What is cognitive subtraction (used in brain imaging)? Why is it necessary?

What is cognitive subtraction (used in brain imaging)? Why is it necessary?

It is a method, whereby brain activity is measured first in a "control state", before a stimulus is presented, and again while the stimulus is presented. It is necessary to determine the activity that is due to manipulation, by subtracting the control activity from the stimulation activity.

It is necessary because we cannot directly measure the time it takes for a decision to be made. So we infer the result from the thing we can observe, which is behavior, in this case by the method of cognitive subtraction.

It is necessary because we cannot directly measure the time it takes for a decision to be made. So we infer the result from the thing we can observe, which is behavior. In this case the behavior is the control and stimulation activity and by the method of cognitive subtraction we can infer the amount of time it takes to reach a decision.

It is the findings on how we know which areas are active when seeing, saying or thinking of a word. Basically where things happen in the brain. If we subtract the activity associated with seeing a cross from the activity associated with seeing a word BURGER, we may know which parts are active when people see the word, instead of something else.

The cognitive substraction is a method to measure which areas in our brain are active while doing a cerrtain activity or seeing specific words.

We know that by "substracting" the activity of the brain before hearing an information and after hearing it. The result is an activity in the brain connected with this word.