. Subtraction methodfunctional neuroimaging research
Assumption of the subtraction technique is that only a single feature is added from one condition to another, which means that after subtracting one condition from another, any differences between the two images must be due to this single feature.
A typical use of the subtraction method is a comparison between a reference or baseline condition and an active condition in which a new cognitive process is added to the cognitive processes present in the reference condition.
The PET and fMRI only examine differences in brain activity relative to a control or baseline
Changes are usually very small (5-20%)
Important that only a single feature be added or removed across conditions
Ultimately this is a very difficult problem
8. fMRI
Used to monitor changes in blood flow and blood volume in the brain within a couple of hundred milliseconds, better spatial......
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