Is there a brain area for mind-wandering? For religious experience? For reorienting attention? A recent study casts serious doubt on the evidence for these ideas, and rewrites the rules for neuroimaging.
Brain mapping experiments attempt to identify the cognitive functions associated with discrete cortical regions. They generally rely on a method known as "cognitive subtraction." However, recent research reveals a basic assumption underlying this approachthat brain activation is due to the additional processes triggered by the experimental taskis wrong
"It is such a basic assumption that few researchers have even thought to question it," said Anthony Jack, assistant professor of cognitive science at Case Western Reserve University. "Yet study after study has produced evidence it is false."
Brain mapping experiments all share a basic logic. In the simplest type of experiment, researchers compare brain activity while participants perform an experimental task and a control task. The experimental task might involve showing participants a noun, such as the word "cake," and asking them to say aloud a verb that goes with that noun, for instance "eat." The control task might involve asking participants to simply say the word they see aloud.
"The idea here is that the control task involves some of the same cognitive processes as the experimental task, in this case perceptual and articulatory processes," Jack explained. "But there is at least one process that is differentthe act of selecting a semantically appropriate word from a different lexical category."
By subtracting activity recorded during the control task from the experimental task, researchers try to isolate distinct cognitive processes and map them onto specific brain areas.
Jack and former Case Western Reserve student Benjamin Kubit, now at the University of California Davis, challenge a key assumption of the subtraction method and several tenets of Ven
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Case Western Reserve University