The presence of a strong negative correlation corresponded to shorter reaction times and better overall performance, while a reversal of such dynamic, captured by looking at second-by-second BOLD fMRI
activity, leads to a general worsening of attention.
Unlike BOLD fMRI, ASL does not require repeated emptying and filling of the bladder.
Of these, BOLD fMRI and ASL have gained wide applications because both use endogenous tracers and are therefore noninvasive.
Kim, "Cortical depth-dependent gradient-echo and spin-echo BOLD fMRI
at 9.4T," Magnetic Resonance in Medicine, vol.
However, in ASL fMRI, a much shorter TE is usually used than in BOLD fMRI, which reduces the signal loss due to susceptibility effects and provides better spatial specificity than BOLD MRI, where large draining veins can contribute artifactual signal.
Thus NIRS can measure amounts of hemoglobin and deoxyhemoglobin in tissue, which BOLD fMRI cannot, because BOLD fMRI signal changes arise from a complex mixture of CBF, CBV, and oxygenation changes.
Reviews of NIRS and BOLD fMRI studies of stroke and brain tumors  and of NIRS studies of stroke rehabilitation  provide an assessment of the opportunities and challenges.
The smallest single unit measured by BOLD fMRI
, called a voxel, is often a few millimeters on each side, dwarfing the size of individual neurons.
As mentioned above, BOLD fMRI
measures hemodynamic response, that is, the blood-oxygen-dependent signal that is related to blood flow and that scientists therefore assume is related to brain activity.
For each patient, time series data were extracted from the BOLD fMRI
images, for each of the four ROIs.
Absolute quantification also allows the resting state to be characterized, in contrast to BOLD fMRI, which primarily detects differences between two or more experimentally manipulated conditions.
Alterations in the BOLD fMRI signal with ageing and disease: A challenge for neuroimaging.
Technique What It Measures BOLD fMRI Indirect measure of blood flow, BOLD signal changes originate in venules.
There is also some resting-state studies reporting that EEG is not directly linked to the changes in neural activity as measured by BOLD fMRI
Luk, "Cervical spinal cord BOLD fMRI
study: modulation of functional activation by dexterity of dominant and nondominant hands," NeuroImage, vol.