a noninvasive method to measure brain function. This imaging modality has high spatial resolution and reproducibility, giving a robust signal. It has been used to study systems involving sensory-motor functions, visuospatial orientation, attention, and memory.

Also, fMRI is a tool for researching addiction behaviour and functional brain mapping by applying the venous blood oxygenation level-dependent (BOLD) contrast method. The significance of the BOLD signal is an indirect measure of neuronal activity, which is a consequence of the changes in the volume of regional cerebral blood flow and oxygenation levels.

Therefore, the principle behind fMRI measurement is an increase in local neuronal activity, which stimulates higher energy consumption and increased blood flow.  Brain function is the transfer of information between neurons and is shown on a statistical map to reflect the regional activity of functional magnetic resonance imaging.

These neural communications facilitate metabolical processes and require an increased flow of oxygenated blood. The influx of oxygenated blood alters the ratio of oxygenated (OXY) arterial blood to deoxygenated (DEOXY) venous blood.  Therefore, the increase in the OXY/DEOXY-haemoglobin ratio increases the MRI signal compared to the surrounding tissues.  

However, the increase in local neuronal activity will delay the onset of regional vasodilation, resulting in increased blood flow.  This mode of action is a local vascular network function called the haemodynamic response function (HRF). 

Functional magnetic resonance imaging (fMRI) is also used in neuroimaging to map the disease state in the clinical setting. Furthermore, fMRI is used in real-time neurofeedback to treat several disorders, such as obsessive-compulsive disorders and Schizophrenia.

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