PRES: The Subcortical Cocktail Problem Flashcards
What is the subcortical cocktail problem?
The challenge of separating mixed BOLD signals from the subthalamic nucleus (STN) and substantia nigra (SN) due to their close proximity.
What task frequently involves the STN and SN in cognitive studies?
The stop-signal task.
What is the average volume of the STN?
Approximately 119.88 mm³.
What imaging technique helped create probabilistic maps of the STN and SN?
Ultra-high-resolution 7T MRI.
How do spatial smoothing kernels impact fMRI data of the STN and SN?
They spread signals, mixing those from neighboring nuclei.
What is the functional role of the STN?
It acts as a general ‘brake’ to inhibit responses during conflict processing.
What distinguishes the SN from the STN in functional roles?
The SN uses dopamine to activate correct responses and inhibit incorrect ones.
Why are the STN and SN challenging to localize in fMRI studies?
Their small size and proximity lead to mixed signals in typical fMRI resolutions.
What is the most frequently used smoothing kernel size in fMRI studies of STN/SN?
8 mm full-width at half maximum (FWHM).
What is the main finding of signal attribution in this study?
A significant portion of fMRI signals does not originate from the intended nuclei.
Why is ultra-high-resolution imaging essential for studying STN/SN?
It improves signal specificity and reduces signal mixture from adjacent regions.
How were older studies normalized to modern standards?
By converting Talairach coordinates to MNI stereotactic space.
What proportion of signal in the STN originates from outside this nucleus with 8 mm smoothing?
75%.
What do probabilistic atlas maps show about the STN and SN?
Their precise spatial distribution and variability across individuals.
How does aging affect STN location in the brain?
The STN shifts laterally with age.
