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Blood oxygenation level-dependent imaging, or BOLD-contrast imaging, is a method used in functional magnetic resonance imaging (fMRI) to observe different areas of the brain or other organs, which are found to be active at any given time. [1] [2]
The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, [4] discovered by Seiji Ogawa in 1990. This is a type of specialized brain and body scan used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow ( hemodynamic response ) related to energy use by brain ...
Resting state fMRI (rs-fMRI or R-fMRI), also referred to as task-independent fMRI or task-free fMRI, is a method of functional magnetic resonance imaging (fMRI) that is used in brain mapping to evaluate regional interactions that occur in a resting or task-negative state, when an explicit task is not being performed.
The hemodynamic response is the basis for the BOLD (blood oxygen level dependent) contrast in fMRI. [5] The hemodynamic response occurs within seconds of the presented stimuli, but it is essential to space out the events in order to ensure that the response being measured is from the event that was presented and not from a prior event.
Amplitude of Low Frequency Fluctuations (ALFF) and fractional Amplitude of Low Frequency Fluctuations (f/ALFF) are neuroimaging methods used to measure spontaneous fluctuations in BOLD-fMRI signal intensity for a given region in the resting brain. Electrophysiological studies suggest that low-frequency oscillations arise from spontaneous ...
There are different fMRI techniques that can pick up a functional signal corresponding to changes in each of the previously mentioned components of the haemodynamic response. The most common functional imaging signal is the blood-oxygen-level dependent signal (BOLD), which primarily corresponds to the concentration of deoxyhemoglobin. [13]
He was the first scientist who demonstrated that the functional brain imaging is dependent on the oxygenation status of the blood, the BOLD effect. The technique was therefore called blood oxygenation level-dependent or BOLD contrast. Functional MRI (fMRI) has been used to map the visual, auditory, and sensory regions and moving toward higher ...
This finding has an important implication for the interpretation of BOLD fMRI data where this high baseline activity is generally ignored and response to the task is shown as independent of the baseline activity. 13 C MRS studies indicate that this approach can misjudge and even completely miss the brain activity induced by the task. [37]